UNITED STATES OF AMERICA WASHINGTON, D. C. GPO 16—67244-1 HUMAN PHYSIOLOGY; ILLUSTRATED BY ENGRAVINGS. ROBLEY DUNGLISON, M.D., M.A.P.S. * V PROFESSOR OF THE INSTITUTES OF MEDICINE AND MEDICAL JURISPRUDENCE IN JEFFBRSON MEDICAL COLLEGE, PHILADELPHIA ; ONE OF THE ATTENDING PHYSICIANS TO THE PHILADELPHIA HOSPITAL (BLOCKLEY); FELLOW OF THE COLLEGE OF PHYSICIANS OF ■ PHILADELPHIA, ETC. ETC. " Vastissimi studii primas quasi lineas circumscripsi."—Mailer. THIRD EDITION, WITH NUMEROUS ADDITIONS AND MODIFICATIONS. IN TWO VOLUMES?" ~{ ~! ; l? \ TT\f j VOL.I. , ^,C-t-CN 'JUN^AL'S OHFiCfcj i \ukH^j\m j PHILADELPHIA: I Q fa ^ Q \ > j CAREY, LEA AND BLANCHARD. 1838. its? K / Entered, according to the Act of Congress, in the year 1838, by Robley Dunglison, in the Clerk's Office of the District Court of the Eastern District of Pennsylvania. DEDICATION TO THE FIRST AND SECOND EDITIONS. TO JAMES MADISON, EX-PRESIDENT OP THE UNITED STATES, ETC. ETC. Alike distinguished as an illustrious benefactor of his country; a zealous promoter of science and literature, and the friend of mankind— this work, intended to illustrate the functions executed by that being, whose moral and political condition has been with him an object of ardent and successful study, is, with his permission, inscribed, in testi- mony of unfeigned respect for his talents and philanthropy, and of gratitude for numerous evidences of friendship, by his obedient and obliged servant, THE AUTHOR. I DIRECTIONS TO THE BINDER. 1. The plates of the System of Respiratory Nerves, and of the Regular or Symmetrical Nerves, between pages 66 and 67. 2. Plate of the Craniological Division of Gall, at page 296. 3. The plates of the Bones, at page 324. PREFACE TO THE THIRD EDITION. In the brief time which has elapsed since the publication of the second edition of this work, many valuable essays and larger treatises have appeared on various topics of physiological science. Of all these the author has endeavoured to avail himself in the preparation of the present edition. To none of them, however, has he been more indebted than to the valuable Handbuch der Physiologie of Professor J. Muller,—a work, by the way, which is much better adapted for the library as a book of reference, than for a guide or accompaniment to the physiological student,—and to the recent edition of the Physiologie als Erfahrungswis- senschaft of Burdach. In a notice of the first edition of this work, in Professor Silli- man's Journal, it was suggested, that the author should append, in a future edition, references to the various authorities cited; and in a very late number of the " British and Foreign Medical Review," (for January, 1838,) in a complimentary notice of the " Human Physiology," the same sentiment has been expressed. Long, how- ever, before the appearance of the latter, the author had com- menced this labour; but it has afforded him no little satisfaction that his views on this point should have accorded with those of the author of that able article. The various references to authorities—now first added—will, the author trusts, be found of eminent advantage to the more ad- vanced student, whilst they can constitute no impediment in the way of the tyro. Philadelphia, 9 Girard St., Aug. 1,1838. PREFACE TO THE SECOND EDITION. The flattering reception, which this work has met with from the P10^6,10"' demands the grateful acknowledgments of the Author, and his utmost zeai w render the work still more worthy of favour. He has, accordingly, enQeav°ure° to add to this edition whatever of importance has been published sinceline appearance of the first edition in this country, and in the different countries 01 Europe, on the various topics which the work embraces; to deduce correct in- ferences from them, and to make such alterations and improvements as suggested themselves on revision. That these have not been to a trifling extent may be appreciated by a comparison of this with the former edition. For the favourable notices, which have been taken of the work m the different periodicals, the Author is sincerely thankful. He has, on many occasions, pro- fited greatly by their strictures and suggestions. The Author cannot conclude this brief preface without congratulating the pro- fession, and the community in general, that the venerable patriot, to whom he had the honour to dedicate the first edition, is still preserved to his country; and it is with no little gratification, that he embraces another opportunity for express- ing those sentiments, which he so warmly entertains for that distinguished in- dividual. Baltimore, Dec. 1, 1835. PREFACE TO THE FIRST EDITION. The present work was undertaken chiefly for the purpose of forming a text- book for the Author's students in the University of Virginia, in which a full course of lectures on Physiology is made to precede the investigation of Patho- logy, or "diseased Physiology," as it has been, not inappropriately, termed. Of late, the study of Physiology has become much more common both with the professional and unprofessional inquirer. The necessity for studying man physi- cally, as well as morally, has been strongly inculcated by some of the best writers on morals and legislation; and, in France, M. Bourdon has compiled a series of dialogues for the young female student,—such topics being suppressed, as were regarded by him to be unsuitable, but enough being retained to preclude their admission into the library of the American lady. In preparing the present work, the Author has availed himself freely of the labours of his predecessors. His object has been to offer a view of the existing state of the science rather than to strike out into new, and perhaps devious, paths. To the labours of Adelon and Chaussier,—especially of the former,—of Blumen- bach, Richerand, Magendie, Rudolphi, Broussais, Sir Charles Bell and others, who have had the chief agency in raising Physiology to its present elevated con- dition, he has been indebted for essential aid; and many of the illustrations have been taken from the admirable graphic delineations of the last mentioned distin- guished physiologist. Some of these sketches, owing to the distance of the Author from the press, are not so uniform in regard to size, or so unexceptionable in certain other respects, as is desirable; but their general execution reflects credit upon Mr. Drayton, under whose superintendence they were engraved. The Author has to regret his not having seen a copy of the " Principles of Medicine," recently published by Dr. Samuel Jackson; especially as he is satis- fied, from the reputation of the author, as well as from a notice of the work in the nineteenth number of The American Journal of the Medical Sciences from the pen of an able professor in the University of Maryland, that he would' have met with many valuable remarks and suggestions. He has likewise to regret that the useful notes, appended to the third American edition of the translation of Broussais' Physiology applied to Pathology, by Drs. Bell and La Roche__did not reach him in time to be available. University of Virginia, July 3,1832. CONTENTS OF VOL. I. Preliminary Observations. Chap. I. Of Natural Bodies .... 13 1. Difference between Inorganic and Organized Bodies - 13 2. Difference between Animals and Vegetables - 19 General Physiology of Man. Chap. I. On the Material Composition of Man - - 24 a. Organic Elements that contain Azote 27 b. Organic Elements that do not contain Azote - - 30 c. Of the Solid parts of the Human Body 33 d. Of the Fluids of the Human Body - - - 38 e. Of the Elementary Structure of Animal Substances 40 /. Physical Properties of the Tissues - - - 44 Chap. II. Of the Functions of Man ... 49 BOOK I. Animal Functions, or Functions op Relation. Chap. I. Of Sensibility or the Function of the Sensations - - 53 1. Of the Nervous System ... 53 2. Physiology of Sensibility - - - • - 80 3. Of the Sensations .... 80 a. External Sensations - - - - 88 Sect. I.—Sense of Tact or Touch 91 1. Anatomy of the Skin, Hair, Nails, &c. - - 91 2. Physiology of Tact and Touch - - 97 Sect. II.—Sense of Taste or Gustation - 106 1. Anatomy of the Organs of Taste - - 107 2. Of Savours - - - - 108 3. Physiology of Taste 112 Sect III.—Of the Sense of Smell or Olfaction - 118 1. Anatomy of the Organ of Smell - - 118 2. Of Odours - - - - 121 3. Physiology of Olfaction ... 127 Sect. IV.—Of the Sense of Hearing or Audition - - 134 1. Anatomy of the Organ of Hearing - - 134 2. Of Sound - - - - - 142 3. Physiology of Audition - - - 148 Sect V.—Of the Sense of Sight or Vision - - 163 1. Of Light 164 ••• CONTENTS. 2. Anatomy of the Organ of Vision 3. Accessory Organs 4. Physiology of Vision 5. Phenomena of Vision Sect. VI.—Additional Senses - 6. Internal Sensations II. Of the Mental Faculties, &c. 1. Physiology of the Intellectual and Moral Faculties Chap. II. Of Muscular Motion, especially of Locomotility or Voluntary Motion 1. Anatomy of the Motory Apparatus - 2. Of the Muscles 3. Of the Bones 4. Physiology of Muscular Motion 5. Of the Attitudes 6. Of the Movements 7. Locomotive Movements a. Walking - 6. Leaping c. Running - d. Swimming - e. Flying - 8. Of the Function of Expression or of Language a. Of the Voice - 1. Anatomy of the Vocal Apparatus 2. Physiology of the Voice 3. Timbre or Quality of the Voice 4. Of Natural or Inarticulate Language 5. Of Artificial or Articulate Language 6. Of Singing b. Of the Gestures - - - - BOOK II. Nutritive Functions. Chap. I. Of Digestion - - - . 452 1. Anatomy of the Digestive Organs - - 452 2. Of the Food of Man ... 475 3. Physiology of Digestion ... 486 4. Digestion of Solid Food - - - 486 a. Hunger .... 496 6. Prehension of Food ... 493 c. Oral or Buccal Digestion ... 495 d. Deglutition .... 499 e. Chymification - 593 /. Action of the Small Intestines - - 533 5. Digestion of Liquids ... ggg 6. Of Eructation, Regurgitation, Vomiting, &c. - 537 HUMAN PHYSIOLOGY. PROLEGOMENA. I. ON NATURAL BODIES. The extensive domain of Nature is divisible into three great classes:—Minerals, Vegetables, and Animals. This division was universally adopted by the ancients, and still prevails, especially amongst the unscientific. When, however, we carefully examine their characteristics, we discover, that the animal and the vegetable resemble each other in many essential particulars. This resem- blance has given occasion to the partition of all bodies into two classes;—the Inorganic, or those not possessing organs, or instru- ments adapted for the performance of particular actions or func- tions, and the Organized, or such as possess this arrangement. In all ages, philosophers have attempted to point out a " Vast chain of being, which from God began, Natures ethereal, human, angel, man, Beast, bird, fish, insect, what no eye can see, No glass can reach—" the links of which chain they have considered to be constituted of all natural bodies; passing by insensible gradations through the in- organic and the organized, and forming a rigid and unbroken series, and in which, they have conceived, "------each moss, Each shell, ea*ch crawling insect, holds a rank Important in the plan of Him who framed This scale of beings—holds a rank which, lost, Would break the chain, and leave behind a gap Which Nature's self would rue." Crystallization has been esteemed by them as the highest link of the inorganic kingdom; the lichen, which encrusts the stone, as but one link higher than the stone itself; the mushroom and the coral, as the connecting links between the vegetable and the animal; and the immense space, which separates man—the highest of the mam- malia—from his Maker, they have conceived to be occupied, in succession, by beings of gradually increasing intelligence. If, however, we investigate the matter minutely, we discover that many links of the chain appear widely separated from each other; vol. i. 2 14 NATURAL BODIES. and that, in the existing state of our knowledge, the catenation can- not be esteemed rigidly maintained.* ,. Let us inquire into the great characteristics of the different King- doms, and endeavour to describe the chief points in which living bodies differ from those that have never possessed vitality, and into the distinctions between organized bodies themselves. 1. Difference between Inorganic and Organized Bodies. Inorganic bodies possess the common properties of matter. Their elements are fixed, under ordinary circumstances. Their study con- stitutes Physics, in its enlarged sense, or Natural Science. Organized bodies have properties in common with the inorganic, but they have likewise others superadded, which control the first in a singular manner. They are beings, whose elements are undergoing constant mutation, and the sciences treating of their structure and functions are Anatomy and Physiology. They differ from each other in— 1. Origin.—Inorganic bodies are not born ; they do not arise from a parent; they spring from the general forces of matter—the parti- cles being merely in a state of aggregation, and their motions are regulated by certain fixed and invariable laws. The animal and the vegetable, on the other hand, are the products of generation; they must spring from beings similar to themselves, and they possess the principle of life, which controls the ordinary forces of matter. Yet it has been supposed that they are capable of creating life ; in other words, that a particular organization presupposes life. This is not the place for entering into the question of generation. It will be sufficient at present to remark, that in the upper classes of animals, the necessity of a parent cannot be contested; the only difficulty, that can possibly arise, regards the very lowest classes, and analogy has appeared, in their case, to warrant the conclusion, that every living being must spring from an egg or a seed. 2. Shape.—The shape of inorganic bodies is not fixed in a deter- minate manner. It is true, that by proper management, every mineral can be reduced to a primitive nucleus, which is the same in all minerals of like composition ; still the shape of the mineral, as it presents itself to us, differs. Carbonate of lime, for example, al- though it may always be reduced to the same primitive nucleus, assumes various appearances; being sometimes rhomboidal; at others, in regular hexaedral prisms; in solids, terminated by twelve scalene triangles, or in dodecaedrons, whose surfaces are pentagons. In organized bodies, on the contrary, the shape is constant. Each animal and vegetable has the one that characterizes its species, so that no possible mistake can be indulged; and this applies not only to the whole body, but to every one of its parts, numerous as they are. 3. Size.—The size of an inorganic body is by no means fixed. It * Fleming's Philosophy of Zoology, I. 4. Edinburgh, 1822. INORGANIC AND ORGANIZED. 15 may be great, or small, according to the quantity present of the par- ticles, that have to form it. A crystal, for example, may be minute or the contrary, according to the number of saline particles in the solution. On the other hand, organized bodies attain a certain size, —at times by a slow, at others by a more rapid growth,—but in all cases the due proportion is preserved between the various parts,— between the stem and the root, the limb and the trunk. Each vege- table and each animal has its own size, by which it is known; and although we occasionally meet with dwarf or gigantic varieties, these are infrequent, and mere exceptions proving the position. 4. Chemical character.—Great difference exists between inor- ganic and organized bodies in this respect. In the mineral kingdom are found all the elementary substances, or those which chemistry, at present, considers simple, amounting to at least fifty-four, and comprising oxygen, hydrogen, boron, carbon, phosphorus, sulphur, selenium, iodine, fluorine, chlorine, bromine, azote, silicon, zirconium, thorinum, aluminum, yttrium, glucinum, magnesium, calcium, stron- tium, baryum, sodium, potassium, lithium, manganese, zinc, iron, tin, arsenic, molybdenum, vanadium, tungsten, columbium,chromium, antimony, uranium, cerium, cobalt, titanium, bismuth, cadmium, cop- per, tellurium, lead, mercury, nickel, osmium, rhodium, silver, gold, platinum, palladium, and iridium.* In the organized, a few only of these elements of matter are met with, viz. oxygen, hydrogen, azote, carbon, sulphur, phosphorus, &c. In inorganic bodies, the composition is more simple; several consist of but one element; and, when composed of more, the com- bination is rarely higher than ternary. The organized body, on the other hand, is never simple nor even binary. It is always at least ternary or quaternary.! The simplest vegetable consists of a union of oxygen, carbon, and hydrogen; the simplest animal, of oxygen, hydrogen, carbon, and azote. The composition of the mineral again is constant. Its elements have entirely satisfied their affinities, and all remains at rest. In the organized kingdom, however, the affinities are not satisfied; com- pounds are formed to be again decomposed, and this happens from the earliest period of fetal formation till the cessation of life: all is in commotion, and the chemical character of the corporeal fabric is incessantly undergoing modification. In chemical nomenclature, the term element has a different accep- tation, according as it is applied to inorganic or organic chemistry. In the former, it means a substance, which, in the present state of the science, does not admit of decomposition. We say, " in the present state of the science," for several bodies, now esteemed * Chemistry, Meteorology, &c. By Wm. Prout, M. D., F. R. S. (Bridgewater Treatise.) Amer. edit, p. 73. Philad., 1834. t Allgemeine Anatomie des menschlichen Ktirpers, von H. E. Weber, s. 66. Braun- schweig, 1830:—being the first volume of the fourth edition of Weber's Hildebrandt's Handbuch der Anatomie des Menschen. 16 NATURAL BODIES. compound, were not many years ago, classed amongst the simP1(? °r elementary. It is not more than twenty-eight years since the aiKa- lies were found to be composed of two elements. Previously, tney were considered simple. In the animal and the vegetable, we nna substances, also called elements, but with the epithet organic, because only found in organized bodies, and therefore the exclusive products of organization and life. For example, in both animals and^vege- tables we meet with oxygen, hydrogen, carbon, azote, and different metallic substances : these are chemical or inorganic elements, and we further meet with albumen, gelatine, fibrine, ozmazome, &c. sub- stances, which constitute the various organs, and which, therefore, have been termed organic elements or compounds of organization; yet they are capable of decomposition, and in one sense, therefore, not elementary. In the inorganic body, all the elements, that constitute it, are form- ed by the agency of general chemical affinities; but, in the organized, the formation is* produced by the force, that presides over the forma- tion of the organic elements themselves—the force of life. Hence the cause why the chemist is able to recompose many of the inor- ganic bodies, whilst the products of organization and of life set his art at defiance. The different parts of an inorganic body enjoy an existence inde- pendent of each other; whilst those of the organized are materially dependent. No part can, indeed, be injured without the mass and the separated portion being more or less affected. If we take a piece of marble, which is composed of carbonic acid and of lime, and break it into a thousand fragments, each portion will be found to consist of carbonic acid and of lime. The mass will be destroyed, but the pieces will suffer from the disjunction. They will continue as fixed and unmodified as at first. Not so with an organized body. If we tear the branch from a tree, the stem itself participates more or less in the injury; the detached branch speedily undergoes striking changes; it withers; becomes shrivelled, and, in the case of the succulent vegetable, undergoes decomposition; a portion of its constituents, no longer held in control by the vital agency, enters into new combinations, is given off in the form of gas, and the re- mainder sinks to earth. Changes, no less impressive, occur in the animal when a limb is separated from the body. The parent trunk suffers ; the system re- coils at the first infliction of the injury, but subsequently arouses itself to a reparatory effort,—at times with such energy as to destroy its own vitality. The separated limb, like the branch, is given up, un- controlled, to new affinities; and putrefaction soon reduces the mass to a state in which its previously admirable organization is no longer perceptible. Some of the lower classes of animals may indeed be divided with impunity, and with no other effect than that of multiply- ing the animal in proportion to the number of sections, but these cases are exceptions; and we may regard the destructive process,__ INORGANIC AND ORGANIZED. 17 set up when parts of organized bodies are separated,—as one of the best media of distinction between the inorganic and organized classes. 5. Texture.—In this respect the inorganic and organized differ considerably,—a difference which has given rise to their respective appellations. To the structure of the latter class only can the term texture be with propriety applied. If we examine a vegetable or animal substance with attention, we find, that it has a regular and determinate arrangement or structure; and we readily discover, that it consists of various parts;—in the vegetable, of wood, bark, leaves, roots, flowers, &c.; and in the animal, of muscles, nerves, vessels, &c.; all of which appear to be instruments or organs for specific purposes in the economy of the being. Hence the body is said to be organized, and the result, as well as the process, is often called organization. Properly, organiza- tion means the process by which an organized being*is formed; organism, the result of such process, or the organic structure.* The particles of matter in an organized body, so far as we can detect them, constitute fibres, which in- terlace and intersect each other in all Fig. 1. directions, and form a spongy areolar texture or tissue. (Fig. 1.) Of these tis- sues the various organs of the body are composed. In the inorganic substance, the mass is homogeneous; the smallest particle of marble consists of carbonic acid and lime; and all the particles con- cur alike in the formation and preserva- tion of the body. Lastly, whilst an inorganic body, of a determinate species, has always a fixed composition, the living being, although constituting a particular species, may present individual differences, giving rise, in the animal, to various temperaments, constitutions, &c. 6. Mode of preservation.—Preservation of the species is, in the organized, the effect of reproduction. As regards individual preserva- tion, that of the mineral is dependent upon the same actions that effected its formation, on the persistence of the affinities of cohesion and combination, which united its various particles. The animal and the vegetable, on the other hand, are maintained by a mechanism peculiar to themselves. From the bodies surrounding them, they lay hold of nutritious matter, which, by a process of elaboration, they assimilate to their own composition; at the same time, they are constantly absorbing or taking up particles of their own struc- ture, and throwing them off. The actions of composition and de- composition are constant whilst life exists, although subject to par- * Rudiments of Physiology. By John Fletcher, M. D., F. R. C, S. E. Part I., p. 2. Edinburgh, 1835. 2* ig NATURAL BODIES. ticular modifications at different periods of existence, and under different circumstances. A.n(,p, Again:—the inorganic and organized are alike subject to changes during their existence; but the character of these changes, n the two classes, differs essentially. The mineral retains its form, unless acted upon by some mechanical or chemical force. Within, all me particles are at rest, and no internal force exists which can subject them to modification. There is no succession of conditions which can be termed ages. How different is the case with organised bodies! Internally, there is no rest; from birth to death all is in a state of activity. The plant and the animal are subject to incessant changes. Each runs through a succession of conditions or ages. We see it successively develope its structure and functions, attain maturity, and finally decay. Characteristic differences likewise exist in the external conlorma- tion of the beings of the two divisions, as well as in their mode of increase. Inorganic bodies have no covering to defend them, no exterior envelope to preserve their form: a stone, for example, is the same at its centre as at its circumference;—whilst organized bodies are protected by an elastic and extensible covering, differing from' the parts beneath, and inservient to valuable purposes in the economy. Every change, to which an inorganic body is liable, must occur at its surface. It is there that the particles are added or abstracted when it experiences increase or diminution of size. This increase— for growth it can scarcely be termed—takes place by accretion or juxtaposition, that is, by the successive application of fresh particles upon those that form the primitive nucleus; and diminution in bulk is produced by the removal of the external layers or particles; but in organized substances, increase or growth is caused by particles deposited internally, and diminution by particles substracted from within. We see them, likewise, under two conditions, to which there is nothing similar in the mineral kingdom,—health, and disease. In the former, the functions are executed with freedom and energy; in me latter, with oppression and restraint. 7. Termination.—Every body, inorganic or organized, may cease to exist, but the mode of cessation varies greatly in the two classes. The mineral is broken down by mechanical violence, or it ceases to exist, in consequence of modifications in the affinities, which held it concrete. It has no fixed duration, and its existence may be ter- minated at any moment, when the circumstances, that retained it in aggregation, are destroyed. The vegetable and the animal, on the other hand, can carry on their functions for a period only, which is fixed and determinate for each species. For a time, new particles are deposited internally. The bulk is augmented, and the external envelope distended, until maturity or full developement is attained ; but, after this, decay commences; the functions are exerted with gradually diminishing energy ; the fluids decrease in quantity ; and the solids become more rigid,—circumstances premonitory of the ANIMALS AND VEGETABLES. 19 total cessation of vitality. This term of duration is very different in different species. Whilst many of the lower classes of animals and vegetables have but an ephemeral existence, some of the more elevated individuals of the two kingdoms outlive a century. 8. Motive forces.—Lastly, observation has satisfactorily proved, that there are certain forces which affect matter in general, the in- organic as well as the organized, but that, in addition to these, the organized possess a peculiar force or forces, which modify them in the most remarkable manner. Hence, we have general forces, and special or vital; the first acting upon all matter, the dead and the living, and including the forces of gravitation, cohesion, chemical affinity, &c.; the latter being exclusive to living beings. Such are the chief distinctions to be drawn between the two great divisions of natural bodies, the inorganic and the organized. By the comparison which has been instituted, the objects of physio- logy, the phenomena of life, have been indicated. To inquire into the mode in which a living being is born, nourished, reproduced, and dies, is the legitimate object of this science. We have, however, entered only into a comparison between the inorganic and the organized. The two divisions constituting this latter class differ also materially from each other. Into these differ- ences we shall now inquire. 2. Difference between Animals and Vegetables. The distinctions between these divisions of organized bodies are not so rigidly fixed, or so readily appreciated, as those we have just considered. There are certain functions possessed by each, and hence called vegetative, plastic, or organic—nutrition and reproduction for exam- ple ; but vegetables are endowed with these only. All organized bodies must have the power of assimilating foreign matters to their own substance, and of producing a living being similar to them- selves, otherwise the species, having a limited duration, would perish. In addition to these common functions, animals have two others, sensation and voluntary motion, by the possession of which they are said to be animated. Hence they are termed animals, and the con- dition is called animality. This division of the functions into animal and organic has been adopted, with more or less modification, by the generality of physiologists. Between animals and vegetables, that are situated high in their respective classes, no error can possibly be indulged. The charac- ters are obvious at sight. No one can confound the horse with the oak, the butterfly with the potatoe. It is on the lower confines of the two kingdoms that we are liable to be deceived. Many of the zoophytes have alternately been considered vegetable and animal; and it is not until of modern date, that the sponge has been uni- versally elevated to that kingdom to which it is entitled. Nor is this to be wondered at. In its attachment to the rock, it is as immova- 20 NATURAL BODIES. ble as the lichen is to the slate, and almost equally deficient in the usual characteristics of animality. In general, however, we are able to classify any doubtful substance with accuracy, and the fol- lowing are the principal points of difference. 1. Composition.—The essential elements of organized matter are, carbon, oxygen, hydrogen, and azote, with alkaline and earthy salts, variously combined. Vegetables consist of the three first of these elements, carbon, oxygen, and hydrogen. Azote is possessed in addition by the animal; yet there are many animal substances that contain no azote. Plants have scarcely any; and generally, when it is met with in them, it is found in some part,—scarcely ever dis- tributed through the whole. In the fungi, traces of a vegeto-animal matter have been detected by the chemist, but they have only been traces. In consequence of this difference of composition, animal substances are easily known from vegetable by burning;—a fact, which, as Dr. Fleming* has remarked, is interesting to the young naturalist, if uncertain to which kingdom to refer any substance met with in his researches. The smell of a burnt sponge, of coral, or other zoophytic animal, is so peculiar, that it can scarcely be mis- taken for that of a vegetable body in combustion. 2. Texture.—In this respect, important differences are observable. Both animals and vegetables consist of solid and fluid parts. In the former, however, the fluids bear a large proportion: in the latter the solids. This is the cause why decomposition occurs so much more rapidly in the animal than in the vegetable, and in the succulent than in the dry vegetable. If we analyze the structure of the vege- table, we cannot succeed in detecting more than one elementary tissue, which is vesicular, or arranged in areolae or vesicles, and ap- pears to form every organ of the body, whilst in the animal, we discover at least three of these anatomical elements, the cellular— analogous to that of the vegetable—the muscular, and the nervous. The vegetable again has no great splanchnic cavities containing the chief organs of the body. It has a smaller number of organs, and none that are destined for sensation or volition ; in other words, no brain, no nerves, no muscular system ; whilst the organs, of which it consists, are simple, and readily convertible into each other. This is not the case with the animal. But these differences in organization, striking as they may appear, are not sufficient for rigid discrimination, as they are applicable only to the upper classes of each kingdom. In many vegetables, the fluids appear to preponderate over the solids; numerous ani- mals are devoid of muscular and nervous tissues, and apparently of vessels, and distinct organs; whilst MM. Dutrochet,} Brachet,J and * Philosophy of Zoology, L 41. Edinburgh, 1822, and Sir J. E. Smith's Introduction to Botany, 7th edit., by Sir W. J. Hooker, p. 3. Lond. 1833. t Recherches anatomiques et physiologiques sur la structure intime des animaux et des vegetaux, et sur leur motuite. Paris, 1824. ' X Recherches experimentales sur les fonctions du systeme nerveux ganglionaire &c Paris, 1830. ANIMALS AND VEGETABLES. 21 others,* admit the existence of a rudimental nervous system, even in vegetables. 3. Sensation and voluntary motion.—One manifest distinction exists between animals and vegetables. Whilst the latter receive their nutrition from the objects situated around them—irresistibly and without volition, or the participation of mind—and whilst the func- tion of reproduction is effected without the union of the sexes; voli- tion and sensation are both necessary for the nutrition of the former, and for the acts requisite for the reproduction of the species. Hence, the necessity of two faculties or functions in the animal, which are wanting in the vegetable, viz. sensibility, or the faculty of conscious- ness and feeling; and motility, or the power of moving the whole body or any of its parts at the will of the being. Vegetables are possessed of spontaneous, but not of voluntary motion. Of the former we have numerous examples in the direction of the branches and upper surfaces of the leaves, although repeatedly disturbed, to the light; and in the unfolding and closing of flowers, at stated periods of the day. This, tiowever, is quite distinct from the sensibility and motility that characterize the animal. By sensibility man feels his own existence,—becomes acquainted with the universe,—appre- ciates the bodies that compose it, and experiences all the desires and inward feelings that solicit him to the performance of those external actions, which are requisite for his preservation, as an individual and as a species; and by motility he executes those external actions, which his sensibility may suggest to him. By some naturalists it has been maintained, that those plants, which are borne about on the waves, and fructify in that situation, exhibit to us examples of the locomotility, which is described as characteristic of the animal. One of the most interesting novelties, in the monotonous occurrences of a voyage across the Atlantic to- wards the Gulf of Florida, is the almost interminable quantity of the Fucus natans, Florida weed or Gulph weed, with which the surface of the ocean is covered. But how different is this motion from the locomotility of animals! It is a subtlety to conceive them identical. The weed is passively and unconsciously borne whithersoever the winds and the waves may urge it, whilst locomotion requires the direct agency of volition, of a nervous system that can excite, and of muscles that can act under such excitement. The spontaneity and perceptivity of plants, as they have been termed, must also be explained in a different manner from the ele- vated function of sensibility on which we shall have to dwell. These properties must be referred to the fact of certain vegetables being possessed of the faculty of contracting on the application of a stimulus, independently of sensation or consciousness. If we touch the leaf of the sensitive plant, Mimosa pudica,-\ the various leaflets collapse in rapid succession. In the barberry bush, Berberis vulga- ris, we have another example of the possession of this faculty. In • Sir J. E. Smith, Op. citat. p. 40. f Mayo's Outlines of Human Physiology, 3d. Edition, p. 9. London, 1833. 22 NATURAL BODIES. the flower, the six stamens, spreading moderately, are sheltered under the concave tips of the petals, till some extraneous body, as the feet or trunk of an insect in search of honey, touches the inner part of each filament, near the bottom. The susceptibility of this part is such, that the filament immediately contracts, and strikes its anther, full of pollen, against the stigma. Any other part of the fila- ment may be touched without this result, provided no concussion be given to the whole. After awhile, the filament retires gradually, and may be again stimulated, and when each petal, with its annexed filament, has fallen to the ground, the latter, on being touched, shows as much sensibility as ever.* These singular effects are produced by the power of contractility or irritability, the nature of which will fall under consideration here- after. It is possessed equally by animals and vegetables, and is essentially organic and vital. This power, we shall see, needs not the intervention of volition: it is constantly exerted in the animal without consciousness, and therefore necessarily without volition. Its existence in vegetables does not, consequently, demonstrate that they are possessed of consciousness. 4. Nutrition.—A great difference exists between plants and ani- mals in this respect. The plant, being fixed to the soil, cannot search after food. It must be entirely passive, and obtain its supplies from the materials around, and in contact with it; and the absorbing vessels of nutrition must necessarily open on its exterior. In the ani- mal, on the other hand, the aliment is scarcely ever found in a state fit for absorption: it is crude, and in general—Ehrenbergf thinks al- ways—requires to be received into a central organ, or stomach, for the purpose of undergoing changes, by a process termed digestion, which adapts it for the nutrition of the individual. The absorbing vessels of nutrition arise, in this case, from the internal or lining membrane of the alimentary tube. The analogy, however, that exists between these two kinds of absorption is great, and had not escaped the attention of the ancients:—" Quemadmodum terra arboribus, ita ani- malibus ventriculus sicut humus'"' was an aphoristic expression of uni- versal reception. With similar feelings, Boerhaave asserts, that animals have their roots of nutrition in their intestines; and Dr. Alston J has fancifully termed a plant an inverted animal l Again, in both plants and animals the residue of the matters ab- sorbed is ejected from the body; but the form and character of the rejected portion vary in the two kingdoms. In the plant, the super- fluous quantity is thrown off in gaseous, hydrogenated, or aqueous exhalations: in the animal, the useless portion is excreted, or reiected as excrement, of which azote is a constituent. * Sir J. E. Smith's Introduction to Botany, p. 325. t See Dr. Gairdner's account of Ehrenberg's researches, in Edinb Npw Phil v.- i Journal for Sept. 1831; and ibid, for Jan. 1838, p. 232; also Dr «^S ]°o0phl,Cal Philosophy of Health, vol. 1. p. 35. London 1835. Southwood Smith's X Tirocinium Botanicum Edinburgense, 8vo. Edinb. 1753. § Fletcher's Rudiments of Physiology, part 2. a. p. 9. Edinh lfilfi *• r> ,.. Accroissement, Diet, de Med. torn. 1. Paris, 1821. P dmb"1836- & RuUl<*. art. ANIMALS AND VEGETABLES. 23 After all, the most essential difference consists in the steps that are preliminary to the reception of food. These, in the animal, are voluntary,—requiring prehension, often locomotion, and always con- sciousness. 5. Reproduction.—In this function we find a striking analogy be- tween animals and vegetables; but differences exist, which must be referred to the same cause, that produced many of the distinctions already pointed out—the possession, by the animal, of sensibility and locomotility. For example, every part of the generative act is, in the vegetable, without the perception or volition of the being:—the union of the sexes, fecundation, and the birth of the new individual are alike automatic. In the animal, on the other hand, the approxi- mation of the sexes is always voluntary, and effected consciously— the birth of the new individual being not only perceived, but some- what aided by volition. Fecundation alone is involuntary and irre- sistible. Again, in the vegetable the sexual organs do not exist at an early period, and are not developed until reproduction is practicable. They are capable of acting for once only, and perish after fecun- dation ; and if the plant be vivacious, they fall off after each repro- duction, and are annually renewed. In the animal, on the contrary, they exist from the earliest period of fostal developement, survive repeated fecundations, and continue during the life of the individual. Lastly, the possession of sensibility and locomotility leads to other characteristics of animated beings. These functions are incapable of constant, unremitting exertion. Sleep, therefore, becomes, neces- sary. The animal is also capable of expression or of language, in a degree proportionate to the extent of his sensibility, and of his power over the beings that surround him. But these differences in function are not so discriminative as they may at first appear. There are many animals, which are as irresis- tibly attached to the soil as the vegetables themselves. Like the latter, they must, of necessity, be compelled to absorb their food in the state in which it is presented to them. Sensibility and locomo- tility appear, in the zoophyte, to be no more necessary than in the vegetable. No nervous, no muscular system is required; and, ac- cordingly, none can be traced in them ; whilst many of those spon- taneous motions of the vegetable, which have been described, have been considered by some to indicate the first rudiments of sensibility and locomotility: and Linnaeus* has regarded the closure of the flowers towards night as the sleep, and the movements of vegeta- bles, for the approximation of the sexual organs, as the marriage of plants.f * Amoenit. Academ. Tom. iv. t See also on the differences between Animals and Vegetables, Lepelletier, Physiologie Medicale, &c. I. 34. Paris, 1831 ; Tiedemann, Traits complet de Physiologiede I'Homme. Traduit par A. J. L. Jourdan, I. 166. Paris, 1831; Willis, in art. Animal, of Cyclopaedia of Anatomy and Physiology. Part II. Lond., 1835. Southwood Smith's Philosophy of Health. Part I., chap. i. Lond., 1835; Virey, Philosophic de l'His- toire Naturelle, &c. p. 253. Paris, 1835. Weber, loc. citat. and Moller's Handbuch der Physiologie des Menschen. Coblenz, 1835, 1837, or Baly's translation, part I. p. 40. London, 1837. 24 MATERIAL COMPOSITION OF MAN. II. GENERAL PHYSIOLOGY OF MAN. The observations made on the difference between animals and vegetables have anticipated many topics, which would require con- sideration under this head. Those general properties which man possesses, along with other animals, have been referred to in a cur- sory manner. They will now demand a more special investigation. 1.—On the Material Composition of Man. The detailed study of human organization is the province of the anatomist,—of its intimate composition, that of the chemist. In ex- plaining the functions executed by the various organs, the physio- logist will frequently have occasion to trench upon both of these departments. The bones, in the aggregate, form the skeleton. The base of this skeleton is a series of verlebrce, with the skull as a capital—itself regarded as a vertebra by De Blainville. This base is situated on the median line through the whole trunk, and contains a cavity, in which are lodged the brain and spinal marrow. On each side of this, other bones are arranged in pairs, which by some have been called appendices. Upon the skeleton are placed muscles, for moving the different parts of the body, and for changing its situation with regard to the soil. The body is again divided into trunk and limbs. The trunk, which is the principal portion, is composed of three splanchnic cavities, situated one above the other—the abdomen, thorax, and head. These contain the most important organs of the body—those that effect the functions of sensibility, digestion, respi- ration, circulation, &c. The head comprises the face, which con- tains the organs of four of the senses—those of sight, hearing, smell, and taste,—and the cranium, which lodges the brain—the organ of the mental manifestations, and the most elevated part of the nervous system. The thorax or chest contains the lungs—organs of respira- tion,—and the heart, the great organ of the circulation. The abdomen contains the principal organs of digestion, and (if we include in it the pelvis,) those of the urinary secretion and of generation. Of the limbs, the upper, suspended on each side of the thorax, are instruments of prehension, and are terminated by the hand, the great organ of touch. The lower are situated beneath the trunk, and are agents for supporting the body, and for locomotion. Vessels, emanating from the heart, are distributed to every part; conveying to them the blood necessary for their vitality and nutrition: these are the arteries Other vessels communicate with them, and convey the blood back to the heart,—the veins; whilst a third set communicate also with the arteries, and convey into the circulation, by a particular channel MATERIAL COMPOSITION OF MAN. 25 a fluid called lymph—whence they derive the name of lymphatics. Nerves, communicating with the great central masses of the nervous system, are distributed to every part to complete their vitality; and lastly, a membrane or layer, possessed of acute sensibility—the skin —serves as an outer envelope to the whole body. It has been already remarked, that the animal body consists es- sentially of four ultimate elements—oxygen, hydrogen, carbon, and azote. This is correct as a general principle; but organic che- mistry has shown us, that some of the constituents afford little or no traces of azote. It was likewise observed, that two kinds of ele- ments enter into the composition of the body—the chemical or inor- ganic, and the organic, which are compound, and formed only under the principle of life. The chemical or inorganic elements, met with, are—oxygen, hy- drogen, carbon, azote, phosphorus, calcium; and, in smaller quantity, sulphur, iron, manganese, silicium, chlorine; also, sodium, magne- sium, &c. • 1. Oxygen.—This is widely distributed in the solids and fluids, and a constant supply of it from the atmosphere is indispensable to animal life. It is almost always found combined with other bodies, often in the form of carbonic acid—that is, united with carbon. In a separate state it is met with in the air-bag of fishes, in which it is found varying in quantity, according to the species, and the depth at which the fish has been caught. 2. Hydrogen.—This gas occurs universally in the animal kingdom. It is a constituent of all the fluids, and of many of the solids; and is generally in a state of combination with carbon. In the human intestines it has been found pure, as well as combined with carbon and sulphur. 3. Carbon.—This substance is met with under various forms, in both fluids and solids. It is most frequently found under that of car- bonic acid. Carbonic acid has been detected in an uncombined state in urine, by Proust, and by Vogel* in the blood. It likewise exists in the intestines of animals; but it is chiefly met with in ani- mal bodies, in combination with the alkalies or earths ; and is emitted by all animals in the act of respiration. 4. Azote.—This gas is likewise widely distributed as a component part of animal substances. Indeed, so generally does it prevail, that it often affords a distinctive mark by which they may be known from vegetables. It likewise occurs, in an uncombined state, in the swim- bladder of certain fishes. 5. Phosphorus is found united with oxygen—in the state of phos- phoric acid—in many of the solids and fluids. This is the acid, that is combined with the earthy matter of bones, and with potassa, soda, ammonia, and magnesia, in other parts. It is supposed to give rise to the luminousness of certain animals—as of the fire-fly, the Pyro- soma atlanticum, &c.—but nothing precise is known on this subject. * Annals of Philosophy, vii. 56. VOL. I. 3 26 MATERIAL COMPOSITION OF MAN. 6. Ca/«ttm.—This metal is found only in the state of oxide or lime in the animal economy; and it is generally united withitne phosphoric or carbonic acid. It is the earth, of which the hard parts of animals are constituted. 7. Sulphur is not met with extensively in the animal solids or fluids: nor is it ever found free, but always in combination with oxygen, united to soda, potassa, or lime. It seems to be an invaria- ble concomitant of albumen, and is found in the lower part of the intestines, in the form of sulphuretted hydrogen gas; and as an ema- nation from fetid ulcers. 8. Iron.—This metal has been detected in the colouring matter of the blood; in bile, and in milk. For a long time it was considered to be, in the first of these fluids, in the state of phosphate or sub-phos- phate. Berzelius,* however, showed, that this was not the case; that the ashes of the colouring matter always yielded oxide of iron in the proportion of l-200th of the original mass. That distinguished chemist was, however, unable to detect the condition in which the metal exists in the blood, and could not discover its presence by any of the liquid tests. More recently, Engelhart,t a German chemist, has shown that the fibrine and albumen of the blood, when carefully separated from colouring particles, do not contain a trace of iron; whilst he could procure it from the red globules by incineration. He also succeeded in proving its existence in the red globules by liquid tests, and his experiments have been repeated, with the same results, by Rose of Berlin. J In milk, iron seems to be in the state of phosphate. 9. Manganese has been found in the state of oxide, along with iron, in the ashes of the hair. 10. Silicium.—Silica is found in the hair, urine, and in urinary calculi. 11. Chlorine.—In combination with hydrogen, and forming mu- riatic acid, chlorine is met with in most of the animal fluids. It is generally united with soda. Free muriatic acid has also been found by Prout§ in the stomach of the rabbit, hare, horse, calf, and dog; and he has discovered the same acid in the sour matter ejected from the stomachs of those labouring under indigestion. Mr. Children has made similar observations, and Messrs. Tiedemann and Gmelin,|| Professor Emmet, and the author^ found it in considerable quantity, in the healthy gastric secretions of man. 12. Sodium.—The oxide of sodium, soda, forms a part of all the fluids. It has never been discovered in a free state, but is united, * Medico-Chirurgical Transact., vol. iii. t Commentatio de vera materia? sanguini purpureum colorem impertientis natura. Gotting., 1825. X Turner's Chemistry, fifth ed. p. 963. Lond., 1834. § Philosoph. Transact, for 1824, p. 45. || Recherches experimentales, &c. sur la digestion. Trad, par A. G. L J d T See under the head of" Digestion," and the author's Elements of Hygiene d 222 Philadelphia, 1835. 'v' ORGANIC ELEMENTS. 27 (without an acid,) to albumen. Most frequently, it is combined with the muriatic and phosphoric acids; less so, with the lactic, carbonic, and sulphuric acids. 13. Potassium.—The oxide, potassa, is found in many animal fluids, but always united with acids—the sulphuric, muriatic, phos- phoric, &c. It is much more common in the vegetable kingdom, and hence one of its names—vegetable alkali. 14. Magnesium.—The oxide, magnesia, exists sparingly in bones, and in some other parts, but always in combination with the phos- phoric acid. The Organic Elements, proximate principles, or compounds of organization are the primary combination of two or more of the elementary substances, in definite proportions. Formerly, four only were admitted—gelatine, fibrine, albumen, and oil. Of late, how- ever, organic chemistry has pointed out numerous others, which are divided into two classes—-first, those that contain azote, as albumen, gelatine, fibrine, osmazome, mucus, caseine, urea, uric acid, the red colouring principle of the blood, the yellow colouring principle of the bile, &c.; and secondly, those that do not contain azote, as oleine, stearine, the fatty matter of the brain and nerves, the acetic, oxalic, benzoic, and lactic acids, the sugar of milk, sugar of diabetes, picromel, the colouring principle of the bile, and that of other solids and liquids. a. ORGANIC ELEMENTS THAT CONTAfN AZOTE. 1. Albumen. This is one of the most common organic constitu- ents, and appears under two forms—liquid and concrete. In its purest state, the former is met with in the white of egg—whence its name;—in the serum of the blood, the lymph of the absorbents, the serous fluid of the great splanchnic cavities and of the cellular mem- brane, and in the synovial secretion. It is colourless and transparent, without smell or taste, and is coagulated by acids, alcohol, ether, metallic solutions, infusion of galls, and by a temperature of 165° Fahrenheit. Concrete, coagulated, or solid albumen is white, tasteles's, and elas- tic ; insoluble in water, alcohol, or oil, but readily soluble in alkalies. Albumen is always combined with soda. It exists, in abundance —both liquid and concrete—in different parts of the animal body. Hair, nails, and horn consist of it; and it is, in some form or other, the great constituent of many tumours. 2. Gelatine.—This is the chief constituent of the cellular tissue, skin, tendons, ligaments, and cartilages. The membranes and bones also contain a large quantity of it. It is obtained by boiling these substances for some time in water; clarifying the concen- trated solution; allowing it to cool, and drying the substance, thus obtained, in the air. In this state it is called glue; in a more liquid form, jelly. Gelatine dissolves readily in hot water: it is soluble 28 MATERIAL COMPOSITION OF MAN. in acids and alkalies; insoluble in alcohol, ether, and in thei fixed and volatile oils. Alcohol precipitates it from its solution in wjuer. Gelatine, nearly in a pure state, forms the air-bag ot .d^rem kinds of fishes, and is well known under the name of isinglass. It is used also extensively in the arts, under the forms ot^e ana size, on account of its adhesive quality. What is called portable soup is dried jellv, seasoned with various spices. 3. Fibrine.—This proximate principle exists in the chyle; enters into the composition of the blood; forms the chief-part of muscular flesh, and may be looked upon as one of the most abundant animal substances. It is obtained by beating the blood, as it issues from a vein, with a rod. The fibrine attaches itself to each twig in the form of red filaments, which may be deprived of their colour by repeated washing with cold water. Fibrine is solid, white, flexible, slightly elastic, insipid, inodorous, and heavier than water. It is neither soluble in water, alcohol, nor acids; it dissolves in liquid potassa or soda, in the cold, without much change; but, when warm, becomes decomposed. Fibrine constitutes the buffy coat of blood; and is thrown out from the blood-vessels, as a secretion, in many cases of inflamma- tion, becoming subsequently organized, or penetrated by blood- vessels and nerves. 4. Osmazome.—This is the matiere extractive du bouillon, extrac- tive, and saponaceous extract of meat.—When flesh, cut into small fragments, is macerated in successive portions of cold water, the albumen, osmazome, and salts are dissolved; and, on boiling the so- lution, the albumen is coagulated. From the liquid remaining, the osmazome may be procured in a separate state, by evaporating to the consistence of an extract, and treating it with cold alcohol. This substance is of a reddish-brown colour, and is distinguished from the other animal principles by solubility in water and alcohol—whether cold or at the boiling point—and by not forming a jelly when its solution is concentrated by evaporation. Osmazome exists in the muscles of animals, in the blood, and in the brain. It gives the peculiar flavour of meat to soups ; and, ac- cording to Fourcroy,* the brown crust of roast meat consists of it 5. Mucus.—This term has been applied to various substances; and hence the discordant characters ascribed to it. Applying it to the fluid secreted by mucous surfaces, it varies somewhat according to the source whence it is derived. Its leading characters may be exemplified in that derived from the nostrils, which has the follow- ing properties.—It is insoluble in alcohol and water, but imbibes a little of the latter, and becomes transparent: it is neither coagulated by heat, nor rendered horny; but is coagulated by tannin. Mucus, in a liquid state, serves as a protecting covering to dif- ferent parts. Hence it differs somewhat in its characters, according to the office it has to fulfil. When inspissated, it forms,' according » System of Chemical Knowledge, &c, by W. Nicholson—Vol. i.t., Lond. 1804 ORGANIC ELEMENTS. 29 to some, the minute scales that are detached from the surface of the body by friction, the corns, and the thick layers on the soles of the feet, the nails, and horny parts ; and it is contained in considerable quantity in hair, wool, feathers, scales of fishes, &c. 6. Caseum or Caseine or Caseous matter.—This substance exists only in milk, and is the basis of cheese. To obtain it, milk must be left at rest, at the ordinary temperature, until it is coagulated; the cream that collects on the surface must be taken off; the clot well washed with water, drained upon a filter, and dried. The residuum is pure caseum. It is a white, insipid, inodorous substance, insoluble in water, but readily soluble in the alkalies, especially in ammonia. It possesses considerable analogy with albumen. Proust ascribes the characteristic flavour of cheese to the presence of the caseate of ammonia. 7. Urea.—This proximate principle exists in the urine of the mammalia when they are in a state of health. In human urine it is less abundant after a meal, and it nearly disappears in diabetes, and in affections of the liver. It is obtained by evaporating urine to the consistence of syrup. It is then treated with four parts of alcohol, which are afterwards volatilized by heating the alcoholic extract. The mass, that remains, is dissolved in water, or rather in alcohol, and crystallized. The purest urea that has been obtained assumes the shape of acicular prisms, similar to those of the muriate of strontian. It is colourless, devoid of smell, or of action on blue vegetable colours, transparent, and somewhat hard. Its taste is cool, slightly sharp, and its specific gravity greater than that of water. 8. Uric or lithic acid.—This acid is found in the urine of man, birds, serpents, tortoises, crocodiles, lizards, in the excrements of the silk-worm, and very frequently in urinary calculi. It is obtained by dissolving any urinary calculus which contains it, or the sedi- ment of human urine, in warm liquid potassa, and precipitating the uric acid by the muriatic. Pure uric acid is white, tasteless, and inodorous. It is insoluble in alcohol, and is dissolved very sparingly by cold or hot water, requiring about 10,000 times its weight of that fluid, at 60° of Fahrenheit, for solution. The xanthic acid, found by Marcet in urinary calculi, seems to have been this acid. 9. Red colouring principle of the blood.—It has been already observed that Engelhart and Rose, German chemists, had detected iron in the red globules of the blood, and had not found it in the other principles of that fluid. It has been considered probable, there- fore, that it has something to do with the colour. Engelhart's ex- periments have not, however, determined the manner in which it acts, nor in what state it exists in the blood. The sulpho-cyanic acid which is found in the saliva, forms, with the peroxide of iron, a colour exactly like that of venous blood; and it is possible that the colouring matter may be a sulpho-cyanate of iron. To obtain the red colouring matter, allow the crassamentum or clot, cut into thin pieces, to drain as much as possible on bibulous 3* «jQ MATERIAL COMPOSITION OF MAN. paper, triturating it with water and then evaporating tj® ,s0Juttl°"' at a temperature not exceeding 122° of Fahrenheit. When thus prepared the colouring particles are no longer of a bngni rea colour, and their nature is somewhat modified, in consequence oi which they are insoluble in water. When half dried, they lorm a brownish-red, granular, friable mass; and, when completely dried, at a temperature between 167° and 190°, the mass is tough, hard, and brilliant. 10. Yellow colouring principle of the bile.—This substance is pre- sent in the bile of nearly all animals. It enters into the composition of almost all gall-stones, and is deposited in that organ under the form of magma. It is solid, pulverulent when dry, insipid, inodorous, and heavier than water. When decomposed by heat, it yields car- bonate of ammonia, charcoal, &c. It is insoluble in water, in alcohol, and the oils, but is soluble in the alkalies. b. ORGANIC ELEMENTS THAT DO NOT CONTAIN AZOTE.* 1. Oleine and Stearine.—Fixed oils and fats are not pure proxi- mate principles, as was at one time supposed. They consist of two substances, one of which is solid at the ordinary temperature of the atmosphere, and the other fluid: the former of these is called Stearine, from tfrsap, suet, the latter Elaine, or Oleine from sXaiov, oil. Stearine is the chief ingredient of vegetable and animal suet, of fat and butter, and is found, although in small quantity, in the fixed oils. In the suety bodies, it is the cause of their solidity. Elaine and stearine may be separated from each other by exposing fixed oil to a low temperature, and pressing it, when congealed, between folds of bibulous paper. The stearine is thus obtained in a separate form, and by pressing the bibulous paper under water, an oily matter is procured, which is elaine in a state of purity. 2. Fatty matter of the Brain and Nerves.—Vauquelinf found two varieties of fatty matter in the brain,—the one white, the other red, the properties of which have not been fully investigated. Both pos- sess the property of giving rise to phosphoric acid by calcination, without there being any evidence of an acid, or a phosphate in their composition. They may be obtained by repeatedly boiling the cerebral substance in alcohol, filtering each time, mixing the various liquors, and suffering them to cool:—a lamellated substance is deposited, which is the white fatty matter. By then evaporating the alcohol, which still contains the red fatty matter and osmazome to the consistence of bouillie, and exposing this, when cold, to the action of alcohol, the osmazome is entirely dissolved, whilst the alcohol takes up scarcely any of the red fatty matter. 3. Acetic acid.—This acid exists in a very sensible manner in the sweat, urine, and in milk—even when entirely sweet. It is formed « Thenard, Traite de Chimie, Tom. t. Paris, 1824. f Annales de Chim. lxxsi. 37. ORGANIC ELEMENTS. 31 in the stomach in indigestion; has been found by Professor Emmet and the author* to be contained in the gastric secretions in health, and is one of the constant products of the putrid fermentation of ani- mal or vegetable substances. It is the most prevalent of the vegeta- ble acids, and the most easily formed artificially. 4. Oxalic acid.—This acid,—which exists extensively in the vege- table kingdom, but always united with lime, potassa, soda, or oxide of iron,—is only found as an animal constituent in certain urinary calculi, combined with lime. 5. Benzoic acid.—This acid, found in many individuals of the vegetable kingdom, is likewise met with in the urine of the horse, cow, camel, rhinoceros; and sometimes in that of man, especially of children. 6. Lactic acid.—The acid of milk is met with in the blood, urine, milk, marrow, and also in muscular flesh. Sometimes it is in a free state, but usually united with the alkalies. However much it may be concentrated, it does not crystallize, but remains under the form of syrup or extract. When cold it is tasteless, but when heated has a sharp acid taste. 7. Sugar of milk.—This substance, which is so called because it has a saccharine taste, and exists only in milk, differs from ordinary sugar in not fermenting. It is obtained by evaporating whey, form- ed during the making of cheese, to the consistence of honey; allow- ing the mass to cool, dissolving it, clarifying, and crystallizing. It commonly crystallizes in regular parallelopipedons, terminated by pyramids with four faces. It is white, semi-transparent, hard, and of a slightly saccharine taste. 8. Sugar of diabetes.—In the disease, called diabetes mellitus, the urine, which is passed in enormous quantity, contains, at the expense of the economy, a large amount of peculiar saccharine matter, which, when properly purified, appears identical, both in properties and composition, with vegetable sugar, approaching nearer to the sugar of grapes than to that of the cane. It is obtained in an irre- gularly crystalline mass, by evaporating diabetic urine to the con- sistence of syrup, and keeping it in a warm place for several days. It is purified by washing in cold, or, at the most, gently heated alco- hol, till the liquor comes off colourless, and then dissolving it in hot alcohol. By repeated crystallization it is thus rendered pure. (Prout.)f In the notes of two cases of diabetes mellitus now before us, we find that sixteen ounces of the urine of one of the patients, of the specific gravity 1.034, afforded a straw-coloured extract, which, when cold and consolidated, weighed one ounce and five drachms. The same quantity of the urine of the other patient, specific gravity 1.040, yielded one ounce and seven drachms. Neither extract appeared to contain urea when nitric acid was added, but when a portion was dissolved in water, and subjected to a temperature of 212°, traces of ammonia were manifested on the vapour being presented to the • Elements of Hygiene, p. 222. t Medico-chirurg. Transact, viii. 538. 32 MATERIAL COMPOSITION OF MAN. fumes of muriatic acid. From this a conclusion was drawn that urea was present, as it is the only known animal matter, wnicn is decomposed by the heat of boiling water. During a little more tnan one month the subject of the latter case passed about four hundred and eighty pints of urine, or about seventy-five pounds troy ol dia- betic sugar! . . , ,., . 9. Picromel—Thenard* discovered this principle in the bile ol the ox, sheep, dog, cat, and of several birds; Chevallier, in that of man. To obtain it, the acetate of lead of commerce must be added to bile until there is no longer any precipitate. By this means, the yellow matter of the bile and the whole of the fatty matter are thrown down, united with the oxide of lead; the phosphoric acid of the phosphate of soda, and the sulphuric acid of the sulphate of soda, are likewise precipitated. The picromel may then be thrown down from the filtered liquor by the subacetate of lead. The precipitate, which is a combination of picromel with oxide of lead, must now be washed and dissolved in acetic acid. Through this solution, sul- phuretted hydrogen is passed to separate the lead; the solution is then filtered, and the acetic acid driven off by evaporation. Pure picromel is devoid of colour, and has the same appearance and consistence as thick turpentine. Its taste is at first acrid and bitter, but afterwards sweet. Its smell is nauseous, and its specific gravity greater than that of water. When digested with the resin of the bile, a portion of the latter is dissolved, and a solution is ob- tained, which has both a bitter and a sweet taste, and yields a pre- cipitate with the subacetate of lead and the stronger acids. This is the compound that causes the peculiar taste of the bile. 10. Colouring principle of the bile.—Of the nature of this princi- ple, which exists in the bile of different animals, we have no definite ideas. It is generally precipitated along with the fatty matter; and, by means of ether which dissolves it, may be obtained pure. The colouring principles of other parts of animals are not suffi- ciently known to admit of classification. These inorganic and organic elements, variously combined and modified by the vital principle, constitute the different parts of the animal fabric. Chemistry, in its present improved condition, enables us to separate them, and to investigate their properties; but all the information we derive from this source relates to bodies, which have been influenced by the vital principle, but are no longer so ; and in the constant mutations, that are occurring in the system whilst life exists, and under its controlling agency, the same textures might exhibit very different chemical characteristics, could our researches be directed to them under those circumstances. Whenever, there- fore, the physiologist has to apply chemical elucidations to'opera- tions of the living machine, he must recollect, that all his analogies are drawn from dead matter—a state so widely differing from the * Memoir. d'Arcueil, i. 23, and Traite de Chimie, torn, iii, SOLID PARTS. 33 living as to suggest to him the necessity of a wise and discriminating caution.* The components of the animal body are invariably found under two forms—solids and fluids. Both of these are met with in every animal, the former being derived from the latter; for, from the blood every part of the body is separated; yet they are mutually dependent, for every liquid is contained in a solid. The blood itself circulates in a solid vessel: both, too, possess an analogous composition, are in constant motion, and are incessantly converted from one into the other. Every animal consists of a union of the two, and this union is indispensable to life. Yet certain vague notions, with regard to their relative preponderance in the economy, and to their agency in the production of disease, have led to very discordant doctrines of pathology,—the solidists believing, that the cause of most affections is resident in the solids; the humorists, that we are to look for it in the fluids. In this, as in similar cases, the mean will lead to the most rational result. The causes of disease ought not to be sought in the one or the other exclusively. C. OF THE SOLID PARTS OF THE HUMAN BODY. A solid is a body, wrhose particles adhere to each ether, so that they will not separate by their own weight, but require the agency of some extraneous force to effect the disjunction. Anatomists re- duce all the solids of the human body to twelve varieties: bone, car- tilage, muscle, ligament, vessel, nerve, ganglion, follicle, gland, mem- brane, cellular membrane, and viscus. 1. Bone is the hardest of the solids. It forms the skeleton—the levers for the various muscles to act upon, and serves for the pro- tection of important organs. 2. Cartilage is of a white colour, formed of very elastic tissue, covering the articular extremities of bones to facilitate their move- ments ; sometimes added to bones to prolong them, as in the case of the ribs; at others, placed within the articulations, to act as elastic cushions; and, in the fcetus, forming a substitute for bone; hence cartilages are divided into articular or incrusting, cartilages of pro- longation, inter articular cartilages, and cartilages of ossification. 3. The muscles constitute the flesh of animals. They consist of fasciculi of red and contractile fibres, extending from one bone to another, and are the agents of all movements. 4. The ligaments are very tough, difficult to tear, and under the form of cords or membranes serve to connect different parts with each other, particularly the bones and muscles; hence their division, * See Rudolphi, Grundriss der Physiologie, Berlin, 1821; Berzelius, Traite de Chimie, par Jourdan, torn. v. Paris, 1829; and Adelon, Physiologie de I'Homme, seconde edition, Paris, 1829. 34 MATERIAL COMPOSITION OF MAN. by some anatomists, into ligaments of the bones—as the ligaments of the joints; and into ligaments of muscles—as the tendons and apo- neuroses. ;uiuocs. . , . v ,i 5. The vessels are solids, having the form of canals, in w-hicn tne fluids circulate. They are called—according to the fluid they con- vey— sanguineous (arterial and venous,) chyliferous, lymphatic, and secretory vessels. c ... 6. The nerves are solid cords, consisting of numerous fasciculi. These are connected with the brain, spinal marrow, or great sym- pathetic ; and they are the organs by which impressions are con- veyed to the nervous centres, and by which each part is endowed with vitality. There are three great divisions of the nerves,—those of motion, sensation, and expression. 7. A ganglion is a solid knot, situated in the course of a nerve, and seeming to be formed by an inextricable interlacing of the ner- vous filaments. The term is likewise applied, by many modern anatomists, to a similar interlacing of the ramifications of a lym- phatic vessel. Ganglions may, consequently, either be nervous or vascular; and the latter, again, may be divided into chyliferous or lymphatic, according to the kind of vessel in which they appear. Professor Chaussier, a distinguished anatomist and physiologist, has given the name glandiform ganglions to certain organs, whose nature and functions are unknown to us, but which he considers to be or- gans for the admixture and elaboration of fluids,—as the thymus gland, the thyroid gland, &c. 8. Follicles or crypts are secretory organs, shaped like mem- branous ampullae or vesicles, always seated in the substance of one of the outer membranes of the body—the skin or the mucous sur- faces—and secreting a fluid intended to lubricate them. They are often divided into the simple or isolated, the conglomerate, and the compound, according to their size, or the number in which they are grouped and united together. 9. The gland is also a secretory organ, but differing from the last. The fluid secreted by it, is of greater or less importance. Its organisation is more complex than that of the follicle; and the fluid, after secretion, is poured out by means of one or more excre- tory ducts. 10. Membrane.—This is one of the most extensive and important of the substances formed by the cellular tissue. It is spread out in the shape of a web, and, in man, serves to line the cavities and reser- voirs, and to form, support, and envelope all the organs. Bichat divides membranes into two kinds, the simple and compound, according as they are formed of one or more layers. The simple membranes are of three kinds, the serous, mucous, and fibrous. 1st. The serous membranes are those that constitute all the sacs or shut cavities of the body, those of the chest and abdomen for example. SOLID PARTS. 35 2dly. The mucous, or those that line all the outlets of the body,— the air passages, alimentary canal, urinary and genital organs, &c. 3dly. Fibrous membranes, or those which form tendon, aponeu- rosis, ligament, &c. The compound membranes are formed by the union of the simple, and are divided into fibro-serous as the pericardium; sero-mucous, as the gall-bladder, at its lower part; and fibro-mucous, as the ureters. In the view of Raspail,* the truly simple animal membrane is the paries of a vesicle. In this state of simplicity it is so transparent, that it is only perceptible by the plaits or folds it forms on being moved, but if it were a compound membrane, the rays of light would be reflected. On this ground he disputes the accuracy of the observations of Sir Everard Home,f Edwards,J and others, main- taining that the pretended globules, seen and figured by them, were optical illusions produced by the play of light on the different folds of the membrane. 11. The cellular or laminated tissue—to be described presently— is a sort of spongy or areolar, structure, which forms the frame- work of all the solids, fills up the spaces between them, and serves, at the same time, as a bond of union and of separation. 12. The viscus is the most complex solid of the body, not only as regards intimate organisation but use. This name is given to organs contained in the splanchnic cavities,—brain, thorax, and abdomen, —and hence called cerebral, thoracic, or abdominal. Every animal solid is either amorphous or fibrous; that is, it is either without apparent arrangement, like jelly, or is disposed in minute threads, which are called fibres. The disposition of these threads, in different structures, is various. Sometimes, they retain the form of threads; at others, they have that of laminae, lamellae, or plates. Accordingly, when we examine any animal solid, where the organisation is perceptible, it is found to be either amorphous, or fibrous and laminated. This circumstance led the ancients to endeavour to discover an elementary fibre, or filament, from which all the various organs might be formed. Haller|| embraced the idea, and endeavoured to unravel every texture to this ultimate element,—asserting that it is to the physiologist what the line is to the geometer; and that, as all figures can be constructed from the line, so every tissue and organ of the body may be built up from the filament. Haller, however, admits that his elementary fibre is not capable of demonstration, and * Nouveau Systeme de Chimie organique, p. 76, Paris, 1833. t Philos. Trans, for 1821, and Lectures on Comparative Anatomy, vol. iii. London, 1823. X Sur la structure elementaire des principaux tissus organiques des animaux; in Archives Gen6rales de Medecine, 1823. Tom. iii. and Recherches microscopiques, etc., in Annales des Sciences Naturelles, 1824. Tom. ix. p. 362. || Elementa Physiologie vol. i. lib. i. sect. i. 36 MATERIAL COMPOSITION OF MAN. that it is visible only to the "mind's eye,"—"invisibihs est eafibra, sold mentis acie distinguimus." It must be regarded, indeed, as a pure abstraction; for, as different animal substances have ditterent proportions of carbon, hydrogen, oxygen and azote, it is fair to con- elude, that the elementary fibre must differ also in the ditterent structures. The ancients believed, that the first product of the elementary fibre was cellular tissue, and that this tissue formed every organ of the body;—the difference in the appearance of these organs arising from the different degrees of condensation of its laminae. Anatomists, however, have been unable to reduce all the animal solids to cellular tissue solely. In the upper classes of animals, three primary fibres or tissues, or anatomical elements, are usually admitted,—the cellular or laminated, the muscular, and the nervous, pulpy or medullary. 1. The cellular or laminated fibre or tissue.—This is the most simple and abundant of the animal solids. It exists in every organised being, and is an element of every solid. In the enamel of the teeth only it has not been detected. It is formed of an assemblage of thin laminae of delicate whitish, extensible filaments, interlacing and leaving between each other areolae or cells. (See Fig. 1.) These plates or filaments—although possessed like every living tissue of contractility or the power of feeling an appropriate irritant and of moving responsive to such irritant—do not move perceptibly under the influence of mechanical or chemical stimuli. They are composed of concrete gelatine. The great bulk of animal solids consists of cellu- lar tissue, arranged in the form of membrane. 2. Muscular fibre or tissue.—This is a substance of a peculiar nature, arranged in fibres of extreme delicacy. The fibres are linear, soft, grayish or reddish, (See Fig. 2.) and manifestly possessed of contractility or irritability; that is, they move very perceptibly under the influence of mechanical or chemical stimuli. They are compos- ed, essentially, of fibrine. Prochaska,* a distinguished anatomist of Vienna, maintains, that the ultimate fibre or filament of muscular tissue is discernible; that it is, in every part, of the same magnitude—about TVth part of the diameter of the red globule of the blood, or about ToVoooth part of an inch in diameter. It is probable, however, that were our means of examining minute objects still further improved, we should be able to de- tect a filament even more delicate than this. The muscular fibres, which are arranged in the form of membranous expansions or muscular coats, differ from proper Fig 2. • De came rausculari, &c. p. 25. Vienna, 1778; and Oper. Minor. Part i, PRIMARY AND COMPOUND TISSUES. 37 muscles chiefly in the mechanical ar- Fig. 3. rangement of their fibres. (Fig. 3, a fy b.) But the physical and chemical characters of both are identical. The &|| fibres, instead of being collected into fasciculi, are in layers, and, instead of being parallel, interlace. This tissue does not exist in the zoophytes. 3. Nervous, pulpy, or medullary \ fibre or tissue.—This tissue is much less distributed than the preceding. It is of a pulpy consistence, is composed essentially of albumen united to a fatty matter, and is the organ of sensibility, or for receiving and transmitting impressions to the mind. Of it, the brain, cerebellum, medulla spinalis, nerves and their ganglia are composed. The ultimate nervous filament is considered by Fon- tana,* Reil,f and others, to be about twelve times larger than the ultimate muscular filament. The same remarks, however, may be made here concerning our limited means of observation, as were made on the elementary muscular fibre. Professor ChaussierJ has added another primary fibre or tissue,— the albugineous. It is white, satiny, very resisting, of a gelatinous nature, and constitutes the tendons and tendinous structures. Chaus- sier is, perhaps, the only anatomist that admits this tissue. Others properly regard it as a very condensed variety of the cellular. These various fibres or tissues, by uniting differently, constitute the first order of solids; and these, again, by union, give rise to com- pound solids, from which the different organs, bones, glands, &c. are formed. A bone, for example, is a compound of various tissues, osseous in its body, medullary in its interior, fibrous externally, and cartilaginous at its extremities. Bichat§ was the first anatomist, who possessed any clear views regarding the constituent tissues of the animal frame; and whatever merit may accrue to after anatomists and physiologists, he is entitled to the credit of having pointed out the path, and facilitated the labours of the anatomical analyst.|| In combining to form the different structures, the solids are ar- ranged in a variety of ways. Of these, the chief are in filaments or elementary fibres, tissues, organs, apparatuses, and systems. The filament, we have seen, is the elementary solid. A fibre con- sists of a number of filaments united together. Occasionally, this is called a tissue:—the term tissue usually, however, means a particu- * Sur les poisons, T. ii. t De structura nervorum, c. 1—4. X Table synoptique des solides organiques. § Anatomie generate. Paris, 1801. Tom. I. U For various arrangements of the tissues, see Lepelletier, Physiologie M6dicale. Tom. I. Paris, 1831-1833. Meckel's Handbuch, Doane's translation, vol. i. Phila- delphia, 1832. Grainger's Elements of General Anatomy. Lond., 1829. VOL. I. 4 38 MATERIAL COMPOSITION OF MAN. lar arrangement of fibres. An organ is a compound of several tis- sues. An apparatus is an assemblage of organs, concurring to the same end:—the digestive apparatus consists of the organs of masti- cation, insalivation, and deglutition, of the stomach, duodenum, pan- creas, liver, chyliferous vessels, &c. These organs may be, and are of very dissimilar character, both as regards their structure and functions; but, if they concur in the same object, they form an ap- paratus. A system, on the other hand, is an assemblage of organs, all of which possess the same or an analogous structure. Thus, all the muscles of the body have a common structure and function, and they constitute, in the aggregate, the muscular system. All the vessels of the body, and all the nerves, for like reasons, constitute respectively the vascular, and the nervous systems. OF THE FLUIDS OF THE HUMAN BODY. The positive quantity or proportion of the fluids in the human body does not admit of easy appreciation, as it must obviously vary at different periods, and under different circumstances. The younger the animal, the greater is the preponderance. When we first see the embryo, it appears to be almost fluid. As it becomes gradually developed, the solid parts increase in their relative proportion, until the adult age; after which the proportion becomes less and less as the individual advances in life. During the whole of existence, too, the quantity of fluids in the body fluctuates. At times, there is ple- thora or unusual fulness of vessels; at others, the blood is less in quantity. Experiments have been made for the purpose of ascer- taining the relative proportion of the fluids to the solids. Richerand says that they are in the ratio of six to one; Chaussier,* of nine to one. The latter professor put a dead body, weighing one hundred and twenty pounds, into a heated oven, and dried it. After dessica- tion, it was found to be reduced to twelve pounds. It is probable, however, that some of the more solid portions were driven off by the heat employed, and hence, that the evaluation of the proportion of the fluids was too high. In the Egyptian mummies, which are com- pletely deprived of fluid, the solids are extremely light, not weigh- ing more than seven pounds ; but, as we are ignorant of the original weight of the body, we cannot arrive at any approximation. The dead bodies, found in the arid sands of Arabia, as well as the dried preparations of the anatomical theatre, afford additional instances of this reduction by desiccation. To a less extent, we have the same thing exhibited in the excessive diminution in weight, which occurs in disease, and occasionally in those who are apparently in health. Not many years ago, an Anatomie vivante was exhibited, in Londonj to the gaze of the curious and scientific, whose weight was not more than eighty pounds. Yet the ordinary functions were carried on apparently unmodified. In the year 1830, a still more wonderful * Traite" d' Anatomie descriptive, par H.Cloqntt, I. 5.. Pari? 7B91 »„a tji • ** de la Soc.ete Med. d'Emulation, viii. Paris, 1817. ' ' 1821' a"d R,bes ln Mem" FLUIDS 39 phenomenon was exhibited in New York, who was called the " living skeleton." This extraordinary being was forty-two years old, five feet two inches high, and weighed but sixty pounds. His weight had formerly been one hundred and thirty-five pounds. For sixteen years previously, he had been gradually losing flesh, without any apparent disease, having enjoyed, perfect health and appetite, and eating, drinking, and sleeping as well as any one. We have it also on the authority of Captain Riley,* that, after protracted suffer- ings in Africa, he was reduced from two hundred and forty pounds to below ninety. [?] The fluids are variously contained; sometimes in vessels—as the blood and lymph; at others, in cavities—as the fluids secreted by the pleura, peritoneum, arachnoid coat of the brain, &c.; others are in minute areolae—as the fluid of the cellular membrane; whilst others again are intimately combined with the solids. They differ likewise in density, some existing in the state of halitus or vapour; others being very thin and aqueous—as the fluid of the serous mem- branes; others of more consistence—as the secretion of the mucous .membranes, the animal oils, &c. The physical and chemical properties of the fluids will engage our attention when they fall individually under consideration, and we shall find that one of them at least—the blood—exhibits certain phenomena analogous to those of the living solid. The fluids have been differently classed, according to the particu- lar views that have from time to time prevailed in the schools. The ancients referred them all to four—blood, bile, phlegm or pituita, and atrabilis; and each of these was conceived to abound in one of the four ages, seasons, climates, or temperaments. The blood pre- dominated in youth, in the spring, in cold mountainous regions, and in the sanguine or inflammatory temperament. The pituita or phlegm had the mastery in old age, in winter, in low and moist coun- tries, and in the lymphatic temperament. The bile predominated in mature age, in summer, in hot climates, and in the bilious tempera- ment; and lastly, the atrabilis was the characteristic of middle age, of autumn, of equatorial climes, and of the melancholic tempera- ment. This was their grand humoral system, which has vanished before a better observation of facts, and more improved methods of physical and metaphysical investigation. The atrabilis was a crea- ture of the imagination; the pituitous condition is unintelligible to us; and the doctrine of the influence of the humours on the ages, tem- peraments, &c. is irrational. Subsequently, the humours were classed according to their phy- sical and chemical properties; for instance, they were divided into liquids, vapours, and gases; into acid, alkaline, and neutral; into thick and thin; into aqueous, mucilaginous, gelatinous, and oily; into saline, oily, saponaceous, mucous, albuminous, and fibrinous, &c. In more modern times, endeavours have been made to arrange them * Narrative of the loss of the American brig Commerce, &c., p. 302. New York, 1817. 40 MATERIAL COMPOSITION OF MAN. according to their uses in the economy into 1, recrementitial fluids, or those intended to be again absorbed; 2, excrementitial, or those that have to be expelled from the body; and 3, those which partici- pate in both uses, and are hence termed excremento-recrementitial Blumenbach* divided them into crude humours, blood, and secreted humours, a division which has been partly adopted by Adelon;f and lastly by Professor Chaussier, whose anatomical arrangements and nomenclature have rendered him justly celebrated, reckons five classes:—1, those produced by the act of digestion,—the chyme, and the chyle; 2, the circulating fluids,—the lymph and the blood; 3, the perspired fluids; 4, the follicular; and 5, the glandular. This ar- rangement has been adopted by Magendie,J and is as satisfactory as any that has been proposed. The following is an enumeration of the different fluids or humours of the body, all of which will have to engage attention hereafter. 1. The chyme and the chyle. 2. The blood and the lymph. 3. The perspired or exhaled fluids, including the serous fluids, the synovia, the fat, the medulla, the colouring matter of the skin, the colouring matters of the uvea and choroid of the eye, the three humours of the eye, the liquor of Cotugno, the cephalo-spinal fluid, the fluid of the lymphatic and glandiform ganglions, the humour exhaled from the interior of vessels, the liquor amnii, the water of the chorion and that of the umbilical vesicle, the cutaneous transpiration, the pulmo- nary transpiration, the perspired humours of the digestive apparatus, those of the urinary and genital organs, and in the female during the time she! is capable of fecundation, the monthly exhalation called the catamenia, or menses; and, after delivery, a similar secretion, called the lochia. 4. The follicular fluids are—the sebaceous hu- mour of the skin, the cerumen, the humour of Meibomius, that of the caruncula lachrymalis, the humour secreted at the base of the glans in the male, and within the vulva of the female, the humour of the mucous follicles of the respiratory, digestive, urinary, and genital apparatuses, including that of the tonsils, cardiac glands, prostate, Cowper's glands, &c. 5. The glandular fluids are—the tears, saliva, pancreatic juice, bile, urine, sperm, and milk. e. OF THE ELEMENTARY STRUCTURE OF ANIMAL SUBSTANCES. Anatomists have not been content with endeavouring to reduce the different organized textures to primary fibres and filaments, but, by the aid of the microscope, they have attempted to discover the particular arrangement of the constituent corpuscles. The discovery of that valuable instrument gave the impulse, and very soon the scientific world was presented with the results obtained by numerous observers. These observations have been, from time to time con- tinued until the present day. It is, however, to be regretted, that * Elements of Physiology, by Elliotson, 4th edit. Lond 1828 t Physiologie de I'Homme, 2de edit. I. 124 Paris 1829 X Precis Etementaire de Physiol. 2de edit. 1.20 Paris 1825 ELEMENTARY STRUCTURE. 41 our information, derived from this source, has not been as accurate as it might be. From different quarters we have the most discor- dant statements, exhibiting clearly, either that the narrators em- ployed instruments of very different powers, or that they were blinded, or had the vision depraved, by preconceived theories or hypotheses. One of the very first effects of the discovery of the microscope was the detection of a globular structure of the primitive tissues of the body, by Leeuenhoek,* an announcement that gave rise to much controversy, which has continued, indeed, till the pre- sent time, and has engaged the attention particularly of Prochaska,f Fontana,J Sir Everard Home, Mr. Bauer, the brothers Wenzel,§ Dr. Milne Edwards, MM. PreVost and Dumas,|| Dutrochet, Hodg- kin,T[ Raspail, and others. The observations and experiments of Dr. Edwards especially have occasioned much interesting speculation and inquiry. They may perhaps be taken as the foundation on which the believers in the globular structure rest their opinions. His views were first published in 1823, in a communication, entitled " Memoire sur la structure ele- mentaire des principaux tissues organiques des Animaux;" and in a second article in the Annates des Sciences Naturelles, for December, 1826, entitled " Recherches microscopiques sur la structure intime des tissues organiques des Animaux." He examined all the principal textures of the body, the cellular tissue, the membranes, tendons, muscular fibre, nervous tissue, the skin, the coats of the blood-ves- sels, &c. When the cellular tissue was viewed through a powerful lens, it seemed to consist of cylinders; but, by using still higher magnify- ing powers, these cylinders were found to be formed of rows of globules, all of the same size, that is, about the y^Vo"m or soVo1" of an inch in diameter; (Fig. 4.) separated from each other, and p~igm 4. lying in various directions; crossing and in- terlacing; some of the rows straight, others bent, and some twisted, forming irregular lay- ers, united by a kind of net-work. The membranes, which consist of cellular tissue, were found to present exactly the same kind of arrangement. The muscular fibre, when examined in the like manner, was found to be formed of glo- bules also ^oVom part of an inch in diameter. Here, however, the rows of globules are al- ways parallel. The fibres never intersect * Opera omnia, &c, Lugdun. Batav. 1722. + De structura nervorum. Vind. 1779. X Sur les poisons, ii. 18. § De structura cerebri. Tubing. 1812. || Bibliotheque universelle des Sciences et Arts, T. xvii. IT In Drs. Hodgkin and Fisher's translation of W. Edwards, Sur les Agens physiques, Lond. 1832; and Hodgkin's Lectures on the Morbid Anatomy of the Serous and Mu- cous Membranes, p. 26. Lond. 1836, 4# 42 MATERIAL COMPOSITION OF MAN. Fig. 5. Fig. 6. each other like those of the cellular tissue, and this is the only discernible difference, the form and size of the globules being alike. The size of the globules, and the linear arrangement they assume, seem to be the same in all animals that possess a muscular structure. (Fig. 5.) The nervous structure has, by almost all observers, been esteemed globular—and one of the most recent observers* has satisfied himself that this is certainly the most uniform appearance. The examination of Dr. Edwards yielded similar results. It seemed to be composed of lines of globules of the same size with those that form the cellular membrane and the muscles; but holding an intermediate place as to the regularity of their arrangement, and having a fatty matter interposed between the rows. In regard to the size of the globules, Dr. Edwards differs materially from an accurate and experienced microscopic observer, Mr. Bauer,f who asserts that the cerebral globules are of various sizes. (Fig. 6.) From the results of his own diversified ob- servations, Dr. Edwards concludes, that" sphe- rical corpuscles, of the diameter of jfoin °f a millimeter, constitute, by their aggregation, all the organic textures, whatever may be the pro- perties, in other respects, of those parts, and the functions for which they are destined." The harmony and simplicity, which would thus seem to reign through the structures of the animal body, have attracted great at- tention to the labours of Dr. Edwards. The vegetable kingdom was subjected to equal scrutiny; and, what seemed still more astound- ing, it was affirmed, that the microscope proved it also to be con- stituted of globules exactly like those of the animal, and of the same magnitude, -g-oWn of an inch in diameter; hence, it was assumed, that all organized bodies possess the same elementary structure, and of necessity, that the animal and the vegetable are readily con- vertible into each other under favourable circumstances, and that they differ only in the greater or less complexity of their organiza- tion. Independently of all other objections, however, the animal differs, as we have seen, from the vegetable, in composition; and this difference must exist not only in the whole but in its parts; so that even were it demonstrated, that the globules of the beings of the two kingdoms are alike in size, it would by no means follow, that they should be identical in intimate composition. The discordance which we have deplored, is strikingly applicable * Dr. Luigi Calori, in Bulletino delle Scienze Medich. di Bologna, Sett. 1836, p. 152. + Philosoph. Transact, for 1818; and Sir E. Home's Lectures on Comparative Ana- tomy, vol. iii. lect. 3. Lond. 1823. ELEMENTARY STRUCTURE. 43 to the case before us. The appearance of the memoir of Dr. Ed- wards, excited the attention of Dutrochet, and in the following year his " Researches" on the same subject were published, in which he asserts, that the globules, which compose the different structures of the invertebrated animals, are considerably larger than those of the vertebrated ; that the former appear to consist of cells, containing other globules still smaller; and hence he infers, that the globules of vertebrated animals are likewise cellular, and contain series of still smaller globules. Dr. Edwards, in his experiments, found that the globules of the nervous tissue, whether examined in the brain, in the spinal cord, in the ganglia, or in the nerves, have the same shape and diameter, and that no difference can be distinguished in them, from whatever animal the tissue is taken. Dutrochet, on the other hand, considers, with Sir Everard Home and the brothers Wenzel, that the globules of the brain are cellules of extreme minuteness, containing a medul- lary or nervous substance, which is capable of becoming concrete by the action of heat and of acids. This structure, he remarks, is strikingly evidenced in certain molluscous animals; and he instances the small pulpy nucleus, forming the cere- Fig. 7. bral hemisphere of the Umax rufus, and the helix pomatia, composed of globular, agglomerated cellules, on the parietes of which a considerable number of globular or ovoid corpuscles are perceptible. (Fig. 7.) M. Dutrochet, again, has not found the structure of the nerves to correspond with that of the brain. He asserts, that the elementary fibres, which enter into their composi- tion, do not consist simply of rows of globules, according to the opinion of Edwards and others, but that they are cylinders of a dia- phanous substance, the surface of which is studded with globular corpuscles, and that, as these cover the whole surface of the cylinder, we are led to believe that they are situated internally. After detailing this difference of structure between the brain and the nerves, the former consisting chiefly of nervous corpuscles, the latter chiefly of cylinders or fibres, Dutrochet announces the hypothesis, which ex- hibits too many indications of having been formed prior to his mi- croscopic investigations,—that these cerebral corpuscles are destined for the production of the nervous power, and that the nervous fibres are tubes, filled with a peculiar fluid, by the agency of which nervi- motion is effected. For further developements of the analysis of Dutrochet, the reader is referred to the work itself, which exhibits all the author's ingenuity and enthusiasm, but can scarcely be consi- dered historical. The beautiful superstructure of Dr. Edwards, and the ingenuity of Dutrochet have, however, been most fatally assailed by subse- quent experiments, with a microscope of unusual power, by Dr. Hodgkin. The globular structure of the animal tissues, so often developed, and apparently so clearly and satisfactorily established by 44 MATERIAL COMPOSITION OF MAN. Dr. M. Edwards, is, we are told by Dr. Hodgkin,* a mere deception; and we have again to refer the most minute parts of the cellular membrane, muscles, and nerves to the striated or fibrous arrange- ment. A part of the discrepancy between Messrs. Edwards and Dutrochet may be explained by the fact of the former using an in- strument of greater magnifying power than the latter, who employed the simple microscope only. It has been observed, that when Dr. Edwards used an ordinary lens, the arrangement of a tissue appeared cylindrical, which, with the compound microscope, was distinctly globular. The discordance between Messrs. Edwards and Hodgkin is reconcilable with more difficulty. On the whole subject, indeed, our minds must be kept in a state of doubt, and we must wait until the point is fully ascertained, if it is ever destined to be so. In our uncertainty regarding the existence of the globules themselves, it is hardly necessary to inquire into the opinion, professed by Messrs. Prevost and Dumas, and by Dr. Edwards, that all the proximate principles,—albumen, fibrine, gelatine, &c.—assume a globular form, whenever they pass from the fluid to the solid state, whatever may be the cause producing such conversion. Still more recently, M. Raspailf has ranged himself amongst those, who consider, that the ultimate structure of all organic textures is vesicular, and that the organic molecule, in its simplest form, is an imperforate vesicle, endowed with the faculty of inspiring gaseous and liquid substances, and of expiring again such of their decom- posed elements, as it cannot assimilate;—properties, which he con- ceives it to possess under the influence of vitality. Lastly, J. F. Meckel,J from his observations, infers, that all the solids and fluids of the human body are formed of two elementary substances: first, of an amorphous matter, which is concrete in the former and fluid in the latter; and secondly, of globules. Of these two substances, the former may exist alone, and constitute some of the textures;—for instance, the cellular tissue, the bones, cartilages, &c. The globules, on the contrary, are always united with the amorphous substance, which, in the solids, serves as a bond of union, and in which the globules are immersed in the fluids. This anato- mist believes that the globules differ in shape, size, and number, in different animals, and in different parts of the same animal, and even in the same part, according to age.§ /. PHYSICAL PROPERTIES OF THE TISSUES. The tissues of the body possess the physical properties of matter in general. They are found to vary in consistence,—some being hard, and others soft, as well as in colour, transparency, &c. We find, also, certain physical properties, analogous, indeed, to what are * Op. citat., p. 466. See, also, Grainger's Elements of General Anatomy Lond 1829. J t Op. citat., § 126. X Handbuch, u. s. w. and A. S. Doane's translation, vol. i. Philad , 1832. § Weber's Allgemeine Anatomie, u. s. w., s. 131. Braunschweig, 1830. PHYSICAL PROPERTIES OF TISSUES. 45 met with in several inorganic substances, but generally superior in degree. These axe flexibility, extensibility, and elasticity, which are variously combined and modified in the different forms of animal matter, but exist to a greater or less extent in every organ. Elas- ticity is only exerted under particular circumstances: when the part, for example, in which it is seated, is put upon the stretch or is com- pressed, the force of elasticity restores it to its primitive state, as soon as the distending or compressing cause is removed. The tis- sues, in which elasticity is inherent, are so disposed through the body, as to be kept in a state of distention by the mechanical cir- cumstances of situation ; but, as soon as these circumstances are de- ranged, elasticity comes into play, and produces shrinking of the substance. It is easy to see, that these circumstances, owing to the constant alteration in the relative situation of parts, must be ever varying. Elasticity is, therefore, constantly called into action, and in many cases acts upon the tissues as a new power. The carti- lages of the ribs, joints, &c. are, in this manner, valuable agents in particular functions. We have other examples of the mode in which elasticity exhibits itself, under similar circumstances, when the con- tents of hollow parts are withdrawn, and whenever muscles are divided transversely. The gaping wound, produced by a cut across a shoulder of mutton, is familiar to all. Previous to the division, the force of elasticity is kept neutralized by the mechanical circum- stances of situation,—or by the continuity of the parts; but as soon as this continuity is disturbed, or, in other words, as soon as the me- chanical circumstances are altered, the force of elasticity is exerted and produces recession of the edges. This property has been de- scribed under various names. It has been called tone, or tonicity, contractilite de tissu, contractilite par defaut d'extension, SfC The other properties—-flexibility and extensibility—vary greatly according to the structure of the parts. The tendons, which are composed of the cellular tissue, exhibit very little extensibility, and this for wise purposes. They are the conductors of the force deve- loped by the muscle, and were they to yield, it would be at the ex- pense of the muscular effort; but they possess great flexibility. The articular ligaments are very flexible, and somewhat more extensible. On the other hand, the fibrous or ligamentous structures, which are employed to support weights, or which are antagonists to muscular action,—such as the ligamentum nuchce, or the strong ligament, which passes from the spine to the head of the quadruped,—are very extensible and elastic. Another physical property, possessed by animal substances, is a kind of contractility, accompanied with sudden corrugation and curling. This effect, which Bichat terms racornissement, is pro- duced by heat, and by chemical agents, especially by the strong mineral acids. The property is exhibited by leather when thrown into the fire. An effect, in some measure resembling this, is caused by the eva- poration of the water which is united to animal substances. This 46 MATERIAL COMPOSITION OF MAN. constitutes what Dr. Roget* calls the hygrometric property of animal membranes. It is characteristic of dry, membranous structures, all of which are found to contract, more or less, by the evaporation ot moisture, and to expand again by its re-absorption ; hence the em- ployment of such substances as hygrometers. According to Uiev- reul,f many of the tissues are indebted for their physical properties to the water they contain, or with which they are imbibed. When deprived of this fluid, they become unfit for the purposes for which they are destined in life, and resume them as soon as they have re- covered it. A most important property, possessed by the tissues of organized bodies, is that of imbibition; a property to which attention has been chiefly directed of late years. If a liquid be put in contact with any organ or tissue, in process of time the liquid will be found to have passed into the areolae of the organ or tissue, as it would enter the cells of a sponge. The length of time, occupied in this imbibition, will depend upon the nature of the liquid and the kind of tissue. Some parts of the body, as the serous membranes and small vessels, act as true sponges, absorbing with great promptitude: others resist imbibi- tion for a considerable time,—as the epidermis. Liquids penetrate equally from within to without: the process is then called transudation, but it does not differ from imbibition. Within the last few years some singular facts have been observed regarding the imbibition of fluids and gases. On filling membra- nous expansions, as the intestine of a chicken, with milk or some dense fluid, and immersing it in water, DutrochetJ observed that the milk left the intestine, while the water entered it; and hence he con- cluded, that whenever an organized cavity, containing a fluid, is im- mersed in another fluid, less dense than that which is in the cavity, there is a tendency in the cavity to expel the denser and absorb the rarer fluid. This Dutrochet terms endosmose, or " inward impul- sion ;" and he conceives it to be a new power,—a " physico-organic or vital action." Subsequent experiments showed that a reverse operation could likewise take place. If the internal fluid was rarer than the external, the transmission occurred in the opposite direc- tion. To this reverse process, Dutrochet gives the name exosmose, or " outward impulsion." Soon after the appearance of Dutrochet's essay, similar experi- ments were repeated, with some modifications, by Dr. Faust,§ and by Dr. Togno,|| of Philadelphia, and with like results. The fact of this imbibition and transudation was singular and impressive; and, with so enthusiastic an individual as Dutrochet, could not fail to give birth to numerous and novel conceptions. The energy of the * Art. Physiology, in Supplement to Encyclopaedia Britannica. recherches sur l'endosmose, &c. Paris, 1828; and art. Endosmosis by Dutrochet in Cyclopaedia of Anatomy and Physiology, part x. p. 98, June, 1837. ' § Amer. Journal of the Med. Sciences, vii. 23, Philad. 1830. 0 Ibid, iv. 73, Philad. 1829. PHYSICAL PROPERTIES OF TISSUES. 47 action of both endosmose and exosmose is in proportion, he asserts, to the difference between the specific gravities of the two fluids ; and also, independently of their gravity, their chemical nature affects their power of transmission. These effects—Dutrochet at once de- cided—must be owing to electricity. The cavities, in which the changes take place, he conceives to be like Leyden jars, having their two surfaces charged with opposite electricities, the ultimate effect or direction of the current being determined by the excess of the one over the other. In an interesting and valuable communication by Dr. J. K. Mit- chell,* of Philadelphia, " on the penetrativeness of fluids," many of the visionary speculations of Dutrochet have been sensibly animadverted upon. It is there shown, that Dutrochet had asserted, in the teeth of some of his most striking facts, that the current was from a less dense to a more dense fluid; and that it was from positive to negative, dependent not on an inherent powTer of filtration, a power always the same when the same membrane is concerned, but modified at pleasure by supposed electrical agencies. This view was subse- quently abandoned by M. Dutrochet, in favour of the following prin- ciple. It is well known that porous bodies, as sugar, wood, or sponge, are capable of imbibing liquids, with which they are brought in contact. In such case the liquid is not merely introduced into the pores of the solid, as it would be into an empty space, but it is forcibly absorbed, so that it will rise to a height considerably above its former level. This force is molecular, and is the same that we witness in the phenomena presented by the capillary tube, which affords us the simplest case of the insinuation of a liquid into a porous body. This force alone cannot, however, cause the liquid to pass entirely through the body. If a capillary tube, capable of raising water to the height of six inches, be depressed, so that one inch only be above the surface, the water will rise to the top of the tube, but no part of it will escape. Even if the tube be inserted horizontally into the side of a vessel containing water, the water will only pass to the end of the tube. The same thing occurs when a liquid is placed in contact with one side of a porous membrane: it enters the pores, passes to the opposite side, and is there arrested. But if this membrane communicates with a second vessel containing a different liquid—as a saline solution, capable of mixing with the first, and affected to a different degree by the capillary attraction— then a new phenomenon will be presented. It will be found that both liquids enter the pores, and pass through to the opposite side. They will not, however, be carried through with the same force; that which has the greatest capillary ascension,—that is, which will rise the highest in a capillary tube,—will pass through in the greatest quantity, and cause an accumulation of liquid in the oppo- site side. The facts and arguments, adduced by Dr. Mitchell, clearly exhi- * Amer. Journ. of the Med. Sciences, vii. 23. Phil. 1830. 48 MATERIAL COMPOSITION OF MAN. bit, that imbibition and transudation are dependent upon the pene- trativeness of the liquid, and the penetrability of the membrane: that if two liquids, of different rates of penetrativeness, be placed on op- posite sides of an animal membrane-r-" they will in time present the greater accumulation on the side of the less penetrant liquid, whether more or less dense; but will finally, thoroughly, and uniformly mix on both sides; and at length, if any pressure exist on either side, yield to that and pass to the other side."* A portion of the communication of Dr. Mitchell relates to an ana- logous subject, to which, as M. Magendief has observed, little or no attention has been paid by physiologists—the permeability of mem- branes by gases. " The laminas," Magendie remarks, " of which membranes are constituted, are so arranged that the gases can pene- trate them, as it were, without obstacle. If we take a bladder, and fill it with pure hydrogen gas, and afterwards leave it in contact with atmospheric air, in a very short time the hydrogen will have lost its purity, and will be mixed with the atmospheric air, which has penetrated the bladder. This phenomenon is the more rapid in proportion as the membrane is thinner and less dense. It presides over one of the most important acts of life—respiration—and it con- tinues after death." Dr. Mitchell is the first individual, who directed his observation to the relative penetrativeness of different gases. This he was enabled to discriminate by the following satisfactory experiment, which we give in his own words: "Having constructed a syphon of glass, with one limb three inches long, and the other ten or twelve inches, the open end of the short leg was enlarged and formed into the shape of a funnel, over which, finally, was firmly tied a piece of thin gum elastic. By inverting this syphon, and pouring into its longer limb some clean mercury, a portion of common air was shut up in the short leg, and was in communication with the membrane. Oyer this end, in the mercurial trough, was placed the vessel con- taining the gas to be tried, and its velocity of penetration measured by the time occupied in elevating to a given degree the mercurial column m the other limb. Having thus compared the gases with common air, and subsequently, by the same instrument, and in bottles with each other, I was able to arrange the following gases according to their re alive facility of transmission, beginning with the most powerful: Ammonia, sulphuretted hydrogen, cyanogen, carbonic acid, nitrous ox.de, arsenuretted hydrogen, defiant gas, hydrogen, oxygen, carbonic oxide, and nitrogen " 8 He found that ammonia transmitted in one minute as much in volume as sulphuretted hydrogen did in two minutes and V half • cyanogen, m three minutes and a quarter; carbonic acidXfae minutes and a half; nitrous oxide, in six minutes and a half; arsenu- * See also Amcr. Journal of the Medical Sciences for November lnm ,«„ t Precis 61ementaire de PhysioloSie, 2de edit 1825 I ?o. ''J833'P-100. nomenes physiques de la vie, recueillies par C.James. ' Edit BruieL1837 ""' ^ P^' FUNCTIONS OF MAN. 49 retted hydrogen, in twenty-seven minutes and a half; olefiant gas, in twenty-eight minutes; hydrogen, in thirty-seven minutes and a half; oxygen, in one hour and fifty-three minutes; and carbonic oxide, in two hours and forty minutes. It was found, too, that up to a pressure of sixty-three inches of mercury, equal to more than the weight of two atmospheres, the penetrative action was capable of conveying the gases—the subjects of the experiment—into the short leg through the gum elastic mem- brane. Hence the degree of force exerted in the penetration is con- siderable. The experiments were all repeated with animal membranes, such as dried bladder and gold-beater's skin, moistened so as to resemble the natural state. The same results, and in the same order, followed as with the gum elastic. The more fresh the membrane, the more speedy and extensive was the effect; and in living animals the trans- mission was very rapid. To these experiments we shall have frequent occasion to refer in the course of this work.* All these different properties of animal solids are independent of the vital properties. They continue for some time after the total extinction of life in all its functions, and appear to be connected either with the physical arrangement of molecules, the chemical composition of the substance in which they reside, or with peculiar properties in the body that is made to act on the tissue. They do not, indeed, seem to be affected, until the progress of decomposition has become sensible. Hence, many of these agencies have been termed collectively, by Haller, the vis mortua. II. OF THE FUNCTIONS OF MAN. Having described the intimate structure of the tissues, we pass to the consideration of the functions, the character of each of which is,—that it fulfils a special and distinct office in the economy, for which it has an organ or an instrument, or an evident apparatus of organs. Physiologists have not, however, agreed on the number of distinct offices which are so performed; and hence the difference, in the num- ber and classification of the functions, that prevails amongst them. The oldest division is into the vital, natural, and animal; the vital functions including those of such importance as not to admit of inter- ruption, such as circulation, respiration, and the functions of the brain and spinal marrow; the natural functions including those that effect * See, connected with this subject, the ingenious papers by Drs. Draper, and Robert E. Rogers,—the former in the American Journal of the Medical Sciences, May, 1836, p. 13; the latter in the same Journal for August 1836, p. 276, and Ibid, Nov. 1837, p. 122. VOL. I. 5 FUNCTIONS OF MAN. 50 nutrition, as digestion, absorption and secretion; and the «mma/, those possessed exclusively by animals, as sensation, [ocom°"°n' and voice. This classification is the basis of that which generally prevails at the present day. The character of this work will not admit of a detail ol every classification which has been proposed by the physiologist; that of Bichat, however, has occupied so large a space in the public eye, that it cannot well be passed over. It is the one followed by M. Richerand,* and by many modern writers. Bichat includes all the functions under two heads, according as they work to one or other of two ends —functions of nutrition or life of the individual, and functions of reproduction, or life of the species. Nutrition requires that the being shall establish relations around him to obtain the materials of which he may stand in need; and, in. animals, the functions, which establish such relations, are under the volition and perception of the being. Hence they are divided into two sorts;—those, that commence or precede nutrition, consist of exter- nal relations, are dependent upon the will, and executed with con- sciousness; and those that are carried on within the body, spontane- ously, and without consciousness. Bichat adopted this basis, and to the first aggregate of functions he applied the term animal life, because it comprised those that characterize animality; the latter he called organic life, because the functions comprised under it are common to every organized body. Animal life included sensation, motion and expression; organic life, digestion, absorption, respiration, circulation, nutrition, secretion, &c. In animal life, Bichat recognised two series of actions, opposed to each other, the one proceeding from without and terminating in the brain, or passing from circumference to centre, and comprising the external senses; the other, commencing in the brain and acting on external bodies, or proceeding from centre to circumference, and in- cluding the internal senses, locomotion, and voice. The brain, in which one series of actions terminates and the other begins, he con- sidered the centre of animal life. In organic life he likewise recognised two series of actions; the one proceeding from without to within, and effecting composition; the other passing from within to without, and effecting decomposition. In the former, he included digestion; absorption; respiration, by which the blood is formed; the circulation, by which the blood is conveyed to different parts, and the functions of nutrition, and calori- fication. In the latter, that absorption, which takes up parts from the body; the circulation, which conducts those parts or materials to the secretory or depuratory organs; and the secretions, which separate them from the economy. In this kind of life, the circulation is common to the two movements *Nouveaux Elemens de Physiologie, 13eme Edit, par M. Be>ard, aine, Edit. Beige, p. 42. Bruxelles, 1837, or Amer. Reprint of Copland's Edit, of De Lys's'Translation. New York, 1836. FUNCTIONS OF MAN. 51 of composition and decomposition; and, as the heart is the great or- gan of the circulation, he considered it the centre of organic life and, lastly, as the lungs are united both with animal life, in the re- ception of air, and with organic life, as the organs of sanguification, Bichat regarded those organs as the bond of union between the two lives. Generation constituted the life of the species. The classification adopted in this work, will be that embraced by Magendie ;* and, after him, by Adelon,f who has written one of the best systems of human physiology which we possess. The first class, or functions of relation, or animal functions, in- cludes those that establish our connexion with the bodies surround- ing us ; the sensations, voluntary motions, and expressions. The se- cond class, orfunctions of nutrition, comprises digestion, absorption, respiration, circulation, nutrition, calorification, and secretion, and the third class, the functions of reproduction,—generation. Table of the Functions. 1. Sensibility. 2. Muscular motion. 3. Expression or language. 4. Digestion. 5. Absorption. 6. Respiration. 7. Circulation. 8. Nutrition. 9. Calorification. 10. Secretion. 11. Generation. In studying each of these functions, we shall first of all describe the organ or apparatus concerned in its production; but, so far only as is necessary in a physiological point of view, and shall next detail what has been called the mechanism of the function, or the mode in which it is effected. In many cases it will happen, that some external agent is con- cerned in its production, as light in vision ; sound in audition; odours in olfaction; tastes in gustation, &c. The properties of these agents will, in all instances, be detailed in a brief manner, and as far only as is requisite for the immediate purpose. The difficulty of observing actions, that are carried on by the very molecules of which the organs are composed, has given rise to many hypothetical speculations, some of which are sufficiently ingenious; others too fanciful to be indulged, by the reflecting, for a moment; and, as might be expected, the number of these fantasies generally bears a direct proportion to the difficulty and obscurity of the sub- ject. It will not be proper to pass over the most prominent of these, but they will not be dwelt upon; whilst the results of direct observa- tion and experiment will be fully detailed; and, where differences * Op. citat., I., 32. t Physiologie de I'Homme, 2de edit., I., 116. Paris, 1829. I. Animal or of Relation. Functions. II. Nutritive. III. Reproductive. 52 FUNCTIONS OF MAN. prevail amongst observers, such differences will be attempted to be reconciled, where practicable. , i The functions, executed by different organs of the D°dMa» * deduced by direct observation, although the minute and moiecuiar action, by which they are accomplished in the very tissue ot the organ, may not admit of detection. We see, for example, blood proceeding to the liver, and the vessels that convey it, ramifying m the texture of the viscus, and becoming so minutfsras *°, escaPe vision, even when aided by a powerful microscope. We find, again, other canals in the organ, becoming perceptible, gradually augment- ing in size, and ultimately terminating in a larger duct, that opens into the small intestine. If we examine each of these orders of vessels in their most minute appreciable ramifications, we discover, in the one, always blood, and, in the other, always a very different fluid,— bile. We are hence led to the conclusion, that in the intimate tissue of the liver, and in some part communicating directly or indirectly with both these orders of vessels, bile is separated from the blood; in other words, that the liver is the organ of the biliary secretion. On the other hand, functions exist, which cannot be so demonstra- tively referred to an organ. We have every reason for believing, that the brain is the exclusive organ of the mental and moral mani- festations ; but, as few opportunities occur for seeing it in action, and as the operation is too molecular to admit of direct observation when we do see it, we are compelled to connect the organ and func- tion by a process of reasoning only; yet we shall find, that the re- sults, at which we arrive in this manner, are often by no means the least satisfactory. The forces that preside over the various functions are either gene- ral,—that is, physical or chemical; or special—that is organic or vital. Some of the organs afford us examples of purely physical instruments. We have, for instance, in the eye, an eye-glass, if we may so call it, of admirable construction; in the organ of voice, an instrument of music; in the ear one of acoustics. The circulation is carried on through an ingenious hydraulic apparatus, whilst station and progression involve various laws of mechanics. In many of the functions, again, we have examples of chemical agency, whilst all those, in which innervation is concerned, we are incapable of explain- ing on any physical or chemical principle, and are constrained to esteem vital. ANLMAL FUNCTIONS. 53 BOOK I. ANIMAL FUNCTIONS, OR FUNCTIONS OF RELATION. The functions of relation consist first, of sensibility, and secondly, of muscular motion, including expression or language. All these actions are subject to intermission, constituting sleep; a condition which has, consequently, by many physiologists, been investigated under this head; but as the functions of reproduction are also in- fluenced by the same condition, the consideration of sleep will be deferred until the third class of functions has engaged attention. CHAPTER I. OF SENSIBILITY, OR THE FUNCTION OF THE SENSATIONS. Sensibility is the function by which an animal experiences feeling, or has the perception of an impression. In its general acceptation, it means the property possessed by living parts of receiving impres- sions, whether the being, exercising the property, has consciousness of it or not. To the first of these cases—in which there is con- sciousness—Bichat gave the epithet animal; to the second, organic; the latter being common to animals and vegetables, and presiding over the organic functions of nutrition, absorption, exhalation, secre- tion, &c.; the former existing only in animals, and presiding over the sensations, internal as well as external. Animal sensibility, will engage us here. Pursuing the plan, already laid down, we shall commence the study of this interesting and elevated function, by pointing out, as far as may be necessary, the apparatus that effects it, which com- prises the whole nervous system. 1. Of the Nervous System. Under the name nervous system anatomists include all those or- gans, that are composed of the nervous or pulpy tissue. In man, it is constituted of three portions; first, of what has been called the cerebro-spinal axis, a central part having the form of a long cord, expanded at its superior extremity, and contained within the cavities of the cranium and spine; secondly, of cords, called nerves, in num- ber thirty-nine pairs, according to some,—forty-two according to others,—passing laterally between the cerebro-spinal axis and every part of the body; and, lastly, of a nervous cord, situated on each side of the spine, from the head to the pelvis, forming ganglia oppo- site each vertebral foramen, and called the great sympathetic nerve. 1. Of the encephalon.—Under this term are included the contents of the cranium, namely, the cerebrum or brain proper; the cerebeU 5* 54 NERVOUS SYSTEM. lum or little brain and the medulla oblongata. These various parts ml R lncIuded by some under the name of brain. When we look at a section of the encephalon, and at the three organs in their natural position, we find many distinct parts, and ap- pearances of numerous and separate organs. So various, indeed, are the prominences and depressions observable on the dissection of the brain, that it is generally esteemed one of the most difficult sub- jects of anatomy; yet, owing to the attention paid to it in all ages, it is now one of the structures best understood by the anatomist. This complicated organ affords us a striking illustration of the truth, that the most accurate anatomical knowledge will not neces- sarily teach the function. The elevated actions, which the encepha- lon has to execute, have, indeed, attracted a large share of the attention of the physiologist,—too often, however, without any satis- factory result; yet*it may, we think, be safely asserted, that we have become better instructed regarding the uses of particular parts of the brain, within the last few years, than during the whole of the century preceding. The encephalon being of extremely delicate organization, and its functions easily deranged, it was necessary that it should be securely lodged and protected from injuries. Accordingly, it is placed in a round, bony case; and, by an admirable mechanism, is defended against damage from surrounding bodies. Amongst these guardian agents or tutamina cerebri must be reckoned ;—the hair of the head, the skin, muscles, pericranium, bones of the skull, the diploe sepa- rating the two tables, of which the bones are composed, and the dura mater. It is not an easy matter to assign probable uses to the hair on va- rious parts of the body. On the head its function seems more readily appropriable. It deadens the concussion, which the brain would ex- perience from the infliction of heavy blows, and prevents the skin of the scalp from being.injured by the attrition of bodies. In military service, the former of these uses has been taken advantage of, and an arrangement somewhat similar to that which exists naturally on the head, has been adopted with regard to the helmet. The metallic substance, of which the ancient and modern helmets are formed, is readily thrown into vibration; which vibration, being communicated to the. brain, might, after heavy blows, derange its functions more even than a wound inflicted by a sharp instrument. To obviate this, in some measure, the helmet has been covered with horse-hair; an arrangement which prevailed in the helmet worn by the Roman soldier..- There can be no doubt, likewise, that being bad conductors of caloric, and forming a kind of felt which intercepts the air, the hairs may tend to preserve the head of a more uniform temperature. They are, moreover, covered with an oily matter, which prevents them from imbibing moisture, and causes them to dry speedily An- other use, ascribed to them by Magendie,* is somewhat more'hypo- * Precis Elementaire, edit. cit. I. 177. SKULL. 55 thetical;—that being bad conductors of electricity, they may put the head in a state of insulation, so that the brain may be less affected by the electric fluid ! It is unnecessary to explain in what manner the different layers, of which the scalp is composed, the cellular membrane beneath, the panniculus carnosus or occipito-frontalis muscle, and the pericra- nium covering the bone, act the parts of tutamina. The most im- portant of these protectors is the bony case itself. In an essay written by one of the most distinguished physiologists of the present day,* we have some beautiful illustrations of the wisdom of God as displayed in the mechanism of man, and of his skull in particular, and although some of his remarks may be liable to the censures which have been passed upon them by Dr. Arnott,f the greater part are admirably adapted to the contemplated object. It is impossible indeed, for the uninitiated to rise from the perusal of his interesting essay, without being ready to exclaim with the poet, " how wonder- ful, how complicate is man! how passing wonder He that made him such!" Sir Charles attempts to prove, that the best illustration of the form of the head is the dome; whilst Dr. Arnott considers it to be " the arch of a cask or barrel, egg-shell, or cocoa-nut, &c. in which the tenacity of the material is many times greater than necessary to re- sist the influence of gravity, and comes in aid, therefore, of the curve, to resist forces of other kinds approaching in all directions, as in falls, blows, unequal pressures," &c. The remarks of Dr. Arnott on this subject are just; and it is owing to this form of the cranium, that any blow received upon one part of the skull is rapidly distributed to every other; and that a heavy blow, inflicted on the forehead or vertex, may cause a fracture, not in the parts struck, but in the occipital or sphenoidal bones. The skull does not consist of one bone, but of many. These are joined together by sutures,—so called from the bones seeming as if they were stitched together. Each bone consists likewise of two ta- bles; an external, fibrous and tough, and an internal, of a harder cha- racter and more brittle, hence called tabula vitrea. These two tables are separated from each other by a cel- lular or cancellated structure, call- ed diploe. On examining the mode in which the tables form a junction with each other at the sutures, we find additional evidences of design , _. ., .. skul1- _ , . .. . , rn, , r . ° A. The parietal bone. B. The frontal bone. exhibited. 1 he edges Of the OUter C. The occipital bone. D. The temporal bone. table are serrated, and so arranged K The sphenoid bone- * Sir Charles Bell, in Animal Mechanics—Library of Useful Knowledge, London, 1829. t Elements of Physics, or Natural Philosophy, General and Medical, London, 1827 —reprinted in this country, with notes by Dr. Hays. 56 NERVOUS SYSTEM. as to be accurately dovetailed into each other; the tough row texture of the external plate being well adapted fo'f^ ^»^; On the other hand, the tabula vitrea, which, on account of its greater Fig. 9. Disarticulated bones of the skull. 1. The frontal bone. (The central division between the two bones does not exist in the adult.)— 2. Parietal bone.—3. Occipital bone.—4. Temporal bone.—5. Ethmoid bone.—6. Sphenoid bone.— 7. Superior maxillary bone.—8. Cheek bone.—9. Palate bone.—10. Lachrymal bone.—11. Nasal bone.—12. Inferior maxillary bone. hardness, would be liable to fracture, to chip off, is merely united with its fellow at the suture, by what is called harmony: the tabulae are, in other words, merely placed in contact. The precise object of these sutures is not apparent. In the mode in which ossification takes place in the bones of the skull, the radii from different ossific points must necessarily meet by the " law of conjugation," in the progress of ossification. This has, by many, been esteemed the cause of the sutures, but the explanation is insuf- ficient. However it may be, the kind of junction affords an example of beautiful adaptation. During the foetal state, the sutures do not exist. They are fully formed in youth, are distinct in the adult age, but, in after periods of life, become entirely obliterated, the bone then forming a solid spheroid. It does not seem, however, that after the ENCEPHALON. 57 sutures are established, any displacement of the bones can take place; and observation has shown, that they do not possess much, if any, effect in putting a limit to fractures. In all cases of severe blows, the skull appears to resist as if it were constituted of but one piece. But the separation of the skull into distinct bones, which have a mem- branous union, is of striking advantage to the foetus in parturition. It enables the bones to overlap each other; and, in this way, to occupy a much smaller space than if ossification had united them, as in after life. It has, indeed, been imagined by some, that there is this advan- tage in the pressure made on the brain by the investing bones,—that the foetus does not suffer from the violent efforts made to extrude the child; but that, during the passage through the pelvis, it is in a state of fortunate insensibility; and that pressure suddenly exerted upon the brain is attended with these effects, is well known to the patholo- gist. It is, indeed, the great principle to be borne in mind in the management of apoplexy, fracture of the skull, &c. The uses of the diploe, which separates the two tables of the skull, are not equivocal. Composed of a cancellated structure, it is well adapted to deaden the force of blows, and as it forms, at the same time, a bond of union and of separation, a fracture might be in- flicted upon the outer table of the skull, and yet be prevented from extending to the tabula vitrea. Such cases have occurred, but they are rare. It will generally happen, that a blow, intended to cause se- rious bodily injury, will be sufficient to break through both tables or neither. Lastly, the dura mater, which has been reckoned as one of the tutamina cerebri, lines the skull and constitutes a kind of internal periosteum to it. It may also be inservient to useful purposes, by deadening the vibrations, into which the head may be thrown by sudden concussions; as the vibrations of a bell are arrested by lining it with some soft material. It is chiefly, however, to protect the brain against itself, that we have the arrangement, which prevails. The cerebrum, as well as the cerebellum, consists of two hemi- spheres ; and its posterior part is situated immediately above the cerebellum. It is obvious, then, that without some protection, the hemisphere of one side would press upon its fellow, when the head is inclined to the opposite side; and that the posterior lobes of the brain would weigh upon the cerebellum in the erect attitude. The hemispheres (A A. Fig. 10) are separated from each other bv the falx cerebri, in the upper margin of which is the superior lon- gitudinal sinus (d d.) The falx passes between the hemispheres (a a, Fig. 11). The tentorium cerebello snper-extensum—a pro- longation of the dura mater, passes horizontally forwards (at c c,) so as to support the posterior lobes of the brain, and prevent them from pressing injuriously on the cerebellum (B B.) A process of the dura mater passes also between the hemispheres of the cerebellum (B B.) Independently of the protection afforded to the encephalon, the dura mater lodges the great sinuses into which the veins discharge their 58 NERVOUS SYSTEM. Fig. 10. Posterior view of the encephalon, the cranium and dura mater being removed. blood. These different sinuses empty themselves into the torcular Herophili or confluence of the sinuses, (at d, Fig. 10 & 11,) and ulti- mately proceed in the direction c c, constituting the lateral sinuses, which pass through the temporal bone, and from the internal jugular veins, one of which is represented at e, Fig. 11. Fig. 11. a a. The falx cerebri, d. The torcular Herophili. c c. The lateral si jugular vein. e. The internal ENCEPHALON. 59 The tutamina are not confined to the contents of the cranium. The spine appears to be, if possible, still better protected. In the skull, we see a firm, bony case; in the spine, a structure admitting considerable motion of the parts, without risk of pressure to the spinal marrow. Accordingly, the spine consists of numerous dis- tinct bones or vertebras, with fibro-cartilaginous—technically called intervertebral—substances placed between each, so that, although the extent of motion between any two of these bones may be small, the amount, when all are concerned, is considerable. The great use of this intervertebral substance is to prevent the jar, that would ne- cessarily be communicated to the delicate parts within the cavities of the spine and cranium, were the spine composed entirely of one bone. In falls from a height, upon the feet or breech, these elastic cushions are forcibly compressed; but they immediately return to their former condition, and deaden the force of the shock. In this they are aided by the curvatures of the spine, which give it the shape of the Italic f, and enable it to resist—in the same manner as a steel spring—any force acting upon it in a longitudinal direction. So well is the medulla spinalis protected by the strong bony pro- cesses, jutting out in various directions from the spine, that it is ex- tremely rare to meet with lesions of the part; and it is compara- tively of late years, that any ex-professo treatises have appeared on the subject. Besides the protection* afforded by the bony structure to the deli- cate medulla, Magendie has pointed out another, which he was the first to detect. The canal, formed by the dura mater around the spinal cord, is much larger than is necessary to contain that organ; but, during life, the whole of the intermediate space is filled with a serous fluid, which strongly distends the membrane, so that it will frequently spirt out to a distance of several inches, when a puncture is made in the membrane. To this fluid, he has given the epithet cephalo-spinal; and he conceives, that it may act as one of the tuta- mina of the marrow, (which is, as it were, suspended in the fluid,) and exert upon it the pressure necessary for the healthy performance of its functions. Beneath the dura mater is situated a very delicate membrane, the arachnoid, belonging to the class of serous membranes. It sur- rounds the encephalon in every part, but is best seen at the base of the brain. Its chief use is to secrete a thin fluid, to lubricate the brain. This membrane enters into all the cavities of the organ, and in them fulfils a like function. When the fluid accumulates to a great extent, we have the disease called hydrocephalus chronicus. Anatomists usually describe a third tunic of the brain—the pia mater. As a distinct membrane this is not demonstrable. It is ge- nerally conceived to consist of the minute terminations of the cere- bral arteries, and those of the corresponding veins, forming, at the * Precis, &c. Edit. cit. I. 181. 60 NERVOUS SYSTEM. surface of the brain, a vascular net-work, which passes into the cavities; and, in the ventricles, forms the plexus choroides, and tela choroidea. The dura and pia mater were so called, by the older anatomists, because they were conceived to be the origin of all the other membranes of the body. The cerebrum or brain proper has the form of an oval, larger be- hind. On its outer surface are various undulating eminences, called convolutions, because they have been thought to resemble the folds of the intestines—separated from each other by depressions, called anfractuosities. (See Fig. 13.) In the brain of man, these convo- lutions are larger than in animals, and the anfractuosities deeper. In different brains, the number,-size, and arrangement of these vary. They are not the same, indeed, in the same individual; those of the right hemisphere being disposed differently from those of the left. The hemispheres, we have seen, are separated above by the falx cerebri: below, they are united by a white medullary commissure, the corpus calosum mesolobe or great commissure. If we examine the brain at its base, we find that each hemisphere is divided into three lobes,—an anterior, which rests on the vault or roof of the orbit,—a middle or temporal, filling the middle and lateral parts of the base of the cranium, and separated from the former by a consi- derable depression called the fissure of Sylvius,—and a posterior, which rests on the tentorium cerebelli. This part of the cerebrum is divided into two very distinct portions by the medulla oblongata. Anterior to it are crura cerebri or cerebral peduncles,—by most anatomists considered to be a continuation of the anterior fasciculi which form the spinal marrow and medulla oblongata, and proceeding to form the hemispheres of the brain. Between the anterior extre- mities of the peduncles are two hemispherical projections, called eminenlice mamillares, which are possessed by man exclusively, have the shape of a pea, and are formed of the white nervous tissue externally, of the gray within. Anterior to these again is the infun- dibulum, and, a little farther forwards, the chiasma of the optic nerves, or the part at which these nerves come in contact. Laterally, and at the inferior surface of the anterior lobes, is a groove or furrow, running from behind to before, and from without to within, in which the olfactory nerve is lodged. At the extremity of this furrow is a tubercle, which is trifling in man, but in certain animals is equal to the rest of the brain in bulk. From this the ol- factory nerve has been conceived to arise. It is called the olfactory tubercle or lobe. When we examine the interior of the brain, we find a number of parts to which the anatomist assigns distinct names. Of these the following chiefly concern the physiologist. It has been already re- marked, that the corpus callosum forms at once the bond of union and of separation between the two hemispheres. It is distinctly per- ceived, on separating these parts from each other, in the form of a long and broad white band. Beneath the corpus callosum is the septum lucidum, or median septum, which passes perpendicularly ENCEPHALON. 61 Fig. 12. Base of the Brain. A A. Anterior lobes of the brain—B B. Middle lobes—C C Posterior lobes—D D. Cerebellum--*. Medulla oblongata—J. Pons Variolii—c. Chiasm of the optic nerves—d. Olfactory nerves—e. Crura cerebri—/. Crus cerebelli. downwards and separates from each other the two largest cavities of the brain—the lateral ventricles. It is formed of two laminas, which leave a cavity between them, called the fifth ventricle. The fornix is placed horizontally below the last. It is of a triangular shape, and constitutes the upper paries of another cavity—the third ventricle. Beneath the fornix, and behind it, is the pineal gland, respecting which so much has been said, by Descartes,* and others, as the seat of the soul. Within it, is a small cavity; and, after six or seven years of age, it always contains some concretions. Again, anterior to the pineal gland, and immediately below the fornix, is another cavity—the third ventricle. Its bottom is very near the base of the brain, and is formed by the nervous layer, which unites the peduncles of the brain with the eminentise mamillares. (Fig. 12.) At the sfdes it has the thalami nervorum opticorum. In the lateral ventricles, situated on each side of the corpus cal- losum, some parts exist which demand attention. In the upper or anterior half, commonly called the anterior cornu, and in the ante- rior part of this, two pyriform eminences are seen, of a brownish- gray colour, and which, owing to their being formed of an assem- blage of alternate layers of white and gray substance, are called the corpora striata. Behind these, are two whitish medullary bodies, called thalami nervorum opticorum, which are situated before the * Tractatus de homine, p. 5. VOL. I. 6 62 NERVOUS SYSTEM. corpora quadrigemina, and envelope the anterior extremities of the crura cerebri. The cerebellum occupies the lower occipital fossae, or the whole of the cavity of the cranium, which is beneath the tentorium cerebelli. The size and weight of the cerebellum, like those of the brain, differ according to the individual, and the age of the subject under examination. We do not observe convolutions in it. It appears rather to consist of lamina? in superposition, separated from each other by a furrow. We shall see hereafter that the number of cerebral convolutions has been esteemed, in some respects, to accord with the intellect of the individual; and Malacarne* asserts, that he has observed a similar correspondence, as regards the number of the lamina composing the cerebellum ; that he found only three hundred and twenty-four in the cerebellum of an insane individual, whilst in others he had counted upwards of eight hundred. Fig. 13. espozione della vera struttura del cerveletto humano. Torino, 177G, ENCEPHALON. 63 From the medullary part of the cerebellum, two large white cords pass to the pons varolii, having the same disposition as the crura cerebri. They are the crura cerebelli. Owing to the peculiar arrangement of the white and gray cerebral substances, when one of the hemispheres of the cerebellum is divided vertically, an arborescent appearance is presented,—the trunks of the arborizations being white, the surrounding substance gray. This appearance is called arbor vita. The part where all these arborizations meet, near the centre of the cerebellum, is called cor- pus denticulatum vel rhomboidale. Gall is of opinion, that this body has great agency in the production of the cerebellum. Lastly, the cerebellum covers the posterior part of the medulla oblongata, and forms with it a cavity, called the fourth ventricle. The medulla oblongata is so called, because it is the continuation of the medulla spinalis in the cavity of the cranium. It is likewise termed mesocephale, from its being continuous with the spinal mar- row in one direction, and sending towards the brain strong pro- longations—the crura cerebri; and to the cerebellum similar pro- longations—the crura cerebelli; so that it appears to be the bond of union between these various parts. In its lower portion, (Fig. 12, a.) it appears to be merely a continuation of the medulla spinalis, except that it is more expanded superiorly where it joins the pons varolii, b. This portion of the medulla oblongata is called, by some, the tail of the medulla oblongata; by others, the rachidian bulb; and by others again it is regarded as the whole medulla oblongata. Its lower surface, seen in the figure, rests on the basilary gutter of the occipital bone, and exhibits a groove, which divides the spinal cord into two portions. On each side of this furrow are two oblong eminences, the innermost of which is called corpus pyramidale, the outermost, corpus olivare, (Fig. 14.) which arise from the anterior column of the medulla spinalis, or are a continuation and subdivision of this column. On the posterior surface of the medulla oblongata, the posterior fasciculi separate to form the fourth ventricle; (Fig. 13, 7.) at the sides of this ventricle are the corpora restiformia, or inferior peduncles of the cerebellum, so called, because they seem to aid in the formation of that part of the encephalon; and, on the inner side of each corpus restiforme, is the small body—the posterior pyra- mid. Again, in addition to the corpora pyramidalia and olivaria— which derive their origin from, or are continuous with, the anterior fasciculi of the spinal cord, and are destined, according to some, to form the brain—and the corpora restiformia, which are continuations of the posterior fasciculi, and are destined to form the cerebellum, there exists, according to some anatomists, other fasciculi in the rachidian bulb. All these are interesting points of anatomy, but are not yet of much importance physiologically; if we except, perhaps, the views promulgated by Sir Charles Bell.* He considers, that a * The Nervous System of the Human Body : from Transactions of the Royal Society from 1821 to 1829. London, 1830. Reprinted in this country, (Washington,) 1833. 64 NERVOUS SYSTEM column exists between the corpora olivaria and corpora restiformia, which extends below, through the whole spine, but above, does not proceed farther that the point where the rachidian bulb joins the tuber annulare, and that this column gives origin to a particular order of nerves—those inservient to respiration. The anterior and upper half of the medulla oblongata bears the name pons varolii, tuber annulare, and nodus cerebri; and to this are attached, superiorly, the corpora or tubercula quadrigemina. In the very centre of the pons, the crura cerebri bury themselves; and are, by many, considered to decussate; and by others, to be pro- longations of the anterior column of the spine. Sir C. Bell thinks, that the pons varolii stands in the same relation to the lateral por- tions of the cerebellum that the corpus callosum does to the cere- brum : that it is the great commissure of the cerebellum, uniting its lateral parts and associating the two organs. 2. The spinal marrow extends, in the vertebral canal, from the foramen magnum of the occipital bone, above, to the cauda equina, below. It is chiefly composed of medullary matter, but not entirely so. Within, the cineritious substance is ranged irregularly, but has a crucial form when a section of it is made. From the calamus scriptorius in the fourth ventricle, and the rima—formed by the cor- pora pyramidalia, before—two fissures extend downwards, which divide the spinal marrow into lateral portions. The twro lateral por- tions are divided into an anterior and posterior, so that the cord has four distinct portions. By some, indeed, it is conceived to consist of three columns—an anterior, posterior, and middle. The vertebral canal is connected by a strong ligamentous sheath, running down its whole length. The dura mater likewise envelopes the medulla at the occipital foramen, being firmly united to the liga- ments, but farther down it constitutes a separate tube. The tunica arachnoidea from the brain adheres loosely to the cord, having the cephalo-spinal fluid within it, and the pia mater closely embraces it. 3. Nerves.—The nerves are cords of the same nervous substance as that which composes the encephalon and spinal marrow, extending from these parts, and being distributed to the various organs of the body, many of them interlacing in their course, and forming plexuses; others having knots or ganglions upon them ; and almost all vanish- ing in the parts to which they are distributed. The generality of English anatomists reckon thirty-nine pairs of nerves; the French, with more propriety, forty-two. Of these, nine, according to the English—twelve, according to the French—draw their origin from, or are connected with, the encephalon, and are hence called encephalic nerves; thirty from the medulla spinalis, and hence termed spinal The encephalic nerves emerge from the cranium by means of fora- mina at its base. They are—proceeding from before to behind__the first pair or olfactory, distributed to the organ of smell; the second pair or optic, the expansion of which forms the retina; the third pair, motores oculi, or common oculo-muscular, which send filaments to most of the muscles of the eye; the fourth pair, trochleares, pathetici, or NERVES. 65 internal oculo-muscular, distributed to the greater oblique muscle of the eye; the fifth pair, trifacial, trigemini, or symmetrical nerve of the head, (Bell,) which send their branches to the eye, nose, and tongue; the sixth pair, abdu- centes, or external oculo-mus- cular, which are distributed to the abductor or rectus exter- nus oculi; the facial nerve, portio dura of the seventh pair, nervus communicans faciei, or respiratory nerve of the face, distributed to the muscles of the face; the acoustic nerve, auditory nerve, or portio moU lis of the seventh pair, which passes to the organ of hearing; the eighth pair, pneumogastric, par vagum, or middle sympa- thetic, which is dispersed par-< ticularly to the larynx, lungs, heart, and stomach; the glosso- pharyngeal, often considered as part of the last, and whose name indicates its distribution to the tongue and pharynx; the great hypoglossus, ninth pair, or lingual nerve, distri- buted to the tongue; and the spinal accessory of Willis, which arises from the spinal cord in the cervical region, ascends into the cranium, and issues, by one of the foramina, to be distributed to the muscles of the neck. All these proceed from the medulla oblongata ;—the brain and cerebellum not furnishing one, The spinal nerves are thirty in number on each side. They make their exit by the intervertebral foramina, and are divided into eight cervical, twelve dorsal, five lumbar, and five or six sacral. The encephalic nerves are irregular in their formation, and, with the exception of the fifth pair, originate from one root. Each of the spinal nerves arises from two fasciculi, the one anterior, and the other posterior; these are separated from each other by the ligamentum denticulare; but they unite beyond this ligament, and, near the inter-. vertebral foramina, present one of those knots, known under the name of ganglions or ganglia, in the formation of which the posterior root is alone concerned. When the nerves have made their exit from the cranium and spine, they proceed to the organs to which they have to be distributed, ramifying more and more, until they are ultimately lost sight of, even when vision is aided by a powerful microscope. Of the encephalic nerves, the olfactory, auditory, and acoustic—which are nerves of 6* Base of the brain and origin of the encephalic nerves. A. Anterior lobes of the brain. B. Middle lobes. C Posterior lobes. D. Cerebellum. E. Pons varolii. F. Medulla oblongata. G. Crura cerebri. H. Crura cerebelli. I. Fissure of Sylvius. K. Eminentire ma- millares. L. Infundibulurn. M. Corpora pyrnmidalia. N. Corpora olivaria. o. Roots of olfactory nerves. 1 1. Olfactory nerves. 2 2. Optic nerves. 3 3. Motores oculorum. 4 4. Pathetici. 5 5. Trigemini. 6 G. Abdu- centes. 7 7. Portio mollis and portio dura. 8 8. Glos- sopharyngeal. Par vagum, and Spinal Accessory. 9 9. Hypoglossal. 66 NERVOUS SYSTEM. special sensibility—pass on to their destination, without communi- cating with any other nerve. The spinal nerves, at their exit from the intervertebral foramina, divide into two branches, an anterior and a posterior, one being sent to each aspect of the body. The anterior branches of the four superior cervical pairs form the cervical plexus, from which all the nerves of the neck arise; the four last cervical pairs, and the first dorsal, form the brachial plexus, whence proceed the nerves of the upper extremities, whilst the branches of the five lumbar nerves and the five sacral form the lumbar and sciatic plexuses, the former of which gives rise to the nerves distributed to the parts within the pelvis, and the second to those of the lower limbs. The anterior branches, moreover, at a little distance from the exit of the nerve from the vertebral canal, communicate with an important and unique portion of the nervous system, the great sym- pathetic. Each nerve consists of numerous fasciculi, surrounded by cellular membrane; and, according to Reil,* of an external envelope, called neurilema, which, in the opinion of most anatomists, is nothing more than a cellular envelope, similar to that which surrounds the vessels and muscular fibres. Until of late years, the nerves were universally divided, according to their origin, into encephalic and spinal; but, more recently, ana- tomical divisions have been proposed, based upon the uses they ap- pear to fulfil in the economy. For one of the most beautiful arrange- ments of this kind we are mainly indebted to Sir Charles Bell. We have already seen, that the encephalic nerves are connected with the encephalon by only one root, whilst the spinal nerves arise from two; the one connected with the anterior part of the spinal marrow, the other with the posterior. If these different roots be experimented on, we meet with results varying considerably from each other. If we divide, for example, the anterior root, the part, to which the nerve is distributed, is deprived of the power of motion; whilst if the posterior root be cut, the part is deprived of sensibility. We con- Fig. 15. A. The spinal marrow, viewed in front. B. A spinal nerve. C Anterior part of a D. Ganglion on the posterior root. * De structura nervorum. Hal., 1796. Fatte 67 SYSTEM OF RESPIRATORY NEKVBS. fll Dr. Hall thinks, too, that there is good reason for viewing the fifth, and posterior spinal nerves as constituting an external gan- glionic system, for the nutrition of the external organs; and he pro- poses to divide the ganglionic subdivision of the nervous system, into 1. the internal ganglionic, which includes that usually denomi- nated the sympathetic, and probably filaments of the pneumogastric; and 2. the external ganglionic embracing the fifth and posterior spinal nerves. To the cerebral system he assigns all diseases of sensation, percep- tion, judgment, and volition—therefore all painful, mental, and com- atose, and some paralytic, diseases. To the true spinal or excito- motory system, belong all spasmodic and certain paralytic diseases. He properly adds, that these two parts of the nervous system in- fluence each other both in health and disease, as they both influence the ganglionic system.* The views of Dr. Hall on the excito-motory function, have been embraced by Muller,| Grainger,J and others. All the parts that we have described as constituting the nervous system—brain, cerebellum, medulla spinalis, and nerves—are formed of the primary nervous fibre, the nature of which has been already described. The substance of which they are constituted is soft and pulpy, but the consistence varies in different portions, and, in the whole, at different ages. In the foetus it is almost fluid ; in youth, of greater firmness; and of still greater in the adult. This softness of structure in the encephalon of the foetus is by no means inutile. It admits of the pressure, which takes place to a greater or less ex- tent in all cases of parturition, whilst the head is passing through the pelvis, without the child sustaining any injury. On examining, however, the consistence of different brains, it is necessary to inquire into the period that has elapsed since the death of the individual, as the brain loses its firmness by being kept, and ultimately becomes semi-fluid. It is likewise rendered fluid by dis- ease, constituting the ramollissement du cerveau, or mollescence of the brain, to which the attention of pathologists has been directed of late years but without much important advantage to science. * Principles of the Theory and Practice of Medicine, by Marshall Hall M. D. F. R. S. p. 243, London, 1837, and Lancet, loc. citat. f Handbuch der Physiologie, s. 333, and 688, Coblentz, 1835,1837, and the English Translation, by Mr. Baly, London, 1837. 6 + On the Structure and Functions of the Spinal Cord. London, 1837. NERVOUS TISSUE. 75 When the encephalon is fresh, it has a faint, spermatic, and some- what tenacious smell. This, according to Chaussier, has persisted for several years in brains that have been dried. The substance, of which the nervous system is composed, has been subjected to analysis by Vauquelin,* and found to contain, wa- ter, 80.00 ; white fatty matter, 4.53; red fatty matter, called cere- brine, 0.70; osmazome, 1.12; albumen, 7.00; phosphorus, 1.50; sulphur, acid phosphates of potassa, lime, and magnesia, 5.15. M. Couerbe's analysis of the brainf gives, 1. A pulverulent yel- low fat, stearconote; 2. An elastic yellow fat, cerancephalote ; 3. A reddish yellow oil, eleancephol; 4. A white fatty matter, cerebrate, the white fatty matter of Vauquelin, the myelocone of Kiihn; 5. Cere- bral cholesterine—cholesterote; and the salts found by Vauquelin, lactic acid, sulphur and phosphorus, which form a part of the fats above mentioned.J In the spinal cord, there is more fatty matter, and less osmazome, albumen, and water. In the nerves the albumen predominates, and the fatty matters *are less in quantity. Researches by Lassaigne show, that water constitutes T7o-ths of the nerves, and T8o-ths of the brain ; whilst the proportion of albumen, in the former, is youths; in the latter, T^ths. He found the different parts of the brain to be composed as follows: Water, Albumen, White fatty matter, Red fatty matter, Osmazome, lactic aci Earthy phosphate, 100.0 100.0 100.0§ Raspaily has pointed out two other differences. First, when a nerve is left upon a plate of glass in a dry air, it becomes dry, with- out putrefying, whilst the cerebral substance putrefies in twenty-four hours; and secondly; This dried nerve has all the physical charac- ters of the corneous substances,—nails, hair, and other analogous bodies ; and in their chemical relations, he says, these bodies do not differ sufficiently to repel the analogy. Neither the chemical analysis of the nervous system, nor inquiry into its minute structure by the aid of the microscope, has, however, thrown light upon the wonderful functions executed by this elevated part of the economy. To the naked eye, the nervous substance appears under two * Annales de Chim. lxxxi. 37, Annals of Philosophy, i. 332. t Annales de Chimie, et de Physique, lvi. 160. X See John's Analysis of the white and gray cerebral matter, in Journal de Chimie M6dicale, Aout, 1835. § Journal de Chim. M6dic., and PharmaceutischesCentral Blatt, Nov. 19,1836, s. 765. \ Chimie organique, p. 217. Paris, 1833. The whole brain. While portion. Gray portion. 77.0 73.0 85.0 9.6 9.9 7.5 7.2 13.9 1.0 3.1 0.9 3.7 1 salts, 2.0 1.0 1.4 1.1 1.3 1.2 76 NERVOUS SYSTEM. forms, the one gray, and of a softer consistence, the other white, and more compact. The former is called the cortical, cineritious, or pulpy substance; the latter, the white, medullary, or fibrous. The gray substance is not always, however, at the exterior, nor the medullary in the interior. In the medulla spinalis, their situation is the reverse of what it is in the brain. Ruysch considered, that the cineritious portion owes its colour to the blood-vessels which enter it ;* and, in this opinion, Haller and Adelonf concur; but this is not probable, and it has been by no means demonstrated. The medul- lary portion has the appearance of being fibrous, and it has been so regarded by Leeuenhoek,J Vieussens, Steno, and by Gall and Spurz- heim.§ Malpighi|| believed the gray cortical substance to be an as- semblage of small follicles, intended to secrete the nervous fluid, and the white medullary substance to be composed of the excretory ves- sels of these follicles. Gall and Spurzheim, on the other hand, con- jecture, that the use of the cineritious is to be the source or nourisher of the white fibres. The facts, on which they support their view, are, that the nerves appear to be enlarged when they pass through a mass of cineritious matter, and that masses of this substance are de- posited in all parts of the spinal cord where it sends out nerves; but Tiedemannli has remarked, that in the foetus the medullary is de- veloped before the cortical portion, and he conceives the use of the latter to be—to convey arterial blood, which may be needed by the medullary portion for the due execution of its functions. Sir Charles Bell** affirms, that he has found, at different times, all the internal parts of the brain diseased, without loss of sense, but that he has never seen disease general on the surface of the hemis- pheres, without derangement or oppression of mind during the pa- tient's life; and hence he concludes, that the cineritious matter of the brain is the seat of the intellect, and the medullary of the sub- servient parts. A similar use has been ascribed to the cineritious portion, from pathological observations, by M. M. Foville and Pinel Grandchamp.ff This view would afford considerable support to the opinions of Gall, Spurzheim, and others, who consider the organs of the cerebral faculties to be constituted of expansions of the columns of the spinal marrow and medulla oblongata, and to terminate by radiating fibres on the periphery of the brain; as well as of Desmoulins,JJ and those, who regard the convolutions as the seat of mind. We have, how- ever, cases on record, which signally conflict with this view of the • Oper. Amstel. 1727. \ Physiologie de I'Homme, 2de edit. vol. i. Paris 1829 X Philos. Transact. 1677, p. 899. ' § Recherches sur le systeme nerveux en general, et sur celui de cerveau en oarticu- lier, avec figur. Paris, 1809. r || In Oper. Malpighii, and in Mangeti Bibl. Anat. I, 321. V Anatomie und Bildungsgeschichte des Gehirns mit Tafeln. Ndrnberg 1816 v*tAiDao7my and Pfa^siol°^' 5th American edit., by J. D. Godman, page 29.' New xorK, 1o^7. tt Sur le Systeme nerveux. Paris, 1820. XX Anatomie des systemes nerveux des animaux a vertebres, p. 599. Paris 1825 CIRCULATION OF THE ENCEPHALON. 77 subject; cases in which the cortical substance has been destroyed and yet the moral and intellectual manifestations have been little, if at all, injured. Some years ago the author dissected the brain of an individual of rank in the British army of India, the anterior lobes of which were in such a state, that neither medullary nor cortical por- tion could be distinguished, both one and the other appearing to be broken down into a semi-purulent, amorphous fluid; yet the intel- lectual faculties had been nearly unimpaired, although the morbid process must have been of considerable duration. The encephalon affords us many striking instances of the differ- ent effects produced by sudden and by gradual interference with its functions. Whilst a depressed portion of bone or an extravasation of blood may suddenly give rise to the abolition of the faculties, the gradual compression, produced by a tumour, may scarcely interfere with any of its manifestations. The circulation of blood in the encephalon requires mention. The arteries are four in number,—two internal carotids, and two vertebrals; to these may be added the spinal artery or middle artery of the dura mater or arteria meningcea media. The carotid arte- ries enter the head through the carotid canals, which open on each side of the sella turcica, or of the chiasma of the optic nerves. The vertebral arteries enter the head through the foramen magnum of the occipital bone; unite on the medulla oblongata to form the basilary artery, which passes forward along the middle of the pons varolii, and, at the anterior part of the pons, gives off lateral branches, which inosculate with corresponding branches of the ca- rotids, and form a kind of circle at the base of the brain, which has been called the circuius arteriosus of Willis. The passage of the blood-vessels is extremely tortuous, so that the blood does not enter the brain with great impetus; and the ves- sels become capillary before they penetrate the organ,—an arrange- ment' of essential importance, when we regard the large amount of blood sent to the encephalon. This has been estimated as high as one-eighth of the whole fluid transmitted from the heart. The amount does not admit of accurate appreciation, but it is consider- able. It must of course vary according to circumstances. In hyper- trophy of the heart,* the quantity sent is sometimes increased; as well as in ordinary cases of what are called determinations of blood to the head. Here, too large an amount is sent by the arterial ves- sels ; but an equal accumulation may occur,' if the return of the blood from the head, by means of the veins, be in any manner im- peded,—as when we stoop, or compress the veins of the neck by a tight cravat, or by keeping the head turned for a length of time. Congestion or accumulation -of blood may therefore arise from very different causes. Sir Astley Cooper,f found by experiment, that the vertebral arteries * Bricheteau, Clinique Medicale, p. 133. Paris, 1835 ; or the Author's Translation in the American Medical Library. Philad. 1837. t Guy's Hospital Reports, 1.1472. London, 1836. 7* 78 NERVOUS SYSTEM. are much more important vessels as regards the brain and its functions in certain animals, as the rabbit, than the carotid arteries. The ner- vous power is much lessened by tying them; and, in his experiments, the animal did not, in any case, survive the operation more than a fort- night. In the dog also he tied the carotids with little effect, but the lig- ature of the vertebrals had a great influence. The effect of the opera- tion was to render the breathing immediately difficult and laborious, owing, in Sir Astley's opinion, to the supply of blood to the phrenic nerves and the whole tractus respiratorius of Sir Charles Bell being cut off. The animal became dull, and indisposed to make use of ex- ertion or to take food. Compression of the carotids and the verte- brals at the same moment in the rabbit, destroyed the nervous func- tions immediately. This was effected by the application of the thumbs to both sides of the neck, the trachea remaining quite free from pressure. Respiration entirely ceased, with the exception of a few convulsive gasps. The same fact was evinced in a clearer and more satisfactory manner by the application of ligatures on the four vessels, all of which were tightened at the same instant. Stoppage of respiration and death immediately ensued. The cerebral, like other arteries, are accompanied by branches of the great sympathetic. The encephalic veins are disposed as already mentioned, terminating in sinuses formed by the dura mater, and conveying their blood to the heart by means of the lateral sinuses and internal jugulars. (See Fig. 11.) No lymphatic vessels have been detected in the encephalon; yet, that absorbents exist there is proved by the dissection of apoplectic and paralytic individuals. In these cases, blood is sometimes effused within the brain, the red par- ticles are gradually taken up, with a portion of the fibrinous part of the blood, leaving a cavity called an apoplectic cell, which is at the same time the evidence of previous extravasation and of subsequent absorption. When the skull of the new-born infant, which at the fontanelles, consists of membrane only—or the head of one who has received an injury, that exposes the brain—is examined, two distinct move- ments are perceptible. The one, which is generally obscure, is synchronous with the pulsation of the heart and arteries; the other, much more apparent, is connected with respiration, the organ seeming to sink down at the time of inspiration, and to rise during expiration. This phenomenon is not confined to the brain, but exists likewise in the cerebellum and spinal marrow. The motion of the encephalon, synchronous with that of the heart, admits of easy explanation. It is owing to the pulsation of the circle of arteries at the base of the brain elevating the organ at each sys- tole of the heart. The other movement is not so readily intelligible. It has been attributed to the resistance, experienced by the blood in its passage through the lungs during expiration, owing to which an accumulation of blood takes place in the right side of the heart: this extends to the veins and to the cerebral sinuses, and an augment- PROPERTIES OP THE CEREBRAL SUBSTANCE. 79 ation of bulk is thus occasioned. We shall see hereafter, that one of the forces, conceived to propel the blood along the vessels, is at- mospheric pressure. According to that view, the sinking down of the brain, during inspiration, is explicable:—the blood is rapidly drawn to the heart; the quantity in the veins is consequently dimi- nished, and sinking down of the brain succeeds. On dissection, we find that the encephalon fills the cavity of the cranium; during life, therefore, it must be pressed upon, more or less, by the blood in the vessels, and by the serous fluid exhaled by the arachnoid. The spinal marrow, as we have seen, does not fill the vertebra] canal, but the cephalo-spinal fluid exerts upon it the necessary pressure; added to which, the pia mater seems to press more upon this organ than upon the rest of the cerebro-spinal system. A cer- tain degree of pressure appears, indeed, necessary for the due per- formance of its functions, and if this be either suddenly and consi- derably augmented, or diminished, derangement of function is the result. Magendie,* however, asserts, that he has known animals, from which the fluid had been removed, survive without any sensible derangement of the nervous functions. It is this fluid, which is drawn off by the surgeon when he punctures in a case of spina bifida. When the brain is examined in the living body, it exhibits pro- perties, which, some years ago, it would have been esteemed the height of hardihood and of ignorance to ascribe to it. The opinion has universally prevailed, that all nerves are exquisitely sensible. We shall have many opportunities for remarking how far this senti- ment is founded on fact; but we are now prepared to assert, that even the encephalon itself,—the organ or organs in which perception takes place,—is insensible, in the common acceptation of the term; that is, we may prick, lacerate, cut, and even cauterize it, yet no painful impression will be produced. Experiment leaves no doubt regarding the truth of this, and we find the fact frequently confirmed by pathological cases. Portions of brain may be discharged from a wound in the skull; and yet no pain be evidenced. In his " Anatomy and Physiology," Sir C. Bellf remarks, that he cannot resist stating, that on the morn- ing on which he was writing, he had had his finger deep in the an- terior lobes of the brain, when the patient, being at the time acutely sensible, and capable of expressing himself, complained only of the integument. A pistol ball had passed through the head, and Sir Charles having ascertained that it had penetrated the dura mater by forcing his finger into the wound, trepanned on the opposite side of the head, and extracted it. * Precis elementaire, seconde 6dit. 1.192. See, also, Dr. Skinner, in Amer. Journal of Medical Sciences for Nov. 1836, p. 109. t 5th Amer. Edit. By J. D. Godman, II. 6, 1827. See also, Sir E. Home's Lectures on Compar. Anat., ii. 93. Lond. 1823. 80 SENSATION?. By the experiments, instituted by Magendie* and others, it has been shown, that an animal may live several days, and even weeks, after the whole of the hemispheres has been removed ; nay, that in certain animals, as reptiles, no change is produced in their habitudes by such abstraction. They move about as if unhurt. Injuries of the surface of the cerebellum exhibit, that it also is not sensible to that kind of irritation; but deeper wounds, and especially those that interest the peduncles, have singular results, to be explained here- after. The spinal cord is not exactly circumstanced in the same manner. Its sensibility is very exquisite on the posterior surface; much less on the anterior, and almost null at the centre. These columns as we have seen, have been esteemed the origins of the nerves of sensibility, motion, and respiration.f Considerable sensi- bility is also found within, and at the sides of, the fourth ventricle; but this diminishes as we proceed towards the anterior part of the medulla oblongata, and is very feeble in the tubercula quadrigemina of the mammalia. It has been shown, that the spinal nerves, by means of their poste- rior roots, convey general sensibility to the parts to which they are distributed. But there are other nerves, which, like the brain, are themselves entirely devoid of general sensibility. This has given occasion to a distinction of nerves into those of general and of spe- cial sensibility. As nerves which must be considered insensible or devoid of general sensibility, may be instanced the optic, olfactory, and auditory. Each of these has, however, a special sensibility, and although they may exhibit no pain when irritated, they are capable of being impressed by appropriate stimuli, as by light, in the case of the optic nerve; by odours, in that of the olfactory; and by sound, in that of the auditory. Yet we shall find, that every nerve of spe- cial sensibility requires the influence of a nerve of general sensibility, the fifth pair. Many other nerves appear devoid of sensibility, as the third, fourth, and fifth pairs; the portio dura of the seventh; the ninth pair of encephalic nerves; and, as has been shown, all the an- terior roots of the spinal nerves. The parts of the encephalon, concerned in muscular motion, will fall under consideration hereafter. 2. Physiology of Sensibility. Sensibility we have defined to be—the function by which an ani- mal experiences feeling, or has the perception of an impression. It includes two great sets of phenomena, the sensations, properly so called, and the intellectual and moral manifestations. These we shall consider in succession. I. OF THE SENSATIONS. A sensation is the perception of an impression made on some organ; or, in the language of Gall, it is the perception of any irrita- • Precis elementaire, I. 335. t See, on this subject, the remarks at page 68. SENSATIONS- 81 tion whatever. By the sensations we receive a knowledge of what is passing within or without the body; and, in this way, our notions or ideas of them are obtained. When these ideas are reflected upon, and compared with each other, we exert thought and judgment; and they can be recalled, with more or less vividness and accuracy, by the exercise of memory. The sensations are numerous, but they may all be comprised in two divisions,—the external and the internal. Vision and audition afford us examples of the former, in which the impression, made upon the organ, is external to the part impressed. Hunger and thirst are instances of the latter, the cause here being internal, necessary, and depending upon influences seated in the economy itself. Let us endeavour to discover in what they resemble each other. In the first place, every sensation, whatever may be its nature,— external or internal,—requires the intervention of the encephalon. The distant organ,—as the eye or ear,—may receive the impression, but it is not until this impression has been communicated to the encephalon, that sensation is effected. The proofs of this are easy and satisfactory. If we cut the nerve proceeding to any sensible part, if we put a ligature around it, or compress it in any manner; it matters not that the object, which ordinarily excites a sensible impression, be applied to the part, no sensation is experienced. Again, if the brain, the organ of perception, be prevented in any way from acting, it matters not that the part impressed, and the nerve communicating with it, be in a condition necessary for the due performance of the function, sensation is not effected. We see this in numerous instances. In pressure on the brain, occasioned by fracture of the skull, or in apoplexy, a disease essentially depen- dent upon pressure, we find all sensation, all mental manifestation, lost; and they are not regained until the compressing cause has been removed. The same thing occurs if the brain be stupefied by opium, or any other narcotic; and, to a less degree, in sleep, or when the brain is engaged in intellectual meditations. Who has not found, that in a state of reverie or brown study he has succeeded in threading his way through a crowded street, carefully avoiding every obstacle, yet so little impressed by the objects around him as not to retain the slightest recollection of them 1 On the other hand, how vivid are the sensations when the attention is directed to them! Again, we have numerous cases in which the brain itself engen- ders the sensation, as in dreams, and in insanity. In the former we see, hear, speak, make use of every one of our senses apparently, yet there has been no impression from without. Although we may behold in our dreams the figure of a friend long since deceased, there can obviously be no impression made on the retina from without.* The whole history of spectral illusions, of morbid hallucinations, and maniacal phantasies, is to be accounted for in this manner. * Adelon, Art. Encephale (Phvsiologie) in Diet, de Med. vii. 514, Paris, 1823, and Physiol, de I'Homme, Tom. I., p."239, 2de Edit. Par. 1829. 82 SENSATIONS. Whether, in such cases, the brain reacts upon the nerves of sense and produces an impression upon them from within, similar to what they experience from without during the production of a sensation, will form the subject of future inquiry. Pathology also affords several instances where, the brain engenders the sensation, most of which are precursory signs of cerebral derangement. The appear- ance of spots flying before the eyes, of spangles, depravations of vision, of hearing, &c. and a sense of numbness in the extremities, are referable to this cause, as well as the singular fact well known to the operative surgeon, that pain is often felt in a particular part of a limb, years after the limb has been removed from the body.* These facts prove, that every sensation, although referred to some organ, must be perfected in the brain. The impression is made upon the nerve of the part, but the appreciation takes place in the common sensorium.f There are but few organs of the body, which could be regarded insensible, provided we were aware of the precise circumstances under which their sensibility is elicited.J The old doctrine—as old indeed as Hippocrates§—was, that the tendons and other membra- nous parts are among the most sensible organs of the body. This opinion was implicitly credited by Boerhaave, and his follower Van Swieten,|| and in many cases had a decided influence, on surgical practice especially. As the bladder consists principally of mem- brane, it was agreed for ages by lithotomists, that it would be im- proper to cut or divide any part of it; and therefore, in order to extract the stone, dilating instruments were used, which caused the most painful lacerations of the parts implicated in the operation.il Haller** considered the tendons, ligaments, periosteum, bones, me- ninges of the brain, different serous membranes, arteries, and veins, entirely insensible; yet we know, that these parts are exquisitely sensible when attacked with inflammation. One of the most painful affections to which man is liable is the variety of whitlow that im- plicates the periosteum; and in all affections of the bone, which in- flame or press forcibly upon that membrane, we have excessive sensibility exhibited. Many parts, too, are affected by special irritants; and, after they have appeared insensible to a multitude of agents, will show great sensibility when a particular irritant is applied. Bichat endeavoured to elicit the sensibility of ligaments in a thousand ways, and without success; but when he subjected them to distention or twisting, they immediately gave evidence of it. It is obvious, then, that before we determine that a part is insensible, we must have submitted it to * Porterfield on the Eye, i. 364. t Elliotson's Blumenbach, 4th Edit. p. 215. Lond. 1828. t Mojon's Leggi fisiologiche, . 16. stitute the skin, as it is commonly called; yet all are comprised in the thickness of two or three lines. The cutis vera is united to the struc- , , 77 7 Common Integuments. tUreS below by Cellular i. Cuticle.—2. Rete mucosum.—3. Corpus papillare.—4. Cu- membrane ' and this With *'s vera__*•" Cellular membrane.—6. Panniculus carnosus. the layers external to it, forms the common integument. In certain parts of the body, and in animals more particularly, the cutis vera is adherent to muscular fibres; inserted more or less obliquely, as at 6, Fig. 16. These form the muscular web, mantle or panniculus carnosus. The layer is well seen in the hedge-hog and porcupine, in which it rolls up the body, and erects the spines; and in birds, it raises the feathers. In man, it can hardly be said to exist. Some muscles, however, execute a similar function. By the occipito-frontalis, for instance, many per- sons can move the hairy scalp: and by the dartos, the skin of the scrotum can be corrugated. These two parts, therefore, act as panniculi carnosi. In the skin are situated numerous sebaceous follicles or crypts, which separate an oily fluid from the blood, and pour it over the surface to lubricate and defend it from the action of moisture. They are most abundant, where there are folds of the skin, or hairs, or where the surface is exposed to friction. We can generally see them on the pavilion of the ear, and their situation is often indicated by small dark spots on the surface, which, when pressed between the fingers, may be forced out along with the sebaceous secretion, in the form of small worms. By the vulgar, indeed, these are con- sidered to be worms. The follicular secretions will engage us here- after. At present, it is sufficient to remark, that they differ materi- ally according to the part of the body where they exist;—the cha- racters of the fluid, secreted in the axillae, groins, feet, &c. varying considerably. The consideration of the hair belongs naturally to that of the skin. The roots of the hair are in the form of bulbs, taking their origin in the cellular membrane. Around each bulb there are two capsules, the innermost of which is vascular. The hair itself con- sists of a horny, external covering, and a central part, called the medulla or pith. When we take hold of a hair by the base, with 0,4 SENSE OF TOUCH. the thumb and fore finger, and draw it through them from the root towards the point, it feels smooth to the touch; but it we araw a through, from the point to the root, we feel the surface rough, and it offers considerable resistance. It is, therefore, concluded, that the hair is bristled, or consists of eminences pointing towards its outer extremity, and it is upon this structure, that the operation of felting is dependent—the hairs being mechanically entangled to- gether, and retained in that state by the inequalities of their surface. Observers have, however, frequently failed in detecting this striated appearance, by the aid of the microscope; and Dr. Bostock* affirms, that he had an opportunity of viewing the human hair, and the hair of various kinds of animals, in the excellent microscope of Mr. Bauer, but without being able to detect it. Still, Bichatf and, more recently, Dr. Goring,J have assigned this as their structure;—the fact having been exhibited by the microscope, and, in their minds, admitting of no doubt. The colour of the hair is singularly different in different races and individuals. By some, this is considered to depend upon the fluids contained in the pith. Vauquelin§ analyzed the hair most atten- tively, and found that it consists chiefly of an animal matter, united to a portion of oil, which appears to contribute to its flexibility and cohesion. Besides this, there is another substance, of an oily na- ture, from which he considers the colour of the hair to be derived. The animal matter, according to that chemist, is a species of mucus, but other chemists believe it to be chiefly albumen. Vauquelin found that the colouring matter of the hair is destroyed by acids; and he suggests, that when it has suddenly changed colour and become gray, in consequence of any great mental agitation, this may be owing to the production of an acid in the system, which acts upon the colouring matter. The explanation is purely hypothetical, and is considered, and characterized as such by Dr. Bostock; but the same objection must be admitted to apply to the view he has substi- tuted for it. He conceives it " more probable that the effect depends upon the sudden stagnation of the vessels, which secrete the colour- ing matter, while the absorbents continue to act and remove that which already exists." There is, however, no more real evidence of " stagnation of vessels" than there is of the formation of an acid. Our knowledge is limited to the fact, that a sudden and decided change in the whole pileous system occurs after great or prolonged mental agitation.|| But a similar, though more gradual change, is • Physiology, p. 52, 3d Edit. Lond. 1836. t Anat. general, Tom. iv. X Journal of Science, New Series, vol. i., 433. § Annales de Chimie, Tom. lviii., 41. Paris, 1806. || " My hair is gray, but not with years, Nor grew it white in a single night, As men's have grown from sudden fears." Byron's Prisoner of Ckillon. " Danger, long travail, want and wo, Soon change the form that best we know : ORGANS OF TOUCH. 95 produced by age. We find some persons entirely gray at a very early period of life; and, in old age, the change happens universally. It is not then difficult to suppose, that some alteration in the nutrition of the hair may be induced, resembling that which occurs under these circumstances. Dr. Bostock doubts the fact of such sudden conversions; but the instances are too numerous for us to consider them entirely fabulous. Besides, as we have seen, the cases are not so preternatural as they might at first sight appear. The change induced is identical with that which occurs naturally to every indi- vidual, sooner or later. Lepefletier* ascribes the change of colour to two very different causes.—First, owing to defective secretion of the colouring fluid, without any privation of nutrition. In this case, the hairs may live and retain their hold, as we observe in young individuals:—and secondly, the canals, which convey the fluid into the hair may be obliterated, as in old age. The same cause, acting on the nutritious vessels of the bulb, produces, successively, privation of colour, death and loss of these epidermoid productions. According to other physiologists, the seat of colour is in the horny covering of the hair; and, in the largest hairs or spines of the por- cupine, this seems to be the case, the pith being manifestly white, and the horny covering coloured. The exact relations between the cuticle, the rete mucosum and the hair are not known. It is not determined, whether the layers are simply perforated by the hair in its passage outwards, or whether they furnish it coats as it proceeds along. There is often, however, an intimate relationship observed between the colour of the hair and that of the rete mucosum. The fair complexion is accompanied with light hair;—the swarthy with dark ;—and we see the connexion still more signally displayed in those animals, that are spotted—the colour of the hair being variegated like that of the skin. Hairs differ very materially, according to the part of the body on which they appear. In some parts they are short, as in the armpits, whilst on the head it is not easy to say what would be the precise limit to the growth, were they left entirely to nature. In the Ma- lay, it is by no means uncommon to see them touch the ground. The hair has various names assigned to it, according to the part on which it appears,—as beard, whiskers, mustachios, eyebrows, eye- lashes, &c. In many animals it is long and straight; in others crisped, when it is called wool. If stiff, it is termed a bristle; if in- flexible, a spine. For deadly fear can time outgo, And blanch at once the hair. Hard toil can roughen form and face, And want can quench the eye's bright grace, Nor does old age a wrinkle trace More deeply than despair." Scott's Marmion. * Traite de Physiologie m<5dicale et philosophique, Tom. iii. p. 42. Paris, 1832. 96 SENSE OF TOUCH. The hairs are entirely insensible, and, excepting in their bulbous portion, are not liable to disease. Dr. Bostock affirms, that under certain circumstances they are subject to a species of inflammation, when vessels may be detected, at least in some of them, and they become acutely sensitive. The sensibility of the hair, under any known circumstance, may, however, be doubted. It appears to be almost anorganic, except at its root; and, like the cuticle, resists putrefaction for a great length of time. Bichat and Gaultier were of the opinion of Dr. Bostock;—misled, apparently, by erroneous re- ports concerning the plica polonica; but Baron Larrey* has satisfac- torily shown, that the affection is confined to the bulbs, and that the hairs themselves continue totally devoid of sensibility. It is difficult to assign a plausible use for the hair. That of the head has already engaged our attention; but the hair, which appears on certain parts at the age of puberty and not till then, and that on the chin and upper lip of the male sex only, set our ingenuity at defiance. In this respect, however, the hair is not unique. Many physiologists regard certain parts, which exist in one animal, appa- rently without function, but which answer useful purposes in ano- ther, to be vestiges indicating the harmony which reigns through nature's works. The useless nipple on the breast of one sex might be looked upon in this light; but the tufts of hair on various parts can- not, in any way, be assimilated to the hairy coating, that envelopes the bodies of animals, and is, in them, manifestly intended as a pro- tection against cold. There is another class of bodies, connected with the skin, and analogous in nature to the last described,—the nails. These serve a useful purpose in touch, and consequently require notice here. In the system of De Blainville, they constitute a subdivision of the hairs, which he distinguishes into simple and compound—simple, when each bulb is separated, and has a distinct hair—compound, when several pileous bulbs are agglomerated, so that the different hairs, as they are secreted, are cemented together to form one solid body of greater or less size,—a nail, scale, horn, &c. In man, the nail alone exists, the chief and obvious use of which is to support the pulp of the finger, whilst it is exercising touch. Animals are pro- vided with horns, beaks, hoofs, nails, spurs, scales, &c. All these, like the hair, grow from roots, and are considered to be analogous in their physical and vital properties. Meckel, and De Blainville, Bonn, Walther, Lavagna,f and others, are, indeed, of opinion, that the teeth are of the same class, and that they belong originally, to the skin of the mouth. a For physiological purposes the above description is enough, and more than enough. A few words will be necessary regarding the mucous membranes, which resemble the skin so much in their proper- * M^moires de Chirurgie militaire, t. iii, 108. Paris, 1812. t Art Schleimhaute, in Pierer's Anat.Phys. Real. Worterb. vii, 272. Altenb. 1827. PHYSIOLOGY OF TOUCH. 97 ties, as to be, with propriety, termed dermoid. If we trace the skin into the various outlets, we find, that a continuous, soft, velvety membrane exists through their whole extent; and, if the channel have two outlets, as in the case of the alimentary canal, this mem- brane, at each outlet, commingles with the skin, and appears to differ but slightly from it. So much, indeed, do they seem to form part of the same organ, that physiologists have described the absorption, which takes place from the intestinal mucous membrane, as external. They cannot, however, in the higher order of animals, be considered completely identical; nor is the same membrane alike in its whole extent. They have all been referred to two great surfaces;—the gastro-pulmonary—comprising the membranes of the outer surface of the eye, of the ductus ad nasum, of the nose, of the mouth, and of the respiratory and digestive passages; and the genito-urinary— which line the whole of the genital and urinary apparatuses. In addition to these, a membrane of similar character lines the meatus auditorius externus, and the excretory ducts of the mammae. The analogy between the skin and mucous membranes is farther shown, by the fact, that if we invert the polypus, the mucous mem- brane gradually assumes the characters of the skin, and the same circumstance is observed in habitual descents of the rectum and uterus. In the mucous membranes—especially at their extremities, which appear to be alone concerned in the sense of touch—the same super- position of strata exists as in the skin—viz. epidermis, rete mucosum, corpus papillare, and cutis vera. They have likewise similar folli- cles, called mucous, but nothing analogous to the hairs, unless we re- gard the teeth to be so, in correspondence with the views of Meckel, De Blainville, and others. 2. Physiology of Tact and Touch. In describing the physiology of the sense of touch it will be con- venient to revert to the distinction, already made, between the sense when passively and when actively exerted, or between tact, and touch. The mode, however, in which the impression is made on each is alike, and equally simple. It is merely necessary, that the sub- stance, which has to cause it, should be brought in contact with the physical part of the organ—the cuticle; the nervous part is seated in the corpus papillare, for if the nerves proceeding to this layer of the skin be cut the sense is destroyed. In the exercise of touch, each of the layers seems to have its appropriate office: the corium, which forms the innermost layer—the base on which the others rest—offers the necessary resistance, when bodies are applied to the surface; the rete mucosum is either unconcerned in the func- tion, or keeps the corpus papillare in the necessary state of supple- ness: the erectile tissue, on which the papillae are grouped, probably aids them in their appreciation of bodies ; and the epidermis modifies the tactile impression, which might become too intense, or be pain- vol. i. 9 gg SENSE OF TOUCH ful, did this envelope not exist. The degree of perfection of the sense is, indeed, greatly influenced by the state of the cuticle. Where it is thin,—as upon the lips, glans penis, clitoris, &c—the sense is very acute ; but, where thick and hard, it is very obtuse ; and, where removed,—as by blistering,—the contact of bodies gives pain, but does not occasion the appropriate impressions of touch* It has been supposed, that some of the recorded instances of great resistance to heat have been caused by unusual thickness, and com- pactness of cuticle, together with a certain degree of insensibility of the skin. The latter may be an important element in the explana- tion, but some of the feats, executed by persons of the character alluded to, could hardly have been influenced by the former, as the resistance seemed almost equally great in the delicately organized mucous membranes. A Madame Girandelli,—who exhibited in Great Britain, many years ago,—was not only in the habit of draw- ing a box with a dozen lighted candles along her arm, and of putting her naked foot upon melted lead, but of dropping melted sealing- wax upon her tongue, and impressing it with a seal, without ap- pearing to experience the slightest uneasiness; and, some years ago, (1832,) a man of the name of Chabert excited in this country, the surprise, which followed his exhibitions in London a year or two previously, and which gained him the appellation of the " Fire King." In addition to the experiments performed by Madame Girandelli, Chabert swallowed forty grains of phosphorus, washed his fingers in melted lead, and drank boiling Florence oil with per- fect impunity. In the case of the phosphorus he professed to take an antidote, and doubtless did so. It is probable, also, that agents were used by him to deaden the painful impressions ordinarily pro- duced by hot bodies, when applied to the surface. A solution of borax or alum, spread upon the skin is said to exert a powerful effect of this kind ; but, in addition to the use of such agents, there must be a degree of insensibility about the corpus papillare, otherwise it is difficult to understand why these hot substances did not injure the coats of the stomach. We see, daily, striking differences in the sen- sibility of the mucous membrane of" the mouth and gullet, and are frequently surprised at the facility with which certain persons swal- low fluids, at a temperature, which would excite the most uneasy sensations in others. In this, habit has unquestionably much to dof. In the mucous membranes, tact is effected precisely in the same way as in the skin. The layers, of which it is constituted, partici- pate in like manner; but the sense is more exercised at the extremi- ties of the membrane than internally. The food, received into the mouth, is felt there, but after it has passed into the gullet it excites hardly any tactile impression, and it is not until it reaches the lower 'ft^S? TSi^^nlT^ Eft 1^.^-, Prof. Weber's experiment, vol. "*'<&;"£ ljT'i1°{flwana Bir " iJrewster'8 Letters ™ Natural Magic, Am'erV'Edit. p. 274. New York, looz. ° PHYSIOLOGY OF TOUCH. 99 part of the membrane, in the shape of excrement, that its presence is again indicated by this sense. Pathologically, we have some striking instances of this difference in the different parts of a mucous membrane. If an irritation exists within the intestinal canal, the only notice we may have of it is by itching of the nose,—in other words, at one of the extremities of the membrane. In like manner, a calculus in the bladder is indicated by itching of the glans penis. A similar exemplification is offered during the passage of a gall-stone through the ductus communis choledochus: calculi occasionally form in the biliary passages, and, after a time, enter the common duct in their way to the intes- tine: on their first entrance, the pain experienced is of the most violent character; this, after a time, subsides,—as soon, indeed, as the calculus has got fairly into the canal; but violent irritation is again experienced, when it is about to clear the duct, and enter the intestine. One of the great purposes of the sense of tact is to enable us to judge of the temperature of bodies. This office it executes alone. No other sense participates in it. It requires no previous exercise; is felt equally by the infant and the adult, and requires only the pro- per developement of its organs. The relative temperature of bodies is accurately designated by the instrument called the thermometer; very inaccurately by our own sensations, and the reason of this inaccuracy is sufficiently intelligible. In both cases, the effect is produced by the disengage- ment of a subtile fluid, called caloric or the matter of heat, which pervades all bodies, and is contained in them to a greater or less extent. This caloric is constantly passing, and repassing, between bodies, either by radiation or by positive contact, until they attain the like temperature, or until there is an equilibrium of caloric, and all have the same temperature as indicated by the thermometer. Hence, objects in the same apartment will exhibit, coeteris paribus, the like temperature by this test. From this law, however, the animal body must be excepted. The power which it possesses of generating its own heat, and of counteracting the external influences of temperature, preserves it constantly at the same point. This will fall under consideration in another place. Although, however, all objects may exhibit the same temperature, in the same apartment, when the thermometer is applied to them, the sensations experienced may be very different. Hence the diffi- culty, which the uninstructed have in believing that they are actually of identical temperature;—that a hearth-stone, for instance, is of the same degree of heat as the carpet in a chamber. The cause of the different sensations, experienced in the two cases, is, that the hearth- stone is a much better conductor of the matter of heat than the carpet. The consequence is, that caloric is more rapidly abstracted by it from the part of the body, which comes in contact with it, than it is by the carpet; and the stone appears to be the colder of the two. For the same reason, when these two substances are raised in tern- 100 SENSE OF TOUCH. perature above that of the human body, the hearth-stone will appear the hotter of the two; because, it conducts caloric and communi- cates it more rapidly to the body than the carpet.* When the temperature of the surrounding air is higher than 98°, we receive caloric from the atmosphere, and experience the sensa- tion of heat. The human body is capable of being penetrated by the caloric of substances exterior to it, precisely like those sub- stances themselves; but, within certain limits, it possesses the faculty of consuming the heat and retaining the same temperature. When the temperature of the atmosphere is only as high as our own— an elevation which it not unfrequently attains in many parts of the United States—we still experience the sensation of unusual warmth: yet no caloric is communicated to us. The cause of this feeling is, that we are accustomed to live in a medium of a less elevated temperature, and consequently to give off caloric habitually to the atmosphere. Lastly, in an atmosphere of a temperature much lower than that of the body, heat is incessantly abstracted from us; and, if rapidly abstracted, we have the sensation of great cold. From registers, kept by the illustrious founder of the University of Virginia, Mr. Jefferson, at his residence at Monticello,f lat. 37°, 58', long. 78°, 40', it appears, that the mean temperature of this part of Virginia is about 55^ or 56°; that the thermometer varies from 5^° in the coldest month, to 94° in the warmest. Now, the tem- perature of the human body being 98°, it follows, that heat must be incessantly taken from us, and that we ought therefore to expe- rience constantly the sensation of cold; and this we should unques- tionably do, were we not protected by clothing, and aided by the artificial temperature of our fires during the colder seasons. Yet, accustomed as the body is to give off caloric, there is a tem- perature, in which, clothed as we are, we do not feel cold, although we may be disengaging heat to some extent. This temperature may perhaps be fixed somewhere between 70° and 80°, in the cli- mate of the middle portions of the United States. So much, how- ever, are our sensations in this respect dependent upon the tempera- ture, which has previously existed, that the comfortable point will be found to vary at different seasons. If the thermometer, for instance, has ranged as high as 98°, and if, for a few days, it has maintained this elevation, a depression of 15° or 20° will be accompanied by feelings of discomfort; whilst a sudden elevation from 30° to 75° may occasion an oppressive feeling of heat. During the voyages, made by Captain Parry and others, to discover a north-west pas- sage, it was found, that after having lived for some days in a tem- perature of 15° or 20° below 0, it felt quite mild and comfortable when the thermometer rose to zero. This is the great source of the deceptive nature of our sensations * Turner's Elements of Chemistry, 5th Amer. Edit., by Dr. F. Bache, p. 5. Philad. 1835. f Virginia Literary Museum, p. 26. Charlottesville, 1830. PHYSIOLOGY OF TOUCH. 101 of warmth and cold. They enable us merely to judge of the com- parative conditions of the present and the past; hence it is, that a deep cellar appears warm to us in winter and cold in summer. At a certain distance below the surface, the temperature of the earth in- dicates the medium heat of the climate; yet, although this may be stationary, our sensations on descending to it in winter and in sum- mer would be by no means the same. If two men were to meet each other on the middle of the South American Andes,—the one having descended, and the other ascended,—their sensations would be very different. The one, who had descended, coming from a colder to a warmer atmosphere, would feel warm; whilst the tra- veller, who had ascended, would feel correspondently cool. An experiment, often performed in the chemical lecture-room, although strictly physiological, exhibits the same fact. If, after having held one hand in iced water, and the other in warm water, we plunge both into water of a medium heat, it will seem warm to the one hand and cold to the other. But our sensations are not guided solely by bodies surrounding us. They are often greatly dependent, especially in disease, on the state of the animal economy itself. If the power, which the sys- tem possesses of forming heat, be morbidly depressed—or if, in consequence of old age, or of previous sickness, calorification does not go on regularly and energetically, a temperature of the air, which to the vigorous is agreeable, may produce an unpleasant im- pression of cold. Under opposite circumstances, a feeling of heal may exist. By tact we are likewise capable of forming a judgment of many of the qualities of bodies,—such as their size, consistence, weight, distance, and motion. This faculty, however, is not possessed ex- clusively by the sense in question. We can judge of the size of bodies by the sight; of distances, to a certain extent, by the ear, &c. To appreciate these characteristics, it is neccessary, that the sense should be used actively, and that we should call into exercise the admirable instrument with which we are provided for that purpose. In treating of the external senses generally, it was remarked, that we are capable of judging, by their aid, of impressions made on us by portions of our own body. By the sense of touch we can de- rive information regarding its temperature, shape, consistence, &c. An opinion has, indeed, been advanced, that this sense is best adapted for proving our own existence, as every time that two por- tions of the body come into contact, two impressions are conveyed to the brain, whilst if we touch an extraneous body we have but one. The tact of the mucous membranes is extremely delicate. The great sensibility of the lips, tongue, conjunctiva, Schneiderian mem- brane, lining membrane of the trachea and urethra is familiar to all. Excessive pain is produced in them by the contact of extraneous bodies; yet, in many cases, we see the effect of habit in blunting sensation singularly exemplified. The first introduction of a bougie 9* 102 SENSE OF TOUCH. into the urethra will produce intense irritation; but after a few re- petitions the sensation may become scarcely disagreeable. To appreciate accurately the shape and size of objects, it is neces- sary, that they should be embraced by a part of the body, which can examine their various surfaces and be applied to them in every direction. In man, the organ well fitted for this purpose is the hand. This is situated at the free extremity of a long and flexible member, which admits of its being moved in every direction, and renders it not only well adapted for the organ of touch but for that of pre- hension, as will be seen in another place. Man alone possesses a true hand; for although other animals have organs of prehension very similar to his, they are much less complete. Aristotle, indeed, and Galen term it the instrument of instruments. The chief supe- riority" of the hand consists in the size and strength of the thumb, which stands out from the fingers, and can be brought in opposition to them, so as to enable us to grasp bodies, and to execute various mechanical processes under the guidance of the intellect. So im- portant an organ was the thumb esteemed by Albinus,* that he called it a lesser hand assisting the larger—" manusparva majori adjutrix,"^ and the construction of the hand has been considered worthy of forming the subject of one of the " Bridgewater Treatises"—" on the power, wisdom, and goodness of God, as manifested in the creation," —a task assigned to Sir Charles Bell.J In addition to the advantages referred to, the hand is furnished with a highly sensible integument. The papillae are largely de- veloped, especially at the extremities of the fingers, where they are ranged in concentric circles, and rest upon a spongy tissue, by many physiologists considered to be erectile, and, serving as a cushion. At the posterior extremity of the fingers, the nails are situate, which support the pulps of the fingers behind, and render the contact with bodies more immediate. This happy organization of the soft parts of the hand alone concerns the sense of touch di- rectly. The other advantages, which it possesses, relate to the power of applying it under the guidance of volition. Of the mode in which touch is effected it is not necessary to treat: —being nothing more than tact, exerted by an appropriate instru- ment, the physiology of the two must be identical. Metaphysicians have differed widely regarding the services that ought to be attributed to the touch. Some have greatly exaggerated them, considering it the sense par excellence or theirs* of the senses. It is an ancient notion to ascribe the superiority of man over ani- mals and his pre-eminence in the universe—his intelligence, in short * De Sceleto, p. 465. t Lawrence's Lectures on Physiology and Zoology, &c. Lond. 1819 t The Hand, its mechanism, and vital endowments, as evincing de«i„n imof VA\t Philad. 1833. See also, Kidd on the adaptation of external 2toT* Phy" eal con" dition of man. (Bridgewater Treatise) Amer. Edit. Philad. 1833, p 33 J PHYSIOLOGY OF TOUCH. 103 —to the hand. Anaxagoras asserted, and Helvetius* revived the idea, " that man is the wisest of animals because he possesses hands." The notion has been embraced, and expanded by Condillac,f Buffon,J and many modern physiologists and metaphysicians. Buffon, in particular, assigned so much importance to the touch, that he be- lieved the cause, why one person has more intellect than another, is, his having made a more prompt and repeated use of his hands from early infancy. Hence he recommended, that infants should be al- lowed to use them freely from the moment of birth. Other metaphysicians have considered the hand the source of our mechanical capabilities; but the same answer applies to all these views. The hand can only be regarded as an instrument by which information of particular kinds is conveyed to the brain, and by which other functions are executed, under the direction of the will. The idiot has the sense frequently more delicate than the man of genius or than the best mechanician, whilst the most ingenious artists have by no means the most delicate touch. We have, indeed, some striking cases to show, that the hand is not entitled to this extrava- gant commendation. Not many years ago, a Miss Biffin was exhi- bited in London, who was totally devoid of both upper and lower extremities ; yet she was unusually intelligent and ingenious. It was surprising to observe the facility with which she hem-stitched, turn- ing the needle with the greatest rapidity in her mouth, and inserting it by means of the teeth. She also painted miniatures faithfully, and beautifully;—holding the pencil between her head and neck. All her motions were, in fact, confined to the tongue and lips, and to the muscles of the neck. Magendie,§ alludes to a similar case. He says, that there was, at that time, in Paris, a young artist, who had no signs of arm, fore- arm, or hand, and whose feet had one toe less than usual—the second; yet his intelligence was, in no respect, inferior to that of boys of his own age; and he even gave indications of distinguished ability. He sketched and painted with his feet. Within the last few years, a Miss Honeywell, born without arms, has travelled about this country. She has acquired so much dexterity in the use of the scis- sors, as to be able, by holding them in her mouth, to cut likenesses, watch-papers, flowers, &c. She also writes, draws, and executes all kinds of needlework with the utmost ease and despatch. How fatal are these authentic examples to the views of Helvetius, and others! But, it has been said, the touch is the least subject to error of all the senses, and that it is the regulating—the geometrical sense. In part only is this accurate. It certainly possesses an advantage in allow- ing the organ to be brought into contact with the body that excites the impression, whilst, in the cases of vision and olfaction, the organ * De I'Homme, &c. Tom. I. f Trait6 des Sensations, P. I. X Histoire Naturelle, T. vi. § Precis Etementaire, 2nde edit. I. 154. Paris, 1825. 104 SENSE OF TOUCH. receives only the impression of an emanation from the body; and, in that of audition, only a vibration of an intervening medium. Yet some of the errors into which it falls are as grievous as those that happen to the other senses. How inaccurate is its appreciation of the temperature of bodies! We have attempted to show, that it affords merely relative knowledge,—the same substance appearing hot or cold to us, according to the temperature of the substance previously touched. Nay, this infallibility so little exists, that we have the same sensation communicated to us by a body, that rapidly abstracts caloric from us, as by one that supplies it rapidly. By touching frozen mercury, which requires a temperature of—40° of Fahrenheit to congeal, we experience the sensation of a burn ! Again, if we cross the fingers and touch a rounded body—a mar- ble, for instance—with two of the pulps at the same time; instead of experiencing the sensation of one body, we feel as if there were two,—an illusion produced by the lateral portions of fingers being brought in opposition, which are naturally in a different situation, and at a distance from each other; and, as these two parts habitu- ally receive distinct impressions when apart, they continue to do so when applied to opposite sides of the rounded body. It has been asserted, again, that the touch is the great corrector of the errors into which the other senses fall. But let us inquire, whether, in this respect, it possesses any decided superiority over the other senses. For this purpose, it is well to adopt the distinction of the functions of the senses into immediate and mediate. Each sense has its immediate function, which it possesses exclusively ; for which, in other words, no other can be substituted. The touch instructs us regarding temperature; the taste appreciates savours; the smell, odours ; audition, sound ; and vision, colours*. These are the imme- diate functions of the senses, each of which can be accomplished by its own organs, but by no other. As concerns the immediate func- tions of the senses, therefore, the touch can afford no correction. Its predominance, as regards the mediate functions of the senses, is like- wise exaggerated. The mediate functions are those that are auxili- ary to the senses, consisting in the impressions they furnish to the mind, and by aid of which it acquires its notions of bodies. The essential difference between these two sets of functions is,—that the mediate can be effected by several senses at once. Vision, olfaction, and audition, participate in judging of distances, as well as touch; the sight instructs us regarding shape, &c. It has, indeed, been af- firmed by metaphysicians, that the touch is necessary to several of the senses to give them their full power, and that we could form no notion of the size, shape, and distance of bodies, unless instructed by this sense. The remarks, already made, have proved the inaccuracy of this opinion. The farther examination of it will be resumed un- der the subject of vision.. The senses are, in truth, of mutual assis- tance. If the touch falls into error as in the case of inaccurate ap- preciation of temperature, the sight, aided by appropriate instru- ments, dispels it. It the crossed fingers convey to the brain the sen- PHYSIOLOGY OF TOUCH. 105 sation of two rounded bodies, when one only exists, the sight ap- prises us of the error; and if the sight and touch united impress us with a belief in the identity of two liquids, the smell or the taste will often detect the erroneous inference. But, it has been said by some, touch is the only sense that gives us any notion of the existence of bodies. Destutt-Tracy* has satis- factorily opposed this, by showing that our notion of the existence of bodies is a work of the mind, in acquiring which the touch does not assist more immediately than any other sense. " The tactile sensations," he observes, " have not of themselves any prerogative essential to their nature, which distinguishes them from every other. If a body affect the nerves beneath the skin of my hand, or if it pro- duce certain vibrations in those distributed on the membranes of my palate, nose, eye, or ear, it is a pure impression which I receive; a simple affection which I experience; and there seems to be no reason for believing that one is more instinctive than another; that one is more adapted than another for enabling me to judge that it proeeeds from a body exterior to me. Why should the simple sensation of a puncture, burn, titillation, or pressure, give me more knowledge of the cause, than that of a colour, sound, or internal pain? There is no reason for believing it." There are, indeed, numerous classes of bodies, regarding whose existence the touch affords us not the slightest information, but which are detected by the other senses. On the whole, then, we must conclude, that the senses mutually aid each other in the execution of certain of their functions; but that each has its province, which cannot be invaded by any of the others; and that too much preponderance has been ascribed to the touch by metaphysicians and physiologists. Administering, how- ever, so largely to the mind, it has been properly ranked with vision and audition as an intellectual sense.f By education, the sense of touch is capable of acquiring extraor- dinary acuteness. To this circumstance we must ascribe the sur- prising feats we occasionally meet with in the blind. Saunderson, —who lost his eyesight in the second year of his life, and was Pro- fessor of Mathematics at Cambridge, England,—could discern false from genuine medals, and had a most extensive acquaintance with numismatics.! Baczko, referred to by Rudolphi,§ and who describes his own case, could discriminate between samples of woollen cloth of equal quality but of different colours. The black appeared to him among the roughest and hardest; to this succeeded dark blue and dark brown, which he could not, however, distinguish from each other. The colours of cotton and silk stuff he was unable to discriminate, and he properly enough doubts the case of a Count Lynar, who was blind, and said to be capable of judging of the * Etemens d'Ideologie, Partie 1.114. 2d. edit. Paris, 1804. + Gall, sur les Fonctions du Cerveau, I. 99. Paris, 1825. X Abercrombie's Inquiries concerning the Intellectual Powers; Amer. edit. p. 55. New York, 1832. § Grundriss der Physiologie, Berlin, 1821, &c. 106 SENSE OF TASTE. colour of a horse by the feel. The only means the blind can possess of discriminating colours must be through the inequalities of surface produced by them; and if these were insufficient to enable Baczko to detect the differences between cotton and silk fabrics, it is not pro- bable, that the sleek surface of the horse would admit of such dis- crimination. In animals the organ of touch varies. The monkey's resembles that of man. In other quadrupeds it is seated in the lips, snout, or proboscis. In molluscous animals the tentacula, and in insects, the antennae or feelers, are organs of touch, possessing, in some, very great sensibility. Bats appear to have this sensibility to an unusual degree. Spallanzani observed these animals, even after their eyes had been destroyed and ears and nostrils shut up, flying through intricate passages, without striking against the walls, and dexterously avoiding cords and lines placed in their way. The membrane of the wings is, in the opinion of many, the organ that receives the impres- sion produced by a change in the resistance of the air. M. Jurine, indeed, concludes that neither the sense of touch, hearing, nor smell is the medium through which bats obtain perceptions of the pre- sence and situation of surrounding bodies. He ascribes this extra- ordinary faculty to the great sensibility of the skin of the upper jaw, mouth, and external ear, which are furnished with very large nerves; whilst Sir Anthony Carlisle attributes it to the extreme delicacy of hearing possessed by the animal ;* but certain experiments, made by Mr. Broughton,f sanction the idea, that it may be dependent upon their whiskers. These whiskers, which are found on the upper lip of feline and other animals, are plentifully supplied with nerves, which seem to proceed from the second branch of the fifth pair, and are lost in the substance of the bristles. In an experiment, which Mr. Broughton made on a kitten, he found that whilst the whiskers were entire, it was capable of threading its way, blindfold, out of a labyrinth, in which it was designedly placed; but that it was totally unable to do so when the whiskers were cut off. It struck its head repeatedly against the sides ; ran against all the corners; and tum- bled over steps placed in its way, instead of avoiding them, as it did prior to the removal of the whiskers. From facts like these Mr. Broughton drew the conclusion, that certain animals are supplied with whiskers for the purpose of ena- bling them to steer clear of opposing bodies in the dark. SECT. II.--SENSE OF TASTE OR GUSTATION. The sense of taste teaches us the quality of bodies called sapidity. It is more nearly allied to touch, in its mechanism, than any other of the senses, as it requires the immediate contact of the body with the organ of taste; and as that organ is, at the same time, capable of receiving tactile impressions distinct from those of taste. Of this * Roget's Animal and Vegetable Physiology, ii. 399, Amer. edit., Phila. 1836 f London Medical and Physical Journal, for 1823. ORGANS OF TASTE. 107 we have a striking example. If we touch various parts of the tongue with the point of a needle, we find two distinct perceptions occasioned. In some parts we experience the sensation of a pointed body without savour; and in others a metallic taste is manifested. Pathological cases, too, exhibit, that the sense of taste may be lost, whilst the general sensibility remains,—and conversely. The organ of gustation is not, therefore, restricted to the production of that sense, but participates in the sense of touch. Yet so distinct are those functions, that the touch can, in no wise, supply the place of its fel- low, in detecting the sapidity of bodies. This last is the immediate instruction afforded by gustation. 1. Anatomy of the Organs of Taste. The chief organ of taste is the tongue, or rather the- mucous membrane covering the upper surface, and sides of that organ. The lips, inner surface of the cheeks, the palate, and fauces, participate in the function, especially when particular savours are concerned. Magendie* includes the oesophagus and stomach, but we know not on what grounds. His subsequent remarks, indeed, controvert the idea. The lingual branch of the fifth pair is, according to him, in- contestably the nerve of taste; and, as this nerve is distributed to the mouth, we can understand, why gustation should be effected there, but not how it can be accomplished in the oesophagus and stomach. The tongue consists almost entirely of muscles, which give it great mobility, and enable it to fulfil the various functions assigned to it; for it is not only an organ of taste, but of mastica- tion, deglutition, and articulation. These muscles, being under the influence of volition, enable the sense to be executed passively or actively. As regards gustation, the mucous membrane is the portion that immediately concerns us. This is formed, like the mucous mem- branes in general, of the different layers already described. The corpus papillare, however, requires additional notice. If the sur- face of the tongue be examined, it will be found to consist of my- riads of fine papillae or villi, giving the organ a velvety appearance. These papiLlae are, doubtless, formed like those of the skin, of the final ramifications of nerves, and of the radicles of exhalent and absorbent vessels, united by means of a spongy erectile tissue. Great confusion exists among anatomists in their descriptions of the papillae of the tongue. Those concerned in the sense of taste may, however, all be included in two divisions:—1st, the conical or py- ramidal,—the finest sort being by some called filiform; and 2dly, the fungiform. The former are broader at the base than at the top, and are seen over the whole surface of the tongue, from the tip to the root. The latter, which are larger at the top than at the base, and resemble the mushroom,—whence their name,—are spread * Precis de Physiologie, I. 139. 108 SENSE OF TASTE. Fig. 17. about, here and there, upon the surface of the organ. These papillae of taste must be distinguished from a third set, the papillce capitate, which are mucous follicles, and of course accomplish a very dii- ferent function. All the nerves, that pass to the parts whose office it is to appreciate savours, must be considered to belong to the gustatory apparatus. These are the inferior maxillary, several branches of the su- perior, filaments from the spheno-palatine and naso-pala- tine ganglions, the lingual branch of the fifth pair, the whole of the ninth pair or hypoglossal, and the glosso- pharyngeal. To which of these must be assigned the function of gustation we shall inquire presently. Like the skin and mucous membranes in general, that of the tongue and mouth con- tains, in its substance, nume- rous mucous follicles, which secrete a fluid that lubricates the organ, and keeps it in a condition best adapted for the accomplishment of its func- tions. Some of these are placed very conspicuously in the mucous membrane of the tongue. They are the papillce capi- tatceofmany anatomists,—erroneously named, as they are not formed like the papillae, and, as we have said, execute a very different office. They are mucous follicles, and ought to be so called. They are situated near the base of the tongue, and the last perceptible rows unite anteriorly at an angle close to the foramen ccBcum of Mor- gagni. (Fig. 17.) The fluids, exhaled from the mucous membrane of the mouth, and the secretion of the different salivary glands like- wise aid in gustation; but they are more concerned in mastication and'in salivation, and will require notice under another head. 2. Of Savours. Before proceeding to explain the physiology of gustation, it will be necessary to inquire briefly into the nature of bodies, connected with their sapidity, or, in other words, into savours, which are the cause of sapidity. o. Foramen of Morgagni. b. Fungiform pa- pills, c. Conical papillae, d. Papillae capitats. e. Epiglottis. SAVOURS. 109 The ancients were of opinion, that the cause of sapidity is a pe- culiar principle, which, according to its combination with the con- stituents of bodies, gives rise to the various savours that are found to exist. This notion has long been abandoned; and chiefly, be- cause we observe no general or common characters amongst sapid bodies, which ought to be expected if they were pervaded by the same principle ; and because it is found, that bodies may be deprived of their sapidity by subjecting them to appropriate agents. Many of our culinary processes have been instituted for this purpose: the infusion of tea is indebted for all its attractions to the power we possess of separating, by. boiling water, its savoury from its insipid portions. A savour must, therefore, be esteemed an integrant mole- cule of a body ; not identical in all cases, but as heterogeneous in its nature as the impressions that are made upon the organ of taste. When the notion was once entertained, that savour is an inte- grant molecule, sapidity was attempted to be explained by the shape of the molecule. It was said, for instance, that if the savour be sweet, the molecule must be round; if sharp, angular; and so forth. Sugar was said to possess a spherical,—acids, a pointed or angular molecule. We know, however, that substances, which resemble each other in the primitive shape of their crystal, impress the .organ of taste very differently; and that solution which must destroy most —if not all—of the influence from shape, induces no change in the savour. Others have referred sapidity to a kind of chemical action be- tween the molecules and the nervous fluid. This view has been suggested by the fact, that, as a general principle, sapid bodies, like chemical agents, act only when in a state of solution ; that the same savours usually belong to bodies possessed of similar chemical pro- perties as is exemplified by the sulphates and nitrates; and that, in the action of acids on the tongue and mouth, we witness a state of whiteness and constriction, indicative of a first degree of combina- tion. All these circumstances, however, admit of another explana- tion. There are unquestionably many substances, which do combine chemically,—not with a nervous fluid, of whose existence we know nothing,—but with the mucus of the mouth, and the sapidity re- sulting from such combination is appreciated by the nerves of taste; but there are many bodies, which are eminently sapid, and yet afford us instances of very feeble powers of chemical combination; nay, in numerous cases, we have not the least evidence that such powers are existent. Vegetable infusions or solutions afford us strong examples of this kind,—of which syrup may be taken as the most familiar. The effect of solution is easily intelligible; the particles of the sapid body are in this way separated and come suc- cessively into contact with the gustatory organ; but there is some reason to believe, that solution is not always requisite to give sa- pidity. Metals have generally a peculiar taste, which has been denominated metallic; and this, even if the surface be carefully rubbed, so as to free it from oxide, which is more or less soluble. vol. i. 10 110 SENSE OF TASTE. Birds, too, whose organs of taste are as dry as the corn they select from a mass of equally arid substances, are probably able to ap- preciate savours. The taste produced by touching the wires of a galvanic pile with the tongue has been offered as another instance of sapidity exhibited by dry bodies. This is, more probably, the effect of that chemical action on the fluids covering the mucous membrane of the tongue, which always follows such contact. Such chemical change must, however, be confined to these fluids, and when once produced, the nerve of taste is compelled to appreciate the savour developed in the same manner as it does in cases of mor- bid alterations of the secretion of the mucous membrane, when, it is well known, that a body possessing considerable and peculiar sapidity, may fail to impress the nerves altogether, or may do so inac- curately. The notion of any chemical combination with the nervous fluid must of course be discarded. There is not the slightest shadow of evidence in favour of the hypothesis. Yet the epithet chemical was once applied to this sense on the strength of it, in opposition to the senses of touch, vision, and audition, which w7ere called mecha- nical, and supposed to be produced by vibration of their nerves. The savours, met with in the three kingdoms of nature, are innu- merable. Each body has its own, by which it is distinguished: but few instances occur in which any two can be said to be identical. This is the great source of difficulty, when we attempt to throw them into classes, as has been done by many physiologists. Of these classifications, the one by Linnaeus* is the best known. It will eluci- date the unsatisfactory character of the whole: he divided sapid bodies into sicca, aquosa, viscosa, salsa, acida, styptica, dulcia, pin- guia, amara, acria, et nauseosa. He gives also examples of mixed savours—the acido-acria, acido-amara, amaro-acria, amaro-acerba, amaro-dulcia, dulci-styptica, dulci-acida, dulci-acria and acri-vis- cida; and he remarks, that the majority are antitheses to each other, two and two, as the dulcia and acria; the pinguia and styptica; the viscosa and salsa; and the aquosa and sicca. Boerhaavef again divides them into primary and compound; the former including the sour, sweet, bitter, saline, acrid, alkaline, vinous, spirituous, aromatic, and acerb;—the latter resulting from the union of some of the pri- mary savours. J There is, however, no accordance amongst physiolo- gists regarding those that should be esteemed primary, and those that are secondary and compound ; although the division appears to be fairly admissible. The acerb, for example—which is con- sidered primary by Boerhaave—is by others, with more propriety, classed among the secondary or compound, and believed to consist of a combination of the acrid and acid. Still we understand suffi- ciently well the character of the acid, acrid, bitter, acerb, sweet, &c.; but when, in common language, we have to depict other savours, * Amcenit. Academ. ii. 335. x Prol™* a„ j m _ :„ X Lepelletier, Physiologie Medicale, p. 66. Paris, 1832 ACadem' TwL "' OF SAVOURS. Ill we are frequently compelled to take some well known substance as the standard of comparison. According to Adelon,* the only distinction, which we can make amongst them, is,—into the agreeable and the disagreeable. Yet of the unsatisfactory nature of this classification he himself adduces nume- rous and obvious proofs. It can only, of course, be applicable to one animal species, often even to an individual only; and often " again only to this individual, when in a given condition. Animals are known to feed upon substances, which are not only disagreeable but noxious to other species. The most poisonous plants in our soil have an insect which devours them greedily and with impunity: the southern planter is well aware, that this is the case with his tobacco, unless the operation of worming be performed in due season. The old adage, that " one man's meat is another man's poison," is meta- phorically accurate. Each individual has, by organisation or asso- ciation, dislikes to particular articles of food, or shades of difference in his appreciation of tastes, which may be regarded peculiar; and in certain cases these peculiarities are signal and surprising. Of the strange differences, in this respect, that occur in the same individual under different circumstances, we have a common and forcible instance in the pregnant female, who often has the most ardent desire for substances, which were previously perhaps repug- nant to her, or at all events not relished. The sense, too, in certain diseases—especially of a sexual character, or which are connected with the state of the sexual functions—becomes remarkably depraved, so that substances, which can, in no way, be ranked as eatables, are greedily sought after. Only a short time ago, a young lady was under the care of the author, whose greatest bonne bouche was slate pencils. At other times, we find chalk, brick-dust, ashes, dirt, &c. obtaining the preference. Habit, too, has considerable effect in our decisions regarding the agreeable. The Roman liquamen or garum, the most celebrated sauce of antiquity, was prepared from the half putrid intestines of fish; and one of the varieties of.the 0 ternal belonging to the membrane of the cavity of the tympanum ; and the middle being the membrane proper. On its inner side is distributed the nerve, called chorda tympani, and its centre affords attachment to one extremity of the chain of small bones,—to the handle of the malleus. The proper tissue of the membrana tympani is dry, and it is ge- nerally esteemed to be devoid of fibres, vessels, and nerves. Sir Everard Home,* however, asserts, that the membrane is muscular; that its fibres run from the circumference towards the centre, and are attached to the malleus ; and that if the membrane of the human ear be completely exposed on both sides, by removing the contigu- ous parts, and the cuticular covering be washed off from its ex- ternal surface, and if it be placed in a clear light, the radiated direc- tion of its fibres may be easily detected. This fibrous arrangement, Sir Everard conceives to be muscular, and on this he founds some ingeni- ous speculations, to be hereafter noticed, regarding the appreciation of sounds. The discovery of a fibrous structure would, however, by no means prove, that the membrane is capable of contracting; or that it is formed of muscular tissue. Many of the ligaments, which consist of gelatine, and are consequently not contractile like muscles, are distinctly fibrous in their arrangement. The same may be said of the tendons, whose utility, as conductors of the force developed by the muscle, would be materially interfered with, were they pos- sessed of the same degree of contractility. Again, Ruysch,f Sir Everard Home, and Sir Charles Bell J affirm, that the membrana tympani is very vascular,—Sir Everard assert- ing, that the vessels, in their distribution, resemble those of the iris, and are nearly half as numerous;—their general direction being from the circumference to the handle of the malleus. It is not easy * Philos. Transact, for 1800, P. I., p. 1, and Lectures on Comp. Anat., iii. 262. Lond., 1823. + Epist. Anat. octava, p. 10. Amstel., 1724. X Anat. and Physiol,, edited by J. D. Godman, 5th Amer. edit., ii. 253, New York, 1827. 12* 138 SENSE OF HEARING. to account for this discrepancy amongst anatomists, as to the struc- ture of the membrana tympani. A part of it is probably referable to some having directed their attention to the membrane proper; others to the membrane with its dermoid coverings, which are highly vascular. The inner extremity of the drum is partly osseous, partly mem- branous. Nearly opposite the centre of the "membrana tympani is the foramen ovale or vestibulare, called the fenestra ovalis or vesti- bularis, situated vertically, and forming a communication between the middle and the internal ear. It is closed by a membrane, con- sisting, like the membrana tympani, of three layers, to which is at- tached the base of the stapes,—the inner extremity of the chain that stretches across the cavity. Immediately below the foramen ovale is the bony projection, called the promontory; and beneath this again, a second opening, called the foramen rotundum or cochleare or fenestra rotunda or cochlearis, which forms a communication be- tween the middle ear and the external scala of the cochlea. This foramen is closed by a membrane, similar to that of the foramen ovale ; but not, like it, parallel, or nearly so, to that of the tympanum, —being situated obliquely. There is no communication by a chain of bones between it and the membrana tympani. These small bones, or ossicles are four in number, so connected with each other as to form a bent lever; one extremity of which is attached to the tympanic surface of the membrana tympani,—the other to the membrane of the foramen ovale. These bones are usually termed, from their shape—beginning with the most external, and following their order—malleus, incus, os orbiculare, (by some not considered a distinct bone, but a process of the incus) and stapes. A small muscular apparatus,—consisting of three muscles, the anterior muscle of the malleus; the internal muscle of the same bone; and the muscle of the stapes,—is attached to the chain, which it can stretch or relax ; and of course it produces a similar effect upon the mem- branes to which the chain is attached. They are animated by branches of the portio dura, or facial nerve, which is itself not a nerve of sensibitity, but of motion; yet probably acquires this function by its union with the vidian twig of the fifth pair, in its passage through the aqueduct of Fallopius. It is this nerve which furnishes the chorda tympani. Bellingeri* thinks, that the fifth pair regulates altogether the involuntary motions of the internal ear. At the anterior and inferior part of the cavity is the tympanic extremity of a canal, through which the drum receives the air it contains. This canal, called the Eustachian tube, is about two inches long, and proceeds obliquely forwards and inwards, to the lateral and superior part of the pharynx, into which it opens behind the posterior nares. It is partly osseous, partly fibro-cartilaginous and membranous; and, towards its pharyngeal extremity, it expands, terminating by an oval aperture, resembling a cleft. Throughout * Op. citat, and Edinb. Medical and Surgical Journal, July, 1834, p. 128. ORGAN OF HEARING. 139 its course it is lined by a mucous membrane, which appears to be a prolongation of that of the nasal fossae, and it is capable of being more or less contracted and expanded by the muscles, which com- pose and move the velum palati. The cavity of the tympanum likewise communicates, by a short and ragged canal, with numerous cells contained in the mastoid process. These cells open into each other, and vary in number, size, and arrangement in different individuals, and animals. They are called the mastoid cells. The cavity is larger in those animals, whose sense of hearing is most acute. In man, it is about a quarter of an inch deep, and half an inch broad. It is lined by a prolongation of the same membrane, as that which lines the Eustachian tube. This membrane, as we have seen, covers the membrana tympani, and the membranes of the foramen ovale, and foramen rotundum. It likewise lines the mastoid cells, and is reflected over the small bones. The middle ear does not exist in every animal endowed with hearing. It does not begin to appear lower in the scale than in reptiles; and is by no means equally complex in all. Frequently, the chain of bones is entirely wanting; and at other times we find one bone only. 3. The internal ear or labyrinth is the most important part of the apparatus. It consists of several irregular cavities in the pars petrosa of the temporal bone, in which the nerve of audition is dis- tributed. It is, consequently, in this portion, that the physical part of audition terminates, and the nervous begins. The labyrinth comprises the vestibule, semicircular canals, and cochlea. The vestibule—as its name imports—is the hall, that communi- cates with all the other cavities of the labyrinth. It would appear to be the most essential part of the organ, as it often exists alone. At its inner surface are numerous small foramina, which communi- cate with the bottom of the meatus auditorius internus, and through which the filaments of the auditory nerve reach the labyrinth. Ex- ternally, it communicates with the cavity of the tympanum by the foramen ovale. Posteriorly, it opens into the semicircular canals by five foramina; and, anteriorly, by a single foramen, into the internal scala of the cochlea. There is, also, posteriorly and in- feriorly, near the common orifice of the two vertical semicircular canals, the opening of a small, bony duct, which terminates inter- nally at the posterior surface of the petrous portion of the temporal bone. This duct is called the aquseductus vestibuli. The semicircular canals are three in number, and occupy the hinder part of the labyrinth. They are called superior vertical, posterior vertical, and horizontal. They are cylindrical cavities, curved semicircularly, and are more expanded at their vestibular origin, which has been therefore called ampulla. They are consti- tuted of a plate of bone, situated in the spongy tissue of the pars petrosa, and all of them communicate with the vestibule. The cochlea is the most anterior portion of the labyrinth. It is 140 SENSE OF HEARING. so called in consequence of its resemblance—in man and in the mammalia—to a snail's shell; hence also, its French and German names, limacon and schnecke. It is the most intricate part of the organ of hearing, and does not, by any means, admit of easy de- scription. It is a conoidal canal, spirally convoluted, making two turns upon itself and resting on a bony nucleus or pillar, called modiolus. The base of the nucleus is concave; corresponds to the bottom of the meatus auditorius internus, and is pierced by small foramina, through which the filaments of the auditory nerve reach the cochlea. The spiral canal is divided, in its whole length, by a partition, half osseous and half membranous, called the lamina spiralis: so that two distinct tubes are thus formed. These are the scales of the cochlea. At the apex of the cochlea they run into each other; but, at the base, the one turns into the vestibule, and is hence called the superior or vestibular or internal scala; the other communicates with the cavity of the tympanum by the foramen rotundum, and is called the inferior, tympanic, or external scala. At this scala, near the foramen rotundum, a bony canal begins, which proceeds towards the posterior surface of the pars petrosa on which it opens. It is the aquceductus cochlea1. The cochlea does not exist in all animals that hear. It is not, therefore, of essential importance. It varies, too, greatly, in compli- cation, in different animals. In birds, whose hearing is extremely delicate, it merely consists of a short, hollow, bony process, divided into two scalae but without any spiral arrangement. In reptiles, the cochlea is still more imperfect; and in many species it can scarcely be said to exist. In fishes there is no trace of it. The different cavities of the internal ear are lined by an extremely delicate membrane. In many animals this membrane alone exists without any bony parietes. It exhales at its inner surface a limpid fluid, called theliquor or lymph of Cotugno or Cotunnius, the perilymph of Breschet, which, under particular circumstances, can reflow into the aquasductus vestibuli and aquaeductus cochleae. This fluid is contained in all the cavities of the internal ear. Within the cavity of the osseous labyrinth just described are contained membranes having nearly the shape of the vestibule and semi-circular canals, but not extending into the cochlea. These membranes, which com- pose what has been called the membranous labyrinth, form a con- tinuous but close sac, containing a fluid, termed by De Blainville vitrine auditive, from its supposed analogy to the vitreous humour of the eye, perfectly similar in appearance to the perilymph, which surrounds it on the outer side, and intervenes between it and the sides of the osseous labyrinth so as to prevent any contact. The form of the membranous vestibule requires special notice, as it is not an exact imitation of the osseous cavity, being composed of two distinct sacs which open into each other; one of these is termed the utricle, sinus or alveus utnculosus, sacculus vestibuli, and median sinus; the other, the sacculus. Each sac contains in its in- ORGAN OF HEARING. 141 terior a small mass of white calcareous matter resembling powder- ed chalk, which seems to be suspended in the fluid contained in the sacs, by means of a number of nervous filaments proceeding from the auditory nerves, (G. N. Fig. 21.) From the universal presence of these substances in the labyrinth of all the mammalia, and from their much greater size and hardness in aquatic animals, it is presumable that they perform some office of importance in audition.* They are termed by Breschet, otolithes and otoconies, according as they are of a hard or a soft consistence. The square marginal figures re- present their size and appearance in the dog and the hare. Fig. 21. Osseous labyrinth laid open to show especially the membranous labyrinth. X. V. Z. Semi-circular canals.—A A A. Ampulla;.—P. Perilymph between the osseous and membranous labyrinth.—U. The utricle.—S. The sacculus.—O O. Cretaceous bodies.—G N. Au- ditory nerve.—K. Branch going to the cochlea.—L. Lamina spiralis.—M. Apex of modiolus.— D. Portio dura. It is in the cavities of the internal ear, and on the different parts of the membranous labyrinth, that the auditory or acoustic nerve is distributed. This nerve is the portio mollis of the seventh pair of most anatomists. It arises, like the other nerves of the senses, from the medulla oblongata, and near the anterior paries of the fourth ven- * Breschet, Memoir, de PAcad^m de Medecin, torn. v. Recherches Anatomiques et Physiologiques sur l'organe de l'ouie, &c., Paris, 1836, and Roget's Animal and Vege- table Physiology, ii. 305. Amer. edit. Philad. 1836. 142 SENSE OF HEARING. tricle. From thence it passes obliquely outwards, forwards, and upwards, and enters the meatus auditorious internus, the foramen of which is situated on the posterior surface of the pars petrosa. The base of this meatus corresponds to the inner surface of the vestibule, and to the base of the cochlea. Through the first foramen, near the base of the meatus, the portio dura of the seventh pair or facial nerve passes, to gain the aqueduct of Fallopius, along which it pro- ceeds*, giving off filaments to different parts of the middle ear, and ultimately issuing by the stylo-mastoid foramen, to be lost on the muscles of the face. Below the part of the meatus, where the facial nerve emerges, are several other foramina, through which the filaments of the audi- tory nerve attain the labyrinth. These are distributed to the vesti- bule, semicircular canals, and cochlea; and terminate, by very deli- cate ramifications, in the tissue and at the surface of the membrane, that lines the labyrinth. Such are the organs concerned in the function of audition. Be- fore proceeding to the physiology of these different parts, and the assistance afforded to the mind by this sense, it is necessary to enter into a brief physical disquisition on the subject of sound. 2. Of Sound. If a body, by percussion or otherwise, be thrown into vibration, every vibration will excite a corresponding wave in the air; and these oscillations will be propagated, in all directions, until they are gradually lost in distance; but if they strike on the organ of hear- ing with the necessary force, a sensation is produced, which is called sound or noise. The term, however, is frequently used to signify, not only the sensation, but likewise the affection of the air, or of the sonorous body, by which the sensation is effected. That bodies move or oscillate, when they produce sound, admits of easy detection. We can see it in drums, bells, musical strings, &c., whose vibrations, being extensive, are more perceptible; and we can arrest them, and with them the sound, by putting the hand upon the body, or by muffling it. Whenever a sonorous body is struck, a change in the relative po- sition of its molecules is produced. These, by virtue of their elas- ticity, tend to return to their former condition. This is done by a series of oscillations, which are, at first, more extensive, but become gradually less, until they finally cease. The rapidity of these oscil- lations is greater in bodies that are hard and elastic; and hence it has been concluded, that these two qualities render a body sonorous. It is not, however, a matter of facility to say, what is the precise cause of the difference of sound in analogous bodies. It must, of course, be dependent upon intimate composition, but of a character not easily intelligible to us. There are but one or two individuals in Great Britain, who has been celebrated for the fabrication of the larger or- der of bells—for churches, colleges, &c.—and in certain countries SOUND. 143 the art is comparatively unknown. The resonance is entirely owing to the intimate composition of the body, and is beautifully and sin- gularly exhibited in the Chinese gong, the sound of which will con- tinue to rise for some time after a succession of rapid and forcible blows has been inflicted. But, in order that the oscillations of a sonorous body may affect the organ of sense, an intermediate body is necessary to repeat and transmit them. This body is called the vehicle of sound, and it is usually the air. Lamarck supposes the existence in the atmo- sphere of a vibrative fluid, of great subtilty, which penetrates the globe invisibly as well as the bodies on its surface: and Geoffroy St. Hilaire affirms, that sound " is a matter resulting from the com- bination of the external air with the polarized air of the sonorous body !"—but these are topics that belong to works on higher physics.* The air by virtue of its elasticity is admirably adapted as a vehicle for sound. The loudness of the sound conveyed by it is dependent upon the density of the medium. If we put a bell under the re- ceiver of an air pump, and exhaust the air, the sound will become gradually more and more faint, and when the air is exhausted will not be heard at all. For the same reason a pistol fired on the top of the Himala mountains gives a much feebler report than in the valleys beneath.f Sympathetic sounds afford additional evidences of the carrying power of air. Every sonorous, elastic body can be thrown into oscillations, provided the air around it be made to trem- ble in any manner. Thus, if we sound a note near a piano-forte, whose dampers are raised so as to admit of free vibration, the string, that is in unison with the tone produced, will vibrate; and a wine-glass or goblet may, according to Arnott, be made to tremble, and even to fall from a table, by sounding on a violoncello near it, the note that accords with its own. The strata of air, in proximity with the sonorous body, receive the first impulses; and from these they are successively propagated to others; much in the same manner as the undulations extend from the place in which a stone is cast on a surface of smooth water; except, that the aerial undulations usually extend in every direction, whilst the aqueous proceed only horizontally. In this propagation from stratum to stratum a portion of the sound is necessarily lost; so that the loudest sounds are heard only within certain limits; and, in all cases, the intensity of the sound is inversely as the square of the distance from the sonorous body. By causing the sonorous undulations to proceed entirely in one direction, and preventing their escape in every other, a sound may be rendered audible at a much greater distance. Biot found, that when he spoke in a whisper at one extremity of a cylinder upwards » Adelon, Physiologie de 1'homme, 2d Edit. I. 355. Paris, 1829, and Lepelletier, Physiologie, iii. 111. Paris, 1832. t Pouillet, Etemens de Physique experimentale, iii. 198. Paris, 1832, and Art. Schall, in Pierer's Anat. Physiol. Realworterb, vii. 205. Altenb. 1827. 144 SENSE OF HEARING. of one thousand yards long, he was distinctly heard at the other. In many large manufactories the knowledge of this fact is turned to good account. By having numerous tubes communicating with the different rooms of the establishment, and terminating in his office, the principal is enabled to have his directions readily conveyed, and to receive any information he may require, without the slightest inconvenience. The velocity, with which sound proceeds, admits of easy calcula- tion. Light passes with such rapidity, that it may be regarded as proceeding from objects on the earth instantaneously to the eye. The velocity of sound is incomparably less. We see the flash of a gun at a distance; and, some time afterwards, we hear the report Considering the light then to have reached the eye instantaneously, if we know the distance of the gun, and note the time that elapsed between the appearance of the flash and the report, we can calcu- late accurately the rapidity of sound. This is found to be about eleven hundred and forty-two feet in a second. We can, in this manner, tell the distance of a thunder cloud, by noting the time of the flash, and the time that elapses before hearing the clap. If it be thirty seconds, the cloud is at the distance of thirty times eleven hundred and forty-two feet, or of six miles and a half. This velocity is the same for all kinds of sounds. Biot found, on playing a flute at the end of the tube, above referred to, that the tones arrived at the ear placed at the other extremity in due succes- sion; so that their velocity must have been uniform. When the aerial oscillations meet with a resisting body of a regular surface, as A B, Fig. 22, they are reflected at an angle equal to the angle of incidence: consequently an ear, placed in the course of these reflected waves as Fig. 22. at C, will refer the sound to a distance as far behind the point of reflection, and in the direction of the re- flected ray, as the sonorous body is from the point of ■q reflection. It will seem to be at E. The ear at C will, however, receive the direct oscillations from the bell D, as well as those that pro- ceed along the linesDF and F C; or, in other words, it E will hear both the sound and its echo; and, if the surfaces on which the sonorous undulations impinge be favourably disposed, these echoes may be very numerous. The utility of the ear trumpet, and of the speaking trumpet is to be explained by this law of the reflection of the aerial undulations: and some physiologists are of opinion, that the external ear is inser- SOUND. 145 vient to audition on similar principles. The ear trumpet is a tube, narrow at one extremity, so as to enter the concha; and expanded at the other like a trumpet. It is also curved, so that it may be easily directed to objects. All the sonorous rays, which enter the expanded extremity, after various reflections, are brought to a focus in the auricular end; and the intensity of the sound is, in this way, so much augmented, that a person, who, without it, is entirely deaf to common conversation, may be able to enjoy it. A sheet of paper, folded like a cone, the apex of which is placed in the concha, serves a like purpose; and, to a less extent, the hand held concavely behind the ear. Air is not the only, or the most perfect, vehicle of sound. The personal experiments of divers show, that it can be conveyed through water. The blows of workmen around a diving bell are distinctly heard above; and fishes have manifestly an acute sense of hearing, although this was at one time denied. An experiment, made by the Abbe Nollet, and repeated by Franklin, proves, that water transmits a much stronger vibration than air. When two stones were struck together under water, a shock was given to the ear, which was almost insupportable. The latter philosopher found by experiment, that sound, after travelling above a mile through water, loses but little of its intensity. According to Chladni, the velocity of sound in water is about 4900 feet in a second, or between four and five times as great as in air. Solids, too, are much better conductors of sound than air. If we scratch one end of a wooden rod, the sound will be distinctly heard by the ear applied to the other, although it may be inaudible through the air. Savage tribes are in the habit of discovering the advance of enemies, or of their prey, by applying the ear to the ground; and the watchmen, in some of the towns, instead of springing a rattle, and alarming offenders, strike the pavement with a staff, the sound of which is heard by their fellow watchmen at a considerable dis- tance. It is a common practice to ascertain whether a kettle boils, by putting one end of a poker on the lid, and the other to the ear. The difference between simmering and boiling is in this way easily detected. A knowledge of this fact, and of the ready communica- tion of sound through solids, has lately given rise to a valuable sug- gestion for the discrimination of diseases of the chest, and of various physiological and pathological conditions. By putting the ear to the chest we can hear the rush of the air along the bronchial tubes: the pulsations of the heart, &c. and can discover any aber- ration, that takes place in the execution of their functions. This is what has been called, by the late distinguished Laennec, of Paris— the proposer of the method—immediate auscultation. The direct application of the ear to the chest is, however, frequently inadmis- sible. In these cases Laennec used a hollow cylinder, called a stethoscope, one end of which he applied to the chest—the other to the vol. i. 13 146 SENSE OF HEARING. ear. This plan he termed mediate auscultation.* The suggestion has led to most valuable improvements in diagnosis. Hassenfratz and Biot have made some accurate experiments on the comparative rapidity of the progress of sound through air and solid bodies. The latter found, in the aqueducts of Paris, that a blow, struck upon a pipe nine hundred and fifty-one metres, or about ten hundred and forty yards in length, was heard two seconds and a half sooner through the sides of the pipe than through the air; but the sound did not extend so far. Ice conveys sound even better than water; for if cannon be fired from a distant post—a frozen river intervening—each flash is followed by two distinct reports, the first conveyed by the ice,—the second by the air. It has been already observed, that the vibrations of the air, caused by a sonorous body, are capable of exciting corresponding or sym- pathetic vibrations in solid bodies within their sphere of action. It was an old observation, that such vibrations are excited only in bodies in unison with the sonorous body; in other words, in those that are capable of producing the same tone with the latter. M. Savart has, however, found, that unison is not necessary; and that when a sound is produced in the air, every body receives a vibration, which is a repetition of the one that occasions the sound. This he proved by using small membranes, on which he placed fine sand. These were agitated, and the sand assumed various regular arrangements, whenever a sound was produced in their vicinity. This law of physics is important in its physiological relations. The apparatus of audition consists of several membranous structures, which are thrown into oscillations, whenever the ear receives the impressions of sound. The vibrations, which produce sound, differ much as regards their extent and rapidity; and on these differences are dependent two of the qualities of sound—strength and tone. The strength or intensity of sound depends on the extent of the vibrations of a sonorous body. This is easily seen in a musical string ; the sound of which becomes weaker as the extent of the os- cillations diminishes. The tone, on the other hand, is dependent on the rapidity of the oscillations;—on their number in a given time. The tone, produced by a string or other sonorous body that vibrates quickly, is termed acute or sharp, when compared with the tone of one that vibrates more slowly. The latter is called grave, when compared with the former. The gravest sound, that the ear can appreciate, is ordinarily con- sidered to result from thirty-two vibrations per second; the most acute, from eight thousand one hundred and ninety-two vibrations, according to some;—twelve thousand, according to others. Some well devised experiments, recently made by Savart, largely extend these limits, and appear to indicate, that they cannot yet be rigidly * A Treatise on Diseases of the Chest, and on mediate auscultation, from the French of Laennec. by. Dr. Forbes, 4th Edit. Lond. 1834: reprinted in this country. SOUND. 147 fixed. In his experiments, the ear distinctly appreciated fourteen or sixteen vibrations per second ; and the acutest note, that was audible, proceeded from upwards of forty thousand simple oscillations, per second. The duration of the impression of a sonorous vibration on the ear is about the sixteenth part of a second. If a sonorous body be struck, and the vibrations excited be all per- formed in equal times, a simple and uniform sensation will be pro- duced on the auditory nerve, and one musical tone will be heard. But if the vibrations be various and irregular, they will fall irregu- larly on the organ of hearing, and will excite a harsh impression, as if various sounds were heard together. In other words, a noise or discord will be produced. If two notes, sounded together, afford pleasure, they produce har- mony or concord. This arises from the agreement of the vibrations of the two sonorous bodies, so that some of the vibrations of each strike upon the ear at the same time. If, for example, the vibrations of one sonorous body take place in double the time of another, the second vibration of the latter will strike upon the ear at the same in- stant as the first vibration of the former. This is the concord or harmony of an octave. Between a note and its octave, there are six intermediate notes, constituting the diatonic scale or gamut. If the vibrations of two strings are as two to three, the second vibration of the former will correspond with the third vibration of the latter, pro- ducing the harmony called a fifth. There are other tones, which, although they cannot be struck together without producing discord, if struck in succession, may give the pleasure called melody. Melody is, in truth, nothing more than the effect produced on the brain by pleasing musical tones, sounded in succession. There is another quality of sound which the French call timbre. By some of the translators of the works of the French physiologists, this word has been inaccurately rendered note. It is essentially dif- ferent from note or tone, and is peculiar. By English philosophers it is termed the quality of sound. It is this quality that enables us to recognize various instruments, although sounding the same note or tone; and to distinguish the voices of individuals from each other. Its cause is not evident. By most, it is conceived to depend upon the nature of a sonorous body, if it be a surface,—and at the same time on its shape, if a tube. Biot conjectures, that it is owing to the series of harmonic sounds forming part of every appreciable sound. When any sonorous body is made to vibrate, a distinct sound is heard, which is the fundamental; but, if attention be paid, others will be heard at the same time. These are called harmonics. It is not improbable but that the timbre or quality may be depen- dent as well upon the nature of the sonorous body, as upon the greater or less number of harmonics, that accompany the funda- mental sound. 148 SENSE OF HEARING. 3. Physiology of Audition. In tracing the progress of the sonorous vibrations to the internal ear, we shall follow the order of parts described in the anatomical sketch of the auditory apparatus;—commencing with the external ear. The meatus auditorius externus being always open, sonorous vi- brations can readily attain the membrana tympani. Some of these pass directly to the membrane without experiencing reflection, and communicate their oscillations to it. The pavilion, by most physio- logists, has been regarded as a kind of ear trumpet, for collecting the aerial undulations, and directing them, after various reflections, to the bottom of the auditory canal. In the horse, and in those ani- mals, which have the power of pricking the ears, or of moving them in various directions, this is doubtless the case; but in man we can- not expect any great effect of the kind, if we regard its particular arrangement, and the incapability of moving it from its fixed direc- tion, which is nearly parallel to the head. Boerhaave,* indeed, pre- tended to have proved by calculation, that every sonorous ray, which falls upon the pavilion, is ultimately directed towards the meatus auditorius externus.f Simple inspection of the pavilion will show that this cannot be universally true. Some part of the anthelix is, in almost every individual, more prominent than the helix; and it is therefore impossible for the undulations, that fall upon the posterior surface of the former, to be reflected towards the concha. M. Itard,J a distinguished physiologist and aurist of Paris, asserts, that he has never seen the loss of the pavilion affect the hearing; and that, as is well known, many animals, whose sense of hearing is extremely acute,—the mole and birds, for example,—are devoid of it. Hence he concludes, that it is perhaps rather injurious than favourable to audition, and is more inservient to the expression than to the hearing of the animal. M. Itard's view is doubtless too exclusive.^ The pavilion may have but little agency as an ear trumpet, but it must have some. The concha, being the expanded extremity of the meatus auditorius, must receive more sonorous vibrations than could be admitted by the meatus itself. These are reflected towards the membrana tympani, and reach that expansion in a state of concentration—but to no great extent, it is true. In this way, and perhaps in that suggested by M. Savart,|| the pavilion is useful in audition. That gentleman is of opinion, that the whole of the external ear, the elasticity of which he considers to be capa- ble of slight modification by the action of its proper muscles, is an * Prselect, torn. iv. p. 317; and Buchanan, Physiological Illustrations of the organ of hearing, &c. p. 77. London, 1828. t Magendie, Precis el6mentaire, I. 115. X Traite des Maladies de Poreille et de l'audition, I. 131. Paris, 1821. § Kramer, on the nature and treatment of diseases of the ear, translated from the German, by Dr. J. R. Bennet, Lond. 1837; and Amer. Med. Library edition, p. 17, Philad. 1838. | Annales de Chimie, xxvi. 5; and Journal de Physiologie, iv. 183, and v. 367. PHYSIOLOGY OF THE MIDDLE EAR. 149 apparatus for repeating sonorous vibrations, and transmitting them along its own parietes to the membrane of the tympanum. Accord- ing to this view, the different inequalities of surface in the pavilion admit of explanation. When the membrane is stretched in a direc- tion parallel to a sonorous surface, the oscillations, impressed upon it, are most marked; and, accordingly, as sounds impinge upon the pavilion from various quarters, the inequalities of surface always admit of some being disposed in the most favourable way for the reception of the vibrations. It is true, however, that the pavilion is not essential to audition; the hearing not suffering by its removal for more than a few days ; so that its physiological influence is much more limited than might be conceived. The meatus auditorius externus conducts the sonorous vibrations directly, and by reflection, to the membrana tympani, as well as by its parietes. It is probable, too, that it is useful in protecting the membrane from the direct action of the air and extraneous bodies. This is perhaps the cause of its tortuous character in all animals. If too tortuous, the sense of hearing becomes impaired,—the sono-. rous oscillations not being properly directed towards the membrane. Baron Larrey has published some cases of deafness produced in this manner, which were removed by wearing an artificial concha and meatus, of the natural curvature, made of gum elastic. The down or hairs, at the entrance of the meatus, have also been regarded as protecting agents against the intrusion of extraneous bodies; whilst the cerumen has been looked upon as a fit material for entrapping insects in the slough formed by it, or for destroying them by its poisonous influence. It is probable, however, that the most impor- tant function of the cerumen is to keep the lining membrane of the meatus in a physical condition adapted for the proper fulfilment of its functions. Middle Ear.—In the mode described, the vibrations of a so- norous body attain the membrana tympani. An experiment by Sa- vart would seem to show, that this membrane is thrown into vibra- tions chiefly by the air contained in the meatus. He made a small truncated cone of pasteboard, and closed the smaller extremity by a tense membrane, nearly as the membrana tympani closes the inner extremity of the meatus auditorius; and he found, that when sounds were produced near the parietes of the cone, the membrane vibrated but little; whilst, if they wrere occasioned opposite the base of the cone, so that they could be transmitted to the membrane by the air within the canal, the vibrations were very distinct, even at a distance of thirty yards and upwards. The membrane of the tympanum, then receives and repeats the sonorous vibrations. It has, however, been supposed to be possessed of other functions. Dumas,* for example, conceived it to be com- posed of numerous cords, and each of these to correspond to some » Principes de Physiologie, 2de edit. Paris, 1806. 13* 150 SENSE OF HEARING. particular tone. But of this arrangement we have not the slightest evidence from observation or analogy. By others, it has been supposed, ^and with every probability, that the membrane is capable of being rendered tense, or the contrary, by the bent lever, formed by the chain of small bones. They have farther stated, that this tension or relaxation is adapted to the sounds, which the membrane has to transmit. The ancients believed, that the adaptation was produced by the stretching of the membrane, so as to put it in unison with the sound produced. Independently, however, of the experiment of Savart, which show, that unison is not necessary for the production of vibra- tions, the fact, that we are capable of distinguishing several sounds at the same time, would be sufficient to negative the supposition. Nor can we easily conceive, that the membrane could admit of as many distinct vibrations as the ear is capable of accurately appre- ciating tones, which amount to about eight octaves. Bichat thought, that the degree of tension of the membrane cor- responded (with the intensity of sounds; and that its effect was to cause the sonorous vibrations to attain the internal ear, in a de- gree sufficiently strong to excite the appropriate impression, but not so strong as to cause pain,—the membrane becoming more tense for a feeble sound, and relaxed for one too strong. In support of this view, Bichat cites the case of several persons, who could not hear ordinary sounds, until the ear had been impressed by louder, which, according, to him, roused the membrane to tension. Savart, on the other hand, from the fact, that every membrane vibrates with more difficulty, and less extensively, according to its tension, conjectures,, that the membrane is relaxed in the case of very feeble or agreeable sounds, and that it is rendered tense to transmit the too powerful or the disagreeable. Again, it has been conceived that the tension varies with the tone of the sound,—being augmented according to some physiolo- gists, in the case of acute, according to others, in that of grave, sounds. Sir Everard Home,* it has been remarked, esteems the mem- brana tympani to be muscular: and he affirms, that it is chiefly by means of this muscle, that accurate perceptions of sound are made by the internal organ; and that by it the membrane can alter its degree of tension. It has been already observed, that the muscles, attached to the small bones, are capable of varying this tension; that the internal muscle of the malleus or tensor tympani, for ex- ample, by its contraction, renders it more tense. Sir Everard admits, " that the membrana tympani is relaxed by the muscles of the malleus, but not for the purpose alleged in the commonly re- ceived theory. It is stretched in order to bring the radiated muscle of the membrane itself into a state capable of acting, and of giving those different degrees of tension to the membrane, which em- * Lect. on Comp. Anat. iii. 265. PHYSIOLOGY OF THE MIDDLE EAR. 251 power it to correspond with the variety of external tremors: when the membrane is relaxed, the radiated muscle cannot act with any effect, and external tremors make less accurate impressions." The reader is referred to the remarks already made on the views of Sir Everard in their anatomical relations. His speculations do not, however, end here. He employs the discovery to account for the difference between a musical ear, as it is usually termed, and one which is incapable of discriminating, or feeling pleasure from, the succession of musical tones,—with what success we shall inquire presently. The truth is, that none of the conjectures, which have been pro- posed, regarding the precise effects of tension or relaxation of this membrane, can be looked upon in any other light than as ingenious speculations, based, generally, upon the fact, that the membrane seems certainly capable of being varied in its tension by the move- ments of the chain of bones, but leading us to no certain knowledge of the precise effect on audition of such tension or relaxation.* In fact, although the integrity of the membrana tympani is ne- cessary for perfect hearing, its perforation or destruction does not induce deafness. We have numerous cases of perforation from ac- cidentand otherwise, related byValsalva,f Willis,J Riolan,§Flourens, and others, in which the hearing continued ; and, in certain cases of deafness, the membrane is actually punctured for the purpose of re- storing the hearing.|| The communication of sonorous oscillations from the membrana tympani across the cavity of the tympanum to the internal ear is effected in three different ways; 1, by the air contained in the ca- vity of the tympanum; 2dly, by the chain of bones to the membrane of the foramen ovale; and 3dly, by the parietes of the tympanum. So that, if the membrana tympani should be punctured or destroyed, the aerial undulations, caused by a sonorous body, and which enter the meatus auditorius, may extend into the cavity of the tympanum, and excite corresponding oscillations in the membranes of the fo- ramen ovale, and foramen rotundum. The chorda tympani composed, as we have seen, of a branch of the fifth pair and of the portio dura of the seventh, and distributed on the interior surface of the membrana tympani—probably conveys no acoustic impression to the brain. To it is owing the excessive pain, caused by the contact of an extraneous body with the mem- brane, and that occasioned by a loud noise, or by compressing the air forcibly in the meatus by passing the finger suddenly and strongly into the concha. The uses of the mastoid cells, which communicate with the middle * For the fancied uses of this membrane, see Haller, Element. Physiol, v. 198. t Op. Anat. de Aure Humana, &c. Ed. J. A. Morgagni. Venet. 1740. X Oper. omn. Venet. 1720. § Enchirid. Anat. 1. iv. c. 4. Lugd. Bat. 1649. || Deleau (le jeune), Memoire sur la Perforation du Tympan, &c. Paris, 1822. Itard, in Mem. de l'Academ. Royale de Medecine, torn. v. Fascic. 4. Paris, 1836 ; and a translation, by the author, in the American Medical Library and Intelligencer, for May 1, 1837. Also Kramer, op. citat. 152 SENSE OF HEARING. ear, are not known. It would seem, that the strength of audition is in a ratio with their extent. In no animals are they more ample than in birds, which are possessed of great delicacy of hearing. This effect may be induced either by their enlarging the cavity of the tympanum, and allowing the sonorous oscillations to come in contact with a larger surface; or by the plates, which compose them, being thrown into vibration. It has been conceived, too, that they may serve as a diverticulum for the air in the middle ear, when subjected by the membrana tympani to unusual compression. Sir Charles Bell,* with more warmth than is judicious or cour- teous, combats the idea of the foramen rotundum receiving the undulations of air. The oblique position of the membrane of the foramen, with regard to the membrana tympani, satisfactorily, he thinks, opposes this doctrine. The function which, with Savart, he assigns to it—if not accurately, at least ingeniously—is the follow- ing. As the membrane of the foramen ovale receives the vibrations from the chain of small bones, these vibrations circulate through the intricate windings of the labyrinth and are again transmitted to the air in the tympanum by the foramen rotundum. The different cavi- ties of the labyrinth being filled with an incompressible fluid, no such circulation, he insists, would occur, provided the parts were entirely osseous. As it is, the membrane of the foramen rotundum gives way, " and this leads the course of the undulations of the fluid in the labyrinth in a certain unchangeable direction." The explanation of Sir C. Bell is not as convincing to us as it seems to be to himself. The membrane of the foramen rotundum does not appear to be required for the undulation in the cavities of the labyrinth, which he describes, as the liquor of Cotunnius can readily reflow into the aqueducts of the vestibule and cochlea. The principal use of these canals would seem, indeed, to be, to form diverticula for the liquor, when it receives the aerial impulses. Sir. C. Bell cites the case, often quoted from Riolan, of an indivi- dual, who was deaf from birth, and who was restored to hearing by accidentally rupturing the membrana tympani, and breaking the ossicles with an ear-pick—" disrupit tympanum, fregitque ossicula, et audivit." In these and other cases, in which the membrana tympani and ossicles have been destroyed, and the hearing has still persisted, the vibrations must have been conveyed to the parietes of the internal ear through the air in the cavity of the tympanum, and, notwithstanding the charge of " absolute confusion of ideas," adduced against such individuals as Scarpa,f Magendie, Adelon, and others, who believe that the foramen rotundum receives the undula- tions of the air, we must confess, that the idea of the communication of vibrations through that medium, as well as through the membrane of the foramen ovale, and the osseous parietes of the labyrinth, appears to us most solid and satisfactory. « Op. citat. I. 269. t Anat. disquis. de Auditu et Olfactd., Ticin, 1789; and De Structura Fenestra: Rotundae Auris, &c. Mutin. 1772, PHYSIOLOGY OF THE MIDDLE EAR. 153 The ossicles or small bones have given occasion to the wildest speculations. At the present day, they are considered to fulfil one of two functions;—either to conduct the vibrations from the mem- brana tympani, or to stretch the membranes to which the extremi- ties of the chain are attached. Both these offices are probably exe- cuted by them, the malleus receiving the vibrations from the mem- brana tympani, and conveying them to the incus,—the incus to the os orbiculare,—the os orbiculare to the stapes, and the stapes to the membrane of the foramen ovale by which they are transmitted to the liquor of Cotunnius. Savart conceives, that the chain of ossicles is to the ear what the bridge is to the violin. It has been already observed, that the ossicles are not essential to hearing, although they may be required to perfect it; and that they may be destroyed, with- out deafness being produced, provided the membrane of the foramen ovale remains entire, and the parts within the labyrinth retain their integrity. If, in the removal of the stapes by ulceration or other- wise, the membrane of the foramen were to be ruptured, the liquor of Cotunnius would of course escape, and partial or total deafness be the result. In some experiments, instituted by Flourens on pigeons, he found, that the removal of the malleus and incus did not have much effect upon the hearing; but when the stapes was taken away it was greatly diminished, and still more so when the membranes of the fenestra ovalis and fenestra rotunda were destroyed. The Eustachian tube is an important part of the auditory appa- ratus, and an invariable accompaniment of the membrana tympani, in animals. Without the tube, the membrane would be devoid of function. Pathology shows us, in the clearest manner, that its inte- grity is necessary to audition; and that deafness is the consequence of its closure. Dr. Bostock* thinks, " it is perhaps not very easy to ascertain in what mode it acts, but it may be concluded that the proper vibration of the membrana tympani is, in some way, con- nected with the state of the air in the tube." The name of the cavity to which the tube forms a communication with the external air might have suggested an easy and sufficient explanation of its use. The drum of the ear, like every other drum, requires an aper- ture in some part of its parietes, in order that its membranes may vibrate. The Eustachian tube serves this purpose, and its closure produces the same effect upon the membrana tympani at one end of the cylinder, and on the membrane of the foramen ovale at the other, as would be produced on the parchments of the ordinary drum by the closure of its lateral aperture. We can, in this way, account for the temporary deafness, which accompanies severe cases of in- flammation of the throat: the swelling obstructs the Eustachian tube. During the constant efforts of deglutition the air is renewed in the cavity of the tympanum ; and, as the extremities of the Eusta- chian tube terminate in the pharynx, it always enters at a subdued temperature. * Physiology, 3d Edit., p. 721. Lond. 1836. 154 SENSE OF HEARING. By closing the nose and mouth, and forcing air from the lungs, we can feel a sensation of fulness in the ear, produced by the pres- sure of the air against the internal surface of the membrana tym- pani ; and they, who have the membrane perforated, can send to- bacco smoke copiously out of the external ear. Besides this necessary function, the Eustachian tube has been supposed to possess another,—that of serving as a second meatus auditorius, by permitting sonorous vibrations to enter through the pharyngeal extremity, and, in this way, to attain the internal ear. A simple experiment, first described by Perolle,* exhibits the fallacy of this notion. If we carry a watch far back into the mouth, taking care not to touch the teeth, little or no sound will be heard, but if we draw the watch forward, so as to touch the teeth, the ticking be- comes distinctly audible. If the pharyngeal extremity acted as a second meatus, the sound ought to be heard better when the watch is placed nearer to it; but this is not the case. On the contrary, it is not until the sonorous body is put in contact with the teeth, that the sound is appreciated. This is effected by the vibrations of the watch being conveyed along the bony parietes until they reach the auditory nerve. Again, if the meatus auditorius externus be completely closed, we cannot hear the voice of one who speaks into the mouth; and can hear but imperfectly our own. The fact of our gaping, when desirous of hearing accurately, has partly led to the belief, that the Eustachian tube acts as a second meatus. It has been properly remarked, however, that this may be merely an act of expression ; and, also, that the meatus auditorius is rendered more open, when we depress the lower jaw, than when it is raised, as can be readily perceived by inserting the little finger into the meatus, when the jaw is in either situation. In addition to these functions, it is probable, that the Eustachian tube acts as a diverticulum for the air in the cavity of the tympa- num, when it is agitated by too powerful sounds. The closure of the Eustachian tube is the cause of that form of deafness, which is relieved by the injection of air or other fluids into the tubef—a fact, the knowledge of which has been the foundation of much em- piricism. Internal Ear.—In the various ways mentioned, the vibrations of a sonorous body reach the internal ear. The membranes of the foramen ovale and foramen rotundum resemble the membrana tym- pani in their physical characteristics ; and when thrown into vibra- tion communicate the impression to the liquor of Cotunnius, which fills the cavities of the internal ear. By this medium the vibrations are conducted to the auditory nerve, which conveys the impression to the brain. The views, entertained regarding the sympathetic vibrations of * Hist, et Mem. de la Societe Royale de Medecine, torn. iii. t Deleau (le jeune) Sur le Catheterisme de la Trompe d'Eustache, et sur les experien- ces de M. Itard, &c. Paris, 1828. Also, Itard, and Kramer, in Oper. citat. PHYSIOLOGY OF THE INTERNAL EAR. 155 the membrana tympani, have almost all been applied to the mem- brane of the foramen ovale: our knowledge, however, is restricted to the fact, that its tension can be varied by the chain of bones, with- out our being able to specify the circumstances under which this takes place. Adelon asserts, that the membrane may be torn, and yet the sense of hearing may not be destroyed. This seems scarcely possible as the liquor of Cotunnius must necessarily escape, and so much morbid action be induced as to render audition apparently impracticable. The membrane of the foramen rotundum, which forms the me- dium of communication between the cavity of the tympanum and the cochlea, has, of course, no chain of bones to modify its tension. Both the vibrations into which it is thrown, and those of the vesti- bular membrane, are imparted, as we have seen, to the liquor of Cotunnius, which is present in every ear, and appears essential to audition. Of the precise uses of the vestibule, semicircular canals, and cochlea, we have very limited notions. The beauty and complexity of their arrangement, has, however, given rise to various conjec- tures. Le Cat* considered the lamina spiralis to consist of numerous minute cords, stretched along it, and capable of responding to every tone. Magendiet affirms, that no one at the present day admits the hypothesis regarding the use of this osseo-membranous septum; but he is in error. Sir C. BellJ asserts, that the cochlea is the most important part of the organ of hearing; or rather, that it is " the refined and higher part of the apparatus;" and he considers the lamina spiralis as the only,, part adapted to the curious and ad- mirable powers of the human ear, for the enjoyment of melody and harmony. The subject of the musical ear will engage us presently. It may be sufficient to remark, in this place, that there is no ratio in ani- mals, between the delicacy of the hearing, and the degree of com- plication of the cochlea. The cochlea of the Guinea pig is more convoluted than that of man, yet we can hardly conceive it to have a better appreciation of musical tones; whilst in birds, whose hear- ing is unquestionably delicate, the organ is, as we have remarked, extremely simple, and has no spiral arrangement. Again, the semicular canals have been compared to organ pipes, adapted for producing numerous tones; and Dr. Young§ supposed them to be " very capable of assisting in the estimation of the acuteness or pitch of a sound, by receiving its impression at their opposite ends; and occasioning a recurrence of similar effects at different points of their length according to the different character of the sound; while the greater or less pressure of the stapes must serve to moderate the tension of the fluid within the vestibule, which serves to convey the impression." " The cochlea," he adds, " seems to be pretty evidently a micrometer of sound." All these are mere * Traite" des Sens, Paris, 1767, and English translation, Lond. 1750. t Precis, .fee. 1.121. 4 Op. citat. ii. 273. § Med. Literature, p. dS. Lond. 1813. 156 SENSE OF HEARING. hypotheses;—ingenious, it is true, but still hypotheses: and, in candour, we must admit, that we have no positive knowledge of the precise functions of either vestibule, cochlea, or semicircular canals. Our acquaintance with them is limited to this; that they contain the final expansions of the auditory nerve; and that it is within them, that this nerve receives its impressions from the oscillations of sonorous bodies. It has been observed, that these vibrations may reach the nerve by the bony parietes, and that the ticking of a watch, held between the teeth, is, in this way, heard. A blow upon the head is distinctly audible; and Ingrassias* relates the case of a person, who had be- come deaf in consequence of obstruction of the meatus auditorius externus, and yet could hear the sound of a guitar, by placing the handle between his teeth, or by making a communication between his teeth and the instrument by a metallic or other rod. The physi- cian has recourse to a plan of this kind for detecting whether a case of deafness be dependent upon obstructed Eustachian tube— upon some affection of the meatus auditorius externus—or upon insen- sibility of the auditory nerve, or of the part of the brain that effects the sensation. If the latter be the case, the ticking of a watch, ap- plied to the teeth, will not be audible, and the case may necessarily be one of a hopeless character. If, on the other hand, the sound be perceived, the attention of the physician may be directed, with well founded expectation of success, to the physical parts of the organ, or to those concerned in the transmission of vibrations. Frequently, it will happen, in such cases, that the Eustachian tube is impervious, and properly directed efforts may succeed in removing the ob- struction ; or, if this be impracticable, temporary, if not permanent, relief may be obtained by puncturing the membrana tympani, and allowing the aerial undulations, in this way, to reach the middle and internal ear. Lastly—as regards the precise nerve of hearing. In this sense we have the distinction between the nerve of general, and that of special sensibility', more clearly observed, The experiments of Magendief have shown, that the portio mollis of the seventh pair is the nerve of special sensibility;—that it may be cut, pricked, or torn, without ex- hibiting any general sensibility, and that it is inservient only to the sense of hearing. The same experiments demonstrate, that this nerve cannot act, unless the fifth pair or nerve of general sensibility be in a state of integrity. If the latter nerve be divided within the cranium, the hearing is always enfeebled, and frequently destroyed. The experiments of Flourens,J to which allusion has been made, led him to infer, that the rupture of the cochlea was of less consequence than that of the semicircular canals. Laceration of the nerve, dis- * De Ossibus, p. 7. See, also, Boerhaave. Prselectiones, iv. 415, and Haller. Ele- ment. Physiol, torn. v. p. 253. Lausann. 1763. t Precis, «fec. 2de Edit. I. 114. $ Experiences sur la systeme nerveux, p. 42. Paris, 1825. IMMEDIATE FUNCTION OF HEARING. 157 tributed to the vestibule, enfeebled the hearing, and its total de- struction was followed by irreparable deafness. For these, and other reasons furnished by comparative anatomy, Lepelletier* infers, that, in the higher organisms, the vestibule and its nerve constitute the es- sential organ of impression, the other parts being superadded to perfect the apparatus. t The immediate function of the sense of hearing is to appreciate sound; and we may apply to it what has been said of the other senses, that, in this respect, it cannot be supplied by any other sense —that it is instinctive, requires no education, and is exerted as soon as the parts have attained the necessary degree of developement. Amongst the advantages afforded by the possession of this sense, which has been properly termed intellectual, are two of the highest gratifications we enjoy—the appreciation of music, and the plea- sures of conversation. It is to it that we are indirectly indebted for the use of verbal language—the happiest of all inventions—as it has been properly termed, and to which we shall have to advert in the course of our inquiry into the animal functions. Metaphysicians and physiologists have differed considerably in their views regarding the organs more immediately concerned in the appreciations in question. Many, for example, have referred the faculty of music to the ear; and hence, in common language, we speak of an individual, who has a " musical ear," or the con- trary. Others, more philosophically we think, have considered, that the faculty is seated in the encephalon ; that the ear is merely the instrument for conveying the sonorous undulations, which, in due order, constitute melody, but that the appreciation is ultimately effected in the brain, " That it," (the power of distinguishing the musical relations of sounds,) says Dr. Brown,f " depends chiefly or perhaps entirely, on the structure or state of the mere corporeal organ of hearing, which is of a kind, it must be remembered, peculiarly complicated, and therefore susceptible of great original diversity in the parts, and relations of the parts that form it, is very probable; though the difference of the separate parts them- selves, or of their relations to each other may, to the mere eye, be so minute, as never to be discovered by dissection." Many phy- siologists of eminence have regarded the complex internal ear as the seat of the faculty; some looking to the cochlea; others to the semicircular canals; but few referring it to the brain. Sir C. Bell, indeed, asserts, that " we are not perhaps warranted in concluding, that any one part of the organ of hearing bestows the pleasures of melody and harmony, since the musical ear, though so termed is rather a faculty depending on the mind." Yet afterwards he adds— " we think that we find in the lamina spiralis (of the cochlea) the *Traite de Physiologie Medicale et Philosophique, iii. 143. Paris, 1832. See, on the Comparative Physiology of Hearing, Roget's Animal and Vegetable Physiol. Edit. cit. ii., 308. t Lectures on the Philosophy of the Human Mind, Edinb. 1820: and Amer. edit Boston, 1826: vol. i. p. 207. VOL. I. 14 158 SENSE OF HEARING. only part adapted to the curious and admirable powers of the human ear, for the enjoyment of melody and harmony. It is in vain to say, that these capacities are in the mind and not in the outward organ. It is true, the capacity for enjoyment or genius for music is in the mind. All we contend for is, that those curious varieties of sound, which constitute the source of this enjoyment, are communicated through the ear, and that the ear has mechanical provisions for every change of sensation."* A cherished opinion of Sir Everard Homef on this subject has been referred to. Conceiving the membrane of the tympanum to be muscular, he considers the membrana tympani, with its tensor and radiated muscles, to resemble a monochord, " of which the membrana tympani is the string; the tensor muscles the screw, giving the necessary tension to make the string perform its proper scale of vibrations; and the radiated muscle acting upon the mem- brane, like the moveable bridge of the monochord, adjusting it to the vibrations required to be produced;" and he adds, " the differ- ence between a musical ear and one which is too imperfect to dis- tinguish the different notes in music, will appear to arise entirely from the greater or less nicety with which the muscle of the malleus renders the membrane capable of being truly adjusted. If the ten- sion be perfect, all the variations produced by the action of the radiated muscle will be equally correct, and the ear truly musical." In this view,—as unsatisfactory in its basis as it is in some of the details,—Sir Everard completely excludes, from all participation in the function, the internal ear, to which the attention of physiologists, who consider the faculty to be seated in the ear, has been almost exclusively directed. A single case, detailed by Sir Astley Cooper,J prostrates the whole of the ingenious fabric, erected by Sir Everard. Allusion has already been made to the old established fact, that the membrane of the tympanum may be destroyed without loss of hearing necessarily following. Sir Astley was consulted by a gentleman, who had been attacked, at the age of ten years, with an inflammation and suppuration in his left ear, which continued discharging matter for several weeks. In the space of about twelve months after the first attack, symptoms of a similar kind took place in the right ear, from which matter issued for a considerable time. The discharge, in each instance, was thin, and extremely offensive; and in it, bones or pieces of bones were observable. In consequence of these attacks he became deaf, and remained so for three months. The hearing then began to return; and in about ten months from the last attack, he was restored to the state he was in when the case was pub- lished. Having filled his mouth with air, he closed his nostrils and contracted the cheeks; the air, thus compressed, was heard to rush through the meatus auditorius with a whistling noise, and the hair, * Anat. and Physiol. 5th Amer. Edit, by Godman, ii. 273. New York, 1829. f Lect. on Comp. Anat., iii. 268. X Philosoph. Transact, for 1800, p. 151, and for 1801, p. 435. MUSICAL EAR. 159 hanging from the temples, became agitated by the current of air, that issued from the ear. When a candle was applied, the flame was agitated in a similar manner. Sir Astley passed a probe into each ear, and thought the membrane of the left side was totally destroyed, as the probe struck against the petrous portion of the temporal bone. The space, usually occupied by the membrana tympani, was found to be an aperture without one trace of mem- brane remaining. On the right side, also, a probe could be passed into the cavity of the tympanum; but, on this side, some remains of the circumference of the membrane could be discovered, with a circular opening in the centre, about a quarter of an inch in diame- ter. Yet this gentleman was not only capable of hearing every thing that was said in company, but was nicely susceptible to musical tones; "he played well on the flute, and had frequently borne a part in a concert; and he sung with much taste and per- fectly in tune." But, independently of these partial objections, the views, that assign musical ear and acquired language to the auditory apparatus, appear liable to others that are insuperable. The man who is totally devoid of musical ear, hears the sound distinctly. His sense of hearing may be as acute as that of the best musician. It is his appreciation that is defective. He hears the sound, but is incapable of communicating it to others. The organ of appreciation is—in this, as in every other sense—the brain. The physical part of the organ may modify the impression, which has to be made upon the nerve of sense; the latter is compelled to transmit the impression as it receives it; and it is not until the brain has acted, that perception takes place, or that any idea of the physical cause of the impression is excited in the mind. If, from faulty organization, such idea is not formed in the case of musical tones, the individual is said not to possess a musical ear: but the fault lies in his cerebral conformation. We do not observe the slightest relation between musical talent and delicacy of hearing. The best musicians have not necessarily the most deli- cate sense; and, for the reasons already assigned, it will be manifest, why the idiot, whose hearing may be acute, is incapable of singing. as well as of speaking. Again, wre do not see the least ratio in ani- mals between the power and character of their music, and the con- dition of their auditory sense. We are compelled then to admit, that the faculties of music and speech are dependent upon the organiza- tion of the brain; that they require the ear as a secondary instru- ment; but that their degree of perfection is by no means in propor- tion to the delicacy of the sense of hearing. In these opinions, Gall,* Broussais.f Adelon,J and other distinguished physiologists, concur. " Speech," says Broussais, " is heard and repeated by all men, who are not deprived of the auditory sense, because they are all endowed * Sur les Fonctions du Cerveau, v. 96, Paris, 1825. t Traite de Physiologie appliquee a la Pathologie. Paris, 1822. Translation by Drs. Bell and La Roche, p.j84, 3d Amer. Edit. Philad. 1832. X Op. citat. I, 383. 160 SENSE OF HEARING. with cerebral organization fit to procure for them distinct ideas on the subject. Music, when viewed as a mere noise, is also heard by every one; but it furnishes ideas, sufficiently clear to be reproduced to those individuals only, whose frames are organized in a manner adapted to this kind of sensation." Yet, although we must regard the musical faculty to be intel- lectual, and consequently elevated in the scale, it is hardly necessary to say, that its deficiency is no evidence of that mental and moral degradation, which has been depicted by poets and others;—as in the well known anathema of Shakspeare:— " The man that hath no music in himself, Nor is not mov'd with concord of sweet sounds, Is fit for treasons, stratagems and spoils; The motions of his spirit are dull as night, And his affections dark as Erebus: Let no such man be trusted." Merchant of Venice, V. I. Or in that of Beattie— " Is there a heart that music cannot melt ? Alas! how is that rugged heart forlorn; Is there, who ne'er those mystic transports felt Of solitude and melancholy born ! He needs not woo the muse; he is her scorn. The sophist's rope of cobweb he shall twine; Mope o'er the schoolman's peevish page; or mourn, And delve for life in mammon's dirty mine; Sneak with the scoundrel fox, or grunt with glutton swine." Minstret. In the classification of the objects of human knowledge, music has been ranked with poetry; but we meet with striking evidences of their wide separation. Whilst the professed musician is frequently devoid of all poetical talent, many excellent poets have no musical ear. Neither does the power of discriminating musical tones indi- cate that the possessor is favoured with the finer sensibilities of the mind; nor the want of it prove their deficiency. It has been a com- mon remark, that, amongst professed musicians, the intellectual mani- festations have been singularly and generally feeble;—a result partly occasioned by their attention having been almost entirely engrossed from childhood by their favourite pursuit, but not perhaps to be wholly explained by this circumstance; and, whilst we find them often unmarked by any of the kindlier sympathies, we see those, that are " not moved with concord of sweet sounds," alike distin- guished as philosophers and philanthropists. The defect, in these cases, differs probably in an essential manner, from one to which attention has been drawn by the late Dr. Wol- laston.* In that communication he describes many curious facts, regarding, what he terms, a peculiarity in certain ears, which seem to have no defect in the general capacity of receiving sound, or in the perception of musical tones, but are insensible to very acute * Philosophical Transactions for 1820, p. 306. JUDGMENT OF DISTANCE, &c. BY SOUND. 161 sounds. This insensibility commences when the vibrations have attained a certain degree of rapidity, beyond which all sounds are inaudible to ears thus constituted. Thus, according to Wollaston, certain persons cannot hear the chirp of the grasshopper; others the cry of the bat; and he refers to one case in which the note of the sparrow was not audible. Dr. Wollaston himself, was incapable of hearing any sound higher than six octaves above the middle E in the piano forte. The defect would, at first sight, appear to be referable to the phy- sical part of the ear, rather than to the auditory nerve, or to the part of the brain concerned in the appreciation of sounds; the vibra- tions, that are performed with great rapidity, not being responded to by the parts of the organ destined for this purpose; and, con- sequently, never reaching the auditory nerve. Researches, how- ever, by Savart,*—one of the most dexterous and ingenious experi- menters of the day—seem to show, that the defective appreciation of acute sounds, in such cases, is not owing to their acuteness, but to their feebleness; that, if the sound can be made sufficiently in- tense, the ear is capable of hearing a note of upwards of forty thou- sand simple oscillations in a second; and that the cases, referred to by Wollaston, are, consequently, owing to defective hearing, rather than to insensibility to very acute sounds. Another acquired perception of the ear is that of forming a judg- ment of the distance of bodies. This we do by attending to the loudness of the sound; for we instinctively lay it down as a princi- ple, that a loud sound proceeds from a body that is near us, and a feeble sound from one more remote. This is the cause of numerous acoustic errors, in spite of reason and experience. In the theatres, the deception is often well managed, when the object is to give the idea of bodies approaching. The sound—that of martial music, for example—is rendered faint and subdued; and, under such circum- stances, appears to proceed from the remote distance; whilst, by adding gradually and skilfully to its intensity, we are irresistibly led to the belief, that the army is approaching; and the illusion is com- pleted by the appearance of the military band on the stage, allowing its soul-inspiring strains to vibrate freely in the air. In like manner we are deceived by the ventriloquist. He is aware of the law that guides us in our estimation of distance, and, by skilfully modifying the intensity of his voice, according as he wishes to make the sound appear to proceed from a near or distant object, he irresistibly leads us into an acoustic error. It requires education or experience to enable us to appreciate dis- tances accurately by this sense, as well as to judge of their position. In the case, detailed by Magendie,f of a boy, who, after having been entirely deaf until the age of nine, was restored to hearing by M. Deleau, by means of injections thrown into the cavity of the « Magendie's Journal de Physiologie, v. 367. t Ibid, v. 223, 14* 162 SENSE OF HEARING. tympanum through the pharyngeal extremity of the Eustachian tube, one of the most remarkable points was, his difficulty in acquiring a knowledge of the position of sonorous bodies. In forming our judgment on this subject we require the use of both ears. In all other cases an impression made upon one only would perhaps be sufficient. To judge of the direction of a sound we compare the intensity of the impression on each ear, and form our deductions accordingly; and experiment shows, that if we close one ear we are led into errors, which are speedily dissipated by em- ploying both. Still we are often deceived even under these last cir- cumstances, and are compelled to call in the aid of sight. The blind afford us striking examples of accuracy, in this respect, in their acquired perceptions by the ear. In the Belisor of Zeune, the case of a blind man is cited from Diderot; who, guided by the direction of the voice, struck his brother, in a quarrel, on the fore- head, with a missile, which brought him to the ground.* If the sonorous vibrations before reaching the ear are deflected from their course we are liable to deception, mistaking the echo for the direct or radiant sound. The ideas of magnitude, acquired by the ear, are few, and to a trifling extent only. They occasionally enable the blind to judge of the size of apartments, and this they can sometimes do with much accuracy.f It is well known, that if a sound be confined within a small space, it appears much louder than when the sonorous undu- lations can extend farther; hence the greater noise, caused directly by a pistol fired,in a room than in the open air. The sound indirectly produced will necessarily be modified by the different reflections or echoes, that may- be excited. By attending to these circumstances— to the loudness of the voice and to the intensity of the reverberations occasioned by the walls, and by calling into their aid the experience they have had under similar circumstances—in other words, by effecting a strictly intellectual process—the blind attain the know- ledge in question. The velocity of a body is indicated by the rapid succession of the vibrations, that impress the ear, as well as by the change in their intensity if the body be moving along a surface or through the air. A carriage, approaching us with great velocity, is detected by the ear, from the rapidity with which the wheels strike against inter- vening obstacles; and by the gradual augmentation in the intensity of the sound thus produced. When opposite to us the intensity is greatest; and a declension gradually takes place until the sound is ultimately lost in the distance. Lastly, by audition we can form some judgment of the nature of bodies from the difference in the sounds emitted. It has been already remarked, that the timbre or quality of sound, can be accurately appreciated. By this quality we can distinguish be- * Rudolphi, Grundriss, u. s. w. Berlin, 1821, &c. t Darwin's Zoonomia, vol. ii.. and Manchester Memoirs, 2d edit. v. 622. Lond. 1789. SENSE OF SIGHT. 163 tween the sound of wood or of metal; of hollow or solid bodies, &c; but in all these cases we are compelled to call into aid our experience,—without which we should be completely at a loss; and to execute a very rapid, but often a very complicated intellectual operation. To conclude:—audition may be exercised passively as well as actively; hence the difference between simply hearing, and listen- ing. We cannot appreciate, in man, the precise effects produced on the different portions of the ear by volition;—whether, for ex- ample, the advantage be limited to the better direction given to the ear, as regards the sonorous body, and to the avoiding of all dis- traction, by confining the attention entirely to the impressions made on this sense; or whether, by it, the pavilion may not be made somewhat more tense by the contraction of its intrinsic and extrinsic muscles;—the membrana tympani, and the membranes of the fora- men ovale be modified by the contraction of the muscles of the ossi- cles ; or, in fine, the auditory nerve be rendered better adapted for the reception of the impression, and the brain for its appreciation. All these points are insusceptible of direct observation, and experiment, and are, therefore, enveloped in uncertainty. In some animals—as the horse—the outer ear becomes an acoustic instrument under the guidance of volition; and is capable of being turned in every direc- tion in which a sonorous body may be placed. Like the other senses, that of hearing is largely improved by edu- cation or cultivation. The savage, who is accustomed, in the stillness of the forest, to listen to the approach of his enemies or of his prey, has the sense so delicate as to hear sounds, that are in- audible to one brought up in the din of the busy world. The blind, for reasons more than once assigned, afford examples of extreme delicacy of this as well as of their other remaining senses. They are necessarily compelled to cultivate it more'; and, lastly, the musician, by education, attains the perception of the nicest shades of musical tones. The aptitude is laid in cerebral organization, and is developed by the education of the instrument— the ear—as well as of the encephalic or intellectual organ, without which, as we have seen, no such appreciation could be accom- plished. SECT. V.—OF THE SENSE OF SIGHT, OR VISION. The immediate function of the sense of sight is to give us the notion of light and colours. Like the other senses, it is a modifica- tion of that of touch, whether we regard the special irritant—light —as an emanation from luminous bodies, or as the vibration of a subtile, ethereal fluid, pervading all space. Under the latter theory it would most strongly resemble the sense last considered. The pleasures and advantages, derived by the mind through this inlet, are of so signal a kind as to render the organ of vision a sub- 164 SENSE OF SIGHT. ject of universal interest. Every one, who lays the slightest claims to a general education, has made it more or less the subject of study, and is frequently better acquainted with its structure and properties than the medical practitioner. Complicated as its organi- zation may seem, it is, in action, characterized by extreme sim- plicity ; yet, " in its simplicity," as Arnott* has remarked, " so perfect, so unspeakably perfect, that the searchers after tangible evidences of an all-wise and good Creator, have declared their willingness to be limited to it alone in the midst of millions, as their one triumphant proof." Into this structure we shall inquire, so far as is necessary for our purpose, after having described the general properties of light; and then detail the mode in which its various functions are effected, and the knowledge derived by the mind through its agency. The eye is the organ of vision. It varies materially in different animals: in some consisting of a simple capsule, with the final ex- pansion of the nerve of sight distributed on its interior, and com- municating externally by means of a transparent cornea, which admits the light. It is in this simple state, that M. de Blainvillef assimilates it to a bulb of hair, modified for the new function it has to perform. In man, and in the upper classes of animals, the organ is much more complicated in its structure; and in it we have a still clearer example of the distinction between the physical, and ner- vous or vital part of the apparatus, than in any of the other organs of sense—the former consisting of transparent tunics, and humours, which modify the light according to the laws of optics—the latter being a production or expansion of the nervous system, for the reception of the impression of light, and for conveying such impres- sion to the proper part of the encephalon. There is, besides, attach- ed to the organ, a number of accessory parts or tutamina, which are more or less concerned in the proper performance of the func- tion. ' It will be necessary, therefore, to give a succinct view, not only of the eye, properly so called, but also of these accessory or- gans, which serve to lodge, move, protect, and lubricate it. The description will not, however, be clearly understood, without pre- mising some general observations on the properties of light, espe- cially as regards its refraction, on which the phenomena of vision are greatly dependant. 1. Of Light. The sun and the fixed stars are the great sources of light. It is given off also from substances in a state of combustion, and from phos- phorescent bodies; and, by entering the eye directly, or after various reflections or refractions, impinges on the optic nerve, and gives the sensation of light. * Elements of Physics, 2d Amer. edit. vol. ii. P. 1, p. 161. Philad. 1836. + De l'organization des animaux. Paris, 1825. LIGHT. 165 Two great opinions have been entertained regarding the nature of light; the one, propounded by Newton—that it consists of extremely minute particles, emanating from luminous bodies; the other—that of Descartes, Hook, Huygens, Euler,* and others,—that it is a subtile, eminently elastic fluid—an ether—pervading all space, the elastic molecules of which, when put in motion by the oscillations of bodies, impress the eye as sonorous vibrations affect the ear. It is not for us to discuss this question of higher physics. We may merely remark, that difficulties attend both hypotheses. According to that of Descartes, it is not easy to explain, why an opaque body should prevent the undulations from reaching the eye,—or the change of direction, which the light experiences in passing from one medium into another; whilst, according to that of Newton, it is difficult to conceive, how a luminous body, as the sun, can shed its immense torrents of light incessantly, without undergoing rapid diminution; and how, with the extreme velocity of light, these particles should not be possessed of sensible momentum; for it has been found, that a large sunbeam, collected by a burning-glass, and thrown upon the scale of a balance of extreme delicacy, is insufficient to dis- turb the equilibrium. To the hypothesis of Newton it has also been objected, that the particles, being reflected by thousands of bodies, and in innumerable directions, would necessarily jostle and interfere greatly with each other. This objection is not, however, as valid as it appears at first sight. It will be seen hereafter, that the impres- sion of a luminous object remains upon the retina for the sixth part of a second. Admitting it, however, to impress the eye for the 3-f^th part, three hundred particles, per second, would be sufficient to excite a constant and uniform sensation of the presence of light; and since, as we shall find, it traverses sixty-seven thousand leagues in a second of time, if we divide this by three hundred, we shall find a space of six hundred and seventy miles between each parti- cle ; a distance equal to that—in a straight line—between New York and Savannah; and if we suppose six particles to be sufficient per second, each will be separated from the other by a space of thirty- three thousand five hundred miles ! Without deciding in favour of either of the great theories, that of Newton admits of more easy application to our subject, and will, therefore, be employed in the various explanations that may be re- quired. The light, then, proceeding from a luminous body, impinges on the substances, that are within its sphere; and these, by reflecting the whole or a part of it to the eye, become visible to us. In its course, direct or reflected, its velocity is almost inconceiv- able. From observations made on the eclipses of Jupiter's satel- lites, by Romer, Cassini, and other astronomers, it has been calcu- lated, that the light of the sun is eight minutes and thirteen seconds in its passage from that luminary to the earth. The distance be- * Letters of Euler on different subjects of Natural Philosophy; with notes, &c. by Sir David Brewster. Amer. edit, by Dr. Griscom. New York, 1833, vol. i. 87. 166 SENSE OF SIGHT. tween the earth and sun is thirty-three millions of leagues, so that the velocity of light is sixty-seven thousand leagues, or two hun- dred thousand miles per second; in other words, in the lapse of a single second it could pass between Washington and Albany—sup- posing the distance to be three hundred miles—seven hundred times; and could make the tour of the globe in the time it takes us to wink. In consequence of this extreme velocity,—in all calculations, regard- ing the light from bodies on the surface of the globe, it is presumed to reach the eye instantaneously; for, granting that aluminous body at Albany could be seen at Washington, the light from it would reach the eye in the T£o-m part of a second. Inconceivable as this velocity is, it is far surpassed by that of the attractive power exerted between the heavenly bodies. " I have ascertained," says La Place, "that between the heavenly bodies all attractions are transmitted with a velocity, which, if it be not infinite, surpasses several thou- sand times the velocity of light; and we know that the light of the moon reaches the earth in less than two seconds." An annotator on the works of this distinguished mathematician is more definite, affirming, " that the gravific fluid passes over one million of the earth's semi-diameters in a minute of time." Its velocity is eight millions of times greater than that of light. A series of particles, succeeding each other in a straight line, is called a ray of light. The light which proceeds from a radiant point, forms diverging cones, which would be prolonged indefinitely did they not meet with obstacles. In its course, it loses its intensity according to a law, which seems applicable to all influences radiating from a centre. If a taper be placed in the middle of a box, each of whose sides is a foot square, all the light must impinge upon the sides of the box; if it be placed in a box, whose sides are two feet square, the light will shine upon them from double the distance, but it will be distributed over four times the surface. The intensity of the light, then, in this case, as in every other, diminishes according to the square of the distance from the luminous body. According to this rule, those planets, which are nearer the sun than we are, must receive the light and also the heat—for the same law applies to calo- ric—in much greater intensity; whilst the more distant luminaries can receive but little caloric, or light, in comparison with our earth; hence, perhaps, the necessity of the satellites by which they are ac- companied, and by whose agency the light of the sun is reflected to the planet, and the deficiency is, in some measure, compensated. In proceeding from a luminous body, the rays, cones, or pencils of light must traverse intermediate bodies, in order to reach the eye. These bodies are called media. Air is the common medium; and when, in this way, the light has reached the exterior of the organ, the farther transmission is effected through different transparent hu- mours, which consequently form so many media. In its course through the different media, the light may remain unmodified: it may proceed in the same straight line; or it may meet LIGHT. 167 with an obstacle, which arrests it altogether, or reflects it; or, again, it may traverse media of different natures and densities, and be made to deviate from its original course, or be refracted. When a ray of light falls upon an opaque body, as upon a bright metallic or other mirror, the light is reflected from the mirror, in such a manner, that the angle, made by the incident ray with a per- pendicular to the surface of the medium at the point of incidence, is exactly equal to that made by the reflected ray with the same per- pendicular. Suppose I J, (Fig. Fig. 23. 23.) to represent a plate of polished me- tal, or of glass, ren- *>\ dered opaque by a metal spread upon its posterior surface, as in the common looking-glass. The rays, proceeding from an observer at K, will be reflected back to him in the same line KC; that is, in a line perpen- dicular to C, the point of incidence. The observer will, therefore, see his own image; but for reasons to be hereafter mentioned, under the head of optical illu- sions, he will seem to be as far behind the mirror as he really is be- fore it or at E. Suppose, on the other hand, that the observer is at A, and that a luminous body is placed at B; in order that the rays, proceeding from it, shall impinge upon the eye at A, it is ne- cessary that the latter be directed to that point of the mirror, from which a line, drawn to the eye, and another to the object, will form equal angles with the perpendicular; in other words, the angle B C K, or angle of incidence, must, be equal to the angle of reflection, A C K. In this case, again, the object will not appear to be at B, but in the prolongation of the line A C, at H, as far from the point of incidence, C, as B is. Except in the case of illusions, the study of the reflection of light or catoptrics does not concern vision materially. It is on the prin- ciples of dioptrics, that the chief modifications are effected on the progress of the light through the physical part of the organ ; and, without some knowledge of these principles, the subject would be totally unintelligible. It is necessary, therefore, to dwell at some length on this topic. Whenever a ray of light passes through diaphanous or trans- 168 SENSE OF SIGHT. parent bodies of different densities, it is bent or made to deviate from its course, and such deviation is called refraction; the ray is said to be refracted; and, owing to its being susceptible of such refraction, it is held to be refrangible. The point, at which a ray of light enters a medium, is called the point of immersion; and that, by which it issues from such medium, the point of emergence. Instead of considering the medium I J opaque, let us regard it as transpa- rent. C, in this case, will be the point of immersion for the incident rays that meet there; and L and F will be the points of emergence for the rays K E and A C F G, respectively. If a ray of light, as K C, falls perpendicularly on the surface of any medium, it con- tinues its course through the medium without experiencing any mo- dification, and emerges in the same straight line. Hence, a body at L, will appear in its true direction and distance to an observer at K looking directly downwards on a pool of water, I J. If, on the other hand, a ray of light, as A C, after having passed through air, falls obliquely upon the surface of the water at C ; by entering a medium of different density, it is deflected from its course; and, instead of proceeding in the direction C H, it is refracted, at the point of immersion, in the direction C F—that is, towards the per- pendicular K E. If, again, the ray emerges at F into a medium of the same density as that through which it passed in the course A C, it will proceed in a line parallel to A C, or in the direction F G, or it will wander from the perpendicular. The cause of this difference in the deflections, produced by different media, is not easy of expla- nation. The fact alone is known to us, that bodies refract light differently according to their densities and nature. If the light pro- ceeds from a rarer to a denser medium it is attracted or refracted towards the perpendicular; if, on the contrary, it passes from a denser to a rarer medium, it is refracted from the perpendicular. The ray A C passed from a rarer medium,—the air,—into a denser, I J—water: it was refracted in the direction C F, towards the per- pendicular K E. On emerging at F, circumstances were reversed; it wandered from the perpendicular M N, and in the direction F G, parallel to A C, because the media, above and below 1 J, were iden- tical. We can now understand, why water, saline solutions, glass, rock-crystal, &c. have higher refractive powers than air. They are more dense. The nature or character of bodies also influences greatly their refractive powers. Newton observed this, in his experiments upon the subject, and has furnished science with one of its proudest tro- phies, by his prognostic, in the then infant state of chemistry, that water and the diamond would be found to contain combustible ingre- dients. The diamond or brilliant is one of the most refractive of known substances, and this is one of the sources of its brilliancy. The opinion of Newton, it is hardly necessary to say, has been triumphantly confirmed. This refraction of the rays, that fall obliquely upon a medium, gives rise to numerous optical illusions. The ray proceeding from LIGHT. 169 F, in the bent course F C A, will impinge on an eye at A; and the object F will appear to be at /. The pool will consequently seem shallower. In like manner, an object O in the air would not be per- ceptible to an eye in the water at F, in the direction O C F; whilst one at A would be distinctly visible; the ray from it proceeding in the direction A C F, but appearing to come straight to the eye in the direction O C F. All transparent bodies, at the same time that they refract light, reflect a portion of it. This is the cause of the reflections we no- tice on the glass of our windows, and of the image perceptible in the eye. The same substance has always the same refractive power, what- ever may be its shape:—in all cases, the sine of the angle of refrac- tion holding the same ratio to the sine of the angle of incidence, whatever may be the incidence. The angle of incidence is the angle formed by the incident ray with a perpendicular raised from the point of immersion; the angle of refraction, that formed by the re- fracted portion of the ray with the same perpendicular. In Fig. 23, A C K is the angle of incidence of the ray A C; and LCF the angle of refraction. The sines of these angles respectively are the lines P Q and L F. But although the media may refract the rays of light equally, the , form of the refracting body will materially modify their arrange- ment. The perpendiculars to the surface may approach or recede from each other; and if this be the case the refracted rays will ap- proach or recede from each other likewise. Where the body has plane and parallel surfaces as in the glass of our windows, the refraction, experienced by the ray on entering the glass is corrected by that which occurs on its emergence ; and although the light may not pass in one straight line, it proceeds in parallel lines, separated by a space dependent upon the thickness of the refracting body and the obliquity of the incident ray. If the medium be very thin, as in a pane of glass, the rays do not appear deflected from their original direction. In Fig. 23, the interval be- tween the direct ray and the ray A C F after its emergence is that between G and H. If the surfaces of the diaphanous body are plane, but inclined to- wards each other- as in the common prism, the refrac- tion, experienced by the ray on emerg- ing, instead of cor- recting that expe- rienced during its passage through the body, is added to it; and the rays are deflected from their course to an extent equal to the sum of the two vol. i. 15 Fig. 24. 170 SENSE OF SIGHT. refractions. The ray A B, Fig. 24, after impinging upon the side D L of the prism, at B, instead of continuing its course in the direction B J, is refracted towards the perpendicular CBF; the medium being denser than air; and on emerging into the rarer medium, in- stead of continuing its course in the direction G I, it is refracted in the line G H or from the perpendicular K J. Again, if the surfaces of the medium be convex, the rays are so situated, after refraction, as to converge behind the refracting body into a point called the Fig. 25. focus, which is nearer to \ the medium the less the divergence of the rays, or in other words, the more distant the lumi- nous object. Fig. 25 ex- hibits a pencil of rays, proceeding from a ra- diant point at A, and meeting at a focus at B; the dotted lines being the perpendiculars drawn to the surface at the points of immersion and emergence. Lastly, if the surfaces of the medium be concave, as in Fig. 26, the.luminous rays, proceeding from a radiant point as at A, are ren- dered so divergent, that if we look for a focus here it must be ante- rior to the medium or at G. Fig. 26. A knowledge of these facts has given occasion to the construction of numerous invaluable optical instruments, adapted to modify the luminous rays, so as? to change the situation in which bodies are seen, to augment their dimensions, and to render them more lumi- nous, and visible, when remote and minute. It is, indeed, to this branch of science that we are indebted for some of the most im- LIGHT. 171 portant information and advantages, that we possess in the domains of science and art. The simplest of these instruments are bodies, shaped like a lentil, and hence called lenses. They are composed of two segments of a sphere. The medium in Fig. 25 is a double convex lens; that in Fig. 26, a double concave. The manner in which they modify the course of the luminous rays passing through them has been sufficiently described. The study of the refraction of light leads us to the knowledge of an extremely important fact; which, when it was first made known by Newton, excited universal astonishment;—viz. that a ray of light is itself composed of several coloured rays differing from each other in their refrangibility. Fig. 27. ? or *e rndn,Tr?nfp Slgnal statlons'is re^ered less fitted for minute ana near inspection. During the domination of Napoleon, when the conscript laws were tLJ?riS-V3:thG y°Ung men gently induced a myopic state of h?s deL/hP C°nfDt T °f gIasses' of considerable concavity; military service5 "" * 8Ufficient gr0Und of exemPtion *om ex4rm?een1r^wtn, whic\has §iven ™ to much disputation and experiment is, why, as we have two eyes, and the image of an obiect SmZTnd B^ff T^ °f,the^ WG d° n0t See such object doubts femitht and Buffon J consider, that in infancy we do see it double- and that it is not until we have learned by experienc^byhe sense of touch for example,-that one object only exists, that we acqui e ftrSeTnA Smgle ™unu- HtGr the mind has thus become n- s ructed of its error, a habit of rectification is attained, until it is ultimately effected unconsciously. The objections to this hypothesis are many and cogent. We are not aware of any instance on record, in which double visbn has been observed to occur in those, who, having laboured under cata ract from birth, have received their sight b/an operaSon; and we * W. Ch. Wells, Essay upon Single Vision with Two EvM T ™a itoq SINGLE VISION. 227 are obviously precluded from knowing the state of vision in the infant, although the simultaneous and parallel motions of the eyes, which is manifestly instinctive, and not dependent upon habit, would induce us to presume, that the images of objects—as soon as the parts have attained the necessary degree of developement—are made to fall upon corresponding parts of the retina. It may, also, be remarked, in favour of the instinctive nature of this parallel motion of the eyes, that in the blind,—although we may find much irregu- larity in the motions of the eyeball, owing to no necessity existing for the eyes being directed to any particular point,—the eyeballs move together, unless some deranging influence be exerted. The truth is, as we have already observed, the encephalon is com- pelled to receive the impression as it is conveyed to it; and even in cases, in which we are aware of an illusion, the perception of the illusion still exists in spite of all experience. If the finger be pressed on one side of the eyeball, an object, seen in front, will appear double, and the perception of two objects will be made in the brain; although we know from experience, that one only exists. This oc- curs in all the various optical illusions to be presently mentioned. The effect of intoxication has been adduced in favour of this hypothesis. It is said that, in these cases, the usual train of mental associations is broken in upon, and hence double vision results. The proper explanation, however, of this diplopia of the drunkard rests upon other grounds. The effects of inebriating substances on the brain are, to interfere with all the functions of that organ; and most sensibly with the voluntary motions, which become irregularly exe- cuted. The voluntary muscles of the eye partake of this vacillation, and do not move in harmony, so that the impressions are not made on corresponding points of the retina, and double vision necessarily results. Another hypothesis has been, that although a separate impression is made upon each retina,—in consequence of the union of the optic nerves, the impressions are amalgamated, and arrive at the ence- phalon, so as to produce but one perception. This was the opinion of Briggs,* and Ackermann, and at one time it was generally re- ceived. Still more recently, Dr. Wollaston,-)- has supposed the consen- taneous motion of the eyes to be connected with the partial union of the optic nerves. The anatomical and physiological facts, re- lating to the union and decussation of the optic nerves have already engaged us. By a reference to that subject it will be, found, that a true decussation takes place between them; that each eye has, not- withstanding, its distinct nerve, from origin to termination; and that no such semi-decussation, as that contended for by Dr. Wollaston, probably exists. These facts are unfavourable to this hypothesis of amalgamation of impressions; and besides, if we press slightly on the eye, we have a double impression, although the relation of the optic nerves to each other is the same; and, moreover, the same » Nova Visionis Theoria. Lond. 1685. t Philos. Transact, for 1824, p. 222. 228 SENSE OF SIGHT. explanation ought to apply to audition, in which we have two distinct impressions, but only a single perception:—yet no one conceives that the auditory nerves decussate. Another opinion has been maintained ;—that we do not actually receive the perception of two impressions at the same time, but that vision consists in a rapid alternation of the eyes, according as the attention is directed to one or other of them by accidental circum- stances. Such was the opinion of Dutours.* A modification of this view was entertained by Le Cat,f who asserts, that, although the right eye is not always the most powerful, it is the most frequently employed; and Gall openly denies, that we use both eyes at the same time, except in the passive exercise of the function. In active vision, he asserts, we always employ one eye only,—sometimes the one and sometimes the other ; and thus, as we receive but one im- pression, we necessarily see but one object. In support of this view, he remarks, that, in many animals, the eyes are situated at the sides of the head, so as not to be capable of being directed together to the same object. In them, consequently, one eye can alone be used; and he considers this a presumption that such is the case in man. He remarks farther, that in many cases we use one eye by preference, in order, that we may see better; as in shooting or in taking the direction of objects in a straight line, &c.; and that although, in other cases, both eyes may be open, we still use but one. In proof of this, he says, if we place a small object between the eyes and a lighted body, and look at the latter, the shade does not fall between the eyes, on the root of the nose, as it ought to do if the body were regarded with both eyes, but on each eye alter- nately, according as the one or the other is directed to it; and, he adds, if when we squint voluntarily, we see two objects, it is be- cause one eye sees passively, whilst the other is in activity.J Amongst the numerous objections to this view of the subject, a few may be sufficient. Every one must have observed how much more vividly an object is seen with both eyes than with one only. The difference indeed according to Jurin§ is a constant quantity; and in sound eyes of the ordinary degree of power, amounts to one-thirteenth of the whole effect. But we have experiment to show, that a distinct impression is made upon each eye.|J If a solar beam be admitted into a dark chamber and be made to pass through two glasses of tolerable thickness, but of different colours, placed close alongside each other, provided the sight be good, and the eyes of equal power, the light, which is perceived, will not be of the colour of either of the glasses, but will be of an intermediate shade; and, when this does not happen, it will be * Memoir, presentees a l'Academie des Sciences, &c. t. iii. and iv. t Op citat X Adelon. Physiologie, 2d Cdit. i. 457. Paris, 1829. § Essay appended to Smith's Optics. Cambridge, 1738; and Haller. Element. Phy- siolog. lib. xvi. 4. 0 Steinheim, in Hecker's Annalen, 1836; and Dublin Journal of Medical Sciences Jan. 1837. SINGLE VISION. 229 found that the eyes are of unequal power. When such is the case, the light will be'of the colour of the glass, that is placed before the stronger eye. These results were obtained in the Cabinet de Physique of the Faculte de Medecine of Paris, by M. Magendie,* in the presence of M. Tillaye the younger. The existence of this double impression is proved in another way. If we place any tall, slender object a few feet before us, and examine its relative situation, compared with a spot on a wall in the distance, we find, that if the spot be hidden by the stick, when both eyes are open, it will become visible to each eye, when used singly; and will be seen on the side of the stick corresponding to the eye that is employed. All these facts signally demonstrate, that two impressions are really made in all cases,—one on each eye;—and yet the brain has perception of but one. If the law of visible direction, which Sir David Brewster has pointed out (see page 213) be adopted, the cause of single vision with two eyes must be admitted as a neces- sary consequence of it. If we are placed at one end of a room, and direct the axis of both eyes to a circular aperture in a window-shut- ter at the other end, although an image of this aperture may be formed in each eye, yet because the lines of visible direction from similar points of the one image meet the lines of visible direction from similar points of the other image, each pair of similar points will appear as one point, and the aperture seen by one eye will ex- actly coincide with the aperture seen by the other eye. But if, when an object is seen single with both eyes, we press one eye aside, the image formed by that eye will separate from the other image, and the object will appear double; or, if the axis of both eyes are directed to a point either nearer or remote than the aper- ture in the window-shutter, then, in both of these cases, the aperture will, appear double, because the similar lines of visible direction no longer meet at the aperture.f In the course of the preceding remarks, it was said, that the eyes are not always of the same power. The difference is, indeed, some- times surprising. M. AdelonJ mentions the case of a person, one of whose eyes required a convex glass, with a focus of five inches; the other a concave glass with a focus of four inches. In these cases, it is important to use one unassisted eye only; as confusion must necessarily arise from directing both to an object. This is the cause why we close one eye in looking through a telescope. The instru- ment has the effect of rendering the focal distance of the two eyes unequal, and of placing them in the same situation as if they were, originally, of different powers. From what has been said it will be understood, that if from any * Precis, &c. I. 86. See also Dutours, in Mem. presentees a l'Academ. iii. 514, and iv. 499. | Optics, p. 44, in Library of Useful Knowledge, Natural Philosophy, vol. I. London, 1829, and Treatise on Optics, edit. cit. X Physiologie, edit. cit. I. 459. vol. i. 20 230 SENSE OF SIGHT. cause, as from a tumour pressing upon one eyeball, from a morbid debility of the muscles, or from a want of correspondence in the sensibility of the two retinas, the eyes are not properly directed to an object, double vision will be the consequence. In almost all cases, however, of distortion of the eyeballs, the image will fall upon a part of one retina, which is more sensible than the portion of the other on which it impinges; the consequence will be, that the mind will acquire the habit of attending to the impression on one eye only; and the other will be so neglected, that it will assume a posi- tion to interfere as little as possible with the vision of its fellow—so that, although at first, in squinting, there may be a double impres- sion, vision is ultimately single. Buffon,* who was of this opinion, affirms, that he examined the eyes of many squinters, and found that they were of unequal power; the weaker, in all cases, having turned away from its direction, and generally towards the nose, in order that fewer rays might reach it, and consequently vision be less interfered with. Yet, it is always found, if the sound eye be closed, that the other resumes its proper direction; a fact, which disproves the idea of De La Hiref and others, that the cause of strabismus or squinting is a difference of sensibility in the corre- sponding points of the retinas, and that the discordance in the move- ments of the organs occurs, in order that the images may still fall upon points of the retinae, that are equally sensible. According to this view, both eyes must of course act. The fact of the diverted eye resuming its proper direction, when the sound one is closed, is of important practical application. Many of the cases of squinting, which occur in infancy, have been induced by irregular action in the muscles of the eyeball; so that some having been, from accident or from imitation, used more frequently than others, the due equilibrium has not been maintained; double vision has resulted ; and the affected eye has gradually attained its full obliquity. In these cases, we can, at times, remedy the defect, by placing a bright or conspicuous object in such a position as to exercise the enfeebled muscles; or, we can compel the whole labour of vision to be effected by one eye, and that the affected organ, which, under the stimulus, will be correctly exerted, and thus, by perseverance, the inequality may often be obviated. These indeed are the only cases in which we can expect to afford relief; for if the defect be in the interior of the eye, in a radical want of corre- spondence between the retinas, or in inequality of the foci, it is irre- mediable. It would appear, then, that, in confirmed squinting, one eye is mainly, if not solely used, and that vision is single,—that the incli- nation of one eye inwards may be so great as to deprive it of func- tion, or so slight as to allow the organ to receive rays from the same object as its fellow; but, in either case, it would seem, that they, who squint habitually, neglect the impressions on the distorted eye, and see with but one. * Mem. de PAcademie, 1743. t Ibid, tom.ix. 530; also Jurin, in Essay appended to Smith's Optics, § 178—194. MULTIPLE VISION WITH ONE EYE. 231 We have said, that the eyeball of the imperfect eye is drawn towards the nose, in order that as few rays as possible may pene- trate the organ; and the vision of the sound eye be less liable to confusion. Sir Everard Home,* however, conceives, that it takes this direction in consequence of the adductor muscle being stronger, shorter, and its course more in a straight line than that of any of the other muscles of the eye; and Sir Charles Bellf ingeniously applies his classification of the muscles of the eye to an explanation of the same fact. He asserts, that the recti muscles of the eyeball are in activity during attention to the impression on the retina,—but that when the attention is withdrawn, the straight muscles are relieved, and the eyeball is given up to the influence of the oblique muscles, the state of equilibrium between which exists, when the eyeball is turned, and the pupil presented upwards and inwards. Lastly, in persons who are in the habit of taking repeated ce- lestial observations, or in those who make much use of the micro- scope, the attention is so entirely directed to one eye, that the other is neglected, and, in time, wanders about, so as to produce squinting at the pleasure of the individual. In these cases, the eyes become of unequal power, so that one only can be employed where distinct vision is required. So far our remarks have been directed to double vision, where both eyes are employed. We have now to mention a very singular fact, connected with double and multiple vision with one eye only. If a hair, a needle, or any small object be held before one eye—the other being closed—and within the point of distinct vision, so that the bright light of a lamp or from a window shall fall upon the object, in its passage to the eye, or be reflected from it, we appear to see not one object but many. This fact, when it was first observed by the author, appeared to him to have entirely escaped the observation of opticians and phy- siologists, inasmuch as it has not been noticed in any of the works recently published on. optics or physiology. On reference, how- ever, to the excellent " system," of Smith,! on the former subject, he found in the " Essay upon distinct and indistinct Vision," by Dr. Jurin, appended to that work, the whole phenomenon explained, and elucidated at considerable length. The elaborate character of the explanation is probably the cause, why the fact has not been noticed by subsequent writers. The best way of trying the experiment is that suggested by Jurin. Take a parallel ruler, and opening it slightly, hold it di- rectly before the eye, so as to look at a window or lamp through the aperture. If the ruler be held at the visual point, the aperture will appear to form one luminous line; but if it be brought nearer to the eye, it will appear double, or as two luminous lines, with a * Philos. Transact. 1797, and Lectures on Comparative Anatomy, iii. p. 238. Lond. 1823. t Anat. and Physiol, edit, cit ii. 235. X Optics, ed. citat. 232 SENSE OF SIGHT. dark line between them ; and according as the aperture is varied— or the distance from the eye—two, three, four, five or more lumi- nous and dark parallel lines will be perceptible. At first sight, it might seem, that this phenomenon should be re- ferred to the diffraction or inflection, which the light experiences in passing by the edges of the small body,—as the hair or needle. Newton had long ago shown, that, when a beam of light shines upon a hair, the hair will cast several distinct shadows upon a screen, and will, of course, present several images to the eye. Dr. Rittenhouse,* explains, on the same principle, a very curious opti- cal appearance, noticed by Mr. Hopkinson, in which, by the in- flection of light, caused by the threads of a silk handkerchief, a multiple image of a distant lamp was presented. The objections, however, to the explanation by inflection are,— that the image always appears single, if the object be not within the distance of distinct vision; and, secondly, the same multiple image is presented, when the object is seen by reflection, as when we look at a fine line, drawn upon paper; or at a fine needle held in a bright light. In this case, a considerable number of parallel images of the needle may be seen, all equally or nearly equally distinct, and not coloured. Dr. Jurin considers the phenomena to be caused by fits of easy refraction and reflection of light. Newrton demonstrated, that the rays of light are not, in all parts of their progress, in the same disposition to be transmitted from one transparent medium into another; and that sometimes a ray, which is transmitted through the surface of the second medium, would be reflected back from that surface, if the ray had a little farther to go before it impinged upon it. This change of disposition in the rays,—to be either trans- mitted by refraction, or to be reflected by the surface of a transpa- rent medium,—he called their^s of easy refraction, and fits of easy reflection; and he showed, that these fits succeed each other al- ternately at very small intervals in the progress of the rays. Newton does not attempt to explain the origin of these fits, or the cause that produces them; but it has been suggested, that a tolerable idea of them may be formed by supposing, that each par- ticle of light, after its emanation from a luminous body, revolves round an axis perpendicular to the direction of its motion, and pre- sents alternately to the line of its motion an attractive and a repul- sive pole, in virtue of which it will be refracted, if the attractive pole be nearest any refracting surface on which it falls, and reflect- ed, if the repulsive pole be nearest the surface. A less scientific notion of the hypothesis has also been suggested; by supposing a body with a sharp and a blunt end passing through space, and successively presenting its sharp and blunt ends to the line of its motion. When the sharp end encounters any soft body it penetrates it: but when the blunt end encounters the same body, it will be reflected or driven back. t Amer. Philos. Transact, vol. ii. MULTIPLE VISI0X WITH ONE EYE. 233 to the phenomenon in question, Jurin presumes, Fig. 41. In applying this that the light, in passing through the humours of the eye, experi- ences these fits of easy refraction and easy reflec- tion. This will be understood by the marginal figure, Fig. 41. From the point A, sup- pose a number of rays of light to proceed and to impinge, with dif- ferent degrees of obliquity, on the denser medium, B C ; all the rays, which are in fits of easy refraction, will pass through the medium to the point D; whilst those, that are in fits of easy re- flection, will be thrown back into the medium ABC; so that we may presume, that all the rays, which fall upon the parts of the medium B C, corresponding to the bases of the dark cones will bo reflected back, whilst those, that correspond to the bases of the light cones, will pass to a focus at D. Now, if all the bundles of rays, transmitted through the surface B C, be accurately collected into a focus, no other consequence will arise from the other bundles of rays having been reflected back, than that the focus will be less luminous, than it would have been had all the rays been transmitted through it. This explains why, at the distance of dis- tinct vision, we have only a single impres- sion made on the eye. But if we approach the object A, so that the focus is not thrown,—say upon the screen 11 T, which may be presumed to re- present the retina—but behind it; the dark and light spaces will be represented upon the screen, and, of course, in concentric cir- cles. This happens to the eye, when the hair or needle or other object, is brought nearer to it than the visual point. We can thus un- derstand, why concentric circles, of the na- ture mentioned, should be formed upon the retina; but how is it, that the objects seen preserve their linear form? Suppose a b, Fig. 42, to be a luminous cone, which in a fit of easy refraction, has impinged upon the retina: and A B, b a, the concentric circles, corresponding to the rays, that have 20* 234 SENSE OF SIGHT. been reflected. It is obvious that every point of the object will be the centre of so many concentric circles on the retina; and if we imagine the fits of easy reflection and refraction to be the same around those points, we shall have the dark and lucid lines repre- sented by the tangents to these circles; and hence we can compre- hend why, instead of having one lucid line e f, we have three, separated by dark lines parallel to them; and if the light from the luminous point be strong enough to form more lucid rings than are represented in Fig. 42, and the breadth of those rings be not too minute to be perceived, we may have the appearance of five, seven, or more lucid lines, separated by parallel dark lines. We proceed now to consider the advantages, which the mind derives from the possession of this sense, so pre-eminently entitled to the epithet intellectual. Its immediate function is to give us the sensation of light and colour. In this it cannot be supplied by any of the other senses. The action is, therefore, the result of organization; or is a " law of the constitution;" requires no education; but is exercised as soon as the organ has acquired the proper developement. Yet, occasion- ally, we meet with singular cases, in which the eye appears to be totally insensible to certain colours, although capable of performing the most delicate functions of vision. Sir David Brewster* has col- lected several of these cases from various sources. A shoemaker, of the name of Harris, at Allonby, in Cumberland, could only distin- guish black and white; and, whilst a child, could not discriminate the cherries on a tree from the leaves, except by their shape and size. Two of his brothers were almost equally defective. One of them constantly mistook orange for grass green, and light green for yellow. A Mr. Scott, who describes his own case,f mistook pink for a pale blue, and a full red for a full green. His father, his maternal uncle, one of his sisters, and her two sons, had all the same defect. A Mr. R. Tucker, son of Dr. Tucker, of Ashburton, mistakes orange for green, like one of the Harrises; and cannot distinguish blue from pink, but almost always knows yellow. He mistakes red for brown, orange for green, and indigo and violet for purple. A tailor at Ply- mouth, whose case is described by Mr. Harvey,J of Plymouth, regarded the solar spectrum as consisting only of yellow and light blue; and he could distinguish, with certainty, only yellow, white and gray. He regarded indigo and Prussian blue as black, and purple as a modification of blue. Green puzzled him exceedingly; the darker kinds appearing to him brown, and the lighter kinds a pale orange. On one occasion he repaired an article of dress with crimson instead of black silk; and, on another occasion, patched the elbow of a blue coat with a piece of crimson cloth. A still more striking case is given by Dr. Nicholls§ of a person in the British navy, who pur- chased a blue uniform coat and waistcoat, with red breeches to * Optics, edit. cit.; Letters on Natural Magic; and art. Optics, in Library of Useful Knowledge, t Philos. Trans, for 1778. X Edinb. Phil. Transact, x. 253. § Medico-Chirurgical Transactions, vii. 477, and ix. 359. INSENSIBILITY OF THE EYE TO COLOURS. 235 match. Sir David Brewster refers to a case, that fell under his own observation, where the gentleman saw only the yellow and the blue colours of the spectrum. This defect was experienced by Mr. Dugald Stewart,* who was unable to perceive any difference between the colour of the scarlet fruit of the Siberian crab and that of its leaves. Dr. Dalton,f the chemist and philosopher, cannot distinguish blue from pink by daylight; and, in the solar spectrum, the red is scarcely visible; the rest of it appearing to consist of two colours, yellow and blue. Mr. Troughton, the optician, is fully capa- ble of appreciating only blue and yellow; and when he names colours, the terms blue and yellow correspond to the more or less refrangible rays;—all those, that belong to the former, exciting the sensation of blueness; and those, that belong to the latter, that of yellowness. The opinions of philosophers have varied regarding the cause of this singular defect in eyes otherwise sound, and capable of perform- ing every other function of vision in the most delicate and accurate manner. By some, it has been presumed to arise from a deficiency in the visual organ; and by such as consider the ear to be defective in function, in those that are incapable of appreciating musical tones, this deficiency in the eye is conceived to be of an analogous nature. " In the sense of vision," says Dr. Brown,J " there is a species of defect very analogous to the want of musical ear,—a defect, which consists in the difficulty, or rather the incapacity, of distinguishing some colours from each other—and colours, which, to general ob- servers, seem of a very opposite kind. As the want of musical ear implies no general defect of mere quickness of hearing, this visual defect, in like manner, is to be found in persons who are yet capable of distinguishing, with perfect accuracy, the form, and the greater or less brilliancy of the coloured object; and I may remark, too, in confirmation of "the opinion, that the want of musical tone depends on causes not mental but organic, that in this analogous case some attempts, not absolutely unsuccessful, have been made to explain the apparent confusion of colours by certain peculiarities of the external organ of sight." . Dr. Dalton, who believes the affection to be seated in the physical part of the organ, has endeavoured to explain his own case, by sup- posing that the vitreous humour is blue, and therefore absorbs a great portion of the red and other least refrangible rays, and Sir David Brewster, in the Library of Useful Knowledge,^ appears to think, that it may depend upon a want of sensibility in the retina, similar to that observed in the ears of those who are incapable of hearing notes above a certain pitch; but as this view is not con- tained in his more recent Treatise on Optics, it is probably no longer considered by him to be satisfactory. * Elements of the Philosophy of the Human Mind, ch. iii. t Manchester Memoirs, v. 28. X Lectures on the Philosophy of the Human Mind, vol. i. Boston, 1826. § Natural Philosophy, vol. i.—Optics, p. 50. Lond. 1829. 236 SENSE OF SIGHT. The defect in question—difficult as it is to comprehend*—has always appeared to us entirely cerebral, and to strikingly resemble, as Dr. Brown has suggested, the " want of musical ear." As we have already endeavoured to establish, that the latter is dependent upon a defective mental appreciation, the parity of the two cases will, of course, compel us to refer the visual defect, or the want of the " faculty of colouring," to the same cause. It has been re- marked, that the eye, in these cases, exercises its function perfectly, as regards the form and position of objects, and the degree of illu- mination of their different portions. The only defect is in the im- perfect conception of colour. The nerve of sight is probably accu- rately impressed, and the deficiency is in the part of the brain, whi- ther the impression is conveyed, and where perception is effected, which is incapable of accurately appreciating those differences be- tween rays, on which their colour rests; and this we are glad to find is the view taken of it by one of the most eminent philosophers of the present day, Sir J. F. W. Herschel. The mediate or auxiliary functions of vision are numerous; and hence, the elevated rank that has been assigned to this sense. By it, we are capable of judging, to a certain extent, of the direction, position, magnitude, distance, surface, and motion of bodies. Meta- physicians have differed greatly in their views on this subject; the majority believing, that, without the sense of touch, the eye is inca- pable of forming any accurate judgment on these points; others, that the sense of touch is no farther necessary than as an auxiliary; and that a correct appreciation could be formed by sight alone. The few remarks, that may be necessary on this subject, will be de- ferred, until the physical and other circumstances, which enable us to judge of distance, &c, have been canvassed. The direction or position of objects has already been considered, so far as regards the inverted image, formed by them on the retina. The errors, that arise on this point, are by no means numerous, and seldom give rise to much inconvenience. The direction of the light, that impinges on the retina, is always referred, as we have attempted to demonstrate, in the direction of a line, drawn from the luminous point through the centre of visible direction. Whenever, therefore, the luminous cone meets with reflection or refraction, before reaching the eye, the retina conveys erroneous information to the sensorium, and we experience an optical illusion. To ascertain the magnitude, distance, and surface of bodies, we are obliged to take into consideration several circumstances con- nected with the appearance of the object—such as its apparent size, the intensity of light, shade, and colour, the convergence of the axes of the eyes, the size or position of intervening objects, &c. • Purkinje, Art Achromatopsia, in Encyclopadisches Worterbuch der Medicinischen Wissenschaften, u. s. w, Band i, S. 261. Berlin, 1828; and Brewster's Optics, edit cit. p. 261. APPRECIATION OF DISTANCES. 237 Porterfield* enumerates six methods, which are employed in appre- ciating the distance of objects—1. Their apparent magnitude ; 2. The vivacity of their colours ; 3. The distinction of their smaller parts ; 4. The necessary conformation of the eye for seeing distinctly at different distances; 5. The direction of their axes; and 6. The inter- position of objects. Dr. Brownf reduces them to three—1. The difference of the affec- tions of the optic nerve; 2. The different affections of the muscles, employed in varying the refracting power of each eye, according to the distance of objects, and in producing that particular inclina- tion of the axes of the two eyes, which directs them both equally on the particular object; and 3. The previous knowledge of the distance of other objects, " which form with that we are considering a part of one compound perception." Lastly, Dr. ArnottJ enumerates four modes by which this is effected —1. The space and place, occupied by objects in the field of view, measured by what is termed the visual angle. 2. The intensity of light, shade, and colour. 3. The divergence of the rays of light— and 4. The convergence of the axes of the eyes. This enumeration may be adopted, with some slight modifications. The circumstances, in our opinion to be considered, are :— 1. The visual angle, or that formed by two lines, which shave the extremities of Fig. 43. an object and cross at the centre of the crystalline; so that the visual angle, subtended by the object, as a d, Fig. 43, is exactly equal to that subtended by its image i u on the retina. It is obvious, from this figure, that if all objects were equidistant from the eye, and of the same magnitude, they would subtend the same angle; and, if not of the same magnitude, the difference would be accurately indicated by the difference in the visual angle subtended by them; thus, the comparative size of the two crosses a d and b d is represented by that of the images i u and i o. The cross c e, however, which is twice the size of b d, subtends the same visual angle, and is alike represented on the retina by the image i o. It is clear, then, that the visual angle does not, under such circumstances, give us a correct idea of the relative magnitudes of bodies, unless we are acquainted with their respective distances from the eye; and, conversely, we cannot judge accurately of their distances, without being aware of their magnitudes. » A Treatise on the Eye, ii. 409. Lond. 1759. t Lectures on the Philosophy of the Human Mind, vol. i. Boston, 1826. X Elements of Physics, 2d Amer. edit. vol. ii. P. 1, p. 175. Philad. 1836. 238 SENSE OF SIGHT. A man on horseback, when near us, subtends a certain visual angle; but, as he recedes from us, the angle becomes less and less; yet we always judge accurately of his size, because aware of it by experience; but if objects are at a great distance, so as not to admit of their being compared with fearer objects by simple vision, we are in a constant state of illusion—irresistibly believing, that they are much smaller than they really are. This is the case with the heavenly bodies. The head of a pin held close to the eye will subtend as large a visual angle as the planet Jupiter, which is one thousand two hundred and eighty-one times bigger than this earth, and is eighty-six thousand miles in diameter. In like manner, a five- cent piece, held at some distance from the eye, will shut off the sun, although its diameter is eight hundred and eighty-eight thousand miles. The sun and moon, again, by subtending nearly the same visual angle, appear to us of nearly the same size; and the illusion persists in spite of our being aware of the mathematical accuracy, with which it has been determined, that the former is ninety six millions of miles from us, and the latter only two hundred and forty thousand. The visual angle, again, subtended by an object, differs greatly according to the position of the object. A sphere has the same ap- pearance or bulk, when held at a certain distance from the eye, whatever may be the position, in which it is viewed; and, accord- ingly, the visual angle, subtended by it, is always identical. Not so, however, with an oval. If held, so that the rays from one of its ends shall impress the eye, it will occasion a circular image, and subtend a much smaller angle, than if viewed sideways, when the image will be elliptical, or oval. The same thing must occur with every object, whose longitudinal and transverse diameters differ. It is obvious, that if any such object be held in a sloping position to- wards the eye, it will appear more or less shortened; precisely in the same manner as the slope of a mountain or inclined plane would appear much greater, if placed perpendicularly before the eye. This appearance is what is called foreshortening; and it may be eluci- dated by the following figure. Suppose a man to be standing on a level plain, with his eye at c, looking down on the plain. The por- tion of the surface a d, which is next to him, will be seen without any foreshortening; but if „. we suppose him to regard &' successively the portions a e d f, f g, and g b of the plain, the angle, subtended by each portion, will di- minish ; so that if the an- gle a c d be 45°, d c f will be 18° ; / c g 8°, and so on ; until, at length, the obliquity will be so great, that the angle becomes inappreciable. This is the cause why, if we look obliquely upon a long avenue of trees, we are unable to see the intervals^ between the farthest in the series; al- APPRECIATION OF DISTANCES. 239 though that between the nearest to us may be readily distin- guished. In all paintings, of animals especially, the principle of foreshorten- ing has to be rigidly attended to : and it is owing to a neglect of this, that we see such numerous distorted representations—of the human figure particularly. It has been already stated, that objects appear smaller according to their distance; hence, the houses of a street, or the trees of an avenue, that are nearest to Fig. 45. us, or in the foreground, will form the largest images on the retina, and there will be a gradual diminution, so that, if we could imagine lines to be drawn along the tops and bottoms of the objects, and to be sufficient- ly prolonged, they would appear to meet in a point, as in Fig. 45. The art which traces objects, with their various degrees of ap- parent diminution on ac- count of distance, and of foreshortening on account of obliquity of position, is called perspective. 2. The intensity of light, shade, and colour.—It has been shown, that the intensity of light diminishes rapidly, according to the dis- tance of the body,, from which it emanates ; so that it is only one- fourth as powerful when doubly distant, one sixteenth when quad- ruply distant, and so on. This fact is early recognised; and the mind avails itself of it to judge, with much accuracy, of relative distances. It is, however, a pregnant source of optical illusions. In a bright sunshine, the mountains appear much nearer to us than when seen through the haze of our Indian Summer.* In a row of lamps along a street, if one be more luminous than the rest, it will seem to be the nearest; and, in the night, we incur the strangest errors, in judging of the distance of any luminous body. The sky appears nearer to the earth directly above, than it does towards the horizon; because the light from above having to pass only through the atmosphere, is but slightly obstructed, whilst a por- tion only of that, which has to pass through the dense heterogeneous * A delightful season, in the southern and western parts of North America more espe- cially, generally occurring in October or November; and having nothing similar to it, so far as we are aware, in any other part of the globe. It is dependent upon some meteoro- logical condition of the atmosphere, and occurs only when the wind is southerly, or from the warmer regions; disappearing immediately as soon as it veers to the north. By some, this phenomenon has been supposed to be caused by the large fires in the western prairies ; but the warmth that attends the haze cannot be explained on this hypothesis, independently of other sufficient objections to it. 240 SENSE OF SIGHT. air, near the surface of the earth, arrives at the eye. The upper part of the sky being, therefore, more luminous, seems nearer; and, in the same manner, we explain, in part, why the sun and moon ap- pear larger at rising and setting. The shade of bodies" keeps pace with their intensity of light; and accordingly, the shadows of objects near us, are strongly defined;— whilst in the distance they become confused, and the light altogether so faint, that the eye at last sees an extent of distant blue mountain or plain; "appearing bluish," says Dr. Arnott,* "because the trans- parent air, through which the light must pass, has a blue tinge, and because the quantity of light arriving through the great extent of air is insufficient to exhibit the detail." " The ridge called Blue Mountains," he adds, " in Australia, and another of the same name in America, and many others elsewhere, are not really blue, for they possess all the diversity of scenery, which the finest climates can give; but to the discoverer's eye, bent on them from a distance, they all at first appeared blue, and they have ever since retained the name." As regards the Blue Ridge of America, Dr. Arnott probably la- bours under misapprehension. Within a very few miles from the whole of this extensive chain, as well as from a distance, the blue tinge is perceptible, especially when the air is dense and clear, soon after the sun has descended behind it; so that the name is as appro- priate in the vicinity as it was when " the discoverer's eye was bent on it from a distance." It is obvious, that without the alternation of light and shade we should be unable to judge, by the eye, of the shape of bodies; to dis- tinguish a flat circle from a globe ; or any of the prominences and depressions, that are every where observable. The universe would appear a flat surface, the outlines of which would not even be per- ceptible ; and the only means of discriminating objects would be by their difference of colour. It is partly by attending to the varying intensity of light and shade, that the painter succeeds in representing the near as well as the distant objects in an extensive landscape: those in the foreground are made bold and distinct; whilst the remote prospect is made to become gradually less and less distinct, until it fades away in the distance. This part of his art is called aerial perspective. 3. Convergence of the axes. When objects are situated at a mode- rate distance from us, we so direct the eyes, that if the axes were prolonged they would meet at the object. This angle will, of course, vary inversely as the distance; so that if the axes be turned to a nearer object, the angle will be greater; if to one more distant, less. By this change in the direction of the axes the mind is capable of judging, to a certain extent, of near distances. A definite mus- cular effort is required for each particular case ; and the difference in the volition necessary to effect it enables the brain to discrimi- * Op. cit. vol. ii, P. 1, p. 203. APPRECIATION OF DISTANCES. 241 nate, precisely in the same manner as it judges of the height of a body, by the muscular action, required to carry the axis from one extremity of the object to the other.* We have the most satisfactory evidence, that such convergence of the axes is indispensable for judging accurately of distance, in near vision. If we fix a ring to a thread suspended from a beam, or attach it to a stand, and endeavour, with one eye closed, to pass a hook, fixed to the extremity of a rod four or five feet long, into the ring, we shall find it impracticable unless by accident or by touching the ring with the rod. The hook will generally be passed on the far or near side of the ring; but if we use both eyes, we can readily succeed. They, however, whose eyes are of unequal power, cannot succeed with both eyes. The fact is strikingly corroborated by the difficulty experienced by those who have lost an eye. Magendief says it sometimes takes a year, before they can form an accurate judgment of the distance of objects placed near the eye. We know, however, one or two interesting examples, in which the power was never regained; not- withstanding every endeavour to train the remaining organ. It need scarcely be said, that the convergence of the axes is no guide to us in estimating objects, which are at such a distance, that the axes are nearly parallel,—as the sun and moon, or any of the celestial luminaries. 4. The interposition of known objects. Another mode of esti- mating the magnitude or distance of objects is, by a previous knowledge of the magnitude or distance of interposed or neigh- bouring objects; and if no such objects intervene, the judgment we form is extremely inaccurate. This is the reason, why we are so deceived in the extent of an unvaried plain or in the distance at which a ship, on the ocean, may be from us: it is also another cause, why the sky appears to us to be nearer at the zenith than it is at the horizon. The artist avails himself of this means of judging of magnitude in his representations of colossal species of the animal or vegetable kingdom; or of the works of human labour and ingenuity; by placing a well known object alongside of them as a standard of comparison. Thus, the representation of an elephant or a giraffe might convey but imperfect notions to the mind, without that of his keeper being added as a corrective. It is in consequence of the interposition of numerous objects, that we are able to judge more accurately of the size and distance of those that are on the same level with us, than when they are either much above or much below us. The size and distance of a man on horseback are easily recog- nized by the methods already mentioned, when he is riding before us on a dreary plain; the man and the horse appearing more dimi- * Sir C. Bell, in Philos. Transact, for 1823. t Precis, &c. I. 88. VOL. I. 21 242 SENSE OF SIGHT. nutive, but, being seen in their usual position, they serve as mutual sources of comparison. When, however, the same individual is viewed from an elevated height, his apparent magnitude, like that of the objects around him, is strikingly less than the reality. Beau- tifully and accurately is this effect depicted by the great drama- tist :— " How fearful And dizzy 'tis to cast one's eyes so low ! The crows and choughs, that wing the midway air, Show scarce so gross as beetles. Half way down Hangs one that gathers samphire; dreadful trade ! Methinks he seems no bigger than his head. The fishermen, that walk upon the beach, Appear like mice; and yon tall anchoring bark, Diminish'd to her cock; her cock a buoy Almost too small for sight." The apparent diminution in the size of objects seen from a height is not to be wholly explained by the foreshortening, which deprives us of our usual methods of judging. It is partly owing to the ab- sence of intervening bodies; and still more perhaps to our not being accustomed to view objects so circumstanced. Similar remarks apply to our estimates of the size and distance of objects placed considerably above us. A cross, at the summit of a lofty steeple, will not appear more than one-fourth of its real size, making allowance for the probable distance; yet a singular ano- maly occurs here:—the steeple itself seems taller than it really is, and every one supposes, that it would extend much farther along the ground, if prostrated, than it would in reality. The truth, however, is, that if the steeple were laid along the ground, unsurrounded by objects to enable us to form an accurate judgment, it would appear to be much shorter than when erect, on the principles of foreshorten- ing, already explained. The cause of this small apparent magni- tude of the cross and upper part of the steeple is, that they are viewed without any surrounding objects to compare with them: they, therefore, seem to be smaller than they are; and, being smaller, the mind irresistibly refers them to a greater distance. For these reasons, then, it becomes necessary, that figures, placed on lofty columns, should be of colossal magnitude. It is owing partly to the intervention of bodies, that the sun and moon appear to us of greater dimensions, when rising or setting, although the visual angle, subtended by them, may be the same. " The sun and moon," says Arnott,* " in appearance from this earth are nearly of the same size, viz:—each occupying in the field of view about the half of a degree, or as much as is occupied by a circle of a foot in diameter, when held one hundred and twenty- five feet from the eye—which circle, therefore, at that distance, and at any time, would just hide either of them. Now, when a * Op. cit. vol. ii. P. ii, p. 196. APPRECIATION OF THE MOTION, Sec. OF BODIES. 243 man sees the rising moon apparently filling up the end of a street, which he knows to be one hundred feet wide, he very naturally be- lieves, that the moon then subtends a greater angle than usual, until the reflection occurs to him, that he is using, as a measure a street known, indeed, to be one hundred feet wide, but of which the part concerned, owing to its distance, occupies in his eye a very small space. The width of the street near him may occupy sixty de- grees in his field of view, and he might see from between the houses many broad constellations instead of the moon only ; but the width of the street far off may not occupy, in the same field of view, the twentieth part of a degree, and the moon, which always occupies half a degree, will there appear comparatively large. The kind of illusion, now spoken of, is yet more remarkable, when the moon is seen rising near still larger known objects,—for instance, beyond a town or a hill which then appears within the luminous circle." Such are the chief methods by which we form our judgment of the distance and magnitude of bodies;—1st, by the visual angle— 2dly, by the intensity of light, shade, and colour—3dly, by the con- vergence of the axes of the eyes—and 4thly, by the interposition of known objects. The eye also enables us to appreciate the motion of bodies. This t does by the movement of their images upon the retina; by the variation in the size of the image ; and by the altered direction of the light in reaching the eye. If a body be projected with great force and rapidity, we are inca- pable of perceiving it;—as in the case of a shot fired from a gun, especially when near us. But if it be projected from a distance, as the field of view is very extensive, it is more easy to perceive it. The bombs, sent from an enemy's encampment, can be seen far in the air for some time before they fall, in the darkness of night; and afford objects for interesting speculation regarding their probable destination. To form an accurate estimation of the motion of a body, we must be ourselves still. When sailing on a river, the objects, that are stationary on the banks, appear to be moving, whilst the boat, which is in motion, seems to be at rest. Bodies, that are moving in a straight line to or from us, scarcely appear to be in motion. In such cases, the only mode we have of detecting their motion is by the gradual increase in their size and illumination, when they approach us; and the converse, when they are receding from us. If at a distance, and the visual angle between the extreme points of observation be very small, the motion of an object will likewise appear extremely slow; hence the difference between a carriage dashing past us in the street, and the same object viewed from a lofty column. A balloon maybe moving along at the rate of nearly one hundred miles per hour; yet, except for its gradual diminution in size and in intensity of light, it may appear to be at rest; and, when bodies are extremely remote from us, however astonishing may 244 SENSE OF SIGHT. be their velocity, it can scarcely be detected. Thus, the moon re- volves round the earth at the rate of between thirty and forty miles a minute—above forty times swifter than the fleetest horse; yet her motion, during any one moment, completely escapes detection; and the remark applies still more forcibly to those luminaries, which are at a yet greater distance from the earth. These are cases in which the body moves with excessive velocity, yet the image on the eye is almost stationary ; but there are others, in which the real motion is extremely slow, and cannot be at all ob- served, as that of the hour-hand of a clock or watch. It will be obvious, from all the remarks that have been indulged, regarding the information derived by the mind from the sense of sight, that a strictly intellectual process has to be executed, without which no judgment can be formed; and that nothing can be more erroneous than the notion,—at one time prevalent,—that the method by which we judge of distance, figure, &c, is instinctive or dependent upon an original " law of the constitution," and totally independent of any knowledge gained through the medium of the external senses. It has already been remarked, that metaphysicians may be considered as divided into those, who believe that, without the sense of touch, the eye would be incapable of forming any accurate judgment on these points; and those, who think, that the sense of touch is no farther necessary than as an auxiliary, and that a correct appreciation can be formed by sight alone.—INlolyneux,* Berkeley,! Condillac,J &c. support the former view; Gall,§ Adelon,|| &c. the latter. Of the precise condition of the visual perception, during early in- fancy, we are of course entirely ignorant. So far as our own re- collections would carry us back, we have always been able to form a correct judgment of magnitude, distance, and figure. Observa- tion, however, of the habitudes of infants would seem to show, that their appreciation of these points—especially of distance—is singularly imprecise, but whether this be owing to the sense not yet having received a sufficient degree of assistance from touch, or from want of the necessary developement in the structure or func- tions of the eyeball or its accessory parts, we are precluded from judging. The only succedaneum is the information to be obtained, regard- ing their visual sensations, from those who have been blind from birth, and have been restored to sight by a surgical operation. Although in the numerous operations of this kind, which have been performed, it might seem, that cases must have frequently occurred for examining into this question, such is not the fact; and meta- physicians and physiologists have generally founded their obser- vations on the celebrated case described by Cheselden.T * Locke's Essay on the Human Understanding, Book ii. Chap. 9. +Essay on Vision, 2d edit. Dublin, 1709. t Traite des Sensations, Part. I. § Sur les functions du Cerveau, I. 80. Paris, 1825. || Physiologie de I'Homme, edit. cit. I. 466. T The Anatomy of the Human Body, 13th edit. Lond. 1792. APPRECIATION OF MAGNITUDE, ETC 245 The subject of this was a young gentleman, who was born blind, or lost his sight so early, that he had no remembrance of ever having seen, and was " couched," so says Cheselden, " between thirteen and fourteen years of age." Magendie* affirms, that there is every reason to believe that the operation was not that for cata- ract, but consisted in the incision of the pupillary membrane. It need hardly be remarked, that Cheselden must be the best possible au- thority on this subject. "When he first saw," says Cheselden, "he was so far from making any judgment about" distances, that he thought all objects whatever touched his eyes, (as he expressed it,) as what he felt did his skin, and thought no objects so agreeable as those which were smooth and regular, though he could form no judgment of their shape, or guess what it was in any object that was pleasing to him. He knew not the shape of any thing, nor any one thing from ano- ther, however different in shape or magnitude; but upon being told what things were, whose form he before knew from feeling, he would carefully observe, that he might know them again; but having too many objects to learn at once, he forgot many of them; and, (as he said,) at first he learned to know, and again forgot a thousand things in a day. At first he could bear but very little light, and the things he saw he thought extremely large; but, upon seeing things larger, those first seen he conceived less, never being able to imagine any lines beyond the bounds he saw; the room he was in, he said, he knew to be but part of the house, yet he could not conceive that the whole house could look bigger." A much more interesting case, in many respects, than this of Cheselden's, which has always appeared to us too poetical, was laid before the Royal Society of London, in 1826, by Dr. Ward- rop.f It was that'of a lady born blind, who received sight at the age of forty-six, by the formation of an artificial pupil. During the first months of her infancy, this lady was observed to have some- thing peculiar in the appearance of her eyes: and, when about six months old, a Parisian oculist operated on both eyes, with the effect of complete destruction of the one, and not the slightest improve- ment to the other. From this time, she continued totally blind, being merely able to distinguish a very light from a very dark room, but without the power of perceiving even the situation of the window through which the light entered, though, in sunshine or bright moonlight, she knew its direction; she was, therefore, in greater darkness than the boy in Cheselden's case, who knew black, white, and scarlet, apart from each other; and, when in a good light, had that degree of sight, which usually exists in an eye affected with cataract; whilst in this lady the pupil was completely shut up, so that no light could reach the retina, except such rays as could pass through the substance of the iris. After a third operation had been performed, for the formation of * Precis, &c. i. 95. + Philos. Transact. 1826, p. 529. 21* 246 SENSE OF SIGHT. an artificial pupil, she returned from Dr. Wardrop's house in a carriage, with her eyes covered with only a loose piece of silk. The first thing she noticed was a hackney-coach passing by, when she exclaimed, "What is that large thing that has passed by us?" In the course of the evening she requested her brother to show her his watch, and she looked at it a considerable time, holding it close to her eye. " She was asked what she saw, and she said there was a dark and a bright side ; she pointed out to the hour of twelve and smiled. Her brother asked her if she saw any thing more; she replied yes, and pointed to the hour of six, and to the hands of the watch. She then looked at the chain and seals, and observed that one of the seals was bright, which was the case, being a solid piece of rock crystal." On the third day she observed the doors on the opposite side of the street, and asked if they were red. They were of an oak colour. In the evening she looked at her brother's face, and said she saw his nose; he asked her to touch it, which she did; he then slipped a handkerchief over his face, and asked her to look again, when she playfully pulled it off, and asked, " What is that V* On the thirteenth day, she walked out with her brother in the streets of London when she distinctly distinguished the street from the foot pavement, and stepped from one to the other, like a person accustomed to the use of her eyes. " Eighteen days after the last operation," says Dr. Wardrop, " I attempted to ascertain, by a few experiments, her precise notions of the colour, size, and forms, posi- tion, motions and distances of external objects. As she could only see with one eye, nothing could be ascertained respecting the ques- tion of double vision. She evidently saw the difference of colours ; that is, she received and was sensible of different impressions from different colours. When pieces of paper, one and a half inch square, differently coloured, were presented to her, she not only distinguished them at once from one another, but gave a decided preference to some colours, liking yellow most, and then pale pink. It may be here mentioned, that, when desirous of examining an object, she had considerable difficulty in directing her eye to it, and finding out its position, moving her hand as well as her eye in various directions, as a person, when blindfolded or in the dark, gropes with his hand for what he wishes to touch. She also dis- tinguished a large from a small object, when they were both held up before her for comparison. She said she saw different forms in various objects, which were shown to her. On asking what she meant by different forms, such as long, round, and square, and de- siring her to draw with her finger these forms on her other hand, and then presenting to her eye the respective forms, she pointed to them exactly; she not only "distinguished small from large objects, but knew what was meant by above and below; to prove which, a figure drawn with ink was placed before her eye, having one end broad, and the other narrow, and she saw the positions as they really wrere, and not inverted.(!!) She could also perceive motions ; for when a glass of water was placed on the table before her, on APPRECIATION OF MAGNITUDE, ETC. 247 approaching her hand near it, it was moved quickly to a greater distance, upon which she immediately said, 'You move it; you take it away.' She seemed to have the greatest difficulty in finding out the distance of any object; for, when an object was held close to her eye, she would search for it by stretching her hand far beyond its position, while on other occasions she groped close to her own face for a thing far remote from her." We have given the particulars of this case at some length, inas- much as they are regarded by Dr. Bostock*—and apparently by Dr. Wardrop himself—as strikingly confirmatory of those of Che- selden, than which we cannot imagine any thing more dissimilar. It will have been noticed, that, from the very first after the recep- tion of sight, she formed an imperfect judgment of objects, and even of distances, although she was devoid of the elements necessary for arriving at an accurate estimate of the latter—the sight of both eyes. This was, doubtless, the chief cause of that groping for objects, which is described by Dr. Wardrop. Of forms, too, she must have had at least an imperfect notion, for we find, that, on the 13th day after the operation, she stepped from the elevated foot-pavement to the street, " like a person accustomed to the use of her eyes." The case is, we think, greatly in favour of the view, that the sight does not require much education to judge with tolerable accu- racy of the position, magnitude, distance, surface, and motion of bodies; and that, by a combination of the methods we have already pointed out, or of some of them, this imperfect knowledge is ob- tained, without the aid of any of the other senses; but is of course acquired more easily and accurately with their assistance, espe- cially with that of touch. What other than visual impressions could have communicated to the mind of Miss Biffin—whose case was referred to under another head (p. 103)—the accurate and minute information, which she possessed regarding the bodies surrounding her, at all distances'? Or how does the animal, immediately after birth, acquire its knowledge of distance? We observe the youno- of some animals immediately after they are extruded from the uterus, turn round and embrace the maternal teat; whilst others, as the par- tridge, follow the mother immediately after they have burst the shell. The experience required for obtaining an imperfect knowledge of distance, shape, &c. must, therefore, be trifling; although an accu- rate acquaintance may demand numerous, and careful comparisons. This first degree of knowledge is probably obtained, by comparing the visual angle with the intensity of light, shade, and colour—the more accurate appreciation following the use of the other methods already described. That the convergence of the axes requires education is demonstrated in the case of the infant. It has been remarked, that the eyeballs harmonize instinctively in their parallel motions; but the convergence requires an effort of volition, and it is some time before it can be effected, which is probably the great * Physiology, 3d Edit. p. 703. Lond. 1836. 248 SENSE OF SIGHT. cause of the mal-appreciation of near distances, which we notice in the infant; whilst it seems to exhibit its capability of judging more correctly of objects, that are somewhat more remote, and where less convergence, and, consequently, less muscular effort is necessary. The numerous optical illusions, which, we have been compelled to describe, in the progress of the preceding remarks, will render it necessary to refer to but few under this head. It has" already been said, that we lay it down as a rule, that the progress of light to the eye is always in a straight line from the luminous object; and, accordingly, if the course of the rays be mo- dified before they reach the organ, we fall into an optical illusion. Such modifications arise either from the reflection or refraction of the rays proceeding from the object that causes the sensation. By reflection of the rays, we experience the illusion caused by mirrors. A ray of light, K C, Fig. 22, falling upon a plane mirror, I J, is reflected back in the same line; but, as we have seen, the object will not appear to be at K, but at E. Again, a ray of light, proceeding obliquely from B, and impinging on a plane mirror at C, will be reflected in the direction of C A; but to the eye at A, the object B will appear to be at H, in the prolongation of the ray that reaches the eye. If the mirror be concave, the object will appear magnified, pro- vided the light from the upper part of the object, as A B, Fig. Fig. 46. 47, be reflected to an eye at F, and that from the lower part of q\"""--... the object meet the other at this '":"" point. To an eye so placed, i the object will appear magni- ; fied and seem to be at C D, or -q| ....-.....'" in the prolongation of the rays which fall upon the cornea. If the mirror, as in Fig. 49, be convex, for like reasons, the cross will seem to be smaller. The cornea constitutes a mirror of this class, in which we have an accurate miniature representation of objects. Fig. 47. Ray?, that are refracted in passing through different media, also give rise to visual illusions. We have seen, that the ..p ray from an object at F, Fig. 23, in the ! pool of water, I J, does not proceed into j the air in the direction of F C O, but in '"' that of the line F C A; and if we suppose the eye to be placed at A, the object will not be seen at F, but will appear to be at/; the pool will, consequently, appear shallower than it really is, by the space at which / is situated above the bottom. We can now understand, why rivers should appear shallower than they really are, when viewed obliquely; and why the lower end of a pole, immersed in water, should, when seen obliquely, ap- OPTICAL ILLUSIONS. 249 pear to be bent towards the surface. In shooting fish in the water, or in attemping to harpoon them, this source of error has to be cor- rected. Those birds, too, that live upon the inhabitants of the water, will have to learn, from experience, to obviate the optical illusion; or to descend perpendicularly upon their prey, in which direction, as we have seen, no refraction takes place. Similar remarks apply- to the fish that leap out of the streams to catch objects in the air. The Chcetodon rostratus, about six or eight inches long, frequents the sea-shores in the East Indies: when it observes a fly, sitting on the plants that grow in shallow water, it swims to the distance of five or six feet, and then, with surprising dexterity, ejects out of its tubular mouth a single drop of water, which never fails to strike the fly into the sea, where it soon becomes its prey.* Hommel—a Dutch governor—put some of these fish into a tub of water, and then pinned a fly on a stick within their reach. He daily saw the fish shoot at the fly, and, with such dexterity, that they never failed to hit their mark.f Pallas describes the Sicena Jaculatrix as securing flies by a similar contrivance.J If the light, before reaching the eye, passes through bodies of a lenticular shape, it undergoes modifications, which have given occa- sion to the formation of the useful instruments, that have been de- vised for modifying the sphere of vision. If the lens be double con- vex, the body, seen through it, appears larger than it is, from the illusion so often referred to, that we always refer the object in the direction of the line, that impinges upon the retina. The object, consequently, appears to be greatly augmented. (See Fig. 29.) For the same reasons an object seems smaller to an eye at A, Fig 26, when viewed through a double concave lens. Again, if the light, before reaching the cornea, is made to pass through a diaphanous body, which is itself coloured, and conse- quently allows only the rays of its own colour to traverse it, the object is not seen of its proper colour, but of that of the transparent body. An impression of light continues to affect the retina for the sixth part (M. D'Arcy says the seventh part,) of a second. If, therefore, a live coal be whirled round a circle, six or seven times in a second, it will seem to be a continuous circle of fire. It is owing to this circumstance, that meteors seem to form a line of light,—as in the case of the falling star,—and that the same impression is conveyed by a sky-rocket in its course through the air. We have an elucida- tion of this fact in the instrument or toy—called, by Dr. Paris, the Ihaumatrope—which consists of a circle, cut out of a card, and having two silken strings attached to opposite points of its diameter: by twisting these with the finger and thumb the card may be twirled round with considerable velocity. On one side of the card an ob- ject is drawn—as a chariot—and on the other, the charioteer. If * Fleming's Philos. of Zoology, I. 195. t Philos. Trans, liv. 89. X Ibid. lvi. 186—also, Mr. Sharon Turner's Sacred History of the World. Amer. Edit., i. 205. New York, 1832. 250 ADDITIONAL SENSES. the card be twirled round six or seven times in a second the chario- teer will be seen in the chariot; the duration of the impressions on the retina being such as to cause the figures, drawn on both sides of the card, to be seen at the same time. Lastly,—it is by accurate attention to various optical illusions, and to the laws of the animal economy on which they are founded, that many of them can be produced in the arts at pleasure. Paint- ting is, in truth, little more than depicting on canvass the various optical errors, which we are habitually incurring. To conclude,—the sense of sight differs materially in the scale of animals: in few is the organization more perfect or the function better executed than in man. Situated at the upper and anterior part of the body, it is capable of directing its regards over a large extent of surface; of converging the axes of the two organs upon objects in various situations, which cannot be effected by many animals; and it is very movable, and under the domination o£ a muscular apparatus of admirable arrangement. Still, it is not as delicately organized as in some animals, which are capable of seeing objects at a distance, that would be totally beyond the reach of the visual powers of man. Like the other senses, sight can be exerted actively and passively; hence the difference between simply seeing and looking. In the latter, the eye is directed to the object by the proper muscles; and it is not improbable but that the nerve may be aroused to a more accurate and delicate reception of impressions, as we have some reason for believing it to be in the case of the othersenses. Like them, it admits of great improvement by education. The painter, and the worker in colours are capable of great discrimination, and detect the minutest shades of difference with the greatest facility: In savage life, where the tracks or marks through the almost in- terminable forests, or over the pathless wilds, are the only guides. the greatest acuteness of vision is necessary; and, accordingly, we find the North American Indian, in this respect, eminently distin- guished. The mariner, too, accustomed to look out for land, or for a hos- tile sail, will detect it in the distant horizon long before it can be perceived by the landsman, and will appreciate its distance and course with signal accuracy,—education, in this case, not only communicating to his eye facility in being impressed, but improving the intellectual process, by which he arrives at the estimation of distances. SECT. VI.—ADDITIONAL SENSES. The five senses, which have been considered, constitute so many special nervous systems, each concerned in its appropriate function; and, although conveying ideas of the external world to the brain, and connected with that organ, to a certain extent independent of it. The generality of physiologists admit only these five; but some ADDITIONAL SENSES. 251 have suggested others, differing, in general, however, from the five, in having no organ at the surface of the body exclusively concerned in the function. Buffon regarded, as a sixth sense, the intense sen- sation experienced during the venereal act; but this can only be esteemed a peculiar variety of tact in the mucous membrane of the genital organs;—differing from ordinary tact in those parts, by re- quiring in both sexes a special condition of the membrane; and, in the male, one such, that the sperm, when excreted, shall make the necessary impression upon it; and, consequently, appertaining to both the external and internal sensations;—the state of the mem- brane being referable to the latter, and the effect of the contact of the sperm to the former. Some have spoken of a sense of heat and cold:—this we have described under the head of tact;—others of*a muscular sense, by which we acquire a knowledge of the motions to which muscular contractions give rise, and thus learn to apportion the effort to the degree of effect to be produced. The animal magnetizers, again, have suggested a sixth sense, to which man owes the capability of being acted upon by them ; but this is entirely supposititious, and the facts admit of a more ready and satisfactory explanation. A sense of hunger has been described as situated at the upper orifice of the stomach:—a sense of thirst in the oesophagus, and a pneumatic sense in the lungs; but all these are more properly internal sensations. The German physiologists have suggested another sense, which they term ccenccsthesis, gemeingefuhl, gemeinsinn, kbr- pergefuhl, lebensgefiibl, lebenssinn, individual— itatssinn, and sel bs tgefiihl (" common feeling, common sen- sation; bodily feeling, feeling of life, sense of life, sense of individu- ality, and self-feeling.") This is not seated in any particular part of the body, but over the whole system, and hence termed g e m e i n, or common. It is indicated by the lightness and buoyancy, which we occasionally experience, apparently without any adequate cause ; as well as by a sense of lassitude and fatigue, unconnected with mus- cular action or disease. To it likewise, belongs the involuntary shuddering, glow, or chilliness, experienced under similar circum- stances. It is manifestly one of the numerous internal sensations felt by the frame, and every portion of it, according as they are in a per- fect state of health, or labouring under some cause of irritation or op- pression; but can scarcely be regarded as an additional or sixth sense.* Again, it has been supposed, that certain animals may possess other senses than the five we have mentioned. Of this we can have no positive evidence. We are devoid of all means of judging of their sensations; and if we meet with an additional organ, which * Dissert, prass. J. Chr. Reil. resp. Fr.Chr. Httbner. Hal. 1794. Greiner, art. Gemein. geftihl, in Pierer's Anat. Phys. Worterb. iii. 489. Leipz. 1819. Purkinje, in art. Ccenaes- thesis, in Encyclopad. Worterb. der Medicinischen Wissenschaften, viii. 116. Berlin, 1832. Hempel's Einleitung in die Physiologie und Pathologie, &c. p. 459, Getting. 1828; and Puchelt, System der Medicin, Th. I. s. 173. Heidelb. 1835. 252 SENSE OF SIGHT. seems adapted for such a purpose, we have nothing but conjecture to guide us. Under the sense of touch (page 106) it was said, that Spallanzani found the bat capable of avoiding obstacles, placed in its way intentionally, when the eyes, nostrils, and ears had been closed up; and it readily returns to the holes in the caverns to which it is habituated. Spallanzani supposed, that this was owing to its being possessed of a sixth sense. We have seen, that the circum- stance is explicable by these animals being possessed of unusual de- licacy of touch. Again, the accuracy with which migratory animals return to their accustomed haunts has given rise to the notion of a sense of locality, which is presumed to preside over this faculty. This is, doubtless, however, a cerebral faculty. Quadrupeds, the ape not excepted, have two bones in the face, in addition to those found in man. These contain the roots of the dentes incisores, when such are present, but they exist in animals also that are destitute of teeth. They are termed ossa intermaxil- laria, ossa incisoria, and ossa labialia, and are situated, as their names import, at the anterior part of the jaw, and between the ossa maxillaria or jaw bones. Jacobson* considers them to be an organ of sense, as they communicate with the exterior, and are largely supplied with vessels and nerves. Accordingly, this has been es- teemed a sensitive apparatus, connected with the season of love in animals; and, by other naturalists, as a sense, intermediate between those of taste and smell, and intended to guide the animal in the proper selection of food. It need hardly be said, that this is all imaginary.f Adelon,J it was remarked, makes two divisions of the external sensations:—those that convey information to the mind; and those that do not. The former have engaged attention; the latter will not occupy us long. They comprise but two—itching and tickling. Both of these occur in the skin and mucous membranes, and near the communication of the latter with the skin; or, in other words, near the termination of the outlets which they line. Itching, however, is not always an external sensation,—that is, not always caused by the contact of a body external to it. It frequently arises from an altered condition of the organic actions of the part in which it is experienced, as in cutaneous affections; in itching at the nose produced by irritation in the intestinal canal; itching at the glans penis in cases of calculi of the urinary bladder, &c, but com- monly the sensation is caused by an extraneous body; and we are irresistibly led to scratch, no matter how it may be produced. When it arises extraneously, it can generally be readily allayed ; but, when * Annales du Musde, xviii. 412. t Magendie's Pr6cis elementaire, I. 158; Richerand, Elemens de Physiologie, 6dit. 13eme par M. Berard ain6; edit. Beige, p. 213. Bruxelles, 1837; Roget's Animal and Vegetable Physiology, Amer. edit. ii. 399. Philad. 1836; and Bostock's Physiology, 3d edit. p. 734. Lond. 1836. X Physiologie de 1'homme, 2de edit. I. 481. Paris, 1829. INTERNAL SENSATIONS. 253 dependent upon a morbid condition of the texture of the part, it becomes a true disease, and the source of much suffering. If the itching be accompanied with a feeling of motion, or of purring in the part, it is called tingling. This kind of purring often occurs without itching. Tickling or titillation is always caused by the contact of some ex- traneous substance, and is therefore a true external sensation. Although occurring in the skin, and in the commencement or ter- mination of the mucous membranes, all parts are not equally suscep- tible of it: and some,—as the lining membrane of the genital organs, —are only, or chiefly so, under particular circumstances. The sides, palms of the hands, and soles of the feet, are the most sensitive in this respect; not, perhaps, because the nerves are more numerous in those parts, but because, owing to thinness or supple- ness of skin, or to other inappreciable circumstances, they are more susceptible of this kind of excitation. We find, too, that individuals differ as much as the parts of the body do in this respect: some being not ticklish, or incapable of being thrown into the spasm, which the act, nay, even a threatening of the act, produces in others. Cases are on record, in which prolonged titillation has produced general convulsions, and even death. Le Cat* terms it an hermaphroditic sensation, inasmuch as, on the one hand, it excites laughter; and, on the other, is insupportable; and, consequently, appears to be inter- mediate between pleasure and pain. b. INTERNAL SENSATIONS. The external sensations make us acquainted with the universe surrounding us; and convey to the mind a knowledge of every thing that can be, in any manner, inservient to our necessities. Such necessities have, however, to be suggested to the mind, before it reacts through the aid of the organs of prehension or otherwise on external bodies, and this is accomplished by the agency of the in- ternal or organic sensations. Without the intervention of any external cause, every organ of the body is capable of transmitting to the brain a number of different impressions, many of which impel the organ to acts, that are ne- cessary not only for the preservation of the individual and of the species, but also for the perfect developement of the faculties. Such are the sensations of hunger and thirst; the impulse that leads to the union of the sexes; and the feeling we have of the necessity for in- termission in the exercise of the muscles and of the intellect. They have been divided into three species by some physiologists: the first arousing, or giving impulse to, the action of organs; and warning the brain of the different necessities of the system. They have been called wants or instinctive desires.f Such are, hunger, * Traits des Sens. Paris, 1767. t Adelon, Art. Besoins, in Diet, de Medecine, i. 367. Paris, 1821: and Physiologie de I'Homme, I. 482. VOL. i. 22 254 INTERNAL SENSATIONS. thirst, the desire to evacuate the urine and fasces; that of respiration, the venereal appetite, accouchement, &c. They belong to those that arise, when it is necessary the organs should act. The second species occur during the action of organs. They are often obscure, but sometimes very acute. Amongst these are the impressions accompanying the different excretions,—as that of the sperm, urine, &c. (although, as we have seen, these partly belong to the external sensations;) the impressions that warn us of our partial or general movements, of the progress of digestion, and of the intellectual labours. The last species succeed to the action of organs, especially when such action has been too long continued ; hence the inward feeling of fatigue, after too long exertion of the functions of the senses, of the intellectual and moral faculties, and of the organs of muscular motion ; the necessity of repose after prolonged muscular exertion; and of sleep, to recruit the nervous system, and to fit it for the ex- ertions it has to make during the waking condition. The mode in which these sensations are effected is analogous to that of the external sensations. There is an impression on the part to which the sensation is referred ; an action of perception, accom- plished by the brain, and one of transmission, executed by a nerve passing between the two parts. The two last actions are probably executed in the same manner as they are in the external sensations. The first, or the mode in which the .impression is effected, and the character of the impression itself, are much more obscure. In the external sensations, we can refer the impression to a known irritant: —special in some of the senses:—more general in others. We know, that light impresses the retina:—aerial undulations the acoustic nerve, &c.: but, in the internal sensations or sentiments, as some of the French writers term them, the source of the irritation is in some modified action of the part itself, in the very tissue of the organ, and hence the result is said to be organic. In the internal sensation of hunger, for example, the impression is engendered in the organ,—how, we know not,—is thence conveyed to the brain; and the sensation is not effected until the latter has acted. The same may be said of all the other internal sensations. They differ, in other respects, from the external sensations. Whilst the latter may be entirely passive, or be rendered active by volition, without either action being the cause of particular pleasure or inconvenience, the former are but little influenced by volition. Constituting the wants—the instinctive desires—which impel to acts, that are necessary for the preservation and full developement of the individual and of the species, such independence is of course essen- tial. On many of them, however, habit or accustomed volition has a certain degree of influence: and they can unquestionably be aug- mented or moderated by licentious indulgence or restraint. The influence of habit is exemplified by the regularity with which the appetite returns at stated intervals; and by the difference between that of the gourmand and of the temperate individual. It is most MORBID SENSATIONS. 255 strikingly evidenced, however,in its influence over the moral wants; which may even spring up from social indulgence, and hence are not instinctive or organic: we are every day, indeed, compelled to notice the striking difference between the individual, who practises restraint upon his wants, and the libertine, who, like the animals'' surrounding him, gives unbridled sway to his natural and acquired appetites. All the internal sensations, when satisfied or responded to in moderation, communicate a feeling of pleasure; but if resisted, pain results. If hunger be prolonged, there is a general feeling of uneasi- ness, which rapidly abates after food is received into the stomach in due proportion; but if satiety be produced, uneasiness follows; and this applies to all the appetites or wants. The particular internal sensations will engage us, when the func- tions to which they belong fall under consideration. Like the ex- ternal sensations they must, of course, administer to the intellect; to an extent which will be seen hereafter. Their influence and nature were entirely neglected, until of comparatively late years: but attention has been directed to them chiefly through the labours of Cabanis* and of Destutt-Tracy,f and they now form subjects for interesting speculation with the metaphysician. The morbid sensations belong more particularly to pathology: a brief notice of them will consequently be all that is necessary here. They are comprised under the term pain. In its enlarged significa- tion, this word, as is well known, means every uneasy or disagree- able sensation or moral affection;—thus including sadness, anger, terror, as well as the painful impressions felt in the extremities or trunks of the nerves. It is the latter only—or physical pain—that concerns us at present. Like every other sensation, although it may be referred exclu- sively to the part impressed, pain requires the intervention of the brain: for if the nerves, proceeding from a part to that organ, be cut, tied, compressed, or stupefied by narcotics; or if the action of the brain itself be blunted from any cause, as by the use of opium, or by any compression, accidental or other, the sensation is no longer experienced. We can thus understand why pain is less felt during sleep; and the astonishing cases of resistance to pain, which we witness in the lunatic, and in religious or other enthusiasts, who have been subjected to bodily torture. An opposite condition of the nervous system is the cause of the great sensibility to impressions, which we witness in the nervous and hysterical. It is obvious, that pain may be either an external or internal sen- sation, according as the cause of irritation is extraneous, or seated in the tissue of organs; and that it must vary considerably, both as regards the precise irritant, and the part affected; hence the difference between the pain caused by a burn, and that by a cutting * Rapport du Physique et du Morale de THomme, torn. ii. Paris, 1802. t Elemcns d'ld^ologie, 2d edit. Paris, 1804. 256 MENTAL FACULTIES. instrument; and hence the immense variety of pains to which the human frame is subject, and the attentive study of which is so indis- pensable to the pathologist. So much for the sensations. These we have seen are innumera- ble, for each sense is capable of myriads of different impressions. We now pass to the consideration of those functions which enable man—though worse provided with means of defence and offence than the beasts surrounding him, and possessing no covering, to protect him from the solar heat or the winter's cold—to provide himself means of defence; to render the animals around him sub- servient to his use; to cover his nakedness and protect himself against atmospheric changes; to devise every mechanical art; to fathom the laws, that govern the bodies by which he is surrounded, and to establish himself undisputed master of the earth. II. OF THE MENTAL FACULTIES. The external senses convey to the brain the different impressions, made upon them by surrounding bodies; but, of themselves, they would be unable to instruct the mind regarding the universe. It is necessary, that the brain should act before any perception, any idea of them, can exist. The mental faculties, in other words, convert the impressions into such ideas. The internal sensations, on the other hand, consist, as we have seen, of the numerous wants and appetites, necessary for the preservation of the individual and of the species. In addition to these, man possesses another series of facul- ties, which influence his character and disposition, and direct his social existence: these are the affective or emotive faculties, or the faculties of the heart. The study of these different mental and moral phenomena em- braces, what has been called, psychology, from a notion that they are exclusively dependent upon the mind. This notion was, at one time, universal, and hence the appellation metaphysician, applied to such as were considered to proceed in their investigations of those subjects beyond what was physical, material, or corporeal. There is no subject, which has given occasion to so much excite- ment and controversy, as that of the connexion of the mental facul- ties with the encephalon. " It has unfortunately happened," says Dr. Bostock,* " that this subject, which is one of great interest and curiosity, has seldom been viewed with that philosophical spirit which should always direct our investigations, and by which alone we can expect to arrive at truth. It is admitted, that certain errors may be so interwoven with our accustomed associations, on topics connected with morals and religion, as to render it doubtful, on some occasions, how far we ought to attempt their removal: but if this concession be made on the one hand, it is incumbent upon us, on the other, not to inflame the prejudices, which may exist on these topics, but to use our endeavours to correct all undue excitement, » Physiology, 3d edit. p. 744. Lond. 1836. MENTAL FACULTIES. 257 and thus to bring the mind into that tranquil state, which may enable it to receive truth without the fear of injury." In such a spirit ought every discussion on this interesting subject to be conducted; and in such a spirit will the few remarks, which we have to make, be offered. The chief opinions, which have been indulged on this subject, are, —1st. That all the mental phenomena are immaterial and the exclu- sive product of the mind. 2dly. That the sentient principle, within us, requires the intervention of an organ, through which it acts; in other words, that mind is a principle superadded to organization; and 3dly. That where there is no organization there is no percep- tion :—that wherever an organized structure, like the brain, exists, perception exists; that where the organization is imperfect, percep- tion is imperfect; where the organization is sound and vigorous, per- ception is clear and vigorous; where it is impaired, perception is impaired ; and that, when the organization ceases, perception ceases also. This last view is materialism. It supposes that a certain con- dition of matter is capable of thinking, reasoning, and understand- ing. The doctrine,—that our intellectual and moral acts are superadded to organization, during life, and that there is an organ of the body concerned in their manifestation,—is the one embraced by the gene- rality of physiologists, and is most consistent with reason and ana- logy; it is but justice, however, to admit that the views of those, who consider that a certain organization produces thought, are not deserving of the anathemas which have been directed against them on the score of irreligion. The charge would rather apply to those who could doubt the power of Omnipotence to endow matter with such attributes.* Were the mental and moral phenomena the exclusive products of the immaterial principle within us, they would hardly form subjects for physiological inquiry. That they are allied to organization is in- ferred from the following reasons. As they constitute so many func- tions, were they not provided with an organ or organs, they would form so many exceptions ;—each of the sensations requiring an or. gan for its accomplishment. Again, our inward feeling induces us to refer them to a particular part of the frame: whilst thought appears to us to be effected within the head, the chief effects of the passions are felt in the region of the heart or stomach. The faculties, more- over, are not the same in every individual. One man is a poet, an- other a mathematician; or one is benevolent, another cruel. If these faculties were the exclusive product of the mind, and of course not to be ascribed to diversity of organization, we should have to admit, that each individual has a different immaterial principle, and of course, that there must be as many kinds as there are individuals. Lastly.—The faculties vary in the same individual according to cir- cumstances. They are not the same in the child as in the adult; * Elliotson's Human Physiology, Lond, 1835, chap, 3, 22* 258 MENTAL FACULTIES. in the adult as in one advanced in life; in health as in disease; in waking as in sleep. During an attack of fever they become tem- porarily deranged, and permanently so in all the varieties of insanity. These facts are inexplicable under the doctrine, that they are the exclusive product of the mind or immaterial principle. An immate- rial or spiritual principle ought to be immutable; yet we should have to suppose it capable of alteration;' of growing with the growth of the body, and of becoming old with it; of being awake or asleep; sound or diseased. All these modifications are impressed by vary- ing organization—of the brain in particular. We may conclude, then, that the intellectual and moral faculties are not the exclusive product of the mind, but that they require the intervention of an organ. That this organ is the encephalon, or a part of it—the brain—is announced by many circumstances. In the first place, they are phenomena of sensibility, and hence we should be disposed to refer them to a nervous organ; and being the most elevated phenomena of the kind, to the highest of the nervous organs. In the second place, inward feeling induces us to refer them thither. We not only feel the process there, during meditation, but the sense of fatigue, which succeeds to hard study, is experienced there likewise. The brain, again, must be in a state of integrity, otherwise the fa- culties are deranged ; or, for the time, abolished. In fever, the brain becomes affected directly or indirectly, and the consequence is—per- version of the intellect, in the form of delirium. If the organ be more permanently disordered, as by the pressure of an exostosis or of a tumour, or by some alteration in its structure or functions—less ap- preciable in its- nature—insanity, in some of its forms, may be the result. In serious accidents to the encephalon, we observe the importance of the cerebral organ to the proper exercise of the mental faculties most clearly evinced. A man falls from a height, and fractures his skull. The consequence of this is depression of a portion of bone, which exerts a degree of compression upon the brain; or extravasa- tion of blood from some of the encephalic vessels, attended with simi- lar results. From the moment of the infliction of the injury, the whole of the mental and moral manifestations are suspended, and do not return until the compressing cause is removed, by the operation of the trephine. Richerand* cites the case of a female, who had a portion of the brain accidentally exposed, and in whom it was found, that pressure upon the brain completely deprived her of all conscious- ness, which was not restored until the pressure was removed. A similar case is related by Lepelletier, de la Sarthe. A patient of a Dr. Pierquien had an extensive caries of the os frontis, with a perfo- ration of the bone, which exposed the brain covered by its mem- » Physiologie Medicale, &c. iii, 242. Paris, 1832. MENTAL FACULTIES. 259 branes. When she slept soundly the organ sank down: when she dreamed, or spoke with feeling, a turgescence and marked oscilla- tions were perceptible; when the brain was pressed upon she stopped in the middle of a sentence or of a word, and when the pressure was removed, she resumed the conversation, without any recollection of the experiment to which she had been subjected. We notice, however, an important difference in the effect, accord- ing to the suddenness or tardiness with which the pressure is pro- duced. Whilst a sudden compression suspends the intellectual and moral manifestations for a time, slow pressure, produced by the gradual formation of a tumour, may exist without exhibiting, in any manner, the evidences of its presence. Accordingly, the anatomist is sometimes surprised to discover such morbid formations in the brains of those who have never laboured under any mental aberra- tion. A negative argument in favour of this function of the brain has been deduced from the fact, that disease of other portions of the body, even of the principal portions, may exist and pass on to a fatal ter- mination, leaving these faculties almost wholly unimpaired. Such is proverbially the case with phthisis pulmonalis, the subject of which may be flattering himself with hopes never to be realized, and devis- ing schemes of future aggrandizement and pleasure, until within a few hours of his dissolution. The intellectual faculties differ in each individual, and vary ma- terially with the sex. The brain is, in all these cases, equally different. Much may depend upon education; but it may, we think, be laid down as an incontrovertible position, that there is an original differ- ence in the cerebral organization of the man of genius and of him who is less gifted ; and that, as a general principle, in the former the brain is much more developed than in the latter. Whilst the brain of the man of intellect may measure from nineteen to twenty-two inches in circumference, that of the idiot frequently does not exceed thirteen, or is not greater than in the child one year old. It was an ancient observation, that a large developement of the anterior and superior parts of the head is a characteristic of genius; and, accordingly, we find, that all the statues of the sages and heroes of antiquity are represented with high and prominent foreheads. In the older poets, we meet with many evidences, that the height of the forehead was regarded as an index of the intellectual or moral cha- racter of the individual—Thus, Shakspeare: " We shall lose our time, And all be turn'd to barnacles, or to apes, With foreheads villanous low." Caliban, in ' Tempest?—Act iv. And again:— " Ay, but her forehead's low, and mine's as high." Julia, in the ' Two Gentlemen of Verona.1—Act iv.* * Kidd, on the Adaptation of External Nature to the Physical Condition of Man, p. 61. Amer. edit. Philad. 1833. 260 MENTAL FACULTIES. The relation between the size of the head and the mental manifes- tations has, indeed, interwoven itself into our ordinary modes of speech. Perhaps, as a general observation, it may be found true, that the mental capacity is in a ratio with the size of the brain, compared to that of the rest of the body. "Let it not be believed," says a dis- tinguished writer,* "an aftair of accident, that a head of considerable dimensions is found, from time to time, to coincide with a distin- guished genius. Although the amour propre may object, the law is general. I have neither met in antiquity, nor in modern times a man of vast genius, whose head ought not to be ranged in the latter class, which I have just established, especially if attention be paid to the great developement of the forehead. Look at the busts and en- gravings of Homer, Socrates, Plato, Demosthenes, Pliny, Bacon, Sully, Galileo, Montaigne, Corneille, Racine, Bossuet, Newton, Leibnitz, Locke, Pascal, Boerhaave, Haller, Montesquieu, Voltaire, J. J. Rousseau, Franklin, Diderot, Stoll, Kant, Schiller, &c." Yet we are not always accurate in estimating the size of the brain from the developement of the head. Dr. Sewallf has clearly shown, that skulls of the same dimensions, as measured by the craniometer, differ largely as to the quantity of cerebral substance which they are capable of containing. With the assistance of Dr. Thomas Jones of Washington, and of Professor Ruggles of the Columbian College, he instituted various experiments. In the first series, he ascertained the volume of each skull, brain included; in the second series, the volume of the brain alone, or the capacity of the cerebral cavitv, and in order to render the difference in capacity more obvious, the volume of each skull, brain included, was reduced to the dimensions of 70 fluid ounces. The results of the experiments on five skulls, delineated in the plates of Dr. Sewall's work, was as follows: PI. ii. Vol. of skull, brain included. Vol. brain. 70 oz. 56.22 oz. . do. . 51.72 do. . 46.21 . do. 34.79 do. . 25.33 In two of these skulls, consequently, of the same external dimen- sions, there was a difference in the volume of brain of 31.89 oz. something more than one-half. Dr. Sewall infers from his ob- servations, that no phrenologist, however experienced, can, by any inspection of the living head, ascertain whether a person has a skull of one inch or one-eighth of an inch in thickness; or whether he has 56.22 ounces of brain, or only 25.33 ounces. To the view, that the mental capacity is in a ratio with the size of the brain there must be numerous exceptions ; for independently * Gall, sur les Fonctions du Cerveau, ii. 342, Paris, 1825. t An Examination of Phrenology ; in two lectures: lect. ii. p. 47. Washington City MENTAL FACULTIES. 261 of bulk there may obviously be an organization, which may be productive of the same results, and in which the largely developed organ may be greatly deficient. Size is only one of the elements of the activity of an organ. The difference between the moral of the male and female is signal; and there is no less in the shape of the encephalon in the two sexes. Observation, not only by anatomists but by sculptors and painters, shows, that the superior and anterior parts of the brain are less de- veloped in the female, whose forehead is, therefore, as a general rule, smaller; whilst the posterior parts are larger than in the male. In the system of Gall, the anterior and superior parts are considered to be connected with the intellectual manifestations, which are more active in man ; whilst the posterior are concerned in the softer feel- ings, which predominate in the character of the female. The mental and moral faculties vary in the same individual, ac- cording to age, health and disease; and in the waking and sleeping state. In all these conditions, we have reason to believe, that the state of the encephalon is as various. The anatomist notices a mani- fest difference between its organization in the infant and in the adult or the aged. Like the other organs of the body, it is gradually de- veloped until the middle period of life; after which it decays along with the rest of the frame. Our acquaintance with the minute or- ganization of the body does not enable us to say on what changes these differences are dependent. We see them only in their results. By the minutest examination of the special nerves of the senses we are incapable of saying, why one should be able to appreciate the contact of sapid bodies—another that of light, &c. During sleep, again, in which the functions of the brain are more or less suspended, the condition of the organ is modified ; and mania or delirium probably never occurs, without the physical condition of the brain having undergone some change, directly or indirectly. It is true, that, on careful examination of the brains of the insane, it has often happened that no morbid appearance has presented itself; but the same thing has been observed on inspecting those, who have died of apoplexy or paralysis, in which cases, not a doubt is enter- tained that the cause is seated in the encephalon, and that it consists in a physical alteration of its tissue. These are a few of the cases, which make us sensible of the limited nature of our powers of ob- servation. They by no means encourage, in the most sceptical, the belief, that the tissue of the organ is not implicated. The investiga- tions of the morbid anatomist consequently afford us but few data, on which to form our opinions on this subject. The effect of intoxicating substances must be mainly exerted on the brain. When taken in moderation, we find all the faculties ex- cited ; but, if pushed too far, the intellectual and moral manifesta- tions become perverted. This can only be through the action of those substances upon the cerebral organ. We can thus understand, how regimen may cause important modifications in the brain. Cli- mate has probably a similar influence: hence the difference between 262 MENTAL FACULTIES. the characters of different nations and races. The skull of the Mongol is strikingly different from that of the Kelto-Goth or of the Ethiopian; and the brain, as well as its functions, exhibits equal diversity. Again, it has been argued, that the facts we notice in the animal kingdom are in favour of the brain being the organ concerned in the manifestations of the mind; that, if each animal species has its own psychology, in each the encephalon has a particular organiza- tion; and that, in all those which exhibit superior powers, the brain is found large and more complicated. To a great extent this is doubt- less true. Nothing, indeed, seems more erroneous than the notion, that even sensibility to pain is equal in every variety of the animal creation. As we descend in the scale, we find the nervous system becoming less and less complicated, until ultimately it assumes the simple original character, which has laid the foundation for one of the divisions of Sir Charles Bell's system; and, although it is im- possible to change places with the animal, we have the strongest reasons for believing, that their sensibility diminishes as we descend; and that the feeling, expressed by the poet, that the beetle, which we tread upon— " In corporal sufferance finds a pang as great, As when a giant dies"— however humane it may be, is physiologically untrue.* The frog will continue sitting, apparently unconcerned, for hours after it has been eviscerated; the tortoise walks about after losing its head; and the polypus, when divided by the knife, forms so many separate animals. Redi removed the whole of the brain from a common land tortoise: the eyes closed to open no more, the animal walked as before, but, as it were, groping its way for want of vision. It lived nearly six months after. All have noticed the independence of the parts of a wasp, when the head has been severed from the body. The head will try to bite, and, for a considerable period, the abdomen will attempt to sting. An illustrative instance of this kind occurred to Dr. Harlan,f of Philadelphia. He cut off the head of a rattlesnake, and grasping the part of the neck, attached to the head, with his finger and thumb, the head twisted itself vio- lently, endeavouring to strike bim with its fangs. A live rabbit was afterwards presented to the head, which immediately plunged its fangs deep into the rabbit; and when the tail was laid hold of, the headless neck bent itself quickly round as if to strike him. The instances of a similar kind, which occur to the naturalist, are numerous and interesting ; and afford signal evidence of crea- tive wisdom, in endowing the frames of those beings of the animal kingdom, that are most exposed to injury and to torture, with a less sensible organization. * Good's Book of Nature, I. 426. Lond. 1826. t Medical and Physical Researches, p. 503. Philad. 1835. MENTAL FACULTIES. 263 On all the above accounts, then, we may conclude,—that the brain is the organ, through which the mind acts, in the production of the different mental and moral manifestations.* Yet, amongst those who admit the accuracy of this conclusion, a difference of sentiment exists; some conceiving that other organs participate in the function. Some have ascribed to each of the known temperaments as many intellectual and moral dispositions. Others have affirmed, that, if the brain be manifestly the organ of the intellect, the passions must be referred to the organs of internal or organic life; whilst others, again, have considered the brain as a great central apparatus, for the reception and elaboration of the different impressions, made upon the external senses; thus conceiv- ing the latter to be direct agents in the execution of the function, as well as the brain. The influence of the temperaments upon the mental and bodily powers is much less invoked at the present day than it was of old. The ancients regarded organized bodies as an assemblage of ele- ments, endowed with different qualities, but associated and com- bined so as to moderate and temper each other. Modern physiolo- gists mean, by the term, the reaction of the different organs of the body upon each other, consistent with health ; so that if one set or ap- paratus of organs predominates, the effect of such predominance may be exerted on the whole economy. In the description of the tem- peraments, in different authors, we find a particular character of in- tellectual and moral faculties assigned to each. The man of the sanguine temperament is described as of ready conception, retentive memory, and lively imagination, inclined to pleasure, and generally of a good disposition, but inconstant and restless. He of the bilious, on the other hand, is said to be hasty, violent, ambitious, and self-willed; whilst the lymphatic bestows feeble passions, cold ima- gination, tendency to idleness ; and the melancholic disposes to dul- ness of conception, and to sadness and moroseness of disposition. Gallf has animadverted on this assignment of any intellectual or moral faculty to temperament. If we look abroad, he affirms, we find the exceptions more numerous than the rule itself; so numer- ous, indeed, as to preclude us from establishing any law on the sub- ject ; and, moreover, the idiot, who possesses a temperament like other persons, has no intellectual faculties. The temperament doubt- less influences the brain within certain limits, as it does other func- tions : this, he suggests, it does probably by impressing them with a character of energy or of languor, but without, in any respect, re- gulating the intellectual sphere of the individual; and it may be re- garded as one of the media of connexion between the mind and the body. "Haller. Element. Pliysiolog. torn. iv. sect. 16. Sommering, Lehre vom Gehirn, u. s. w. S. 373, § 308. Gall, sur les fonctions du Cerveau, ii. 69. Paris, 1825: Adelon, art. Encephale, Diet, de Medec. vii. 517 ; and Physiologie de I'Homme, Ed. cit. I. 496. t Op. citat. ii. 140. 264 MENTAL FACULTIES. Bichat,* again, maintained, that whilst the encephalon is evidently the seat of the intellectual functions, the organic nervous system, and, consequently, the different organs of nutrition, which are sup- plied from this system, are the seat of the emotions or passions. That distinguished physiologist, than whom, as Corvisart wrote to the First Consul, in announcing his death, "personne en si peu de temps n'a fait tant de choses et aussi bien,"-\ rests his views upon the three following considerations:—1st. That whilst inward feeling induces us to refer the intellectual acts to the brain, the passions are felt in the viscera of the thorax or abdomen. 2dly. That the effects of intellectual labour are referred to the encephalon, as indicated by the redness and heat of the face and the beating of the temporal arteries, in violent mental contentions, &c.; whilst the passions affect the organic functions, the heart is oppressed, and its pulsations are retarded or suspended; the respiration becomes hurried and interrupted ; the digestion impeded or deranged, &c.; and, Sdly. That whilst our gestures and language refer the intellect to the en- cephalon, they refer the emotions to the nutritive organs. If we wish to express any action of the mind, or if we are desirous of re- calling something that has escaped the memory, the hand is carried to the head, and we are in a constant habit of designating a strong or weak intellect by the terms a " strong or weak or long head;" and we say, that the possessor has " much or little brain." On the other hand, if we are desirous of depicting the passions, the hand is carried to the region of the stomach or heart; and the possessor of benevolent or uncharitable sentiments is said to have a good or a bad heart. Bichat properly adds, that this idea is not novel, inasmuch as the ancients conceived the seat of the passions to be in the epi- gastric centre; that is, in the nervous plexuses, situated in that region; he remarks, that, amidst the varieties presented by the passions, according to age, sex, temperament, idiosyncrasy, re- gimen, climate, and disease, they are always in a ratio with the degree of predominance of the different nutritive apparatuses ; and he concludes with a deduction, which ought not to have been hazarded without full reflection—that as the functions of. the nu- tritive organs, in which he ranges the passions, are involuntary, and consequently uninfluenced by education, education can have no influence over the passions, and the disposition is consequently inca- pable of modification. The answer of GallJ and Adelon§ to the views of Bichat appears to us irrefragable. How can we conceive that viscera, whose func- tions are known, and which differ so much from each other, are the agents of moral acts 1 The passions are sensorial phenomena, and like all phenomena of the kind must be presumed to be seated in essentially nervous organs. * Sur la Vie et la Mort. Part, i. Paris, 1806. t Eloge de Xavier Bichat, par Miqucl, p. 58. Paris, 1823. i Op. citat. I. 94. § Art. Enceph. (Physiol.) in Diet, de Med. vii, 521, and Physiologie de I'Homme, edit. cit. I. 510. ORGAN OF INTELLECT. 265 Again, when an injury befalls the brain, and the intellectual faculties are perverted or suspended by it, the same thing happens to the affective faculties; and if the viscera fulfil the high office assigned to them, why are not the passions manifested from the earliest infancy, a period when the viscera are in existence and very active'? The argument of Bichat—that the phenomena which attend and succeed to the passions, are referable to the organs of internal life- is not absolute. The functions of animal life are frequently dis- turbed by the passions, as well as those of organic life. It is not uncommon for them to induce convulsions, mania, epilepsy, and other affections of the encephalon. The effect here, as Adelon re- marks, is mistaken for the cause. The heart certainly beats more forcibly in anger, but the legs fail us in fear; and if we refer anger to the heart, we must, by parity of reasoning, refer fear to the legs.* By reasoning of this kind, the passions might be referred to the whole system, as there is no part which does not suffer more or less during their violence. The error arises from our being im- pressed with the most prominent effect of the passion—the feeling accompanying it—and this is the cause of the gesture and the de- scriptive language, to which Bichat has given unnecessary weight in his argument. If, then, the views of Bichat, regarding the seat of the passions, be unfounded, the mischievous doctrine deduced from them—that they are irresistible, and cannot be modified by education, falls to the ground. His notion was, that the nutritive organs are the source of irritative irradiations, which compel the brain to form the determinations that constitute the passion, and to command the movements by which it is appeased or satisfied. A similar view is embraced by Broussais,f who, however, conceives, that the passions can be fomented and increased by attention, until they become pre- dominant. Daily experience, indeed, shows us the powerful effect pro- duced on the passions by a well-directed moral restraint. How many gratifying instances have we of persons, whose habitual indulgence of the lowest passions and propensities had rendered them outcasts from society, having become restored to their proper place in the com- munity by exerting the due control over their vicious inclinations and habits ! We can not only curb the expression of the passions, as we are constantly compelled to do in social intercourse; we can even modify the internal susceptibility, by well-directed habits of repression. Lastly. Many physiologists, we have seen, have considered the brain as a great nervous centre for the reception and elaboration of the different impressions, conveyed thither by the external senses; and absolutely requiring such impression for the mental manifesta- * See also, Elliotson's Human Physiology, p. 22. Lond. 1835. t Examen des Doctrines Medicales, ii. 388, and Physiology applied to Pathology, Drs. Bell and La Roche's Translation, p. 136. Philadelphia, 1832. vol. i. 23 266 MENTAL FACULTIES. tions. They consequently rank, amongst the conditions necessary for such manifestations, not only the brain which elaborates them, but the parts that convey to it the impressions or materials on which it has to act; and they conceive, that a necessary connexion exists between these two orders of parts. The supporters of these opinions ascribe the differences, observed in the intellectual and moral faculties of different individuals, as much to diversity in the number and character of the impressions, as to differences in the encephalon itself. They do not all, however, agree as to the source of the impres- sions, which they conceive to be the raw material for the intellectual and moral manifestations. Condillac* and his school admit only one kind;—those proceeding from the external senses ; and which they term external impressions. Cabanis,f on the other hand, in addition to these, admits others proceeding from every organ in the body, which he terms internal impressions, in contradistinction to the first. The school of Condillac set out with the maxim ascribed to Aris- totle, " nihil est in intellectu quod non prius fuerit in sensu;" and they adopt, as an elucidation of their doctrine, the ingenious idea of Condillac—of a statue, devoid of all sensation, which is made to re- ceive each of the five senses in succession; and which, he attempts to show, from the received impressions, can gradually develope the dif- ferent intellectual and moral faculties. All these, he affirms, are de- rived from the impressions made on the external senses; and he con- siders, that the whole of human consciousness is mere sensation va- riously transformed. The views of Condillac have been largely embraced, with more or less modification; and, at the present day, many metaphysicians believe, that the impressions of the senses are the necessary and ex- clusive materials for all the intellectual acts. Condillac's case of the statue seems, however, to be by no means conclusive. It must, of course, be possessed of a centre for the re- ception of the impressions made upon the different senses, otherwise no perception could occur; and if we can suppose it possible for such a monstrous formation, as a being totally devoid of the external senses, to exist, such a being must not only be defective in the nerves which, in the perfect animal, are destined to convey the impressions to the brain, but probably in the cerebral or percipient part likewise. From defective cerebral conformation, therefore, the different mental phenomena might not be elicited.J If, however, we admit the possibility of the cerebral structure,— particularly those portions that are especially concerned in the func- tion of thought,—being properly organized, it appears to us, that certain mental or moral manifestations ought to exist. Of course, all knowledge of the universe would be precluded, because deprived * Traite de3 Sensations, torn. i. 119. + Rapport du Physique et du Moral de I'Homme, 4eme 6dit., par G. Pariset. Paris, 1824- X Adelon. Op. citat. I. 519. MENTAL SPHERE OF THE DEAF AND DUMB. 357 of the instruments for obtaining such knowledge; but the brain would still act, as regarded the internal sensations. In order, that such a being may live, he must be supplied with the necessary nourishment; he must possess all those internal sensations or wants that are inseparably allied to organization; he must consequently feel the desires of hunger and thirst: but we have seen, that these sensations require the intervention of the brain as much as the ex- ternal sensations. Supposing him, again, to survive the period of puberty, he must experience the instinctive changes, that occur at this period, and which are doubtless dependent upon encephalic organization. In this assumed case, then, a certain degree of mental action might exist; and, under the supposition of a properly organ- ized brain, ideas—limited, it is true, in consequence of the privation of the ordinary inlets of knowledge—might be formed ; and memory, imagination, and judgment, be compatible within certain limits. The objections to the idea, that the intellectual and moral sphere of man and animals is proportionate to the number and perfection of the external senses are overwhelming.* Many animals have the same number of senses as man, and frequently have them more per- fect ; yet, in none is the mental sphere co-extensive. The idiot, too, has the external senses as delicate as the man of genius, and often much more so; many of those of the greatest talents having the senses extremely obtuse. It has been already remarked, that the superiority of the human intellect has been referred entirely to the sense of touch, and to the happy organization of the human hand; but the case of Miss Biffin, more than once referred to, and that of the young artist cited by Magendie,f completely negative this pre- sumption. The senses are important secondary instruments, indispensably necessary for accomplishing certain faculties of the mind; but, in no way, determining its power. The example of the deaf and dumb is illustrative of this matter.J If a child be born deaf, he is necessarily dumb, inasmuch as he is unable to hear those sounds, which, by their combination, constitute language, and he cannot therefore imitate them; yet this connexion between the functions of hearing and speech was not well known to the ancients. For a length of time, these objects of compassionate interest were esteemed to be beyond the powers of any kind of intel- lectual culture, and were permitted to remain in a state of the most profound ignorance. The ingenuity of the scientific philanthropist has, however, devised modes of instruction, by which their mental manifestations have been exhibited in the most gratifying manner, and in one which proves, that the sense of hearing is not absolutely necessary for mental developement; but that its place may be sup- plied, to a great extent, by the proper exercise of others. The deaf and dumb, being deprived of the advantages of spoken • Helvetius, de I'Homme, &c, torn. I. ! Precis, &c. 2de edit. I. 154. { Gall, Op. cit. 1.119. 268 MENTAL FACULTIES. language, are compelled to have recourse to the only kind available to them—that addressed to the eye. In this typical way, by a well- devised system of instruction, they can be taught to preserve their ideas, and to multiply them, as we do by two combined methods—the spoken and the written language—without one or the other of which the human mind would have remained in perpetual infancy. In this way, the deaf and dumb have not only our ideas, but the same words to convey them to others. Yet the deaf and dumb are not so much the objects of our commi- seration as those who have been deprived, from birth or from early infancy, of both the senses of sight and hearing, and who have thus been devoid of two of the most important inlets for the entrance of im- pressions from the surrounding world. In such case, it is obvious, they are shut out from all instruction, except what can be afforded by the senses of touch, smell and taste: yet even here we have the strongest evidence of independent intellect. One of the most striking cases of this kind is that of the Scottish boy Mitchell, the object of much interest to Spurzheim and to Du- gald Stewart,* both of whom have described his case in their writ- ings. It is matter of uncertainty, whether either his deafness or blindness was total. The evidences of the sensation of hearing were, in a high degree, vague and unsatisfactory, but he gave more con- vincing proofs of the possession of partial vision. He could, for ex- ample, distinguish day from night; and, when quite young, amused himself with looking at the sun through crevices in the door, and by kindling a fire. At the age of twelve, the tympanum of both ears was perforated, but without any advantage. In his fourteenth year, the operation for cataract was performed on the right eye, after which he recognized more readily the presence of external objects, but never made use of his sight to become acquainted with the quali- ties of bodies. Before and after this period, red, white, and yellow particularly attracted his attention. The senses, by which he judged of external bodies, were those of touch and smell. His desire to be- come acquainted with objects was signal. He examined every thing he met with, and every action indicated reflection. In his in- fancy, he smelt at every one who approached him, and their odour determined his affection or aversion. He always recognized his own clothes by their smell, and refused to wear those which he found to belong to others. Bodily exercises, such as rolling down a small hill, turning topsy-turvy, floating wood or other objects on the river that passed his father's house, gathering round, smooth stones, laying them in a circle, and placing himself in the middle, or building houses with pieces of turf, &c. were always a source of amusement to him. After the operation on his right eye, he could better distin- guish objects. His countenance was very expressive, and his natural language was not that of an idiot, but of an intelligent being. When * Elements of the Philosophy of the Human Mind &c.; and History of James Mitchell, a boy born blind and deaf. By James Wardrop. London, 1813. MENTAL SPHERE OF THE DEAF AND DUMB. 269 hungry, he carried his hand to his mouth, and then pointed to the cupboard, where the provisions were kept; and, when he wished to lie down, he reclined his head on one side upon his hand, as if he wished to lay it upon the pillow. He easily recollected the signifi- cation of signs, that had been taught him, all of which were of course of the tactile kind. To make him comprehend the number of days before an event would happen, they bent his head as a sign, that he would have to go to bed so many times. Satisfaction was expressed by patting him on the shoulder or arm, and discontent by a sharp blow. He was sensible to the caresses of his parents, and susceptible of different emotions—of hatred, passion, malice, and the kindlier feelings. He was fond of dress, and had great fears of death, of the nature of which he had manifestly correct notions. Mitchell's case has been pregnant with interest to the metaphysi- cian, but it is not so elucidative as it would have been had the priva- tion of the senses in question been total. There is, at present, in the American Asylum at Hartford in Con- necticut, a being, not less deserving of attention than the one to whom allusion has just been made.* Her name is Julia Brace, She is the daughter of John and Rachael Brace, natives of Hartford, and was born in that town in June, 1807; so that she is now, (1838,) thirty-one years old. At four years of age, she was seized with typhus fever ; was taken sick on the evening of Monday, November 29, 1811, and, on the Saturday morning following, became both blind and deaf. Prior to her illness, she had not only learned to speak, but to repeat her letters, and to spell words of three or four syllables; and, for some time after the loss of her sight and hearing, she was fond of taking a book, and spelling words and the names of her acquaintances. She retained her speech pretty well for about a year, but gradually lost it, and appears to be now condemned to per- petual silence. For three years, she could still utter a few wrords, one of the last of which was " mother." At first she was unconscious of her misfortune, appearing to think, that a long night had come upon the world; and often said, " It will never be day." She would call upon the family to " light the lamp," and was impatient at their seeming neglect, in not even answering her. At length, in passing a window, she felt the sun shining warm upon her hand, and pointed with delight to indicate that the sun shone. From the January after her illness, until the following August, she would sleep during the day, and be awake through the night; and it was not until autumn, by taking great pains to keep her awake during the day, that she was set right. At present, she is as regular, in this respect, as other persons. From the period of her recovery, she seemed to perceive the return of Sabbath; and, on Sunday morning, would get her own clean clothes, and those of the other children. If her mother was reading, she would find a book, and endeavour to do so likewise. 'Twenty-first Report of the Directors of the American Asylum at Hartford, for the education and instruction of the deaf and dumb, p. 15. Hartford, 1837, 23* 270 MENTAL FACULTIES. Even now, the intervention of a day of fasting or thanksgiving will confuse her reckoning, and some time elapses before she gets right. During the first winter after her recovery, she was irritable almost to madness; would exhibit the most violent passion, and use the most profane language. The next summer she became calmer; and her mother could govern her, to some extent, by shaking her, in sign of disapprobation; and stroking or patting her head, when she con- ducted herself well. She is now habitually mild, obedient, and affec- tionate. During the first summer after her illness, she was very un- willing to wear clothes and would pull them off violently. At length her mother took one of her frocks and tried it on her sister, with a view of altering it for her. Julia had ever been remarked for her sense of justice in regard to property. This seemed to be awakened, and she took the frock and put it on herself. After this, she was willing to wear clothes, and even cried for new ones. She has ever since been fond of dress. At nine years of age, she was taught to sew; and, since that time, has learned to knit. She has been resi- dent for several years in the American asylum at Hartford, where she is supported in part, by the voluntary contributions of visiters; and, in part, by her own labours in sewing and knitting. A language of palpable signs was early established, as a means of communica- tion with her friends; and this has been so improved as to be suffi- cient for all necessary purposes. Her countenance, as she sits at work, is said to exhibit the strongest evidence of an active mind and a feeling heart: "thoughts and feelings," says a writer who de- scribes her case, " seem to flit across it like the clouds in a summer sky: a shade of pensiveness will be followed by a cloud of anxiety or gloom; a peaceful look will perhaps succeed; and, not unfre- quently, a smile lights up her countenance, which seems to make one forget her misfortunes. But no one has yet penetrated the dark- ness of her prison house, or been able to find an avenue for intel- lectual or moral light. Her mind seems, thus far, inaccessible to all but her Maker." An equally extraordinary example is cited by Dr. Abercrombie,* from the Medical Journals of the time. A gentleman in France is asserted to have lost every sense except the feeling of one side of his face; yet his family acquired a method of holding communication with him, by tracing characters upon the part, which retained its sensation. How strongly do these cases demonstrate the independence of the organ of intellect; requiring, indeed, the external senses for its perfect developement, but still capable of manifesting itself, without the presence of many and probably of any of them; and how inaptly, although humanely, does the law regard such beings. " A person," says Blackstone,f " born deaf, dumb, and blind, is looked upon by the law as in the same state with an idiot, he being supposed • Inquiries concerning the Intellectual Powers, &c. Amer. edit. p. 56. New York, 1832. t Commentaries on the Laws of England, I. 304. VIEWS OF CABANIS. 271 incapable of any understanding, as wanting all those senses which furnish the human mind with ideas." But if he grow deaf, dumb, and blind, not being born so, he is deemed non compos mentis, and the same rules apply to him as to other persons supposed to be lunatics. With regard to the deaf and dumb, they are properly held to be competent as witnesses, provided they evince sufficient understand- ing, and to be liable to punishment for a breach of the criminal laws. Cabanis* embraces the views of Condillac regarding the exter- nal senses; but he thinks, that the impressions from these are insuffi- cient to constitute the materiel of the mental and moral manifesta- tions. In confirmation of this opinion, he observes, that the young infant and animals, at the very moment of birth, frequently afford evidences of complicated intellectual processes; and yet the exter- nal senses can have been scarcely at all impressed. How can we, he asks, refer to the operation of the external senses the motions of the foetus in utero, which are perceptible to the mother, for the latter half of utero-gestation; or the act of sucking executed from the first day of existence 1 Can we refer to this cause the fact of the chick, as soon as it is hatched, pecking the grain that has to nourish it ? or that, so frequently quoted from Galen, of the young kid, scarcely extruded from the maternal womb, which was able to select a branch of the cytisus from other vegetables presented to it? Man and animals, continues Cabanis, during the course of their existence, experience mental changes as remarkable as they are fre- quent; yet nothing in the condition of the senses can account lor such difference. For example, at the period of puberty, a new ap- petite is added; and this, even, when the being is kept in a com- plete state of isolation. This, he argues, it is impossible to refer to any change in the external senses; which, if they furnished the materials at all, must have been doing so from early infancy; and he concludes, that the difference observable in the mental manifesta- tions, according to sex, temperament, climate, state of health or disease, regimen, &c. cannot be referable to the senses, as they re- main the same; and that, consequently, we must look elsewhere for the causes of such difference. These, Cabanis conceives to be, the movements by which the organs of internal life execute their func- tions. Such movements, he says, although deep-seated and im- perceptible, are transmitted to the brain, and furnish that organ with a fresh set of materials. At puberty, for example, when the testicles become developed, and their function is established by the secre- tion of sperm, the organic movements in the process of this secre- tion are the materials of the new desires, which appear at that age. These impressions Cabanis calls internal, in contradistinction to the external, or those furnished by the senses; and he considers, that, whilst the external senses serve as the base of all that we include under the term intellect, the internal impressions are the materials of what are called instincts; and, as the organs of internal life, whence * Rapport du Physique et du Morale, edit. cit. 272 MBNTAL FACULTIES. the internal impressions proceed, vary more than the senses, accord- ing to age, sex, temperament, climate, regimen, &c. it is more easy, he thinks, to find in them organic modifications, which coincide with those exhibited by the mind under these various circumstances. In proof of these opinions, Cabanis adduces, besides others, the following specious affirmations. First. As the venereal appetite appears in man and animals synchronously with the developement of the testicles, and is never exhibited when the testicles are removed in infancy, we have reason to believe, that the impressions, which constitute the materials for this new catenation of ideas, must pro- ceed from the testicle. Secondly. Numerous facts demonstrate, that the condition of the uterus has much influence on the mental and moral manifestations of the female. For example, the period of the developement of that organ is the one at which new feelings arise, and when the whole of those manifestations assume more ac- tivity ; and there is generally a ratio between their activity and that of the uterus. If the state of the uterus be modified, as it is at the menstrual period, or during pregnancy, or after delivery, the mind is so likewise. All these facts ought to induce a belief, he thinks, that impressions are continually emanating from this organ, which, by their variety, occasion the diversity in the state of mental and moral faculties, observed in these different cases. Thirdly. It is impossible in the hypochondriac and melancholic constitutions, to mistake the influence exerted upon the mind by the abdominal or- gans; according as these organs execute their functions more or less perfectly, the thinking faculty is more or less languid or brilliant; and the affections are more or less vivid and benevolent, or the con- trary; hence the expressions melancholy* and hypochondriasis,^ assigned to the state of mind characterizing these constitutions, and which denote that the cause must be referred to the organs of the abdomen. The origin of the alternations of inactivity and ener- gy in the intellect, of benevolent and irascible fits of humour, as well as of insanity, are also referable, he says, to the abdominal viscera. Hence, Cabanis concludes, it is evident, that the abdominal or- gans are to the brain the source of fortuitous and anormal impres- sions, which excite it to irregular acts; and is it not, he asks, pro- bable, that what takes place in excess, in these morbid movements, may happen to a less and more appropriate extent in the state of health; and that thus impressions may emanate, in a continuous manner, from every organ of the body, which may be indispensable to the production of the mental and moral faculties? Cabanis, therefore, considers that the axiom of Aristotle should be extended; and that the statue of Condillac is incomplete, in not having internal organs for the emanation of the internal impressions, which are the materials of the instincts. In this way he accounts for the instincts, which, by some metaphysicians, have been looked upon as ordinary judgments, so rapidly executed, that the process has ceased * From fAt\ttt, black, and %°k», bile. f Disease of the bypochondres. VIEWS OF CABANIS. 273 from habit to be perceptible. Finally, he remarks there is a ratio between the duration and intensity of the intellectual results and the kind of impressions, which have constituted the materials of them. All the mental and moral acts, for instance, that are derived from impressions engendered in the very bosom of the nervous system or in the brain,—such as those of the maniac,—are the strongest and most durable. After these come the instincts, of which the internal impressions are the materials. They are powerful and constant. Lastly; the acts of the intellect are more transient, because they emanate from the external impressions, which are themselves fickle, and somewhat superficial. According to the views, then, of Cabanis and his followers, amongst the organic conditions of the mental and moral manifestations must be placed, not only the encephalon and the external senses, but the different organs of the body, which fur- nish the different internal impressions. The influence of the external senses on the intellectual and moral developement has already been canvassed: we have seen, that they are only secondary instruments for making us acquainted with external bodies, but in nowise regu- lating the intellectual or moral sphere. The notion of internal im- pressions is ingenious, and has led to important improvements in the mode of investigating the different mental and moral pheno- mena. It was suggested, as we have seen, by Cabanis, in conse- quence of the external senses appearing to him insufficient to explain all the phenomena. By Gall, Adelon,* and others, however, all these cases are considered explicable by the varying condition of the brain itself. In the foetus in utero, in the new-born animal, there are already parts of the brain, they say, sufficiently developed and capable of action; and, accordingly, we witness the actions to which reference has been made by Cabanis; and if the intellectual and moral manifestations vary according to sex, temperament, climate, regimen, state of health, &c. it is because the encephalon is, under these circumstances, in different conditions. The chief facts, on which Cabanis rests his doctrine, are,—the coincidence between the developement of the testicle and the appearance of the venereal appetite; and the suppression of this appetite after castration. It must be recollected, however, that these are not the only changes, that happen simultaneously at puberty. The voice also assumes a very different character; but the change in the voice is not a cerebral phenomenon. It is dependent upon the developement. of its organ, the larynx. Yet castration, prior to puberty, has a decided effect upon it; preventing it from becoming raucous and unmelodious. All these developements are synchronous, but not directly consequent upon each other. The generative function has two organs,—one encephalic, the other external; and it is not surprising, that both of these should undergo their developement at the same period. We shall see hereafter that Gall offers us reasons for believing, that the instinct of propagation has its seat in the cerebellum; and as the » Physiologie de I'Homme, 2de edit. i. 251. 274 MENTAL FACULTIES. most intimate connexion and dependence must exist between the encephalic and the external apparatus, it is not surprising, that the removal of the latter should prevent the developement of the former, and of the instinct of which it is the organ. If, however, the operation of castration be performed after puberty, the instinct is not suppressed, because the necessary developement has already taken place, and the cerebellum is in a condition for fulfilling the function. The con- tinuance of the instinct, however, under such circumstances, Adelon conceives to be strong evidence against the existence of such inter- nal impressions; whilst the influence which Cabanis has ascribed to the uterus in females, and to the abdominal organs in the melan- cholic and hypochondriac, are esteemed to belong to that excited by the temperament, or by the different organs of the body on the brain; a subject which has already fallen under discussion.. On the whole, then, we are perhaps justified in concluding, that the encephalon alone is the organ of the intellectual and moral fa- culties. The interesting topic of the various instinctive operations of the frame will be considered in another part of this work. We shall there find, that instinct cannot well be defined, in the language of Broussais,* to consist in sensations originating in the internal and external sensitive surfaces, and which solicit the cerebral centre to acts necessary for the exercise of the functions—such acts being fre- quently executed without the participation of the mind, and even in its absence—inasmuch as it is not confined to beings possessed of brain, but exists also in the vegetable. Having now decided upon the organ of the mental and moral facul- ties, according to the system adopted in this work, it would be necessary to describe its anatomy. But this has been done else- where. 1. Physiology of the Intellectual and Moral Faculties. When the organ of the intellect is exposed by accident, and we regard it during the reception of a sensation, the exercise of volition, or during any intellectual or moral operation, the action is found to be too molecular to admit of detection. At times, during violent mental contention, a redness has been apparent, as if the blood were forced more violently into the vessels; but no light has been thrown by such examinations on the wonderful action, which constitutes thought. We ought not, however, to be surprised at this, when we reflect, that the most careful examination of a nerve does not con- vey to us the slightest notion how an impression is received by it from an external body; and how such impression is conveyed to the brain. All that we witness in these cases is the result; and we are thus compelled to study the intellectual and moral acts by themselves, without considering the cerebral movements concerned in their pro- * Physiol, appliquee & la Pathologie, ch. vii.; and Bell & La Roche's Translation. Philad. 1832. PHYSIOLOGY OF THE MENTAL FACULTIES. 275 duction. Such study is the basis of a particular science—metaphy- sics, ideology or philosophy. Apart from organization, this subject does not belong to physiology; but as some of the points of classifi- cation, &c. are concerned in questions that will fall under consider- ation, it may be well to give a short sketch of the chief objects of metaphysical inquiry; which are, indeed, intimately connected in many of their bearings,—as commonly treated of by the metaphysi- cian,—with our subject. Broussais has considered, that metaphysics and physiology should be kept distinct; and that all the investiga- tions of the metaphysician should be confined to the ideal. " I wish metaphysicians, since they so style themselves," he remarks some- what splenetically, " would never treat of physiology; that they would only occupy themselves with ideas as ideas, and not as modi- fications of our organs ; that they would never speak either of the brain, the nerves, the temperaments, or of the influence of climates, of localities, or of regimen; that they would never inquire whether there are innate ideas, or whether they come through the medium of the senses; that they would not undertake to follow their develope- ments according to age or state of health ; for I am convinced that they cannot reason justly on these points. Such questions belong to physiologists, who can unite a knowledge of the moral nature with that of the structure of the human body." " It is possible," he adds, "that particular circumstances may oblige them to introduce physiological considerations into their calculations; as when it is necessary to estimate the influence of certain laws or customs in relation to temperature, to the nature of the soil, the prevailing dis- eases, &c. but then they should avail themselves of the experience of physiologists and physicians."* A more appropriate recom- mendation would have been, that the metaphysician should make a point of becoming acquainted with physiological facts and reason- ing; and, conversely, that metaphysics should form a part of the study of every physiologist. The cerebral manifestations comprise two very different kinds of acts;—the intellectual and the moral: the former being the source of all the knowledge wre possess regarding -ourselves and the bodies surrounding us : the latter comprising our internal feelings, our appe- tites, desires, and affections, by which we are excited to establish a relation with the beings around us:—the two sets of acts respect- ively embracing the qualities of the mind and of the heart.'] If we attend to the different modes in which the intellectual mani- festations are evinced in our own persons, we shall find that there are several operations, which differ essentially from each other. We are conscious of the difference between perceiving an impression made upon one of the external senses, which constitutes perception, and the recalling of such impression to the mind,—which is the act * De l'lrritation et de la Folic Paris, 1828; or Dr. Cooper's translation. Columbia, N. C. 1831. t Adelon, Facultes de l'Esprit et de Tame, in Diet, de Med. viii. 469. Paris, 1823; and Physiologie de I'Homme, edit. cit. I. 527. 276 MENTAL FACULTIES. of memory; as well as the distinction between feeling the relations, which connect one thing to another, constituting judgment; and the tendency to act in any direction, which we call will. The con- sciousness of these various mental acts has induced philosophers to admit the plurality of the intellectual acts, and to endeavour to re- duce them all to certain primary faculties; in other words, to facul- ties, which are fundamental or elementary; and which, by their combination, give rise to other and more complex manifestations. To this analytical method they have been led by the fact, that these different acts, which they have esteemed elementary, exhibit great variety in their degrees of activity ; that one, for example, may be impressed with a character of great energy—as the memory— whilst another, as the judgment, may be singularly feeble,—and con- versely. Broussais, indeed, conceives, that without the memory we cannot exercise a single act of judgment; since it is always neces- sary, in order to judge, that we should experience two successive perceptions; that is, that we should feel them alternately, which we could not do, unless possessed of the faculty of renewing that, which we felt an instant before; or, in other words, unless we possessed memory. Hence the loss of this faculty, he says, necessarily occa- sions that of judgment, and reduces man to a state of imbecility. To a certain extent this is doubtless true. Total privation of memory must be attended with the results described ; that is, if the individual retains no consciousness of that which has impressed him previously; for it is obvious, that in such a case, there can be no comparison. A man, however, may have an unusual memory for certain things, and not for others; he may astonish us by the extreme accuracy of his recollection of numbers, places, or persons, and yet he may be singularly deficient in judging of ordinary matters;—his memory suggesting only one train of objects for comparison. In enumerating the faculties, which, by their union, constitute the intellect, we observe the greatest discrepancy amongst metaphysi- cians ; some admitting will, imagination, understanding, and sensi- bility ; others sensibility, imagination, memory, and reason; others will, intelligence, and memory; others, again, imagination, reflection, and memory. The views of Condillac* on this subject have perhaps excited more attention than those of any other individual. Professing, as we have seen, that all our ideas are derived from the successive operations of the senses and the mind, he admits the following constituent faculties of the intellect:—sensation, attention, comparison, judgment, reflec- tion, imagination and reason. Sensation he defines—the faculty of the mind, which affords the perception of any sensitive impression. Attention, the faculty of sensation, applied exclusively to a determi- nate object; being, as the word imports, the tension of the mind upon a particular object. Comparison, the faculty of sensation ap- plied to two objects at once. Judgment, the faculty by which the * Op. citat. PHYSIOLOGY OF THE MENTAL ACTS. 277 mind perceives the connexions, that exist between the objects com- pared. Reason, the faculty of running through a succession of judg- ments, which are connected with, and deduced from each other. Reflection, as the word indicates, the faculty by which the mind re- turns upon itself, upon its own products, to prove their correctness, and to subject them again to its power: and imagination, to which Condillac attaches memory, the faculty possessed by the mind of reproducing at will the different impressions, and all the products of its own operations. With regard to the order of catenation of these different faculties, he considers sensation to be first put in play; and if, amongst the perceptions, there is one, of which we have a more lively consciousness, and which attracts the mind to it alone, it is the product of attention; then comes comparison, which is nothing more than a double attention; comparison is irresistibly succeeded by judgment; if, from one judgment, we pass to another deduced from it, we reason; if the mind turns back on its own products, we reflect; and lastly, if the mind spontaneously awakens its different perceptions, imagination is in action. All these faculties are thus made to be deduced from each other; to originate in the first, or in sensation; and all are this first sensation successively transformed. The doctrine of Condillac, abstractly considered, has already engaged attention. The division of the faculties, which, he con- ceives, by their aggregation, form the intellect, is simple and inge- nious, and appears to be more easily referable to physiological prin- ciples than that of other metaphysicians; accordingly, it has been embraced, with more or less modification, by certain physiological writers. The power of reflection, according to Broussais, is the character- istic of the human intellect; and to reflect is to feel. Man not only feels the stimulation produced by external organs, and by the move- ments of his own organs, which constitutes sensation or perception, but he is conscious that he has felt these stimulations; or, in other words, he feels that he has felt; he has consequently a perception of his actual perception. This, he says, constitutes mental reflection. This process man can repeat as often as he thinks fit, and can ob- serve all his sensations, and the different modes in which he felt, whilst occupied with his feelings. From this study he derives an idea of his own existence. " He distinguishes himself in the midst of creation, and paying regard only to his own existence, compared with all that is not himself, he pronounces the word /, (moi,) and says, / am; and viewing himself in action* says, i" act, I do," &c. Perception of himself and of other bodies procures him what are denominated ideas. This is therefore, another result of reflection ; or, in other words, of the faculty he possesses of feeling himself feel; but man feels, besides, that he has already felt—this constitutes memory. In comparing two perceptions with each other, which are felt in succession, a third perception results, which is judgment. Consequently, to judge is only to feel. Hence, he concludes, " sensa- tion, reflection, and judgment, are absolutely synonymous, and pre- vol. i. 24 278 MENTAL FACULTIES. sent to the physiologist nothing more than the same phenomenon. The will, or that faculty by virtue of which man manifests his liberty by choosing, among different perceptions, the one he must obey—- that faculty, which gives him the power of resisting, to a certain extent, the suggestions of instinct, is founded on reflection. Conse- quently, when we consider it in a physiological point of view, we can only discover in it the faculty of feeling ourselves, and of per- ceivingthat we feel ourselves." Some of the later French metaphysicians have proposed certain modifications of the system of Condillac. M. De La Romiguiere,* for instance, denies that sensation is the original faculty, and he derives all from attention. The mind, he remarks, is passive during the reception of sensation, and does not commence action until directed to some object, or until it attends. According to him, the intellect consists of only three faculties—attention; comparison, or double attention ; and reason, or double comparison. Judgment, imagination, and memory, are not primary faculties: judgment is the irresistible product of comparison; memory is but the trace, which every perception necessarily leaves behind it; and imagina- tion is but a dependence on reason. M. Destutt-Tracyf again, re- duces the number of primary faculties to four—perception, memory, judgment, and will or desire. According to him, attention is not an elementary faculty. It is but the active exercise of the intellectual faculties. The same applies to reflection and reason, which are only a judiciously combined employment of those faculties ; and to com- parison and imagination, both of which enter into the judgment. This division is embraced by Magendie.J Stewart's§ classification is into, 1. Intellectual powers, and, 2, Active and moi-al powers; including in the former, perception, attention, conception, abstraction, the associating principle, memory, imagination, and reason. Brown|| reduces all the intellectual states to simple suggestion and relative suggestion, comprising, in the former, conception, memory, and ima- gination,—in the latter, judgment, reason, abstraction, and taste. Abercrombiell considers the mental operations to be chiefly referable to four heads;—memory, abstraction, imagination, and reason, or judg- ment; whilst Kant has twenty-five primary faculties or forms; pure conceptions or ideas a priori. These are a few only of the discrepant divisions of psychologists. The list might have been extended by the classifications of Aris- totle, Bacon, Hobbes, Locke, Bonnet, Hume, Vauvenargues, Dide- rot, Reid, and others. Perhaps the most prevalent opinion at present is, that the original faculties are—perception, memoiy, judgment, and imagination. It is impossible for us, were it even our province, * Lemons de Philosophie, i. 4eme. lecon. t Elemens d'Ideologie, 2d 6dit. Paris, 1804, and Gall sur les Fonctions du Cerveau, i. 39. Paris, 1625. X Precis Elementaire, i. 196. § Elements of the Philosophy of the Human Mind, 3d edit. London, 1808; and Amer. edit. Brattleborough, Vt. 1813. |] Lectures on the Philosophy of the Human Mind, Amer. edit. Boston, 1826. ^ Inquiries concerning the Intellectual Powers. Amer. edit. p. 91. New York, 1832. CLASSIFICATION OF THE AFFECTIVE FACULTIES. 279 to reconcile these discrepancies. They are too considerable for us to hope, that this will ever be effected by metaphysical inquiry. We must, therefore, look to physiological investigation, if not with well founded—with the only—hopes, we can entertain, for the elucida- tion of the subject; and we shall find presently, that the minds of metaphysical physiologists have been turned in this direction, and that many interesting facts and speculations have been the result. A second topic of metaphysical inquiry regards the formation of the intellectual notions we possess. On this, there have been two principal opinions; some, as Plato, Descartes, the Kantists, Kanto- platonists, &c. believing in the existence of innate ideas of things;— others, as Bacon, Locke, and Condillac, denying the existence of such innate ideas, and asserting that the human intellect, at birth, is a tabula rasa, and that the mind has to acquire and form all the ideas it possesses from impressions made on the senses. The truth includes probably both these propositions—the action of the senses and of the intellectual faculties being alike necessary; the former receiving the external and internal impressions, and transmitting them to the mind, which, through the cerebral organ, produces the different intellectual acts. Under the terms affective faculties, affections, and passions, are comprehended all those active and moral powers, which connect us with the beings that surround us, and are the incentives to our social and moral conduct. To this class belong the feeling, which attaches the parent to the child; that which draws the sexes together; and the feeling of compassion, by which we are led to assist a suffering fellow-creature. They are, in truth, internal sensations, but of a higher cast than those of hunger and thirst; the latter being purely physical and announcing physical necessities, the former suggesting social and moral relations. Such affective faculties are the founda- tion of what are called moral wants, and, like the internal sensations in general, are the source of pleasure, when satisfied,—of pain, when resisted; and it is only when they are extreme and opposed, that they acquire the name of passions.* The analysis of these is attended with the same difficulties as that of the intellectual faculties. Their plurality is universally admitted, but still greater discrepancy exists as to their precise number and connexion.-)- Many moralists have united the moral faculties under the head of will or desires. CondillacJ is one of those. Every sensa- tion, he observes, has the character of pleasure or pain, none being indifferent; as soon, therefore, as a sensation is experienced, the mind is excited to act. This tendency is at first but slightly marked, and is only'an uneasiness (malaise:) but it soon increases, becomes restlessness or inquietude; in other words, a difficulty experienced * From potior, I suffer. t Adelon, art. Affection, in Dictionnaire de Medecine, lere edit.; and Physiologie de rilomrne, edit. cit. i. 537. $ Op. citat.: and Dzondi, art. Affect, in Pierer's Anat. Phys. Real Worterb. i. 106. Leipz. und Altenb. 1816. 280 MENTAL FACl.'LTIES. by the mind of remaining in the same situation. This gradually becomes desire, torment, passion, and finally will, excited to the exe- cution of some act. Some have endeavoured, by ultimate analysis, to derive all the affective faculties of the mind, from one principal faculty—that of self-love,—the inward feeling, which induces all men to attend to themselves, their own preservation, and welfare. All the faculties, they assert, are returns of this self-love upon itself; and, as in the case of the intellectual faculties, attempts have been made to classify them; but no two scarcely agree. Some have divided them into the agreeable and the distressing; others into those of love and hatred; many—regarding their effects upon society—into the virtuous, vicious, and mixed;—the first comprising those that are useful to society,—as filial, parental, and conjugal love, which form the foundation of families; goodness, pity, and generosity, which, by inducing men to assist each other, facilitate the social condition; and the love of labour, honour, and justice, which have the same result, by constituting so many social guarantees. The vicious pas- sions, on the contrary, are such as injure man individually and society in general, as pride, anger, hatred, and malice. Lastly, the mixed passions are such as are useful or injurious, according to their use or abuse; such as ambition, which may be a laudable emu- lation, or an insatiable passion, according to its extent and direction. Again, the passions have been divided into the animal or such as belong to physical man, and the social or such as appertain to man in society. The first are guides to him for his own preservation as well as for that of the species. To them belong fear, anger, sad- ness, hatred, excessive hunger, the venereal desires when vehement, jealousy, &c. In the second are included all the social wants, when inordinately experienced. These vary according to the state of civilization of the individual and the community. Ambition, for in- stance, it is said, may be regarded, when inordinate, as excessive love of power:—avarice, as an exaggeration of the desire for for- tune:—hatred and vengeance, as the natural and impetuous desire of injuring those that injure us, &c. Stewart's* division of the active and moral pouers embraces, 1. Instinctive principles, and 2. Rational 'principles: the former in- cluding appetites, desires, and affections, the latter self-love and the moral faculty; all of which Brownf comprises under emotions, im- mediate, retrospective, or prospective;—and lastly, AbercrombieJ refers all the principles, which constitute the moral feelings, to the ollowing head: 1. The desires, the affections and self-love) 2. The uvill; 3. The moral principle, and 4. The moral relation of man to- wards the Deity. It is obvious, that the analysis of the moral faculties has been still less satisfactorily executed than that of the intellectual; and that little or no attempt has been made to specify those that are primary * Op. cilat. t Op. citat. X Philosophy of the Moral Feelings. Amer. edit. p. 35. New Yirk, 1833. MENTAL SPHERE HOW REGULATED. 281 or fundamental, from those that are more complex. The remarks, consequently, which were made regarding the only quarter we have to look to, for any improvement in our knowledge of the intellectual acts, apply a fortiori to the moral; although it must be admitted, that the difficulties attendant upon the investigation of the latter are so great as to appear to be almost, if not wholly, insuperable. As the brain, then, is admitted to be the organ of the intellectual and moral faculties, its structure probably varies according to the number and character of those; and if there be primary or funda- mental faculties, each may be conceived to have a special organ concerned in their production, as each of the external senses has an organ concerned in its production. According to this view, the cere- bral organization of animals ought to differ according to their psycho- logy : where one is simple the other should be so likewise. This seems, so far as we can observe, to be essentially the fact. " In the series of animals," says Adelon,* " we observe the brain more complicated as the mental sphere is more extensive; and in this double respect a scale of gradation may be formed from the lowest animals up to man. If he has the most extensive moral sphere, if he alone possesses elevated notions of religion and morality, he has also the largest brain, and one composed of more parts; so that if the physiology of the brain were more advanced, w:e might be able, by comparing the brains of animals with his, to detect the material condition, which constitutes humanity. If the brain were not con- structed, a priori, for a certain psychology, as the digestive appara- tus is for a certain alimentation, if the mental and moral faculties were not as much innate as the other faculties, there would be no- thing absolute in legislation or morals. The brain and its faculties are, however, in each animal species, in a ratio with the role, which such species is called upon to fulfil in the universe. If man is, in this respect, in the first rank; if he converts into the delicate affec- tions of father, son, husband, and country, those brute instincts, by which the animal is attached to its young, its female, or its kennel; if, in short, he possesses faculties which animals do not,—religious and moral feelings, with all those that constitute humanity,—it is owing to his having a more elevated vocation; to his being not only the king of the universe, but destined also for a future exist- ence, and specially intended to live in society. Hence it was neces- sary that he should not only have an intellect sufficiently extensive to make all nature more or less subject to him, but also a psycho- logy such, that he might establish social relations with his fellows. It was necessary that he should have notions of the just and the un- just, and be able to elevate himself to the knowledge of God;—to those sublime feelings, which cause him so to regulate his conduct as to maintain with facility his mortal connexions, and to deserve the future life to which he is called." * Art. Enceph. in Diet, de Med. vii. 526—and Physiologie de l'Horame, edit. cit. I. 542. 24* 282 MENTAL FACULTIES. But if the intellectual sphere be regulated by the cerebral deve- lopement, can we not, it has been asked, estimate the connexion between them 1 And if there be different primary cerebral faculties, each of which must have an organ concerned in its production, can we not point out such organ in the brain ? Several investigations of this character have been attempted, with more or less success: generally, however, they have added but little to our positive knowledge, and this, principally, from the intricacy of the subject. Until of late years, attention was chiefly paid to the mass and size of the encephalon ; and it was, at one time, asserted, that the larger this organ, in any species or individual, the greater the intellect. Man, however, has not absolutely the largest encephalon although he is unquestionably the most intelligent of beings. The weight of the encephalon of a child six years of age is given by Haller at two pounds three ounces and a half; whilst that of the adult is estimated by Sommering at from two pounds three ounces, to three pounds three ounces and three quarters ;* by Tiedemannf at from three pounds three ounces, to four pounds eleven ounces troy—the brain of the female weighing, on an average, from four to eight ounces less than that of the male. The average weight, after the meninges have been stripped off, is in the healthy adult male, according to LelutJ about 1346 grammes, or three pounds and a half avoirdu- pois; of which the cerebrum weighs 1170, the cerebellum 176 grammes. In the female, the weight of the encephalon he found to be about -j^th less than in the male. The encephalon of the elephant, according to Haller, weighs from seven to ten pounds. This, con- sequently, overthrows the proposition; and, besides, in certain in- sects with very minute brains, as the bee and the ant, we meet with evidences of singular intelligence. The proposition was therefore modified, and it was laid down, that the larger the encephalon, compared with the rest of the body, the greater the mental sphere. When the subject was first investigated in this way, the result, in the case of the more common and domestic animals, was considered so satisfactory, that, without farther comparison, the proposition was considered to be established. More modern researches have shown, that it admits of numerous exceptions, and that several of the mammalia, and many diminutive and insignificant animals have the advantage over man in this respect. It has, indeed, been pro- perly observed by Mr. Lawrence,§ that it cannot be a very satisfac- tory mode of proceeding to compare the body, of which the weight varies so considerably, according to illness, emaciation, or embon- point, with the brain, which is affected by none of these circum- * Weber's Hildebrandt's Handbuch der Anatomie, Band iii. 423—Rudolphi, Grund- riss, u. s. w. ii. 11. t Proceedings of the Royal Society for 1836—and Amer. Medical Intelligencer, 1.368. Phihd. 183a X Gazette Medicale—and Medico-Chirurgical Review for Oct. 1837, p. 507. § Lectures on Physiology, Zoology, &c. Lond. 1819, p. 191—and Buffon, Hist. Nat. ix. RATIO OF THE ENCEPHALON TO THE BODY. 283 stances, and appears to remain constantly the same. This is the cause, why, in the cat, the weight of the encephalon, compared with that of the body, has been stated as 1 to 156 by one comparative anatomist, and as 1 to 82 by another; that of the dog as 1 to 305 by one, and as 1 to 47 by another, &c. The following table, taken chiefly from Haller* and Cuvier,f ex- hibits the proportion, which the encephalon bears to the rest of the body, in man and certain animals. Child, 6 years old Adult. .... Gibbon . . . Sapajous, from . Apes .... Baboons . . . Lemurs . . . Bat (vespertilio) Mole .... Bear .... Hedgehog . . IJOX 4 1 A- to rVtO Wolf . . , Beaver Hare . . Rabbit Rat . . Mouse Wild boar Domestic do. rioto 22 1 3T 1 4? _1 22 _1_ 24 1 1 ST l_ 96 1 ■3 6" _J_ 205 _1 I 6~5 1 2" r «..», VIEWS OF GALL. 293 Olfactus. Giishis Head by Dolci, A. D. 1562. Fig. 51. terior cerebral cavities are for the reception of the images of external objects; the third is the seat of thought; the aqueduct of Sylvius, the seat of the soul, and the fourth ven- tricle that of memory. In 1491, Peter Montagnana published an en- graving, in which were represented the seat of the sensus communis, a cellula imaginativa, cellula estimativa seu cogitativa, a cellula memorativa, and a cellula rationalis. A head, by Ludovico Dolci exhibits a similar ar- rangement. (Fig. 51.)* The celebrated Dr. Thomas Wil- lis, in 1681, asserted, that the corpora striata are the seat of perception; the medullary part of the brain that of memory and imagination: the corpus callosum that of reflection: and the cerebellum, according to him, furnished the vital spirits necessary for the involuntary motions.f These examples are sufficient to show, that the attempt to assign faculties to different parts of the brain, and, consequently, the belief, that the brain consists of a plurality of organs, had been long in- dulged by anatomists and philosophers. The views of Gall are resuscitations of the old; but resembling them little more than in idea. Those of the older philosophers were the merest phantasies, unsup- ported by the slightest observation; the speculations of the modern physiologist have certainly been the result of long and careful inves- tigation, and of the deepest meditation. Whilst, therefore, we may justly discard the former, the latter are worthy of rigid and unpre- judiced examination. Admitting, with Gall, the idea of the plurality of organs in the brain, the inquiry would next be,—how many special nervous sys- tems are there in the human brain, and what are the primary intel- lectual and moral faculties over which they preside ? This Gall has attempted. To attain this double object, he had two courses to adopt; either, first of all, to indicate anatomically the nervous systems that constitute the brain, and then to trace the faculties of which they are the agents; or, on the contrary, to point out first the primary facul- ties, and afterwards to assign to each an organ or particular seat in the brain. The first course was impracticable. The cerebral or- gans are not distinct, isolated in the brain: and if they were, simple inspection could not inform us of the faculty over which they pre- side ; any more than the appearance of a nerve of sense could exhibit the kind of sensation for which it is destined. It was, only, there- * Butler's Anatomy of Melancholy, 11th edit. i. 32. Lond. 1813—See, also, Marga- rita Philosophica, lib. ix. cap. 40. Basil, 1508, cited by Dr. John Redman Coxe, in Ame. rican Medical Intelligencer, I. 58. Philad. 1838. t Gall, sur les Fonctions du Cerveau, ii. 350, Paris, 1825. 25* 294 MENTAL FACULTIES. fore, by observing the faculties, that he could arrive at a specifica- tion of the cerebral organs. But here, again, a source of difficulty arose. How many primary intellectual and moral faculties are there in man? and, what are they? The classifications of the mental phi- losophers, differing, as we have seen they do, so intrinsically and essentially from each other, could lead him to no conclusion. He first, however, followed the notions on which they appeared to be in accordance; and endeavoured to find particular organs for the facul- ties of memory, judgment, imagination, &c. But his researches in this direction were fruitless. He, therefore, took for his guidance the common notions of mankind; and having regard to the favourite occupations, and the different vocations of individuals, to those marked dispositions, which give occasion to the remark, that a man is born a poet, musician, or mathematician, he carefully examined the heads of such as presented these predominant qualities, and endeavoured to discover in them such parts of the brain as were more prominent than usual, and which might be considered as spe- cial nervous systems,—the organs of these faculties. After multi- tudinous empirical researches on living individuals, on a collection of crania, and on casts made for the purpose, attending particularly to the heads of such as had one of their faculties predominant, and who were, as he remarks, geniuses on one point,—to the maniac, and the monomaniac;—after a sedulous study, likewise, of the heads of animals, comparing especially those, that have a particular fa- culty, with such as have it not—in order to see if there did not exist in the brain of the former some part which was wanting in that of the latter; by this entirely experimental method, he ventured to specify, in the brains of animals and man, a certain number of or- gans ; and, in their psychology, as many faculties, truly primary in their character. But, in order, that such a mode of investigation be applicable, it must be admitted, 1st That one of the elements of the activity of a function is the developement of its organ. 2dly. That the cerebral organs end, and are distinct, at the surface of the brain. 3dly. That the cranium is moulded to the brain, and is a faithful index of its shape; for it is, of course, through the skull and the integuments covering it, that Gall attempts, in the living subject, to appreciate the state of the brain. Now, within certain limits, these positions are true. In the first place, we judge of the activity of a function, by the size of the organ that executes it: the greater the olfactory nerve, the more acute we find the sense of smell. In the second place, according to the anatomical theory of Gall, the cerebral con- volutions are the final expansions of the cerebrum: if we trace back the original fasciculi, which, by their expansions, form the hemi- spheres of the brain, they are observed to increase gradually in size in their progress towards the circumference of the organ, and to terminate in the convolutions. Lastly, to a certain extent, the cra- nium is moulded to the brain; and participates in all the changes, which the latter undergoes, at different periods of life, and in disease. PHRENOLOGY. 295 For example, during the first days after the formation of the brain in the fetus, the cranium is membranous, and has exactly the shape of that viscus. On this membrane, ossific points are deposited, so that, when the membrane has become bone, the cranium has still the shape of the brain. In short, nature, having made the skull to contain the brain, has fitted the one to the other, and this so accurately, that its internal surface exhibits sinuosities, correspond- ing to the vessels that creep on the surface; and digitations, corre- sponding to the cerebral convolutions. The brain in fact, rigidly regulates the ossification of the cranium; and when, in the pro- gress of life, the brain augments, the capacity of the cranium is aug- mented likewise; not by the effect of mechanical pressure, but ow- ing to the two parts being Catenated in their increase and nutrition. This remark applies not only to the skull and brain, regarded as a whole, but to their separate parts. Certain portions of the brain are not developed simultaneously with the rest of the organ; and the same thing happens to the portions of the skull that invest them. The forehead, for example, begins to be developed after the age of four months: but the inferior occipital fossae do not increase in propor- tion until the period of puberty. Again, when the brain fades and wastes in advanced life, the cavity of the cranium contracts, and its ossification takes place on a less and less outline. In advanced life, however, according to Gall, the correspondence between the brain and the inner table of the skull is alone maintained; the outer table appearing to be a stranger to all nutritive movement, and preserving its dimensions. Lastly, the cranium partakes of all the variations experienced by the brain in disease. If the brain be wanting, as in the acephalous monster, the cranium is wanting also. If a portion of the brain exist, the corresponding portion of the cranium exists. If the brain be smaller than natural, as in the idiot, the cranium is so likewise. If the brain, on the contrary, be distended by hydroce- phalus, the cranium has a considerable capacity; and this, not owing to a separation, at the sutures, of the bones composing it, but owing to ossification taking place on a larger outline. If the brain be much developed in any one part, and not in another, the cranium is protuberant in the former; restricted in the latter. Lastly, in cases of mania, the cranium is often affected; seeming, for example, to be unusually thick, dense, and heavy. These reasons, adduced by Gall, may justify the admission, that, within certain limits, the skull is moulded to the brain; and, if we admit this, the method followed by him, of specifying the organs of the mental faculties, may be conceived practicable. Such is the basis of the system of craniology, proposed by GalL It also bears the name cranology, organology, phrenology, and cra- nioscopy: though, strictly speaking, it is by cranioscopy that we acquire a knowledge of craniology, or the art of prejudging the intel- lectual and moral aptitudes of man and animals, from an examina- tion of the cranium. It is, of course, limited in its application. Gall admits, that it is not available in old age—owing to the physiological fact before stated;—that the external table of the skull is no longer 296 MENTAL FACULTIES. modified by the changes, that happen to the brain; and he acknow- ledges, that its employment is always difficult, and liable to»numer- ous errors. We cannot, in fact, touch the cranium directly, for it is covered by hair and integument. The skull is, likewise, made rough, in particular parts, by muscular impressions, which must not be confounded with what are termed protuberances; in other words, with the prominences, that are formed by a corresponding develope- ment of the brain. In this respect, craniology presents more diffi- culties in animals, from their heads being more covered with mus- cles, and from the inner table of the skull being, alone, in a ratio with the brain beneath. Other errors again may be indulged from the existence of the frontal sinuses, of the superior longitudinal sinus, and from the possible separation of the hemispheres at the median line. The difficulty is, of course, extremely great in appreciating the parts of the brain, that are situated behind the eyes; and cranio- logy must be entirely inapplicable to those organs of the brain, that do not terminate at its base. Gall has taken especial pains to remark, that by craniology we can only prejudge the dispositions of men, not their actions; and that we can appreciate but one of the elements of the activity of organs—their size—not what belongs to their intrinsic activity, and to the impulse or spring they may receive from the temperament, or general formation. Setting out, however, from the principle, that the predominance of a faculty is in a great measure dependent on the developement of the portion of the brain which is its organ, he goes so far as to particularize, in this developement, what is owing to the length of the cerebral fibres, and what to their breadth; re- ferring the activity of the faculty to the former circumstance, and its intensity to the latter. In applying cranioscopy to animals, he observes, that the same cerebral organ frequently occupies parts of the head, which seem to be very different, on account of the dif- ference between station in animals and man, and of the greater or less number of systems, that compose their brain. The cerebral organs, enumerated by Gall, with the corresponding faculties, are as follows;—the numbers corresponding with those of the accompanying engravings. 1. Instinct of generation, of reproduc- f~ tion; amativeness. Instinct of pro- V Seated in the cerebellum. It is manifested at pagation; venereal instinct. J the surface of the cranium by two round {German.) Zeugungstrieb, \ protuberances, one on each side of the nape Fortpflanzungstrieb, J of the neck. Geschlechtstrieb. (^ 2. Love of progeny; philoprogeni- f tiveness. l Indicated at the external occipital protube. (G.) Jungenliebe, Kinder- 1 ranee. 1 i e b e. ' 3. Attachment, friendship. \ About the middle of the posterior margin of (G.) Freundschaftsinn. ) the parietal bone; anterior to the last. 4. Instinct of defending self and pro- f~ perty; love of strife and combat ;\ Seated a little above the ears; in front of the combativeness; courage. < last, and towards the mastoid angle of the (6?.) Muth, Raufsinn. ) parietal bone. Zanksinn. ( I'KANlOI.OGIl'Al. DIVISION of GALL. I'-W 296 CEREBRAL ORGANS ENUMERATED BY GALL. 397 5. Carnivorous instinct; inclination to murder; destructiveness; cruel- ty. (G.) Wurgsinn, Mordsinn. 6. Cunning; finesse; address; secre- tiveness. {G.) L i s t, S c h 1 a u h e i t, K 1 u g- h e i t. 7. Desire of property; provident in- stinct ; cupidity ; inclination to robbery; acquisitiveness. (G.) Eigenthumssinn, Hang zu stehlen, Einsamm- lungssinn, Diebsinn. 8. Pride ; haughtiness; love of au- thority; elevation. (G.) S t o 1 z, H 0 c h m u t h, H 0 h e n- sinn, Herrschsucht. 9. Vanity; ambition; love of glory. (G.) Eitelkeit, Ruhmsucht, E h r ge i z. 10. Circumspection; foresight. (G.)Behutsamkeit, Vorsicht, Vorsichtigkeit. 11. Memory of things; memory oft facts; sense of things ; educability ; perfectibility; docility. (G.) Sachgedachtniss, E r- ziehungsfahigkeit, Sach- sinn. 12. Sense of locality; sense of the re- lation of space; memory of places. (G.) Ortsinn, Raumsinn. 13. Memory of persons; sense of per- sons. (G.) Personensinn. 14. Sense of words; sense of names; verbal memory. (G.) Wortgedachtniss, Na- me n s i n n. 15. Sense of spoken language; talent of philology ; study of languages. (G.) Sprachforschungssinn, Wortsinn, Sprachsinn. 16. Sense of the relations of colour; talent of painting. (G.) Farbensinn. 17. Sense of the relations of tones; musical talent. (G.) Ton s i n n. 18. Sense of the relations of numbers; mathematics. (G.) Z a h le n s i n n. 19. Sense of mechanics; sense of con- struction ; talent of architecture; industry. (G.) Kunstsinn, Bausinn. 20. Comparative sagacity. (G.)Vergleichender Scharf- sinn. Greatly developed in all the carnivorous ani- mals; forms a prominence at the posterior and superior part of the squamous surface of the temporal bone, above the mastoid process. Above the meatus auditorius externus, upon the sphenoidal angle of the parietal bones. Anterior to that of cunning, of which it seems to be a prolongation, and above that of me- chanics, with which it contributes to widen the cranium, by the projection, which they form at the side of the frontal bone. Behind the top of the head, at the extremity of the sagittal suture, and on the parietal bones. Situated at the side of the last, near the poste- rior internal angle of the parietal bones. Corresponds to the parietal protuberances. 1 Situated at the root of the nose, between the two eyebrows, and a little above them. Answers to the frontal sinuses, and is indi- cated externally by two prominences at the inner edge of the eyebrows, near the root of the nose, and outside the organ of memory of things. At the inner angle of the orbit. Situated at the posterior part of the base of the two anterior lobes of the brain, on the frontal part of the bottom of the orbit, so as to make the eye prominent. Also at the top of the orbit, between the pre- ceding and that of the knowledge of colour. The middle part of the eyebrows; encroaching a little on the forehead. A little above and to one side of the last; above the outer third of the orbitar arch. On the outside of the organ of the sense of the relations of colour, and below the last. A round protuberance at the lateral base of the frontal bone, towards the temple, and behind the organs of music and numbers. At the middle and anterior part of the frontal bone, above that of the memory of things. 298 MENTAL FACULTIES. 21. Metaphysical penetration; depth of mind. (G.) Metaphysischer Tief- s i n n. 22. Wit. (G.)Witz. 23. Poetical talent. (G.) Dichtergeist. 24. Goodness; benevolence; mild- ness ; compassion ; sensibility ; moral sense; conscience; bonhom- mie. (G.) Gutmuthigkeif, Mitlei- den, moralischer Sinn, Ge- wi s s e n. 25. Imitation; mimicry. (G.) Nachahmungssinn. 26. God and religion; theosophy. (G.) Theosophisches Sinn. 27. Firmness; constancy; perseve- rance; obstinacy. (G.) Stetigkeit, Fester Sinn. Fig. 52. In part, confounded with the preceding. In- dicatcd, at the outer side of this last, by two protuberances, which give to the forehead a peculiar hemispherical shape. At the lateral and outer part of the last; and giving greater width to the frontal promi- nences. On the outer side of the last; divided into two halves by the coronal suture. | Indicated by an oblong prominence above the organ of comparative sagacity; almost at the frontal suture. At the outerside of the last. At the top of the frontal bone and at the supe- rior angles of the parietal bones. The top of the head; at the anterior and most elevated part of the parietal bones. Fig. 53. ORGANS ACCORDING TO SPURZHEIM. 1. Amativeness. 2. Philoprogenitiveness. 3. Inhabitiveness. 4. Adhesiveness or At- tachment. 5- Combativeness. (>. Destiuctiveness. 7. Constructiveness. 8 Acquisitiveness. 9. Secretiveness. 10. Self esteem. / II. Love or about a third part of that of a blood globule. The muscles of organic life he found to be composed, not of fibres similar to those described, but of filaments only; these filaments being interwoven, and forming a kind of un- traceable network. The fibres of the heart appeared to possess a somewhat compound character of texture: the muscles of the pharynx exhibited the character of those of animal life: whilst those of the oesophagus, the stomach, the intestines, and the arterial system pos- sessed that of inorganic life. He was unable to determine the exact nature of the muscular fibres of the iris. The intimate structure has likewise given rise to extraordinary contrariety of sentiment;—some, as Santorini, Heister, Cowper,J Vieussens, Mascagni,§ Prochaska,|| Borelli,H John Bernouilli, &c. believing the filaments to be hollow; others as Sir A. Carlisle,** Fon- tana,ff to be solid; some believing them to be straight; others zig- zag, spiral, or waved; some jointed; others knotted, &c. &c.JJ Borelli and J. Bernouilli announced, that the fibre consists of a series of hollow vesicles, filled with a kind of spongy substance or marrow;—the shape of these vesicles being, according to the former, rhomboidal,—according to the latter spheroidal. Deidier conceived it to be a fasciculus, composed of an artery, vein, and lymphatic, enveloped by a nervous membrane, and held together by nervous filaments:—Prochaska, to consist of blood-vessels turned spirally around an axis of gelatinous or fibrinous substance, into the interior of which the blood rushed at the time of contraction. He says, that the visible fibres are not cylindrical, as they had been described by many observers, but of a polyhedral shape; and that they are gene- rally flattened, or thicker in one direction than in the other. They are not all of the same diameter; differing in different animals, and in different parts of the same animal: they are smaller, too, in young subjects. The filaments, or ultimate fibres, which can only be seen with the microscope, have the same shape as the visible fibres; they are, however, always of the same magnitude. Sir Anthony Carlisle,§§ whose opinions, on many subjects at least, are not entitled to much weight, describes the ultimate fibre as a solid cylinder, the covering of which is a reticular membrane, and * Transactions of the Royal Society, for 1836. t See Hare's Views of the Structure, Functions, and Disorders of the Stomach, p. 28. London, 1821. X Myotomia Reforrnata. Lond. 1724. § Prodromo, p. 97. || Oper. Minor. P. I. 198. IT De motu animalium. Addit. Johan. Bernouilli, M. D. Meditationes Mathematic. Musculorum. Lugd. Bat. 1710. ** Phil. Trans, for 1805, p. 6. tt Sur les Poisons, torn. ii. 228. XX Elliotson's Physiology, p. 476. §§ Op. citat. 312 MUSCULAR MOTION. the contained part a pulpy substance, regularly granulated, and of very little cohesive power when dead. The extreme branches of the blood-vessels and nerves, he says, are seen ramifying on the surface of the membrane inclosing the pulp, but cannot be traced into the substance of the fibre. Mr. Bauer* and MM. Prevost and Dumas,f again, differ essentially from the observers already men- tioned. Mr. Bauer found, that the muscular fibre was composed of a series of globules, arranged in straight lines; the size of the glo- bule being 2 oVoth part of an inch in diameter; and lastly, RaspailJ considers that the intimate structure of the muscular tissue, when it is in its most simple state, consists of a bundle of cylinders, inti- mately agglutinated together, and disposed, in a very loose spiral form, around the ideal axis of the group. These tubes are filled with a substance not wholly miscible with water, and may be re- garded as elongated vesicles, united at each end to other vesicles of a similar character. When a muscular fibre is seen through an ordinary microscope, it appears to be composed of longitudinal filaments, each consisting of a string of globules, about -joVo-tn °f an mcn m diameter. " But with a better instrument," says Mr. Mayo,§ " such as that which Mr. Lister possesses, the delusion vanishes, and the parallel lines, which traverse the fibre, appear perfectly clean and even. Mr. Lister politely gave me an opportunity of examining this appear- ance, which was discovered by himself and Dr. Hodgkin." The ultimate fibre's, or filaments, when united in bundles, form fasciculi or lacerti: and these, by their aggregation, constitute the various muscles. Each fibre, each lacertus, and each muscle, is surrounded by a sheath of cellular tissue, which enables them to move readily upon each other, and preserves them in situ. The fibres'are not the same at the extremities as they are at the middle. The latter only consist of the proper muscular tissue; the extremi- ties being formed of cellular tissue. If we examine a muscle, we find, that the proper muscular fibres become gradually fewer, and at length cease to be perceptible, as they approach the tendon at one or other extremity. In this way, the cellular membrane, which surrounds every fibre, becomes freed from the muscular tissue; its divisions approximate, and become closely united and condensed, so as to form the cord or tendon, which, of course, holds a relation to each fibre of the muscle; and when they all contract, the whole force is exerted upon it. This arrangement will explain the close union which exists between the muscle and its tendon, and which has given occasion to the belief, that the latter is only the former condensed. An examination of some of the physical and vital properties of the two will show, that they differ as essentially * Sir E. Home, Lectures on Comp. Anat. v. 240. Lond. 1828. t Appendix to Edwards' De l'Influence des Agens Physiques sur la Vie. Paris, 1824; and Hodgkin and Fisher's Transaction. Lond. 1832. X Chimie Organique, &c. p. 211. Paris, 1833. § Outlines of Human Physiology, Chap. 3, 3d edit. London, 1833. MUSCLES. 313 as any two of the constituents of the body that could be selected. The tendon consists chiefly of gelatine, and does not exhibit the same irritability; whilst the muscle is formed essentially of fibrine, and contracts under the will, as well as on the application of certain mechanical and chemical irritants. The differences, in short, that exist between the two, are such as distinguish the pri- mary fibrous and cellular tissues; yet the opinion of their identity prevailed in antiquity, was embraced by Boerhaave and his school, and, as Dr. Bostock* observes, was so generally admitted, even in the middle of the last century, that Hallerf and SabatierJ scarcely ventured to give a decided opposition to it. Similar remarks are applicable to the notion of Cullen,§ that mus- cles are only the moving extremities of nerves. The fibres of the muscle were supposed by him to be continuous with those of the nerve;—to be, indeed, the same substance, but changed in struc- ture, so that when the nerve is converted into muscle, it loses the power of communicating feeling, and acquires that of producing motion. Every muscle and every fibre of a muscle is probably supplied with blood-vessels, lymphatics and nerves. These cannot be traced into the ultimate filament, but, as this must be possessed of life and be contractile under the will, it must receive through the blood- vessels and nerves the appropriate vital agents. MM. Dumas and PreVost,|| however, affirm, that the microscope shows, that neither the one nor the other terminates in the muscle. The vessels merely traverse the organs; the arteries terminating in corresponding veins; so that the nutrition of the muscles is effected merely by the transudation of the blood through the parietes of the artery;—a notion, which is liable to weighty objection, inasmuch as blood is not muscle, but requires a true action of selection or of elaboration to be exerted upon it, before it can become so. A similar distribu- tion they assign to the nerves. All the branches they assert, enter the muscle in a direction perpendicular to that of the fibres com- posing it; and their final ramifications, instead of terminating in the muscular fibres, surround them loopwise and return to the trunk that furnished them, or anastomose with some neighbouring trunk. In their view, each nervous filament, distributed to the muscles, sets out from the anterior column of the spinal marrow, forming part of a nervous trunk, turns round one or more muscular fibres, and re- turns along the same or a neighbouring trunk to the posterior column of the marrow. The red colour of muscles is usually ascribed to the blood dis- tributed to them, as it may be removed by repeated washing and * An Elementary System of Physiology, p. 84, 3d edit. London, 1836. t Elem. Physiol, ii. 1. 18. X Traite complet d'Anatomie, i. 242. Paris, 1791. § Institutions of Medicine, § 29, 94. | Magendie's Journal de Physiologie, torn. iii. VOL. I. 27 3J4 MUSCULAR MOTION. maceration in water or alcohol, without the texture of the muscle being modified. By some, it has been thought, that a quantity of red blood remains attached to the fibres, and is extravasated from the vessels; by others, it is presumed, with more probability per- haps, to be still contained in the vessels. Bichat* conceived, that the colour is dependent upon some foreign substance combined with the fibre ; and he grounds his opinion upon the circumstance, that, in the same animal, some of the muscles are always much redder than others; and yet they do not appear to have a greater quantity of blood sent to them; and also that, in different classes of animals, the colour of the muscles does not appear to corre- spond with the quantity of red blood circulating through their ves- sels. The fact, however, that, when muscles have been long in a state of inaction, they become pale; and that, on the other hand the colour becomes deeper, when they are exercised, is an addi- tional evidence, that their colour is dependant upon the blood they receive, which is found to diminish or increase in quantity, accord- ing to the degree of inactivity or exertion. The muscles differ, like the primary fibre, at their extremities and centre; the former being composed of condensed cellular mem- brane, the latter of the muscular or fibrous tissue. The centre of a muscle is usually called its venter or belly, and the cellular texture at the extremities is variously termed;—the part, from which it appears to arise, being called the head or origin; and that, into which it is inserted, the tail, termination or insertion. These terms are not sufficiently discriminative. We shall find, that a muscle is capable of acting in both directions, so that the head and the tail— the origin and insertion—reciprocally change places. In ordinary language, however, the extremity at which the albugineous tissue, (if we adopt Chaussier's nomenclature,) assumes a round form, so as to constitute a cord or tendon, is called the insertion. When this tissue is expanded into a membrane, it is termed an aponeurosis: and in this state it exists at the head or origin of the muscle; so that by tendon and aponeurosis the muscles are inserted into the parts, which they are destined to move, if we except those that are inserted into the skin. Muscles are divided into simple and compound. The simple are those whose fibres have a similar course and arrangement. They may be either flat or ventriform, or radiated or penniform. The compound arise from different parts; their origins are, consequently, by distinct fasciculi, or they may terminate by distinct insertions. Fig. 55, which is a representation of the biceps—a flexor muscle of the forearm—is one of these. It has, as its name imports, two heads running into one belly. It is, also, an example of the ventri- form muscle. * Anat. General, torn. ii. MUSCLES. 315 Fig. 55. In the pectoralis major, Fig. 56, we have an example of the ra- diated muscle, or of one in which the fibres converge towards their tendinous insertion. Fig. 56. In the penniform muscle, the fibres run in a parallel direction, but are all inserted obliquely into the tendon, like the feathers of a quill. Fig. 57 is a representation of a double penniform muscle. Muscles may, also, be complicated: that is, with one belly, and several ten- dons, having the fibres variously inserted into them, or having seve- ral bellies with the tendons interlaced. Fig. 57. They are, again, partitioned into the long, broad, and short. The long muscles are situated chiefly on the limbs, and are concerned in locomotion. The broad generally form the parietes of cavities; they are not so much enveloped as the long muscles by strong fibrous aponeuroses or fasciae, owing to their being obviously less lia- ble to displacement; and the short muscles are situated in parts, where considerable force is required, and but little motion; so that their fibres are very numerous and short. The number of muscles of course varies in different animals ; and is in proportion to the extent and variety of motion they are called upon to execute. In man, the number is differently estimated by anatomists; some describing several distinct muscles under one name; and others dividing into many what ought to belong to one. According to the arrangement of Chaussier, three hundred and sixty-eight distinct muscles are admitted; but others reckon as many as four hundred and fifty. 316 MUSCULAR MOTION. When muscles are subjected to analysis, they are found to con- sist of fibrine, osmazome, jelly, albumen, phosphates of soda, ammo- nia and lime, carbonate of lime, muriate, phosphate, and lactate of soda; and, according to Fourcroy and Vauquelin,* sulphur and po- tassa are present. The great constituents of the pure muscular tissue are,—fibrine, and probably osmazome;—the gelatine, which is met with, being ascribable to the cellular membrane that enve- lopes the muscular fibres and lacerti. The membranous structures of young animals contain a much greater quantity of jelly than those of the adult; and it is probably on this account, that the flesh of the former is more gelatinous;—not because the muscular fibre contains more gelatine. Thenard assigns the muscles, on final analysis, the following con- stituents :—Fibrine, albumen, osmazome, fat, substances capable of passing to the state of gelatine, acid (lactic,) and different salts. They have likewise been analyzed by Berzelius and Braconnot.f It must be borne in mind, as RaspailJ has properly remarked, that all these are the results of the analysis of the muscle, as we meet with it. The analysis of the muscular fibre has yet to be accom- plished. In this, too, and every analogous case, the analysis only affords us evidence of the constituents of the dead animal matter; and some of the products may even have been formed by the new affinities, resulting from the operations of the analyst. They can afford but an imperfect judgment of the constitution of the living substance. The muscular structure is liable to a singular kind of conversion, under particular circumstances, to which it may be well to advert.^ When, about the latter part of the last century, it was determined, for purposes of salubrity, to remove the bodies from the churchyard of Les Innocens at Paris||—which had been the cemetery for a con- siderable part of the population of Paris for centuries—the whole area, occupying ab'out seven thousand square yards, was found con- verted into a mass, consisting chiefly of animal matter, and raising the soil several feet above its natural level. On opening the ground, to remove the prodigious collection of dead bodies, they were found to be strangely altered in their nature and appearance. What had constituted the soft parts of the body was converted into an unctuous matter, of a gray colour, and of a peculiar, but not highly offensive, smell. According to their position in the pits,—for the bodies were deposited in pits or trenches, about thirty feet deep, each capable of holding from twelve hundred to fifteen hundred bodies,—and accord- ing to the length of time they had been deposited, this transformation * Annales de Chimie. lvi. 43. t Mailer's Handbuch der Physiologie, and Baly's translation, P. i. p. 369, Lond. 1837. X Op. citat. p. 214. § See, on the general Anatomy of Muscles, Weber's Hildebrandt's Handbuch der Anatomie, I. 387. Braunschweig. 1830. || Thouret, Journal de Physique, xxxviii. 255. MUSCLE CONVERTED INTO ADIPOCIRE 317 had occurred to a greater or less extent. It was found to be most complete in those bodies, which were nearest the centre of the pits, and when they had been buried about three years. In such case, every part, except the bones, the hair, and the nails, seemed to have lost all its properties, and to be converted into this gras des cime- tieres, which was found to be a saponaceous compound, consisting of ammonia, united to adipocire,—a substance, as its name imports, possessing properties intermediate between those of fat and wax. When the adipocire was freed from the ammonia, and obtained in a state of purity, it was found to resemble strongly spermaceti, both in physical and chemical qualities. It was afterwards discovered, that the conversion of muscular flesh into adipocire might be caused by other means. Simple im- mersion in cold water, especially in a running stream, was found by Dr. GibbesJ to produce the conversion more speedily than inhuma- tion. It can be caused, too, still more rapidly by the action of dilute nitric acid. The chemical is not the only interest attached to this substance. It has been adduced in a court of justice, for the purpose of enabling some judgment to be formed regarding the period that a body may have been immersed in the water. It is probable that this must differ greatly according to various circumstances;—the time that has elapsed between the death of the individual, and the period of immersion ; the conditions of the fluid as to rest or m6tion, tempera- ture, &c.; and the temperature of the atmosphere; so that any attempt to fix a period for such conversion must be liable to much inconclusiveness. Yet the opinion of a medical practitioner, on this subject, has been the foundation of a juridical decision. At the lent assizes, holden at Warwick, England, in the year 1805, the follow- ing case came before the court. A gentleman, who was insolvent, left his home, with the intention,—as was presumed from his pre- vious conduct and conversation,—of destroying himself. Five weeks and four days after that period, his body was found floating down a river. The face was disfigured by putrefaction, and the hair sepa- rated from the scalp by the slightest pull; but the other parts of the body were firm and white, without any putrefactive appearance. On examining the body, it was found that several parts of it were converted into adipocire. A commission of bankruptcy having been taken out against the deceased a few days after he left home, it became an important question, to the interest of his family, to ascertain whether or not he was living at that period. From the changes sustained by the body, it was presumed that he had drowned himself on the day he left home; and to corroborate the presumption, the evidence of Dr. Gibbes was requested, who, from his experiments on this subject, it was thought, was better acquainted with it than any other person, Dr. Gibbes stated on the trial, that he had procured a small quantity * Philosophical Transactions for 1794 and 1795. 27*' 318 MUSCULAR MOTION of this fatty matter, by immersing the muscular parts of animals in water for a month, and that it required five or six weeks to make it in any large quantity. Upon this evidence, the jury were of opinion that the deceased was not alive at the time the commission was taken out, and the bankruptcy was accordingly superseded.* 3. Of the Bones. The bones are the hardest parts of the animal frame; and, con- sequently, serve as a base of support and attachment to the soft parts. They constitute the frame-work of the body, and determine its general shape. The principal functions they fulfil are,—to form defensive cavities for the most important organs of the body—the encephalon, spinal marrow, &c.—and to act as so many levers for transmitting the weight of the body to the soil, and for the different locomotive and partial movements. To them are attached the dif- ferent muscles, concerned in those functions. In man and the higher classes of animals, the bones are, as a general rule, within the body; his skeleton is, consequently, said to be internal. In the Crustacea, the testaceous mollusca, and in certain insects, the skeleton is exter- nal, the whole of the soft parts being contained within it. The lob- ster and crab are familiar instances of this arrangement. The stature of the human skeleton is various, and may be taken, on the average, perhaps,—in those of European descent,—at about five feet eight or nine inches.f We find, however, examples of con- siderable variation; from this average. A skeleton of an Irish giant, in the museum of the Royal College of Surgeons of London, mea- sures eight feet four inches. On the other hand, Bebe, the dwarf of Stanislaus, king of Poland, was only thirty-three inches high; and a Polish nobleman, Borvvlaski, measured twenty-eight French inches. He had a sister, whose height was twenty-one inches.J The bones may be divided into the short, broad or flat, and long. The short bones are met with in parts of the body, which require to be both solid and moveable:—in the hands and feet for example, and in the spine. The flat or broad bones form the parietes of cavities, and they aid materially in the movements and attitudes, by affording an extensive surface for the attachment of muscle. The long bones are chiefly intended for locomotion, and are met with only in the extremities. The shape of the body or shaft, and of the extremities * Male's Epitome of Forensic Medicine, in Cowper's Tracts on Medical Jurispru- dence. Philad. 1819 ; Beck's Medical Jurisprudence, 5th edit. ii. 164; also Devergie, in Annales d'Hygiene publique, 1829. tSee Quetelet, Sur I'Homme, &c, Paris, 1835; and Prof. Forbes's Experiments on the weight, heighth, and strength of above eight hundred persons,—English, Scotch, Irish, and Belgian,|in Lond. and Edinb.—Philad. Magaz. Mar., 1837 p 197 and Amer' Med. Intelligencer, p. 74, May 15, 1837. X Lectures on Physiology, Zoology, &c, by W. Lawrence, p. 434. Lond. 1819. BONES. 319 merits attention. The shaft or middle portion, is the smallest in diameter, and is usually cylindrical. The extremities, on the other hand, are expanded; a circumstance, which not only adds to the solidity of the articulations, but diminishes the obliquity of the inser- tion of the tendons, passing over them, into the bones. In their in- terior is a medullary canal or cavity, which contains the medulla, marrow, or pith:—a secretion, whose office will be a theme for after inquiry. One great advantage of this canal is, that it makes the bone a hollow cylinder, and thus diminishes its weight. On many of the bones, prominences and cavities are perceptible. The emi- nences bear the generic name of apophyses or processes. Their great use is, to cause the tendons of muscles to be inserted at a much greater angle into the bones they have to move. It will be seen hereafter, that the nearer such insertion is to the perpendicular to the lever, the greater will be the effect produced. The cavities are of various kinds. Some are articular: others for the insertion, reception, or transmission of parts. Those of insertion and reception afford space for the attachment of muscles; those of transmission, &c. are frequently incrusted with cartilage, converted into canals by means of ligament, and furnished with a synovia] membrane, which lubricates them, and facilitates the play of the tendons, for the passage of which they are destined. The mechanical structure of bone is a laminated frame-work, incrusted by an earthy substance, and penetrated by exhalant and absorbent vessels, arteries, veins, and nerves. Herissant,* appears to have been one of the first who stated, that bone is essentially composed of two substances:—the one a cartilaginous basis or parenchyma, giving form to the part,—the other a peculiar earthy matter deposited in this basis, and communicating to it its hardness. These two constituents can be readily demonstrated; the first, by digesting the bone in dilute muriatic acid, which dissolves the earthy part, without acting on the animal matter; and the second, by burn- ing the bone, until all the animal matter is consumed, whilst the earthy part is left untouched. If we take a long bone and divide it longitudinally, we find, that it is composed of three different substances, all of which may, how- ever, be regarded as the same osseous tissue, in various degrees of condensation. These are,—the hard or compact substance, the spongy or areolar, and the reticulated. The first is in the most con- densed form; it exists at the exterior of the bone, and constitutes almost the whole of the shaft. The second is seen towards the extremities of the long bone, and in almost the whole of the short bones. In it, the laminae are less close, and have a cancellated appearance,—the cellules bearing the name of cancelli. The reticulated substance is a still looser formation; the laminae being situated at a considerable distance, and the space between filled up with a series of membranous * Memoir, de l'Academ. des Sciences de Paris, p. 322, pour 1758. 320 MUSCULAR MOTION. Fig. 58. cells, which lodge the marrow. The marginal figures represent a longitudinal section of the os femoris, and os humeri, m which this arrangement is well exhibited. We have seen the advantages of the ex- panded extremities of long bones, as regards the insertion of muscles; but it is obvious, that if these portions of the bone had consisted of the heavy compact tissue, the increased weight of the limbs would have destroyed the advan- tages, which would otherwise have accrued; whilst, if the shaft of the bone, exposed, as it is, to external violence, had consisted of the spongy tissue only, it would not have been able to offer the necessary resistance. It is, therefore, formed almost entirely of the compact tissue; so that a section of one inch in height, taken from the body of the bone, will not differ es- sentially in weight from an inch taken from the extremity. Nor does the cavity, within the bones, diminish their strength as might be at first sight presumed. By enlarging the cir- cumference, the contrary effect is produced ; for we shall see, in the mechanical proem to the particular movements, that of two hollow columns, formed of an equal quantity of mat- ter and of the same height, that, which has the larger cavity, is actually the stronger. A very important use of the cancellated or spongy texture of the bones was suggested by a distinguished individual of this country, to whom surgical science, in particular, has been so largely indebted. Dr. Physick* asserts, that it serves to diminish, and, in many cases, to prevent, concussion of the brain, and of the other viscera, in falls and blows. The demonstration, which he gives of this, is simple and satisfactory. If we suspend a series of six ivory balls by threads; raise the ball at one extremity, and allow it to fall on the next to it, we find, that the farthest ball in the series is impelled to a distance, which corresponds with the momentum communicated by the first ball to the second. But if we substitute, for the middle ball of the series, a ball made of the cellular structure of bone, we find that almost the whole of the mo- mentum is lost in this osseous structure; especially, if it be previously filled with tallow or well soaked in water, so as to bring it to a closer approximation to the natural, living condition. Bones consist of earthy salts and animal matter intimately blend- ed. The latter is chiefly cartilage, gelatine, and the peculiar fatty matter—the marrow. On reducing bones to powder and digesting * Horner's Special and General Anatomy, 4th edit. Philad. 1836. ANALYSIS OF BONES. 321 them in water, the fat rises and swims upon its surface, and the gelatine is dissolved. According to the analysis of Berzelius, 100 parts of dry human bones consist of animal matter, 33.3; phosphate of lime, 51.04; car- bonate of lime, 11.30; fluateoflime, 2; phosphateof magnesia, 1.16; soda, muriate, of soda, and water, 1.2. Fourcroy and Vauquelin did not detect" any fluoric acid, but they found oxides of iron and manganese, silica, and albumen. Hatchett detected, also, a small quantity of sulphate of lime.* Schregerf gives the following as the proportions of the animal and earthy parts of bone: INFANTS. ADULTS. AGED. 47.20 20.18 12.20 48.48 74.84 84.10 95.68 95.02 96.30 The bones are enveloped by a dense fibrous membrane, termed, in the abstract, periosteum: but assuming different names according to the part it covers. On the skull, it is called pericranium: and its extensions over the cartilages of prolongation, are called perichon- drium. The chief uses of this expansion are, to support the vessels in their passage to and from the bone, and to assist in its formation ; for we find, that if the periosteum be removed from a bone, it be- comes dead at the surface previously covered by the membrane, and exfoliates. In the foetus, it adds materially to the strength of the bone, prior to the completion of ossification. In the long bones, ossi- fication commences at particular points; one generally in the shaft, and others at the different articular and other processes. These ossified portions are, for some time, separated from each other by the animal matter, which, alone, composes the intermediate portions of the bone; and, without this fibrous envelope, they would be too feeble perhaps to resist the strains to which they are exposed. The periosteum, moreover, affords a convenient insertion for the muscles destined to act upon the bones; and enables them to slide more readily when in action; hence friction is avoided. The cavity of long bones is lined by a membrane—called the medullary membrane or internal periosteum—which is supplied with numerous vessels, adheres to the interior surface of the bone, and is not only concerned in its nutrition, but also in the secretion of the marrow,—and likewise of a kind of oily matter, which differs from * Turner's Elements of Chemistry, 4th Amer. edit. p. 576. Philad. 1832. See also Dr. Davy, in Monro's Outlines of Anatomy, I. 36, and Meckel's Handbuch der Anato- mie, I. 358; Rudolphi, Grundriss der Physiologie, I. 160. Berlin, 1321; and Moller's Handbuch, Baly's translation, P. i. p. 370. + Osteochemiae Specimen. Viteberg. 1810: Miescher De ossium genesi, structura et vita. Dissert. Anat. Phys. inaugural, p. 47. Berol. 1836; and American Med. Intelligencer for June 15, 1837, p. 115. Weber's Hildebrandt's Handbuch der Anato- mie, I. 316. Braunschweig, 1830; and Purkinje and Deutsch, De penitiori ossium structura. Vratisl. 1834, and Dublin Journal of Med. Science, Sept. 1836. Animal matter Earthy matter 322 MUSCULAR MOTION. marrow merely in being more fluid, and is contained in the cells, formed by the spongy substance, and in the areolae of the compact substance. This is called the oil of bones. The marrow is considered to be lodged in membranous cells, formed by an extension of the internal periosteum; whilst, accord- ing to Howship,* the oil of bones is probably deposited in longitudi- nal canals, which pass through the solid substance of the bone, and through which its vessels are transmitted. The nature and fancied uses of the marrow and of the oil of bones will be considered in another part. The bones, periosteum and marrow are, in the sound state, amongst the insensible parts of the frame. They are certainly not sensible to ordinary irritants; but, when morbid, they exhibit intense sensibility. This, at least, applies to the bones and periosteum; the sensibility, which has been ascribed to the marrow, in disease, being probably owing to that of the prolongations of the membrane, in which it is contained. The number of the bones in the body is usually estimated at two hundred and forty, exclusive of the sesamoid bones, which are al- ways found in pairs at the roots of the thumb, and great toe, be- tween the tendons of the flexor muscles and joints, and, occasionally, at the roots of the fingers and small toes. In the following Table of the Bones, the numbers on the left hand correspond with those of the accompanying plates of the skeleton. TABLE OF THE BONES. Bones of the Head. Bones of the Cranium or Skull, lBones of the Face, - IDentes or Teeth, Bone of the Tongue, Bones of the Ear, - 1. Frontal, - 2. Parietal, - 5. Occipital, 3. Temporal, Ethmoid, - 4. Sphenoid, - 7. Superior Maxillary, 6. Malar or cheek, Nasal, Lachrymal, Palatine, - ' - Inferior Spongy, Vomer, 8. Inferior Maxillary, Slncisores, - Cuspidati, - Molares, - Hyoid, r Malleus, - J Incus, j Orbiculare, [_ Stapes, HOW MANY. 1 - 2 - 1 - 2 1 1 - 2 2 - 2 2 2 2 1 1 8 4 . 20 1 2 2 2 2 * Medico. Chirurg. Transact, vii. 393. TABLE OF THE BONES. 323 Vertebra, Sacrum, ■ Bones of the j Os Coccygis, * The Thorax, The Pelvis, 'The Shoulder, - The Arm, ^The Forearm, Bones of the upper extremity. f9. 13 Dorsal, - Lumbar, .... 25. 'Carpus or Wrist, 22., .The Hand,< 'The Thigh, LThe Leg, 23. Metacarpus, .24. Phalanges, 14. Sternum, .... ,15.16. Ribs H?-Jr"e T m8'and ( lb. False ribs, 28. Innominatum, comprising 29. Ilium, 30. Ischium, and ! 31. Pubis, 17. Clavicle, .... 18. Scapula, .... 19. Humerus, .... 21. Ulna, .... 20. Radius, .... Naviculare, Lunare, .... Cuneiforme, ... Orbiculare, ... Trapezium, ... Trapezoides, ... Magnum, ... Unciforme, 12 5 1 1 1 24 Bones of the, LOWER EXTREMITY. Tarsus or Ankle or 36.. The Foot, 38.) Instep, '39. Metatarsus, 40. Phalanges, Femur, Patella, - Tibia, Fibula, - . Os Calcis, - Astragalus, Cuboides, - Naviculare, Cuneiforme, Total, 2 2 2 2 2 2 2 2 2 2 2 2 2 10 28 2 2 2 2 2 2 2 2 6 10 28 240 The bones are connected by means of articulations or joints, which differ materially from each other. To all the varieties names are appropriated, which form a difficult task for the memory of the anatomical student. Technically, every part at which two bones meet and are connected, is called an articulation, whether any degree of motion is permissible or not. This, indeed, is the foundation of the division that prevails at the pre- sent day, the articulations being separable into two classes: the immovable or synarthroses: and the movable or diarthroses. xirP6 synarthroses are variously termed, according to their shape. When the articular surfaces are dove-tailed into each other, the joint is called a suture. This is the articulation that prevails between the bones of the skull. Harmony is when the edges of the bones are even, and merely touch, as in the bones of the head in quadru- peds and birds. When a pit in one bone receives the projecting extremity of another, we have a case of gomphosis. It is exhibited m the union between the teeth and their sockets. Lastly, schindylesis 324 MUSCULAR MOTION. is when the lamina of one bone is received into a groove of another; as in the articulation of the vomer, which separates the nasal fossas from each other. The movable articulations comprise two orders:—the amphiar- throses, in which the two bones are intimately united by an inter- mediate substance, of a soft and flexible character, as in the junc- tion of the vertebrae with each other, and the diarthroses, properly so called. The last admit of three subdivisions—the enarthroses or ball and socket joints; the condyloid, in which, owing to the head being oval, the movements are not as easy in all directions as where the head is spherical; and the ginglymoid or ginglymus, in which the motion can occur in only one direction as in a hinge. The farther subdivision of the joints belongs more to anatomy than physiology. The articular surfaces of the bones never come into immediate contact. They are tipped with a firm, highly elastic substance, called cartilage; which, by its smoothness, enables the bones to move easily upon each other, and may have some influence in deadening shocks, and defending the bones, which it covers. The arrangement of the cartilage varies according to the shape of the extremity of the bone. If it. be spherical, the cartilage is thick at the centre, and gradually diminishes towards the circumference. In a cavity the reverse is the case: the cartilage is thin at the centre, and becomes thicker towards the circumference; and on a trochlea or pulley, its thickness is nearly every where alike. An admirable provision against displacement of the bones at the articulations exists in the ligaments. These, by the French anato- mists, are distinguished into two kinds—the fibrous capsules, and the ligaments properly so called. The former are a kind of cylindrical sac, formed of a firm, fibrous membrane; open at each extremity, by which they closely embrace the articular end of the bones; and loose, when the joint admits of much motion. In this way, the arti- culation is completely inclosed: they generally bear the name of capsular ligaments. The ligaments, properly so called, are bands of the same kind of £ tissue, which extend from one bone to another; by their resistance preserving the bones in situ; and by their suppleness admitting of the necessary motion. The interior of all these articulations is lubricated by a viscid fluid, called the synovia. This is secreted by a peculiar membrane of a serous nature; and its use is to diminish friction, and, at the same time, to favour adhesion. The mode in which it is secreted, and its chief properties and uses, will be the subject of future inquiry. In certain of the movable articulations, fibro-cartilaoinous sub- stances, frequently called inter articular cartilages, are found be- tween the articular surfaces, and not adherent to either of them. These have been supposed to form a kind of cushion, which, by yielding to pressure, and returning upon themselves, may thus pro- tect the joints to which they belong; and, accordingly, it is asserted, Plate I. JMmni TniJPemi Engraved by .1Drayun Drawn lnj J.Fwy 3'itTitnti' ?>" J-Brautfr. PHYSIOLOGY OP MUSCULAR MOTION. 325 that they are met with in the joints, which have to sustain the greatest pressure; but Magendie* properly remarks, that they do not exist in the hip-joint, or in the ankle-joint, which have constantly to support the strongest pressure. The use, which he suggests, is more specious;—that they may favour the extent of motion, and prevent displacement. The stability of the joints is likewise aided by the manner in which the muscles or tendons pass over them. These are contained in an aponeurotic sheath, to prevent their displacement; and thus the whole limb becomes well protected, and dislocation infrequent, even in those joints, as that of the shoulder, which, as regards their osseous arrangement, ought to be very liable to displacement. 4. Physiology of Muscular Motion. By voluntary motion we mean a contraction of the muscles under the influence of volition or the will. This influence is propagated along the nerves to the muscles, which are excited by it to contrac- tion. The encephalon, spinal marrow, nerves, and muscles, are, therefore, the organs of voluntary contraction. Volition is one of the functions of the encephalon, and might have been, with much propriety, included under the physiology of the intellectual and moral acts; but as it is so intimately concerned with muscular motion, it was judged advisable to defer its consideration until the present occasion. That volition is a product of encephalic action is proved by many facts. If the brain be injured in any manner;—by fracture of the skull, for example, or by effusion of blood, producing apoplectic pressure on some part of it;—or if it be deprived of its functions by the use of a strong dose of any narcotic substance;—or if, again, it be in a state of rest, as in sleep:—volition is no longer exerted, and voluntary motion is impracticable. This is the cause why the erect attitude cannot be maintained during sleep; and why the head falls forward upon the chest, when the somnolency is to such an extent as to deprive the extensor muscles of the back and head of their stimulus to activity.f That an emanation from the encephalon is necessary is likewise proved by the effect of tying, cutting, compressing, or stupefying the nerve proceeding to a muscle: it matters not, that the will may act; the muscle does not receive the excitant, and no motion is pro- duced ; a fact which proves, that the nerves are the channels of communication between the brain and the muscles. If, again, we destroy the medulla oblongata and medulla spinalis, we abolish all muscular motion, notwithstanding the brain may will, and the muscles be in a state of physical integrity; because we have destroyed the parts whence the nerves proceed. In like manner, by * Precis Elementaire, 2de Edit. i. 292. Paris, 1823. t Adelon, Art. Encephale (Physiol.) in Diet, de Med. ?ii. 516. Paris, 1823; and Physiol, de I'Homme, II. 25. 2de edit. Paris, 1829. vol. i. 28 326 MUSCULAR MOTION. Successively slicing away the medulla spinalis from its base to the occiput, we paralyze, in succession, every muscle of the body, which receives its nerves from the spinal marrow. Experiments of different physiologists have confirmed the view, that the encephalon is the chief seat of volition. When it has been sliced away to a certain extent, the animal has been thrown into a state of stupor, attended with the loss of sensibility, of the power of locomotion, and especially of spontaneous motion; and in writing, dancing, speaking, singing, &c. we have indisputable evidence of its direction by the intellect. It is not so clear, that the seat of volition is entirely restricted to the encephalon. There are many actions of the yet living trunk, which appear to show, that an obscure volition may be exerted, even after the brain has been separated from the rest of the body; and acephalous children have not only moved perceptibly when in utero, but at birth. Without referring to the lower classes of ani- mals, which, as we have already had occasion to remark, execute voluntary motions for a long time after they have been bisected, every one must have noticed the motions of decapitated fowls, which will continue, for a time, to run and leap, and, apparently, to suffer uneasiness in the incised part. The feats of the emperor Commodus are elucidative of this mat- ter. Herodian relates, that he was in the habit of shooting at the ostrich, as it ran across the circus, with an arrow having a cut- ting edge; and, although the shaft was true to its destination, and the head was severed from the body, the ostrich usually ran se- veral yards before it dropped. Kaauw Boerhaave—nephew of the celebrated Herrmann, and himself an eminent medical teacher at St. Petersburgh—asserts, that he saw a cock, thus decapitated, run for a distance of twenty-three feet afterwards. Some cases are also recorded of men walking a few steps after decapitation, striking their breasts, &c.; but they can scarcely be regarded as authentic* In those countries, where judicial execution consists in decapitation by the sword, sufficient opportunities must have presented them- selves for testing this question; but no zealous Naturforscher appears to have been present to record them. Similar opportunities have likewise occured, under the operations of the guillotine. Legallois,f in some experiments, which he instituted, for the pur- pose of determining the nervous influence on the. heart, &c, found, that rabbits, which he had decapitated and deprived of their hinder extremities, but still kept alive by artificial respiration, moved their fore paws, whenever he stimulated them by plucking some of their hairs.J With regard to complete acephali, or those foetuses which are * Adelon, Op. citat. ii. 28—and Dr. J. R. Coxe, in Amer. Med. Intelligencer for May 15,1837. -fOZuvres. Paris, 1824. X See, also, Sir Gilbert Blane in Select Dissertations on several subjects of Medical Science. Lond. 1822, p. 262—and Berard, Rapports du Physique et du Moral, p. 97. Paris, 1823. VOLITION SEATED IN THE ENCEPHALON. 327 totally devoid of encephalon,—although they may vegetate in utero, they quickly expire after birth, owing to their being devoid of the organs of the animal functions, and to the consequent impossibility of respiring. Some monsters have, however, been born without the brain, but with part of the encephalon. These have been called, by way of distinction, anencephali or hemicephali. Where the medulla oblongata exists, they possess the nervous system of the senses, and are, consequently, able to live for some time after birth, and to exert certain muscular movements, such as sucking, moving the limbs, evacuating the excretions, &c. Professor Adelon asserts, that none of these facts ought to shake the proposition, which he embraces; that in the superior animals, and consequently in man, the medulla spinalis and the nerves are merely the conductors of volition, or of the locomotive will; and that, in the encephalon alone, volition is produced. His arguments on this point, however, are not characterized by that ingenuousness and freedom from sophism, for which his physiological disquisitions are generally distinguished. " First of all," he observes, " the fact of the progression and motions of men and quadrupeds, after de- capitation, is manifestly apocryphal; and even if we must admit, that certain animals still execute some movements after decapitation, are such movements evidently regular and ordained? And, sup- posing them to be so, may not this have arisen from the conforma- tion of the parts, or from habits contracted by the organs'? This last appears to us most probable; for if, from any cause whatever, the muscles of a part contract, they will cause the part to execute such motions as the joints, entering into its composition, require; and which may, therefore, be similar to those that the will pro- duces." He farther attempts to deny the facts related of the lower classes of animals, and asserts, that " they are not evinced in the experiments instituted in our day." The cases, which are adduced to prove the defective sensibility of the lower tribes of animated nature, are, however; incontestable; —the trunk of the wasp will attempt to sting after the head is re- moved ; and the experiment, which was made by Dr. Harlan,* in the presence of Capt. Basil Hall, certainly demonstrates something like design in the headless trunk. Our conclusion ought probably to be, from all these cases,—that volition is chiefly seated in the encephalon, but that an obscure voli- tion may, perhaps, extend over the whole of the cerebro-spinal axis. This conclusion, of course, applies only to the higher classes of ani- mals; for we have seen, that the polypus is capable of division into several portions, so as to constitute as many distinct beings; and it is probable, that the principal seat of volition may extend much lower down in the inferior tribes. « Medical and Physical Researches, Philad. 1835. See, also, Richerand's Elements de Physiologie, 13eme, edit, par M. Berard, aine\ 6dit. de Bruxelles, p. 252. Bruxelles, 1837. 328 MUSCULAR MOTION. Attempts, and of a successful nature, have been made to discover, whether the whole brain is concerned in volition, or only a part. Portions of the brain have been disorganized by disease, and yet the individual has not been deprived of motion; at other times, as in paralysis, the faculty has been impaired; and again, considera- ble quantities of brain have been lost, owing to accidents, (in one case the author knew nineteen tea-spoonfuls,) with equal immunity, as regards the function in question. The experiments, executed on this subject, go still farther to con- firm the idea, that volition is not seated exclusively in the encepha- lon. Rolando and Flourens* performed several, with the view of detecting the seat of the locomotive will; or of that which presides over the general movements of station and progression; and they fixed upon the cerebral lobes. Animals, from which these were re- moved, were thrown into a sleepy, lethargic condition; were devoid of sensation and spontaneous motion, and moved only when pro- voked. On the other hand, Magendiet affirms, that the cerebral hemispheres may be cut deeply in different parts of their upper surface, without any evident alteration in the movements. Even their total removal, if it did not implicate the corpora striata, he found to produce no greater effect; or, at least, none but what might be easily referred to the suffering induced by such an experi- ment. The results, however, are not alike in all the classes of ver- tebrated animals. Those, detailed, were observed on quadrupeds, and particularly on dogs, cats, rabbits, Guinea-pigs, hedge-hogs, and squirrels. In birds, the removal or destruction of the hemispheres —the optic tubercles remaining untouched—was often followed by the state of stupor and immobility, described by Rolando and Flou- rens; but, in numerous cases, the birds ran, leaped, and swam, after the hemispheres had been removed, the sight alone appearing to be destroyed. In reptiles and fish, the removal of the hemispheres seemed to exert but little effect upon their motions. Carps swam with agility; frogs leaped and swam as if uninjured, and the sight did not appear to be affected. MagendieJ properly concludes, from these experiments, that the spontaneity of the movements does not belong exclusively to the hemispheres; that in certain birds,as the pigeon, the adult rook, &c. this seems to be the case; not so in other birds; but as regards the mammalia, reptiles, and fish,—at least such of them as were the subjects of his experiments,—his conclusion is applicable. Of the nature of the action of the brain, in producing volition, we know nothing. It is only in the prosecution of direct experi- ments upon the organ, that we can have an opportunity of seeing it, during the execution of the function; but the process is too mi- nute to admit of observation. Our knowledge is confined to the fact, that the encephalon does act, and that some influence is pro- * Op. citat. t Precis eleraentaire, I. 335. X Ibid. I. p. 336. NERVOUS CENTRE OF MUSCULAR CONTRACTION. 32Q jected from it along the muscles, which excites them to action, and accurately regulates the extent and velocity of muscular contraction. Yet volition is not the sole excitant of such contraction. If we ir- ritate any part of the encephalon or spinal marrow, or any of the nerves proceeding from them, we find, that muscular movements are excited; but they are not regular, as when under the influence of volition. The whole class of involuntary motions is of this kind, including the action of many of the most important organs—the heart, intestines, blood-vessels, &c. All the involuntary muscles equally require a stimulus to excite them into action ; but, as their name imports, they are removed from the influence of volition, and instead of receiving their nerves directly from the brain or spinal marrow,—as the organs of voluntary motion do,—they are supplied from the organic nervous system, or the system of the great sympa- thetic. In certain diseased conditions, we find, that all the voluntary muscles assume involuntary motions; but this is owing to the ordi- nary volition being interfered with, and to some direct or indirect stimulation, affecting the parts of the cerebro-spinal axis concerned in muscular contraction; or, if the effect be local, to some stimula- tion of the nerve proceeding from the axis to the part. Of this kind of general involuntary contraction of voluntary muscles, we have a common example in the convulsions of children; and one of the partial kind, in cramp or spasm. The will, then, is the great but not the sole regulator of the sup- ply of voluntary nervous influence. This is confirmed by experi- ment. If a portion of the spinal marrow be divided, so as to sepa- rate it from all communication with the encephalon, the muscles cannot be affected by the will; but they contract on irritating the part of the spinal marrow, from which the nerves proceed. It has, hence, been presumed, by some physiologists, that volition is only the exciting and regulating cause of the nervous influence; and that the latter is the immediate agent in producing contraction; and they • affirm, that as, in the sensations, the impression is made on the nerve, and perception is effected in the brain; so, in muscular motion, voli- tion is the act of the encephalon, and the nervous influx corresponds to the act of impression. With regard to the seat of this nervous centre of muscular con- traction, much discrepancy has arisen amongst recent physiolo- gists. It manifestly does not occupy the whole encephalon; as certain parts of it may be irritated, in the living animal, without exciting convulsions. Parts, again, may be removed without pre- venting the remainder from exciting muscular contraction when irritated. In the experiments of Flourens, the cerebral lobes were removed, yet the animals were susceptible of motion, when stimu- lated ; and, whenever the medulla oblongata was irritated, convul- sions were produced. Its seat is not, therefore, in the whole ence- phalon. Rolando refers it to the cerebellum. He asserts that, on removing the cerebellum of living animals, without implicating any of the other parts of the encephalon, the animals preserved their 28* 330 MUSCULAR MOTION. sensibility and consciousness, but were deprived of the power of motion. This occurred to a greater extent in proportion to the severity of the injury inflicted on the cerebellum. If the injury was slight, the loss of power was slight; and conversely. Impressed with the resemblance between the cerebellum of birds and the galvanic apparatus of the torpedo; and taking into consideration the lamellated structure of the cerebellum, which, according to him, resembles a voltaic pile; and the results of his experiments, which showed, that the movements diminished in proportion to the injury done to the cerebellum, Rolando drew the inference, that this part of the encephalon is an electro-motive apparatus, for the secretion of a fluid analogous to the galvanic. This fluid is, according to him, transmitted along the nerves to the muscles, and excites them to contraction. The parts of the encephalon, concerned in volition, would in this view, regulate the quantity in which the motive fluid is secreted, and govern the motions; whilst the medulla oblongata which, when alone irritated, always occasions convulsions, would put the encephalic extremity of the conducting nerves in direct or indirect communication with the locomotive apparatus. This ingenious and simple theory is, however, overthrown by the fact, mentioned by Magendie,* that he is annually in the habit of exhibiting to his class animals deprived of cerebellum, which are still capable of executing very regular movements. For example, he has seen the hedge-hog and Guinea-pig, deprived not only of brain but of cerebellum, rub its nose with the paw, when a bottle of strong acetic acid was held to it; and he properly remarks, that a single positive fact of this kind is worth all the negative facts that could be adduced. He farther observes, that there could be no doubt of the entire removal of the brain in his experiments. These experiments of Magendie are equally adverse to the hypo- thesis of Flourens, that the cerebellum is the regulator or balancer of the movements. Some anatomical observations, however, by Mr. Solly ,f would seem to show that there is a direct communication be- tween the motor tract of the spinal marrow and the cerebellum. The corpora pyramidalia have been generally supposed to be formed by the entire mass of the anterior or motor columns of the spinal cord, but Mr. Solly shows that not more than one half of the anterior columns enters into the composition of these bodies; and that another portion, which he terms the " antero-lateral column," when traced on each side in its progress upwards, is found to cross the cord below the corpora olivaria, forming after mutual decussation, the surface of the corpora restiformia; and ultimately being continuous with the cerebellum. Others, again, have esteemed the encephalon to be the sole organ of volition, and have referred the nervous action, which produces the " locomotive influx," as it is termed, exclusively to the spinal * Precis, &c. i. 340. t Transactions of the Royal Society for 1836; Bostock's Physiology, p. 201, 3d edit. 1836; and Solly on the Brain. Lond. 1836. NERVOUS CENTRE OP MUSCULAR CONTRACTION. 331 marrow; and, hence, they have termed the spinal marrow and the nerves issuing from it, the " nervous system of locomotion." It is manifest, however, that the encephalon must participate with the medulla spinalis in this function; inasmuch as not only does direct irritation of several parts of the former excite convulsions, but we see them frequently as a consequence of disease of the encephalon; yet, as has been remarked, there is some reason for believing, that, in the upper classes of animals, an obscure volition may be exercised for a time, even when the encephalon is separated from the body. It need scarcely be said, that we are as ignorant of the character of this influx, as we are of that of the nervous phenomena in general. The parts of the encephalon and spinal marrow, concerned in muscular motion, are very distinct from those that receive the im- pressions of external bodies. The function of sensibility is com- prised in the medulla oblongata and in the posterior column of the spine, whilst the encephalic organs of muscular motion appear to be the corpora striata, the thalami-nervorum opticorum, at their lower part; the crura cerebri, the pons varolii, the peduncles of the cere- bellum, the lateral parts of the medulla oblongata, and the anterior column of the medulla spinalis. This is proved by direct experi- ment, as will be seen presently; and, in addition to this, pathology furnishes us with numerous examples of their distinctness. In va- rious cases of hemiplegia or palsy of one side of the body,—which is of an encephalic character,—we find motion almost lost, yet the sensibility slightly or not at all affected; and, on the other hand, instances of loss of sensation have been met with, in which the power of voluntary motion has continued. The recent discoveries in the system of vertebral nerves exhibit clearly how this may hap- pen ; and that a considerable space may exist between the roots of a nerve, one of which shall be destined for sensation, the other for motion; yet both may pass out enveloped in one sheath;—the same nervous cord thus conveying the two irradiations, if they may be so termed. According to Sir Charles Bell's system (p. 67), the spinal column is divided into three tracts; the anterior for motion; the posterior for sensibility; and the two are kept separate and united by the third—the column for respiration. The experiments performed of late years,—by the French phy- siologists especially,—for the purpose of discovering the precise parts of the encephalon concerned in muscular motion, have attracted great and absorbing interest. We wish it could be said, that the results have been such as to afford us determinate notions on the subject. According to those of Flourens, the cerebral lobes preside over volition, and the medulla oblongata over the locomotive influx; to the latter organ he assigns, also, sensibility. We have seen, that the results of his experiments have been contested, and with them, of course, his deductions. The facts and arguments, which we have stated, will have shown, too, that the last proposition is alone correct—which refers sensibility to the medulla oblongata; 332 MUSCULAR MOTION. and even it is not restricted to that organ, or group of organs— whichever it may be considered. MM. Foville and Pinel Grand-Champ* have affirmed, that the cerebellum is the seat of sensibility. To this conclusion they were led by the remarks they had made, in the course of their practice, that the cases of paralysis of sensibility, which fell under their notice, succeeded more especially to morbid conditions of the encephalon. In this view they conceive themselves supported by the discovery of columns in the spinal marrow, destined for particular functions; and, as the posterior column is found to be the column of sensibility, and as the cerebellum seems to be formed from this column, they think it ought to be possessed of the same functions. Adelonf re- marks, that Willis professed a similar notion, and that he considered the cerebral lobes to be the point of departure for the movements, and the cerebellum the seat of sensibility. In his first volume, however, he had cited, more correctly, the views of Willis.—" Willis says positively," he remarks, " that the corpora striata are the seat of perception; the medullary mass of the brain, that of memory and imagination; the corpus callosum, that of reflection : and the cere- bellum, the source of the motive spirits." Willis, in truth, regarded the cerebellum as supplying animal spirits to the nerves of involuntary functions, as the heart, intestinal canal, &c. The opinions of Foville and Pinel Grand-Champ are subverted by the experiments of Rolando, Flourens, and Magendie, which show, that sensation continues, notwithstanding serious injury, and even entire removal of the cerebellum. By other'physiologists, the two functions have been assigned re- spectively to the cineritious and medullary parts of the brain; some asserting, that the seat of sensibility is more especially in the latter, and the motive force in the former. According to Treviranus, the more medullary matter an animal has in its brain and spinal marrow, in proportion to the cineritious, the greater will be its sensibility. To this, however, M. DesmoulinsJ properly objects, that in many ani- mals, the spinal marrow is composed exclusively of medullary matter ; and consequently they ought not only to be the most sensible of all, but to be wholly devoid of the power of motion. Others, again, as MM. Foville and Pinel Grand-Champ have re- versed the matter; assigning sensibility to the cineritious substance; and motility to the medullary. From these conflicting opinions, it is obviously impossible to sift any thing categorical; except that we are ignorant of the special seat of these functions. A part of the discrepancy, in the results of the experiments, must be ascribed to organic differences in the ani- mals, which were the subjects of the experiments. This was strikingly exemplified in those, instituted by Magendie, which have been described. Similar contrariety exists in the experiments and hypotheses, re- * Sur le Systeme Nerveux. Paris, 1820. f Op. citat. ii. 38, X Anatomie des Systeraes Nerveux, &c. Paris, 1825, NERVOUS CENTRE OF MUSCULAR CONTRACTION. 333 garding the particular parts of the encephalon, that are concerned in determinate movements of the body. The results of many of those are, indeed, so strange, that did they not rest on such eminent authority, they might be classed among the romantic. It has been already remarked, that Rolando considered the ce- rebellum to be an electro-motive apparatus, producing the whole of the galvanic fluid necessary for the motions. Flourens, on the other hand, from similar experiments, independently performed, and with- out any knowledge of those of Rolando, affirmed it to be the regula- tor and balancer of the locomotive movements; and he asserted, that, when removed from an animal, it could neither maintain the erect attitude, nor execute any movement of locomotion; nor al- though possessing all its sensations, could it fly from the danger it saw menacing it. The same view has been advocated by Bouillaud, who has detailed eighteen experiments, in which he cauterized the cerebellum, and found that, in all, the functions of equilibration and progression were disordered. The experiments of Magendie* on this subject, are pregnant with important novelty. We have already referred to those that concern the cerebral hemispheres and cerebellum, as the encephalic organs of the general movements, in the mode suggested by Rolando and Flourens, and others. He affirms, in addition, " that there exist, in the brain, four spontaneous impulses or forces, which are situated at the extremity of two lines, cutting each other at right angles; the one impelling forwards ; the second backwards ; the third from right to left, causing the body to rotate; and the fourth from left to right, occasioning a similar movement of rotation." The first of these impulses he fixes in the cerebellum and medulla oblongata; the second in the corpora striata; and the third and fourth in each of the pe- duncles of the cerebellum. 1. Forward Impulse.—It has often been observed by those who have made experiments on the cerebellum, that injuries of that or- gan cause the animals to recoil, manifestly against their will. Ma- gendie* asserts, that he has frequently seen animals, wounded in the cerebellum, make an attempt to advance, but be immediately com- pelled to run back; and he says that he kept a duck for eight days, the greater part of whose cerebellum he had removed, which did not move forwards during the whole of lhat time, except when placed upon water. Pigeons, into whose cerebella he thrust pins, constantly walked, and flew backwards, for more than a month afterwards. Hence, he concludes, that there exists, either in the cerebellum or medulla oblongata, a force of impulsion, which tends to cause ani- mals to go forward. Magendie thinks it not improbable that this force exists in man; and he states, that Dr. Laurent, of Versailles, exhibited to him, and to the Academie Royale de Medecine, a young girl, who, in the at- tacks of a nervous disease, was obliged to recoil so rapidly that she • Op. citat. i. 345. t Precis, i. 341. 334 MUSCULAR MOTION. was incapable of avoiding bodies or pits behind her; and was, con- sequently, exposed to serious falls and bruises. This force, he affirms, only exists in the mammalia and in birds;—certain fish and reptiles, on which he experimented, appearing to be unaffected by the entire loss of the cerebellum. 2. Backward Impulse.—When the corpora striata are removed, Magendie* found that the animal darted forward with great rapidity; and, if stopped, still maintained the attitude of running. This was particularly remarked in young rabbits; the animal appearing to be impelled forward by an inward and irresistible power; and passing over obstacles without noticing them. These effects were not found to take place, unless the white, radiated part of the corpora striata was cut: if the gray matter was alone divided, no modification was produced in the movements. If only one of the corpora was re- moved, it remained master of its movements, and directed them in different ways; stopping when it chose; but, immediately after the abstraction of the other, all regulating power over the motions ap- peared to cease, and it was irresistibly impelled forwards. In the disease of the horse, called, by the French, immobility the animal is often capable of wralking, trotting, and galloping forward with rapidity; but he does not back; and frequently it is imprac- ticable to arrest his progressive motion. Magendief asserts, that he has opened several horses which died in this condition ; and that he found, in all, a collection of fluid in the lateral ventricles, which had produced a morbid change on the surface of the corpora striata, and must have exerted a degree of compression on them. Similar pathological cases appear to occur in man. Magendie relates the case of a person, who became melancholic, and lost all power over his movements; continually executing the most irregular and fantastic antics; and frequently compelled to walk exclusively forwards or backwards until stopped by some obstacle. In this case, however, the patient got well; and accordingly there was no oppor- tunity for investigating the encephalic cause. M. Itard, also, de- scribes two cases, in which the patients were impelled, in paroxysms, to run straight forward, without the power of changing their course, even when a river or precipice was immediately before them. A case is related by M. Piedagnel,J which is more to the purpose than those just mentioned, inasmuch as an opportunity occurred for post mortem inquiry. The subject of it was, also, irresistibly im- pelled to constant motion. " At the time of the greatest stupor," says M. Piedagnel, " he suddenly arose; walked about in an agitated manner; made several turns in his chamber, and did not stop until he was fatigued. On another occasion the room did not satisfy him; he went out, and walked as long as his strength would permit. He remained out about two hours, and was brought back on a litter." M. Piedagnel adds, " that he seemed impelled by an insurmountable * Op. citat. 1.337. + Ibid. p. 338. X Journal de Physiologie, torn. 3. and Precis elementaire, I. 338. NERVOUS CENTRE OF MUSCULAR CONTRACTION. 335 force," which kept him in motion, until his powers failed him. On dissection, several tubercles were found in the right cerebral hemi- sphere, especially at its anterior part; and at the side of the corpora striata. These had produced considerable morbid changes in that hemisphere; and had, at the same time, greatly depressed the left. From these facts, Magendie infers it to be extremely probable, that, in the mammalia and in man, a force of impulsion always exists, which tends to impel them backwards, and which is, conse- quently, the antagonist to the force seated in the cerebellum. 3. Lateral Impulse.—Again, if the peduncles of the cerebellum— the crura cerebelli—be divided in a living animal, it immediately be- gins to turn round, as if impelled by some considerable force. The rotation or circumgyration is made in the direction of the divided peduncle; and, at times, with such rapidity, that the animal makes as many as sixty revolutions in a minute. The same kind of effect is produced by any vertical section of the cerebellum, which impli- cates, from before to behind, the whole substance of the medullary arch, formed by that organ above the fourth ventricle, (See Fig. 13,) but the movement is more rapid, the nearer the section is to the origin of the peduncles; in other words, to their point of junction with the pons varolii. Magendie* affirms, that he has seen this movement continue for eight days without stopping, and apparently, without suffering. When any impediment was placed in the way, the motion was ar- rested ; and, under such circumstances, the animal frequently re- mained with its paws in the air, and ate in this attitude. What he conceives to have been one of his most singular experiments was, the effect of the division of the cerebellum into two lateral and equal halves: the animal appeared to be alternately impelled to the right and left, without retaining any fixed position: if he made a tuVn or two on one side, he soon changed his motion and made as many on the other. M. Serresf—who is well known as a writer on the comparative anatomy of the brain, and must have had unusual opportunities for observation at the Hospital La Pitie, to which he is attached—gives the case of an apoplectic, who presented, amongst other symptoms, the singular phenomenon of turning round, like the animals in the experiments just described; and, on dissection, an apoplectic effu- sion was found in this part of the encephalon. On dividing the pons varolii vertically, from before to behind, MagendieJ found, that the same rotary movement was produced: when the section was to the left of the median line, the rotation was to the left, and conversely; but he could never succeed in making the section accurately on the median line. From these facts, he concludes, that there are two forces, which are equilibrious by passing; across the circle formed by the pons varolii and cerebellum. To put this beyond all question, he cut * Precis, &c. i. 343. t Magendie's Journal de Physiologie, iv. 405. X Precis, &c. p. 344. 336 MUSCULAR MOTION. one peduncle, when the animal immediately rolled in one direction; but on cutting the other, or the one on the opposite side, the move- ment ceased, and the animal lost the power of keeping itself erect, and of walking. From the results of all his experiments, Magendie infers, that an animal is a kind of automatic machine, wound up for the per- formance of certain mo- tions, but incapable of pro- Fig. 59. ducing any other. The marginal figure of the base of the brain will explain, more directly, the impulses described by that physiolo- gist. The corpora striata are situated in each hemi- sphere, but their united impulses may be repre- sented by the arrow A ; the impulse, seated in the cere- bellum, by the arrow B; and those in each peduncle of the cerebellum, p. p, by the arrows C and D re- spectively. When the im- pulse backwards is from any cause destroyed, the animal is given up to the forward impulse, or to that represented by the arrow B, and conversely. In like manner, the destruction of one lateral impulse leaves the other without an anta- gonist, and the animal moves in the direction of the arrow placed over the seat of the impulsion that remains. In a state of health, all these impulsions being nicely antagonized, they are subjected to the influence of volition; but in disease they may, as we have seen, be so modified, as to be entirely withdrawn from its control. These four are not the only movements excited by particular injuries done to the nervous system. Magendie* states, that a circular movement, to the right or left, similar to that of horses in a circus, was caused by the division of the medulla oblongata, to the outer side of the corpora pyramidalia anteriora. When the section was made on the right side, the animal turned, in this fashion, to the right; and to the left, if it was made on that side. Pathology has, likewise, indicated the brain as the seat of dif- ferent bodily movements. Diseases of the encephalon have been found not only to cause irregular movements or convulsions, but, also, paralysis of a part of the body, leaving the rest untouched. X Ibid, p, 345. ENCEPHALIC ORGANS OF MUSCULAR MOTIONS. 337 Hence it has been concluded, that every motion of every part has its commencing point in some portion of the brain. The ancients were well aware, that in cases of hemiplegia the encephalic cause of the affection is found in the opposite hemi- sphere. Attempts have accordingly been made to decide upon the precise part of the encephalon, where the decussation takes place. Many have conceived it to be in the commissures; but the greater number, perhaps, have referred it to the corpora pyrami- dalia. These, the researches of Gall and Spurzheim* had pointed out as decussating at the anterior surface of the marrow.f and as being apparently continuous with the radiated fibres of the corpora striata; and an opinion has prevailed, that the paralysis is of the same side as the encephalic affection or of the opposite, according as the affected part of the brain is a continuation of fasciculi, which do not decussate—of the corpora olivaria for example—or of the corpora pyramidalia, which do. Serres,J however, affirms, that affections of the cerebellum, pons varolii, and the tubercula quadri- gemina, exert their effects upon the opposite side of the body; and he supports his opinion by pathological cases and direct experiment. Magendie,§ again, divided one pyramid from the fourth ventricle; yet no sensible effect was produced on the movements; certainly there was no paralysis, either on the affected side or on the opposite one: more than this, he divided both pyramids about the middle, and no apparent derangement occurred in the motions;—a slight difficulty in progression being alone observable. The section of the posterior pyramids was equally devoid of perceptible influence on the general movements; and to cause paralysis of one-half the body, it was necessary to divide the half of the medulla oblongata, and then the corresponding side became—not immovable, for it was affected by irregular movements, and not insensible, for the animal moved its limbs when they were pinched,—but incapable of executing the determinations of the will. These views are not exactly in accordance with the general idea, that disease confined to one hemisphere of the brain, or cerebellum, and to one side of the mesial plane in the tuber annulare, constantly affects the opposite side,—whilst disease, confined to one of the lateral columns of the medulla oblongata and medulla spinalis, affects the corresponding side of the muscular system:—the ence- phalon having a crossed effect,—the medulla a direct effect.|| The result of the examination of morbid cases has induced some physiologists to proceed still farther in their location of the encephalic organs of muscular motion; and to attempt some ex- * Recherches sur le Systeme Nerveux, &c, sect. vi. Paris, 1809. t See also, Berard, Chassaignac, and Montault in Archives generates de Medecinc. Fevrier, 1835. t Anatomie Comparec du Cerveau. Paris, 1824. § Ibid. p. 347. || Lectures on the nervous system and its diseases, by Marshall Hall, M. D. &.c. Lond. 1836, p. 34, and Amer. Edit. Philad. 1836. Addon's Physiologie de I'Homme, 2de edit. I. 158. Bostock's Physiology, 3d edit. p. 133. Lond. 1836. Richerand's Ele- mens, &c. edit, de Bruxelles, p. 253. Bruxelles, 1837. vol. I. 29 338 MUSCULAR MOTION. planation of paraplegia, or of those cases, in which one half the body, under the transverse bisection, is paralyzed. MM. Serres, Foville, and Pinel Grand-Champ assert, that the anterior radiated portion of the corpora striata presides over the movements of the lower limbs; and the optic thalamus over those of the upper; and that according as the extravasation of blood, in a case of apoplexy, occurs in one of these parts, or in all, the paralysis is confined to the lower or to the upper limbs, or extends to the whole body. In 1768, Saucerotte* presented a prize memoir to the Academie Royale de Chirurgie, of Paris, in which a similar view was expressed. He had concluded, from experiments, that affections of the anterior parts of the encephalon paralyzed the lower limbs, whilst those of the posterior parts paralyzed the upper. M. Chopart,—in a prize essay, crowned in 1769, and contained in the same volume with the last—refers to the result of some experiments by M. Petit, of Na- mur, which appeared to show, that paralysis of the opposite half of the body was not induced by injury of the cerebral hemisphere, un- less the corpora striata were cut or removed. The experiments of Saucerotte were repeated by M. Foville, and are detailed in a memoir, crowned by the Academie Royale de Medecine, of Paris, in 1826. They were attended with like results. In cats and rabbits, he cauterized, in some, the anterior part of the encephalon; in others, the posterior part; and in every one of the former, paralysis of the posterior, in the latter, of the anterior ex- tremities succeeded. Having, in one animal, mutilated the whole of the right hemisphere, and only the anterior part of the left, he found, that the animal was paralyzed in the hinder extremities, and in the paw of the left fore-leg, but that the paw of the right remained active.f Lastly, the motions of the tongue, or of articulation, are some- times alone affected in apoplexy. The seat of this variety of mus- cular motion has been attempted to be deduced from pathological facts. Foville places it in the cornu ammonis and temporal lobe; and BouillaudJ in the anterior lobe of the brain, in the medullary substance; the cineritious being concerned, he conceives, in the in- tellectual part of speech.^ It is sufficiently obvious, from the whole of the preceding detail, that the mind must still remain in doubt, regarding the precise part of the encephalon engaged in the functions of muscular motion. The experiments of Magendie are, perhaps, more than any of the others, entitled to consideration. They appear to have been insti- tuted without any particular bias; to subserve no particular theory; and they are supported by pathological facts furnished by others. M. Magendie is, withal, an accurate and practised experimenter, * Prix de l'Acad£mie Royale de Chirurgie, vol. iv. p. 373. Paris, 1819. t Adelon, Physiologie de I'Homme, 6dit. cit. ii. 44. t Magendie's Journal de Physiologie, torn. x. § Prichard, in Retrospective Address, in Transact, of the Provincial Med. and Surg. Association, iv. 20. Lond. 1836. NERVES OF MOTION. 339 and one to whom physiology has been largely indebted. His vivi- sections have been more numerous, perhaps, than those of any other individual. • His investigations, however, on this subject clearly show, that owing to the different structures of animals, we cannot draw as extensive analogical deductions from compara- tive anatomy and physiology as might be anticipated. The greatest source of discrepancy, indeed, between his experiments and those of MM. Rolando and Flourens, appears to have been the employ- ment of different animals. Where the same animals were the sub- jects of the vivisections, the results were in accordance. The ex- periments demand careful repetition, accompanied by watchful and assiduous observation of pathological phenomena; and, until this is effected, we can, perhaps, scarcely feel justified in deducing, from all these experiments and investigations, more than the general pro- positions, regarding the influence of the cerebro-spinal axis on mus- cular motion, which we have already enunciated. The nerves, it has been shown, are the agents for conducting the locomotive influence to the muscles. At one time, it was univer- sally believed, that the same nerve conveys both sensation and voli- tion ; but the pathological cases, that not unfrequently occurred, in which either sensation or voluntary motion was lost, without the other being necessarily implicated, and of late years, the beautiful additions to our knowledge of the spinal nerves, for which we are mainly indebted to Sir Charles Bell* and Magendie,f have satisfied the most sceptical, that there are separate nerves for the two func- tions, although they may be enveloped in the same neurilema, or nervous sheath; or, in other words, may constitute the same nervous cord. We have more than once asserted, that the posterior part of the spine, with the nerves proceeding from it, is chiefly concerned in the function of sensibility, and that the anterior co- lumn, and the nerves connected with it, are inservient to muscular motion; whilst a third column intervenes, which, in the opinion of Sir Charles Bell, is the source of all the respiratory nerves and of the various movements connected with respiration and expression. It is proper here again, to observe, that although these two distin- guished physiologists agree in their assignment of function to the anterior and posterior columns of the spinal marrow, BellingeriJ has deduced very different inferences from the same experiments. He asserts, that having divided, on living animals, either the ante- rior roots of the spinal nerves, and the anterior column of the me- dulla spinalis, or the posterior roots of these nerves, and the poste- rior column of the marrow, he did not occasion, in the former case, paralysis of motion, and in the latter, of sensation; but only, in the * The Nervous System, . ^„„„. „..-. j ° Canal for containing the spinal mar. erect attitude. row. c. Spinous process, dd. Trans- It need scarcely be said, that the longer vc!l!!sptocessea- ee- Ani™^sw- and more horizontal the spinous processes, the greater will be the arm of the lever; and the less the muscular force necessary to pro- duce a given effect. The weight of the whole of the upper part of the body is trans- mitted to the pelvis; which, resting upon the thigh bones as upon pivots, represents a lever of the first kind, the fulcrum of which is in the ilio-femoral articulations; the power and resistance being situated before and behind. The pelvis supports the weight of a part of the abdominal vis- cera ; and the sacrum that of the vertebral column, which, by rea- son of its shape, transmits the weight equally to the ossa femorum, through the medium of the ossa ilii. When the pelvis is, therefore, in equilibrium on the heads of the thigh bones, this is owing to many causes. The abdominal viscera, pressing upon the anterior part of the pelvis, which is naturally inclined forwards, tend to depress the os pubis; whilst the vertebral column, by its weight, tends to press down the sacrum. As the weight of the latter is much more con- siderable than that of the former, muscles would seem to be required to keep it in equilibrium, as1 well as muscles passing from the femur to be inserted into the os pubis by the contraction of which the ex- cess of weight of the vertebral column may be counterbalanced. Such muscles do exist, but, as Magendie* remarks, they are not the great agents in producing the equilibrium of the pelvis on the thigh bones; for the pelvis, instead of having a tendency to be depressed posteriorly, would appear to bear forwards, inasmuch as the mus- cles, that resist the tendency which the spine itself has to bear for- wards, have their fixed point on the pelvis; and, consequently, exert a considerable effort to draw it upwards. The strong glutasi muscles, which form the nates, and are inserted into the os femoris, are the great agents of the equipoise; and as * Precis, &c. edit. cit. 1.296. ATTITUDES. 379 the hip-joint is nearer to the pubis than it is to the sacrum, these muscles act with a greater leverage. The thigh bones transmit the weight of the trunk to the tibia; and here we see the advantage of the neck of the thigh bone, which, as represented in Fig. Fig. 82. 82, B, joins the shaft of the bone at a consi- derable angle. The trochanters D and C are for muscular attachments; and are, of course, advantageous to the muscles, which are insert- ed into them. The cervix femoris directs the head of the bone A obliquely upwards and in- wards, so that, whilst it supports the vertical pressure of the pelvis, it resists the separation of the ilia, which the pressure of the sacrum, with its superincumbent weight, has a tendency to produce. But another and important advantage is, that of affording additional strength in adventitious circumstances. When we are standing perfectly erect, the necks of the thigh bones are very oblique, compared with the line of direction of the body; but if we are thrown forcibly to one side, the line of direction of gravitation corre- sponds more nearly with that of the neck of the thigh bone, and fracture is rarely produced in this manner. The most common cause of fracture of the neck of the thigh bone is, slipping off a curbstone in towns, or unexpectedly slipping from a slight elevation, with one foot, upon a firm substance beneath, and the fracture, in such case, is generally transverse. The advantage of this arrangement of the neck of the thigh bone has been compared not inaptly to that resulting from the dishing of a wheel; or the oblique position of the spokes from the nave out- ward to the felly, which strengthens the wheel so essentially, against the strains produced by the wheel sinking with force into a rut or other hollow.* The femur transmits the weight of the body to the large bone of the leg__the tibia; but, from the mode in which the pelvis presses upon it, its lower extremity has a tendency to bear forwards. This is prevented by the action of the extensors of the leg—the rectus and triceps cruris—whose power is augmented by the presence of the patella, a sesamoid bone, seated behind their tendon. The muscles of the posterior part of the leg, which are attached to the condyles of the thigh bone, aid also in preserving the equi- librium. The tibia is the sole agent for the transmission of the superincum- bent weight to the foot. Its upper extremity has, however, a ten- * See Fig. 62, and the plates of the skeleton, p. 322; also, Sir C. Bell, Animal Me- chanics, p. 21, Library of Useful Knowledge. Lond. 1S29. 380 MUSCULAR MOTION. dency to bear forwards like the lower part of the os femoris. This is prevented by the contraction of the gastrocnemii, tibialis posticus, and the other muscles on the posterior part of the leg. The foot sustains the whole weight of the body; and its shape and structure are well adapted for the purpose. The sole has some extent, which contributes to the firmness of the erect attitude. The skin and epidermis are thick; and beneath the skin is a thick, adi- pous stratum, in greater quantity at the parts of the foot which come in contact with the soil. This fat forms a kind of elastic cushion, adapted for deadening or diminishing the effect of pressure. The whole of the sole of the foot does not come into contact with the ground. The weight is transmitted by the heel, the outer mar- gin, the part corresponding to the anterior extremity of the metatar- sal bones, and the extremities or pulps of the toes. The tibia transmits the weight to the astragalus; and, from this bone, it is distributed to the others that compose the foot; but the heel conveys the largest share. When the foot rests upon a flat surface, it is entirely passive; but when it is upon a slippery soil, the flexors of the toes, especially of the great toe, are firmly contracted, so as to fix the shoe, as far as possible, and render the attitude more stable. The use of shoes interferes largely with the exercise of the toes, which, in the savage, are capable of diversified and considerable action. The use of the fibula is, to serve, as its name imports, the purpose of a clasp. The tibia exerts its pressure chiefly towards the inner part of the foot, and, consequently, were it not for the fibula, which passes down below the articulation, dislocation outwards would be constantly menacing us. The fibula has no participation in the transmission of the weight to the ground. The conditions for equilibrium, as applicable to /man, have been already indicated. If the base of sustentation be rendered extensive in any one direction, by widely separating the feet, the attitude is more firm in one direction, but less so in the other. It is as firm as possible in every direction, when the feet are turned forwards in a parallel manner, and are separated by a space equal to the length of one of them. Whatever diminishes the base of sustentation, diminishes, in like proportion, the stability of the erect attitude. Hence the difficulty of walking on stilts or on wooden legs, on the toes, tight rope, &c. It seems, that the inhabitants of Les Landes,* in the south-west of France, are enabled by habit to use stilts with singular facility. The sandy plains, that bear this name, afford tolerable pasturage for sheep; but, during one part of the year, they are half covered with water; and during the remainder, they are very unfit walking ground, on account of the deep, loose sand, and thick furze. The natives, in consequence, habituate themselves to the use of stilts or wooden poles, the former of which are put on and off as regularly * Arnott's Elements of Physics, 3d Amer. edit. I. 15. Philad. 1835. ATTITUDES. 381 as the other parts of their dress. With these they walk readily over the loose sand or through the water, with steps eight or ten feet long. The difficulty, in this kind of progression, does not arise solely from the smallness of the base of sustentation, but from the greater height to which the centre of gravity is thrown, which renders the equilibrium unstable. Standing on one foot is necessarily more fatiguing, as it requires the strong and sustained contraction of the muscles, which surround the hip-joint, to keep the pelvis in equilibrium on the os femoris; especially as the body has a strong tendency to fall to the side that is unsupported. The muscles, that prevent the trunk from falling in this direction, are the glutasi, the gemelli, the tensor vaginas fe- moris, the pyramidalis, the obturators, and the quadratus femoris. The use of the neck of the thigh bone and of the great trochanter is here manifest. The base of sustentation, in this case, is the space occupied by the foot in contact with the soil simply; and it need hardly be said, that if this be still farther diminished, by attempting to stand on the toes, the attitude cannot be sustained. In the attitude on the knees, the centre of gravity is brought lower, but the base of sustentation is smaller than on the feet. The patella has to bear the chief pressure; and as it is not provided with such a fatty cushion as exists at the sole of the foot, the position becomes painful and the surface soon abraded. These remarks apply to the case, in which the knees only come in contact with the soil. When the feet are allowed to touch by the points of the toes, the attitude is much more easy and firm, as the base of sustentation is largely aug- mented,—comprising the space between the knees and toes plus the space occupied by those parts. The sitting posture admits of variety, and is easily intelligible. In every variety in which the back is unsupported, the weight of the body is conveyed to the soil by the pelvis; and the broader this base the firmer the attitude. When we sit upon a stool without any back, and with the legs raised from the ground, the whole of the weight is conveyed by the parts in contact with the seat; but if the feet touch the ground, the weight of the lower extremities is transmitted to the soil by the feet, whilst the pelvis transmits that of the upper part of the body. In both these cases, if the attitude be long maintained, fatigue is felt in the back, owing to the continued action of the extensor muscles in keeping the body erect. Sitting in an ordinary chair differs somewhat, in part of the body being supported. Fatigue is then felt in the neck, which is unsup- ported, and requires the sustained contraction of the extensor mus- cles of the head. To support all the parts, as far as possible, the long-backed chairs have been introduced, which sustain the whole body and head; and, by being provided with rockers, a position approaching to the easiest 382 MUSCULAR MOTION. of all attitudes can be assumed. To produce a similar effect in a common chair, the body is often throwrn back until the chair rests on its hinder legs only. When the feet of the individual are on the ground, this position is stable; the base of sustentation being large, and comprised between the legs of the chair and the feet of the individual, added to the space occupied by the parts themselves, that are in contact with the soil; but as soon as he raises his feet, the equilibrium is destroyed from the impracticability of making the vertical line fall within the base of sustentation, which is now reduced to the space occupied by the legs of the chair plus the space between them. In all the varieties of the sitting posture, equilibrium is facilitated by the centre of gravity being brought nearer to the ground. Lastly. The horizontal posture is the only one, that requires no muscular effort. Hence it is the attitude of repose and of the sick and the feeble. The base of sustentation is here extremely large; and the centre of gravity very low. Accordingly, the attitude can be maintained for a long time; the only inconvenience being,—that which results to the skin from prolonged pressure on those parts that chiefly convey the weight to the bed,—as the back of the pelvis, the region of the great trochanter, &c.—an inconvenience, which attracts the attention of the physician, more or less, in all protracted and consuming maladies. The reason, why we prefer soft, elastic beds, is not simply to prevent abrasion of those parts of the body that are most exposed to pressure, but to enable a greater portion of the body to transmit the weight; and thus to occasion a more equable partition of the pressure. There are numerous other attitudes, which may be assumed; as, that upon one knee, on the head, astride, &c.; but they do not merit explanation, their physiology being obvious after what has been said. 6. Movements. The movements, of which the body is susceptible, are of two kinds—partial and locomotive; the former simply changing the rela- tive situation of parts of the body; the latter the relation of the whole body to the soil. Many of the partial movements constitute an inherent part of the different functions, and are considered under those heads. In the erect attitude, whilst the body holds the same correspon- dence with the soil, the position of the upper parts of the body may be varied in all directions, provided the vertical line falls within the base of sustentation. Accordingly, to produce this effect, if the upper part of the body be inclined in one direction, the lower part will have to be thrown more to the opposite. The head may be turned forwards, backwards, or to one side; and it is capable of a rotatory motion to the right and left. The three first movements occur in the articulation of the occipital bone MOVEMENTS. 383 and atlas, when they are slight; but if to a greater extent, the whole of the cervical vertebras participate in them. The rotatory motion is effected essentially in the articulation between the first and second vertebras; the latter of which has an arrangement admirably adapt- ing it for this purpose. A tooth-like or odontoid process arises from its anterior part, on which the posterior surface of the anterior part of the atlas or first vertebra turns as on a pivot. This arrangement has obtained the second vertebra the name vertebra dentata: and its function, that of axis. Rotation to the right is effected by the contraction of the left sterno-mastoid and splenius and of the right complexus, to the left by the action of the opposite muscles of the same name. . The motions of the head aid the senses of sight, hearing, and smell; and are useful in the production of the different vocal tones, by occasioning elongation or decurtation of the trachea and vocal tube. They are, likewise, inservient to expression. The spine, as a whole, and each of the vertebras composing it, are capable of flexion, extension, lateral inclination, and circumduc- tion. These motions occur in the fibro-cartilages between the ver- tebras ; and they are more easy and extensive, in proportion to the thickness and width of the cartilages. This is one cause, why the motions of the cervical and lumbar portions of the vertebral column are freer than those of the dorsal. The intervertebral substances or fibro-cartilages possess a remarka- ble degree of elasticity. They yield somewhat, however, to prolonged pressure; and hence, after long continuance in the erect attitude, our stature may be sensibly curtailed. We can thus understand, that at night we may be shorter than in the morning. Buffon asserts, that the son of one of his most zealous collaborateurs, M. Gueneau de Montbeillard— a young man of tall stature,—lost an inch and a half after having danced all night.* The loss must be partly ascribed to the condensation of the adipous tissue beneath the foot. During the flexion of the spine, these cartilages are depressed on the side°of the flexure, but they rise on the other; and, by their elasticity, they are important agents in the restoration of the body to the erect position. Where they are thickest the greatest extent of motion is permitted, and this is a cause, why the spine admits of the greatest motion anteriorly. In rotation, the whole is pressed upon and undergoes elongation in the direction of its constituent laminas. In old age, the cartilages become shrivelled; and this, with the loss of muscular power, is one of the causes why old people bend forwards. When we assume different positions with the trunk, the centre of motion of the vertebras becomes modified. If we bend forwards, it is thrown to the anterior part of the body of the vertebras, if to * Richerand's Elcmens de Physiologie, edit. cit. § clxxi. p. 268. Bruxelles, 384 MUSCULAR MOTION. one side, to the articulating processes, &c. Each vertebra, we have seen, is a lever of the first kind; and as the centre of motion be- comes altered the leverage must be so likewise. It is when the body has been bent forwards, and the object is to restore it to the erect position, that the power acts with the greatest advantage,— the fulcrum being thrown to the anterior part of the body of the vertebra, and the arm of the power being the distance between this point and the extremity of the spinous process, into which the power is inserted. Each vertebra has but a slight degree of motion; but the sum of all their motions is considerable; and it is estimated by multiplying the single motion by the number of vertebras. The result, however, can only be regarded as approximate, as the extent of motion, of which the different vertebras are capable, necessarily varies. The arrangement of the spinous processes of the vertebras—espe- cially of the dorsal-*-prevents any considerable flexion of the body backwards: and when we find the tumbler bending his body back until his head touches his heels, it is owing to the arrangement of the spine having been modified, in early life, by constant efforts of this kind, until they are no longer obstacles to the movement. The motions of the vertebras are frequently united to those of the pelvis on the thigh bones, so that they seem to be more extensive than they really are. This is the case, when we make a low bow. The motions of the spine are inservient to those of the head, and of the superior and inferior extremities. The upper limbs are capable of various motions; some of which have been already described, and others will be, hereafter. They are useful in the different attitudes; and, at times, by transmitting to the soil a part of the weight of the body, and thus enlarging the base of sustentation; as when we employ a stick, rest on the hands and knees, or support the head on one or both elbows. They are of great use, likewise, in preserving equilibrium when we walk on a very narrow base ; serving in part the purpose of the pole, employed by the dancer on the tight rope. The lower extremities are, of course, locomotive organs ; but they are susceptible of partial movements likewise; as when we kick with one foot, try the consistence of the ground, cross the legs, tread the foot-board of a lathe, &c. Thus much for the attitudes. We shall now consider the mode in which the relation of the body to the soil is altered, comprising the physiology of walking, leaping, running, swimming, flying, &c, which constitute the different varieties of locomotion or progression. 7. Locomotive Movements. a. Walking. Walking is a motion on a fixed surface, the centre of gravity be- ing alternately moved by one of the extremities and sustained by the other, without the latter being, at any time, completely off the WALKING. 385 ground. It consists of a succession of steps, which are effected— in the erect attitude and on a horizontal surface—bv bending one of the thighs upon the pelvis and the leg upon the thigh, so as to detach the foot from the ground by the general decurtation of the limb. The flexion of the limb is succeeded by its being carried forward; the heel is then brought to the ground, and, successively, the whole of the inferior surface of the foot. *lg- 83. jf me bones of the leg were per- pendicular to the part which first touches the ground, we should experience a jolt, but, instead of that, the foot descends in an arc of a circle, the centre of which is the point of the heel.* In order that the limb shall be thus carried forward, the pelvis must have described a movement of rotation on the head of the thigh bone of the limb, which has not been moved, and have carried forward the corresponding side of the body. As yet, only one limb has advanced. The base of sustentation has been modified, but there has been no progression. The limb, remaining behind, has now to be raised and brought for- ward, so as to pass the other, or to be on the same line with it, as the case may be ; and this finishes the step. In order to bring up the limb, which is behind, the foot must be successively detached from the soil, from the heel to the toe. In this way, an elongation of the limb is produced, which assists in advancing the correspond- ing side of the trunk, and excites the rotation of the pelvis on the head of the thigh bone first carried forward. A succession of these movements constitutes walking; the essence of which consists in the heads of the thigh bones forming fixed points, on which the pelvis turns alternately, as upon a pivot, describing arcs of circles, which are more extensive in proportion to the size of the steps. Walking in a straight line requires, that the arcs of circles de- scribed by the pelvis, and the extension of the limbs when carried forward, shall be equal; otherwise, the body will be directed towards the side opposite to that of the limb, whose movements are more ex- tensive. Without the aid of vision, it would be impracticable for us to make the arcs equal; or, in other words, to walk straight for- ward. Walking backwards differs somewhat from this. The step is commenced by bending the thigh upon the pelvis, and, at the same time, the leg upon the thigh. The extension of the thigh on the pelvis succeeds, and the whole limb is carried backwards, the leg is afterwards extended upon the thigh, the point of the foot is brought to the ground, and the remainder of its under surface in succession. The other foot is then raised on its point, by which the correspond- * Sir. C. Bell, Op. cit. p. 18. vol. I. 33 386 MUSCULAR MOTION. ing limb is elongated; the pelvis, being pushed backwards, makes a rotation on the limb which is behind, and is, by the action of ap- propriate muscles, carried on a level with, or behind, the other, to afford a new pivot in its turn. Walking laterally is different from the two last in no arcs being described. In this case, one of the thighs is first slightly bent upon the pelvis, in order to detach the foot from the ground; the whole limb is then moved away by the action of the abductors, and is brought down to the ground. The other limb follows. If we walk up hill, the fatigue is much augmented; because the flexion of the limb, first carried forward, has to be more con- siderable; and the limb, that remains behind, has not only to cause the pelvis to execute the movement of rotation, but it has to raise the whole weight of the body, in order to transport it upon the limb, which is in advance. To aid in throwing the weight forwards, the body is bent forward, so that the centre of gravity may be as favourably disposed as possible; and the extensor muscles of the leg carried forward are powerfully contracted to raise the trunk; hence, the feeling of fatigue, which we experience in the knee and anterior part of the thigh, on ascending a long flight of stairs. Fatigue is likewise felt in the calf of the leg, on account of the strong efforts developed in extending the foot, and projecting the body forwards. Walking down hill is, also, more fatiguing than on level ground. In this case, there is a tendency in the body to fall forwards; great effort is, consequently, required to keep the vertical line within the base of sustentation, and, accordingly, the muscles, employed in the extension of the head and vertebral column, experience fa- tigue. In all these kinds of progression, the character of the soil is a matter of importance. It must be firm enough to afford support to the limb, that presses upon it, otherwise fatigue is experienced, and progression is slow and laborious. This occurs, whenever the soil is too soft or too smooth ; the former yielding to the foot, and the latter presenting no inequalities, by which the foot can attach itself. The soil, too, has some influence, in particular cases, by virtue of its elasticity. Such, at least, is the opinion of Borelli ;* but Barthezf thinks, that the influence of the soil is limited to the degree in which it furnishes a firm support. If the soil, again, be movable, as the deck of a vessel, the line of gravity is apt to fall outside the base of sustentation ; and to avoid this, the base of sustentation is enlarged by separating the legs so as to give a characteristic air to the gait of the mariner;—and, lastly, if the base be very narrow, as on the tight rope, the steps are obliged to be rapid, and the arms are aided—in modifying the centre of gravity, as may be required— by the use of a long and heavy pole. * De Motu Animalium, &c. Lugd. Bat. 1710. t Nouveaux elemens de la Science de I'Homme. Paris, 1806. LEAPING. 387 b. Leaping. In the action of leaping, the whole body is raised from the ground; and is, for a short period, suspended in the air. It consists, essen- tially, in the sudden extension of the limbs, after they have under- gone an unusual degree of flexion. Leaping may be effected directly upwards, forwards, backwards, or laterally. In the ordinary case of the vertical leap, the head is slightly bent on the neck ; the vertebral column is curved forwards; the pelvis is bent upon the thigh; the thigh upon the leg; and the leg upon the foot; the heoJ generally pressing but lightly on the soil, or not touching it at all. This state of general flexion is suddenly suc- ceeded by a quick extension of all the bent joints; so that the dif- ferent parts of the body are rapidly elevated, with a force surpass- ing their own gravity, and to an extent dependant upon the force developed. In this general muscular movement, the muscles, that form the calf of the leg, and are inserted into the heel, have to develope the greatest force, inasmuch as they have to raise the whole body, and to give it the impulse, which surmounts its gravity. They are, how- ever, favourably circumstanced for the purpose; being remarkably strong; inserted perpendicularly into the heel; and having the ad- vantage of a long arm of a lever. Figure 80 will show, that whenever the body is bent in the posi- tion it -assumes preliminary to a leap, opposite impulses must be communicated, by the restoration of the different parts to the verti- cal line B F. The leg B will tend to impel the body backwards, by following the curved line C G. CD, on the other hand, by de- scribing the curve D I, will lend to impel it forward; whilst the head and trunk, represented by the line D E, will describe the curve E F, and give an impulse backwards. Every vertical leap must, therefore, be a mean between these different impulses, or rather the backward and forward impulses must destroy or neutralize each other ; and that which is concerned in the elevation of the trunk be alone effective. In the forward leap, the movement of rotation of the thigh pre- dominates over the impulses backwards, and the body is projected forward. On the other hand, the impulses of the vertebral column, and of the leg on the foot prevail in the backward leap. The length of the lower limbs is favourable to the extent of the leap. The for- ward leap, in particular, is greatly dependant upon the length of the femur, the part in which the forward impulse is situated. It does not appear, that any kind of impulse is communicated to the body by the surface on which we rest, at the moment of leaping, unless it be very elastic. In this last case, however, its reaction is added to the effort of the muscles, that occasion the elevation of the body; hence, the wonderful leaps of the performers in our circuses and on the tight rope. On the other hand, if the soil do not afford the necessary resistance, and yields to the feet, leaping is almost or wholly impracticable. 388 MUSCULAR MOTION. The upper extremities are not without their use in leaping. They are brought close to the body, whilst the joints are bent, and are separated from it, at the moment when the body leaves the soil. By being held firmly in this manner, they allow the muscles, that pass from the os humeri to the trunk, to "exert a degree of traction up- wards, and thus to assist the extensors of the foot in the projection of the body. It is with this view, that the ancients employed their «Xips£, (halteres or poisers) in leaping; and that the moderns use bricks, stones, or other solid, heavy bodies, with a like intent. It is, likewise, manifest, that by steadying the arms, and then moving them rapidly backwards, a backward impulse may be given to the upper part of the trunk.* The effect of a run, before we leap, is to add to the force—deve- loped by muscular contraction—that of the impulse acquired by the body whilst running. The leap is, under such circumstances, neces- sarily more extensive. Some of the smaller animals surprise us by the extent of their leap. The jumping maggot, found in cheese, erects itself upon its anus, forms its body into a circle, by bringing its head and tail into contact, and, having contracted every part as much as possible, it unbends with a sudden jerk, and darts forward to an astonishing distance. Small animals, indeed, leap much farther than the larger, in proportion to their size; and, as Mr. Sharon Turner has re- marked,! " exhibit muscular powers still more superior to those of the greatest animals than their comparative minds." He has given some amusing representations of this difference :—for example, Lin- nasus observes, that if an elephant were as strong in proportion as a stag beetle, he would be able to tear up rocks and to level moun- tains. A cock-chafer is, for its size, six times as strong as a horse.J The flea and the locust leap two hundred times their own length, as if a man should leap three times as high as St. Paul's.^ The cuckoo- spit frog-hopper will sometimes leap two or three yards, which is more than two hundred and fifty times its own length, as if a man should vault at once a quarter of a mile.j| MouffetH relates, that an English mechanic made a golden chain as long as a finger, with a lock and key, which was dragged by a flea: and Latreille** men- tions a flea, of moderate size, dragging a silver cannon on wheels, that was twenty-four times its own weight. This cannon was charged with powder and fired, without the flea seeming to be alarmed. • c. Running. This variety of progression consists of a series of low leaps, per- formed by each leg in alternation. It differs from walking, in the * Magendie, Precis, &c. £dit. cit. I. 330. \ Sacred History of the World. Amer. edit. p. 372. New York, 1832. t Kirby and Spence's Introduction to Entomology, iv. 190. § Nat. History of Insects, I. 17. || Insect Transformations, v. 6. p. 179. t Theatr. Insect, 275. ** Nouv. Diet. d'Histoire Natur. xxviii. 249; and Kirby, Op. cit. SWIMMING. 389 body being projected forward at each step, and in the hind foot beino- raised before the fore-foot touches the ground. It is more rapid than the quickest walk, because the acquired velocity is pre- served and increased, at each bound, by a new velocity. Running, therefore, cannot be instantaneously suspended, although a stop may be put to walking at any moment. In running, the body is inclined forward, in order that the centre of gravity may be in a proper position for receiving an impulse, in that direction, from the hind leg; and the fore leg is rapidly ad- vanced, to keep the vertical line within the base of sustentation, and thus to prevent the body from falling. There is, consequently, in running, a moment in which the body is suspended m the air. d. Swimming. Although Magendie* affirms, that the human body is, in general, specifically heavier than water, and that consequently, if left to itself in a considerable quantity of that fluid, it would sink to its lowest portion, the question respecting its specific gravity has not been rUrously determined; and many eminent practical philosophers have even held an opinion the reverse of that of .Magendie Borelht accords with him ; and a writer of a later period-Mr. Robertson,! who details a set of experiments, on this subject, seems to have origi- nally coincided with him also. He weighed, however, ten different indi- viduals in water, comparing the weight with that of the fluid displaced by their bodies; and he affirms, that, with the exception of two, every man was lighter than his equal bulk of fresh water, and much more so than his equal bulk of sea water;-« consequently, he says "could persons, who fall into water, have presence of mind enough to avoid the fright, usual on such accidents, many might be preserved from drowning." In corroboration of this inference, Mr. Robertson relates a circumstance connected with his own personal knowledge. A voun- gentleman, thirteen years of age, little acquainted with swimminVfell overboard from a vessel in a stormy sea; but having Ed presence of mind enough to turn immediately upon h* back, he remained a full half hour, quietly floating on the surface of the water, unfil a boat was lowered from the vessel. He had used the pre- caution to retain his breath, whenever a wave broke over him, until ^fcterg,'fen in the Rev. Mr. Maude's Visit to Niagara, in 1803, which s tS ngly corroborative of Mr. Robertson's view of this matter The aShor was on board a sloop on Lake Champlain when a boy named Catlin, who was on deck cutting bread and cheese with^X, was knocked overboard by the captain jibbing the boom Se mis'sed catching hold of the canoe, which was drag. ging as^rn, and an attempt of Mr. Maude's servant to untie or cut * Precis 6lementaire, I. 333. 01_ 33 * 390 MUSCULAR MOTION. the rope, which fastened it, that it might drift to his assistance, also failed. Catlin was known to be unable to swim. It was in the night and very dark, and it was with difficulty, that the captain, who con- sidered that there was no hope of saving his life, was at last prevailed upon to go in the canoe to attempt it. He succeeded, however, in picking the boy up, and brought him on board again in about a quar- ter of an hour. " Catlin's relation," proceeds Mr. Maude, " almost exceeds probability. He had heard my exclamation to seize the canoe, which he was on the point of doing, when it gave a sudden swing and baffled him; but, finding he could support his head above water, he dismissed all fear, expecting that the canoe would come every moment to his assistance. When he no longer heard our cheers from the sloop, hope began to fail him, and he was on the point of resigning himself to a watery grave, when he heard the captain's life-restoring voice. On telling Catlin that we despaired of his safety, as we understood that he could not swim, he replied, ' nor can I. I was never before out of my depth ; but I am fond of bath- ing, and have often seen lads what they call tread the water, and that's what I did.' The truth of this account was made manifest, by the boy notonly retaining his hat on his head, but its being per- fectly dry; and what adds to the singularity of this event, the boy never quitted his grasp of the knife, that he was eating his bread and cheese with." Knight Spencer found, that he was buoyant on the surface of the sea, when he held stones, weighing six pounds avoirdupois in his hands. In the water, however, the stones lost two pounds five ounces in weight, so that he was really freighted with no more than three pounds eleven ounces. He himself weighed one hundred and thirty pounds.* Dr. Franklin,f again, whilst he considers the detached members of the body, and particularly the head, as of greater weight than their bulk of water, acknowledges the body, in the aggregate, to be of less specific gravity, by reason of the hollowness of the trunk. He thinks, that a body, immersed in water, would sink up to the eyes, but that if the head were inclined back, so as to be supported by the water, the mouth and nostrils would remain above,—the body rising one inch at every inspiration, and sinking one inch at every expiration; and also, that clothes give additional weight in the water, although, in stepping out of it, the case is quite otherwise. He concludes, therefore, that if a person cOuld avoid struggling and plunging, he might remain in the posture described with safety. That the body is to a certain degree buoyant he refers to the expe- rience of every one, who has ever attempted to reach the bottom of deep water, the effort required sufficiently proving, that something resists our sinking. The truth would appear to be, that there is only a slight difference between the specific gravity of the human body and that of water; * Fleming's Philos. of Zoology, vol. i. Edinb. 1822. t Works.'ni. 374, Philad. 1808; and Sparks's edit. vi. 289, Boston, 1838. SWIMMING. 391 but that the former is something greater, otherwise there would be no reason, why the dead body should sink to the bottom, as it is known to do.* It would seem, however, where the deposition of fat is excessive the body may be of less specific gravity than water.f The old notion was, that, in the living state, the specific gravity of the body is decidedly less; but that, in death from drowning, a quantity of water always enters the lungs and stomach, and that thus, these cavities, being no longer occupied with air, the buoyancy is lost and the body sinks. Nothing is now better established than that no water gets into the stomach, except what is accidentally swallowed during the struggling, and, that no water must be looked for in the lungs; a quantity of frothy mucus being all that is gene- rally perceptible there. Yet, in courts of justice, the absence of water in these situations has been looked upon as evidence,—where a body has been found in the water, that death had not occurred from drowning; and attention has, consequently, been directed to other causes, which might have produced it; the presumption being, that the person had been first killed and then thrown into the water for the purpose of averting suspicion. Another erroneous opinion, at one time prevalent, was, that if a person goes alive into water he will sink; if dead, he will swim; and that, therefore, it is necessary, that some weight should be attached to a body, when committed to the deep, to make it sink. All these fallacious notions are dwelt upon in a case, deeply inte- resting to all jurists, medical and others; that of Spencer Cowper, Esq. a member of the English bar, who, with three other individuals, was tried at the Hertford assizes, in 1699, for the murder of Mrs. Sarah Stout.J The speeches of the counsel, with the evidence of many of the medical witnesses, sufficiently testify the low condition of medico-legal knowledge at that period. Mr. Jones,—the counsel for the prosecution—affirmed, that " when her (Mrs. Stout's) body came to be viewed, it was very much won- dered at; for, in the first place, it is contrary to nature, that any per- sons, that drown themselves, should float upon the water. We have sufficient evidence," he adds, " that it is a thing that never was: if persons go alive into the water, then they sink; if dead, then they swim." In confirmation of this strange opinion, two seamen were examined, one of whom deposed as follows:—" In the year '89 or '90, in Beachy fight, I saw several thrown overboard during the engagement, but one particularly I took notice of, that was my friend and killed by my side. I saw him swim for a considerable distance from the ship, &c. Likewise in another engagement, where a man had both his legs shot off and died instantly, they threw over his legs; though they sunk, I saw his body float; likewise I have seen several men, who have died natural deaths at sea; they have, * Art. Schvvimmen, in Pierer's Anat. Phys. Real WGrterb. vii. 392. Altenb. 1827. t See vol. ii. under Adipous Exhalation. X Hargrave's State Trials, vol. v.; Beck's Med. Jurisprudence, 5th edit. p. 169. Albany, 1835. 392 MUSCULAR MOTION. when they have been dead, had a considerable weight of ballast made fast to them and so were thrown overboard; because we hold it for a general rule that all men swim if they be dead before they come into the water, and, on the contrary, I have seen men when they have been drowned, that they have sunk as soon as the breath is out of their bodies," &c.—The weights are, however, attached to the dead, when they are thrown into the sea, not for the purpose of facilitating their descent, but to prevent them from rising, when putrefaction renders them buoyant, by the disengagement of air into the splanchnic cavities. On the same trial, Drs. Coatsworth, Burnet, Nailor, and Wood- house deposed, that when a person is drowned, water will be taken into the stomach and lungs, and, as none was found in the case of Mrs. Stout, they were of opinion, that she came to her death by other means. From all that has been said, it would appear, that the great re- quisite for safety to the inexperienced, who may fall accidentally into the water, is a firm and sufficient conviction of the fact, that the living body naturally floats, or that it can be easily made to do so. This conviction being acquired, no more than a common share of presence of mind would seem to be necessary to insure, that the portion of the body, which is the great outlet of the respiratory or- gans, shall be above the surface. The movements, adapted to the progression of the body, are to be acquired in the same manner as a child learns to walk;—proficiency in this, as in every thing else, being the result of practice. Swimming nearly resembles leaping, except that the effort in it does not take place from a fixed surface. Both the upper and lower extremities participate in it. Whilst the former are brought to a point anterior to the head, and form a kind of cut-water, the lower extremities are drawn up and suddenly extended, as in leaping. The water, of course, yields to their impulse, but not as rapidly as it is struck, and hence the body is projected forwards. The upper limbs are now separated, and carried circularly and forcibly round to the sides of the body, by which the impulse is maintained: the legs are, in the mean time, drawn up; and, by a succession of these movements, progression is effected, the hands and feet being turned outwards to present as large a resisting surface as possible. The chest is, at the same time, kept dilated, to augment the bulk of the body, and, of course, to render it specifically lighter, and the head is raised above the surface to admit of respiration. This action is analogous to that of the propulsion of a boat by oars. The body resembles the boat; and the upper and lower extremities are the oars or sculls. The practised swimmer can execute almost as many movements in the water as he can on land. e. Flying. If the human body sinks in water, how little can it be susceptible OTHER VARIETIES OP MUSCULAR ACTION. 393 of suspension in the air by its own unassisted muscular powers. This is a mode of progression, which is denied to man ; and, accordingly, most of the attempts at flying, since the mythical exploits of Daeda- lus and Icarus, have been confined to enabling the body to move from one place to another, by means of ropes and appropriate ad- juncts. Not many years ago, a native of this country exhibited a curious variety of progression, at Dover, England. He was called the "flying phenomenon :" and his plan, so far as we can recollect, was to have a rope extending from the heights to the beach beneath, along which he descended, by means of rings attached to different parts of his person, and which had the rope passing through them. The sources of difficulty, in flying, are;—the great weight of the body, and the insufficient force, which the muscles are capable of exerting. It is by no means impossible, however, that by some con- trivance, of which the lightest gases might form a part, and by an imponderous apparatus, which would enlarge the surface of the upper extremities, progression, in this manner, might be effected;— but to a limited and unmanageable extent, only. /. Other Varieties of Muscular Action. Connected with this subject, w7e may refer, briefly, to some va- rieties of muscular action, the nature of which will be easily intel- ligible. In bearing a load, we have simply a variety of walking in the erect attitude, with this addition, that the extensor muscles of the head, neck, or back,—according to the part on which the burden may be placed,—have to contract forcibly to support it. The position of the individual has, also, to be so regulated, that the centre of gravity shall be always over the base of sustentation. Hence, if the load be on a man's back, he leans forward; if borne be- fore him, he leans backward; and this is the cause of the portly and consequential appearance of the corpulent. If the load be on his head, he stands as upright as possible, for a like reason. In propelling a body forwards, either by the hands or shoulders, the feet are firmly fixed on the ground; the limbs are in a state of semi-flexion, and the centre of gravity is directed forwards, so as to aid the force that has to be developed by the muscles. The limbs are then suddenly extended, the body is thrown forward, and the whole power exerted on the obstacle which has to be moved. On the other hand, when we drag a weight after us, or attempt to dislodge a stake from the earth; the feet are equally fixed firmly on the ground, but the body is in a state of extension, and is directed as far as practicable backwards, in order that the tendency to fall, owing to the centre of gravity overhanging the base of sustentation, may aid the force that has to be developed by the muscles of the arms, which embrace the substance to be moved, or are attached to it indirectly. The flexor muscles are, then, powerfully contracted, and the whole force is exerted upon the object. As, in both these cases, there is danger of falling should the body yield suddenly, the feet are so placed as to obviate this! as far a s 394 MUSCULAR MOTION. possible; by being separated in the direction in which the force is exerted. Squeezing consists in laying hold of the object, either between the arms and body, or by the fingers; and then forcibly contracting the flexor muscles. In all these, and other varieties of strong muscular contraction, the respiration is interrupted, in order that the thorax may be ren- dered fixed, and serve as an immovable point of origin for the muscles of the head, shoulders, and arms. This is effected by taking in a full inspiration; strongly contracting the respiratory muscles; and, at the same time, closing the glottis to prevent the exit of the air. Lastly, as organs of prehension, the upper extremities are of admirable organization; possessing great mobility; and, at the same time, solidity. The joint at the shoulder allows of extensive mo- tion ; and the bones, to which the arm is attached at this joint—the scapula and clavicle—are themselves movable. The forearm is, likewise, susceptible of various movements on the arm, of which those of pronation and supination are not the least important; whilst the hand possesses every requisite for an organ of prehension. It is composed of numerous bones, and is capable of being applied to the most irregular surfaces. The great superiority of the human hand arises, however, from the size and strength of the thumb, which can be brought into a state of opposition to the fingers; and is, therefore, of the highest use in enabling us to seize hold of, and grasp spherical bodies; to take up any object; to lay firm hold of whatever we seize, and to execute the various useful, and ornamental processes of the arts. These processes require the most accurate, quick, and com- bined movements of the muscles. How quick, for example, is the motion of the hand in writing, and in executing the most rapid move- ments on the piano-forte I How accurate the muscular contraction, which stops the precise part of the violin-string to bring out the note or semi-tone in the most allegro movements; and what a multitude of combinations must be invoked in all these cases! As an organ of touch, the advantages of the upper extremity'have already been depicted; and much of what was then said applies to it as an organ of prehension. " In this double respect," observes Adelon,* " man is the best provided of all animals. How much, in fact, does he stand in need of an ingenious instrument of prehension! As we have several times remarked, he has, in his organization, neither the offensive nor defensive arms, that are bestowed on other animals. Naked from birth, and exposed to the inclemencies of the atmosphere, without means of attack or defence against animals, he must incessantly labour to procure what he requires. It was not, consequently, enough that he should possess an intellect, capable of making him acquainted with, and of appropriating to himself, the universe. He must have an instrument adapted for the execution of all that his intellect conceives. Such instrument is his upper ex- • Physiologie de I'Homme, ii. 201. 2de 6dit. Paris, 1829. VOICE.-ANATOMY OF THE VOCAL APPARATUS. 395 tremity. In short, whilst other animals find every thing in nature— necessary for their different wants—more or less prepared, man, alone, is obliged to labour to procure what he requires. He must make himself clothes, construct his habitations/and prepare his food. He is the labouring and producing animal, par excellence; and hence he needs not only an intellect to conceive, but an instrument to execute." 9. Of the Function of Expression or of Language. Under this head will be included those varieties of muscular con- traction, by which man and animals exhibit the feelings that im- press them, and communicate the knowledge of such feelings to each other. It comprises two different sets of actions:—those that are ad- dressed to the ear, or the phenomena of voice: and those that are appreciated by the senses of sight and touch, or the gestures. Of these we shall treat consecutively. a. Of the Voice. By the term voice—or by phonation, which has been proposed by Chaussier—is meant the sound produced in the larynx, whilst the air is passing through it, either to enter, or issue from, the trachea. 1. Anatomy of the Vocal Apparatus. The apparatus concerned in the production of the voice, is com- posed, in man, of the muscles concerned in respiration; of the larynx ; and of the mouth and nasal fbssas. The first are merely agents for propelling the air through the instrument of voice. They will fall under consideration when we are on the subject of respiration; whilst the anatomy of the mouth and nasal fossas have been, or will have to be, described in other places. The larynx, and its primary dependencies, which are immediately concerned in the production of voice, will, therefore, alone engage us at present. The larynx is situated at the anterior part of the neck, and forms the projection so perceptible in that of the adult male, called pomum Adami. An attentive examination of the various parts which compose the larynx, so far as they concern its physiological relations, will be necessary; it will exhibit the imperfect knowledge of several writers on the voice, and the false and insufficient views that have been entertained on the subject. If we look along the larynx from the trachea, of which it is a continuation, we find that the tube becomes gradually narrower from side to side; and at length, presents an oblong cleft, called the glottis, the sides of which are the essential organ of voice. The larynx is composed of four cartilages—the cricoid, thyroid, and two arytenoid. The cricoid is the lowest of these, and is the in- ferior part of the organ ;—that by which it joins the trachea. It is shaped like a ring, whence its name, but is much deeper behind than 396 MUSCULAR MOTION. Fig. 84. before. The thyroid is situated above the cricoid, with which it is articulated in a movable manner, by means of its inferior cornua. It is the large cartilage that occupies the anterior, prominent, and lateral part of the larynx. The arytenoid cartilages are two in number. They are much smaller than the others, and are articulated with the posterior part of the cricoid;—also, in a movable manner. Around this articula- tion is a synovial capsule,—close before and behind, but loose within and without. Before it, is the thyro-arytenoid ligament; and, be- hind, a strong, ligamentous fascia, called, by Magendie,* from its at- tachments—crico-arytenoid. The arrangement of this articulation would appear to permit only of lateral movements of the arytenoid cartilages on the cricoid; all motion anteriorly or posteriorly, or in any other direction, being impracticable. The joint, consequently, is a lateral ginglymus. Three fibro-cartilages likewise form part of the constituents of the larynx. These are—the epi- glottis, and two small bodies, that tip the arytenoid cartilages, and are met with only in man—the capitula Santorini or the supra- arytenoid cartilages, or the capitula cartilaginum arytenoidarum. On examining the interior of the larynx, we discover, that there are two clefts,—one above the other; the uppermost being usually oblong-shaped, ten or eleven lines long, and two or three broad, having the shape of a triangle, the base of which is forwards. It is circumscribed, anteriorly, by the thyroid cartilage and epiglottis; posteriorly, by the arytenoid car- tilages; and, laterally, by two folds of the mucous membrane, C C, Fig. 86, which pass from the epiglottis to each arytenoid car- tilage, and are called the superior ligaments of the glottis, and the superior vocal cords. A few lines below this is a second cleft, also oblong from before to behind, (4, Figure 85,) and of a triangular shape, the base of which is behind. It is bounded, anteriorly, by the thyroid cartilage; posteriorly, by a muscle extending from one ary- tenoid cartilage to the other—the Larynx seen externally. 1. Os hyoides.—2. Lesser cornu of do.—3. Greater cornu of do.—4. Extremity of the Epiglottis.—5. Hyo-thyroid membrane.—6. Tbvroid Cartilage.—7. Cricoid Cartilage.— 8. Trachea. * Precis elementaire, I. 235. VOICE—ANATOMY OF THE VOCAL APPARATUS. 397 Glottis seen from above. 1 1. Thyroid Cartilage.—2 2. Greater cornu of do.—3 3. Vocal Cords.—4. Glottis.—5 5. Arytenoid Cartilages.—6. Cricoid Cartilage. arytenoideus; and, laterally, by two folds, formed of the thyro- arytenoid ligament, passing from the anterior part of the arytenoid cartilage to the posterior part of Fig. 85. the thyroid, and of a muscle of the same name. These folds are called the inferior ligaments or lips of the glottis, or the inferior vocal cords. They are represented by Nos. 3, 3, in Fig. 85, and by B B, Fig. 86. Between these two clefts are the sinuses or ventricles of the larynx, V V, Fig. 86. The infe- rior, exterior and superior sides of these are formed by the thyro- arytenoid muscle. By means of these ligaments—superior and in- ferior—the lips of the superior and inferior apertures are per- fectly free, and unencumbered in their action.* Anatomical descriptions will be found to Fig. 86. give different significations to the word glot- tis. Some have applied it to the upper cleft, some to the lower; some, again, to the ven- tricles of the larynx; and others to the whole space, comprised between the inferior liga- ments and the top of the larynx. It is now, generally perhaps, restricted to the part of the larynx engaged in the production of voice, or usually considered to be so engaged—the space between the inferior ligaments with the ligaments themselves—and in this significa- tion it will be employed by us. The mucous membrane, which lines the larynx, is continuous, above, with that of the mouth ; below, with that of the trachea. It contains several mucous follicles, some of which are agglomerated near the superior section of the Larynx, ligaments of the glottis and the environs of the ventricles of the larynx, seeming to con- stitute distinct organs, which have been called arytenoid glands. A similar group exists between the epiglottis behind, and the os hyoides and thyroid cartilage before, which has been termed the epiglottic gland. The uses of this body are not clear. Magendief conceives, that it favours the frequent slidings of the thyroid cartilage over the posterior surface of the os hyoides; that it keeps the epiglottis sepa- * Mr. Hilton in Guy's Hospital Reports, No. V. for April, 1837, p. 519. t Precis, &c. I. 237. VOL. I. 34 398 MUSCULAR MOTION. rated above from this bone; and, at the same time, furnishes it a very elastic support, which may aid it in the functions it has to exe- cute, connected with voice and deglutition. The larynx is capable of being moved as a whole, as well as in its component cartilages. It may be raised, depressed, or carried forwards or backwards. The movements, however, which are most concerned in the production of the voice, are such as are ef- fected by the action of the intrinsic muscles, as they have been termed. These are, 1st. The crico-thyroid, a thin, quadrilateral muscle, which, as its name imports, passes obliquely from the upper margin of the cricoid cartilage to the lower margin of the thyroid. Magendie* affirms, that its use is not, as generally imagined, to de- press the thyroid on the cricoid, but to elevate the cricoid and ap- proximate it to the thyroid, and even to make it pass slightly under its inferior margin. 2dly. The crico-arytenoidei postici, and the crico-arytenoidei laterales; the former of which pass from the poste- rior surface of the cricoid to the base of the arytenoid; and the latter from the side of the cricoid to the base of the arytenoid car- tilages. The use of these muscles is to carry the arytenoid carti- lages backwards, separating them at the same time from each other. 3dly. The arytenoid muscle—of which there is only one. It ex- tends across from one arytenoid cartilage to the other ; and, by its contraction, brings them towards each other. 4thly. The thyro- arytenoid muscle, which, according to Magendie.f is the most im- portant to be known of all the muscles of the larynx, as its vibra- tions produce the vocal sound. It forms the lips of the glottis, and Magendie describes it as constituting, also, " the inferior, superior, and lateral parietes of the ventricles of the larynx." Generally, it is considered to arise from the posterior surface of the thyroid car- tilage, and the ligament connecting it with the cricoid, and to be inserted into the anterior edge of the arytenoid cartilage. Lastly. The muscles of the epiglottis—the thyro-epiglotticus and aryteno- epiglotticus, and some fibres that may be looked upon as the vestiges of the glotto-epiglotticus, which exists in many animals. These mus- cles,—the position of which is indicated by the name,—by their contraction, modify the situation of the epiglottis. The intrinsic muscles of the larynx receive their nervous influ- ence from the eighth pair. Shortly after this nerve has issued from the cranium it gives off a branch called the superior laryngeal, which is distributed to the arytenoid and crico-thyroid muscles; and, after its entrance into the thorax, it furnishes a second, which ascends towards the larynx, and is, on that account, called the recur- rent or inferior laryngeal. It is distributed, to the crico-arytenoidei postici and crico-arytenoidei laterales, and to the thyro-arytenoid muscles. No ramification of this nerve, according to Magendie, goes to the arytenoidei, or thyro-arytenoidei muscles. In these * Ibid. p. 236. t Ibid. p. 236, and his Memoire sur 1'Epiglotte. VOICE.—PHYSIOLOGY. 399 views, he is supported by Cloquet* and many other anatomists. Other distinguished anatomists, however, maintain that the arytenoidei muscles receive a filament from each of the inferior laryngeals.f Dr. Reid asserts, that he has repeatedly satisfied himself of the exist- ence of this arytenoid branch of the inferior laryngeal, and the dis- section is one, he says, which can leave no kind of doubt on the matter. In each animal species, the glottis has a construction, correspond- ing to the kind of voice that has to be elicited ; and, when it is ex- amined on a living animal—on dogs for example—it enlarges and contracts alternately, the arytenoid cartilages separating when the air enters the lungs, and approximating during expiration. To the trachea the larynx is attached by a fibrous membrane, which unites the cricoid with the first ring of the trachea; and, above, it is connected with the os hyoides by a similar membrane— the hyo-thyroid, No. 5, Fig. 84, as well as by the thyro-hyoid muscle.J Physiology of the Voice. The production of the voice requires, that air shall be sent from the lungs, which, in passing through the glottis, may throw certain parts into vibration, and afterwards make its exit by the vocal tube,— that is, by the mouth and nasal fossas. Simple expiration does not, however, produce it, otherwise we should have the vocal sound accompanying each contraction of the chest. Volition is necessary to excite the requisite action of the muscles of the larynx; as well as of those of respiration \ and by it the tone and intensity of the voice are variously modified. That the voice is produced in the larynx, we have both direct and indirect testimony. An aperture, made in the trachea, beneath the larynx, deprives both man and animals of voice. This occurs also, if the aperture be made in the larynx beneath the inferior liga- ments; but if made above the glottis, so as to implicate the epiglottis and its muscles, the superior ligaments of the glottis, and even the upper portions of the arytenoid cartilages, the voice continues. Ma- gendief and J. Cloquet refer to the cases of two men, who had fistulas in the trachea; and who were unable to speak unless the fistulous openings were accurately stopped by same mechanical means. * Traite d'Anatomie descriptive, ii. 622, Paris, 1816, and Ley, in appendix to Essay on Laryngismus Stridulus, p. 451. Lond. 1836. t Bichat, Traite d'Anatomie descriptive, iii. 216. J. F. Meckel, Handbuch, u. s. w. and Jourdan's Translation, iii. 66: Rudolphi, Grundriss der Physiologie, ii. 374; Swan's Demonstration of the nerves, &c. PI. xvi. Fig. 7; and Cruveilhier, Anatomie descriptive, iv. 963, Paris, 1835, cited by Dr. J. Reid, in Edinb. Med. and Surg. Journ. for Jan. 1838, p. 138. See, also, on the distribution of the superior laryngeal and re- current nerves, C. E. Bach, in Muller's Archiv. fur Physiol. 1836, and Lond. Med. Gaz. May. 1837 ; and Mr. John Hilton, op. citat. X Willis, in Cambridge Philosoph. Transact, for 1832, iv. p. 323. § Precis &c. I. 241. See, also, Magendie's Journal de Physiologie, ix. 119. 400 MUSCULAR MOTION. If, again, we take the trachea and larynx of an animal or of man, and blow air forcibly into the tracheal extremity towards the larynx, no sound is produced, except what results from the friction of the air against the sides of the larynx. But if we approximate the ary- tenoid cartilages, so that they touch at their inner surfaces, a sound will be elicited, bearing some resemblance to the voice of the animal to which the larynx belongs ;* the sound being acute or grave ac- cording as the cartilages are pressed against each other with more or less force; and varying in intensity, according to the degree of force with which the air is sent through the tube. In this experiment, the inferior ligaments can be seen to vibrate. Paralysis of the intrinsic muscles of the larynx likewise produces dumbness; and this can be affected artificially. Much discussion at one time prevailed, regarding the effect of tying or cutting the nerves distributed to these muscles. The experiments of Haightonf induced him to think, that the recurrent branches of the par vagum supply parts, which are essentially necessary to the formation of the voice; whilst the laryngeal branches seemed to him to affect only its modulation or tone. Subsequent experiments have sufficiently shown, that if both the recurrent nerves and the superior laryngeal are divided, complete aphonia must result. MagendieJ found, in- deed, that when both recurrents,—which he considers are distributed to the thyro-arytenoid muscles,—are cut, the voice is usually lost; whilst if one only be divided, the voice is but half destroyed. He noticed, however, that several animals, in which the recurrents had been cut, were still capable of eliciting acute sounds, when labouring under violent pain,—sounds, which were very analogous to those, that could be produced mechanically with the larynx of the dead animal, by blowing into the trachea and approximating the ary- tenoid cartilages; and this he attempts to explain by the distribution of the nerves to the larynx. The recurrents being divided, the thyro-arytenoid muscles are no longer capable of contracting, and hence aphonia results; but the arytenoid muscle, which receives its nerves from the superior laryngeal, still contracts, and, during a strong expiration, brings the arytenoid cartilages together, so that the chink or cleft of the glottis is sufficiently narrow for the air to cause vibration in the thyro-arytenoid muscles, although they may not be in a state of contraction. From these, and other experiments, Bellingeri§ infers, that the superior laryngeal nerve is the anta- gonist of the inferior laryngeal or recurrent,— the former producing constriction, the latter dilatation of the glottis. They, however, who affirm, that the distribution of the laryngeal nerves is not the same as that described by Magendie and others, assign different functions to the particular nerves. Thus, Mr. Hilton,|| infers from his observa- * Biot, Traite Elementaire de Physique, i. 462. t Memoirs of the Medical Society of London, iii. 435. X Precis, <&c. i. 243. § Ragionamenti, Sperienze, &c. comprovatni l'Antagonismo nervoso, &c. Torino, 1833, and Edinb. Med. and Surg. Journal, p. 172, Jan. 1835. || Op. cit. p. 518, and Mr. Cock, on the Crico-Thyroideal Nerve, a branch of the supe. rior caryngeal. Ibid. p. 313. VOICE —MECHANISM. 401 tions—-first, that the superior laryngeal nerve is a nerve of sensation ; because independently of the crico-thyroideal nerve, it is distributed exclusively to the mucous membrane, cellular tissue, and glands; and secondly, that the inferior or recurrent nerve, must be the proper motor nerve to the larynx, as it alone supplies all the muscles which act immediately upon the column of air passing to and from the lungs. Dr. Reid,* too, concludes from his various experiments, first, that the superior laryngeal furnishes one muscle only with motor fila- ments,—the crico-thyroid. Secondly, that the superior laryngeal furnishes all, or at least nearly all, the sensitive filaments of the larynx, and also some of those distributed upon the mucous surface of the pharynx. Thirdly, that the inferior laryngeal or recurrent furnishes the sensitive filaments to the upper part of the trachea, a few to the mucous surface of pharynx, and still fewer to the mucous surface of the larynx; and fourthly, that when any irritation is applied to the mucous membrane of the larynx in a healthy state, this does not excite the contraction of the muscles, which move the arytenoid cartilages by acting directly upon these through the mucous mem- brane, but the contraction takes place by a reflex action, in the per- formance of which, the superior laryngeal is the sensitive, and the inferior laryngeal the motor nerve. It is obvious from this discrepancy amongst observers, that we have yet much to learn before we can pronounce with certainty on the precise function of those nerves. Every part of the larynx, with the exception of the inferior liga7 ments may be destroyed, and yet the voice may continue. Bichat split the upper edge of the superior ligaments of the glottis, without the voice being destroyed ; and the excision of the tops of the ary* tenoid cartilages had no more effect. Magendie divided, with im» punity, the epiglottis and its muscles, and voice was accomplished, until "he cut the middle of the arytenoid cartilages or split the thyroid cartilages longitudinally, when he, of course, destroyed the glottis. Lastly, when the larynx is exposed in a living animal, so that the different parts can be readily seen at the time when voice is accom- plished,—the superior ligaments, according to Bichat and Magendie, who have performed the experiment, are manifestly unconcerned in the function, whilst the inferior ligaments distinctly vibrate, These ligaments must, therefore, be regarded as the essential organs of voice.f The deeply interesting, but difficult problem now presents itself;— to determine the precise mechanism of the vibration of those liga- ments ; and what kind of instrument the vocal organ must be re* garded. The latter question, on which, it might be conceived, so much physical evidence must exist, has been the topic of much dis* gension, and is by no means settled at this day. * Op. cit. p. 145, t Precis &c. 1.242. 34* 402 MUSCULAR MOTION. Aristotle,* Galen,f and the older writers in general, looked upon the larynx as a wind instrument of the flutej kind, in which the in- terior column of air is the sonorous body; the trachea the body of the flute, and the glottis the beak. The air, they conceived, when forced from the lungs, in passing through the glottis or beak, is broken by the inferior ligaments of the larynx; vibrations are, con- sequently, produced, and these vibrations give rise to the sound. Fabricius, of Acquapendente,§ was one of the first to object to this view of the subject. He properly remarked, that the trachea cannot be regarded as the body of the flute, but as a porte-vent to convey the air to the glottis. He was of opinion, that the glottis corresponds to the beak of the flute, and that the vocal tube or all that part above the glottis resembles the body of the instrument. Similar opinions, with more or less modification, have been adopted by Blumenbach,|| S6mmering,1i Savart,** &c. About the commencement of the last century Dodartff laid before the Academie des Sciences of Paris, three memoirs on the theory of the voice, in which he considered the larynx to be a wind instru- ment of the horn, and not of the flute, kind; the inferior ligaments of the glottis being to the larynx what the lips are to the performer on the horn. In 1741, Ferrein,JJ in a communication, also made to the Academie des Sciences maintained that the larynx is a stringed instrument;— the sound resulting from the oscillation caused in what he called the cordcB vocales, or the inferior ligaments of the larynx, by the air in expiration; and a modification of this view was professed by Dr. Young.§§ At the present day, the majority of physiologists and natural phi- losophers regard the larynx as a wind instrument, but of the reed kind; such as the clarionet, hautboy, &c. and they differ chiefly from each other, in explaining the various modifications of the tone and quality of the voice : for almost all are agreed, that it is produced by the vibrations of the inferior ligaments of the glottis.[j|| Piorry, and Jadelot consider the glottis to be an instrument sui generis, emi- nently vital, and which, of itself, executes the movements necessary for the production of vocal sounds ; but all we know, of the physio- logy of the production of the voice, is—that the expired air is sent into the larynx by the muscles of expiration,—that the intrinsic muscles of the larynx give to the inferior ligaments sufficient tension to divide the air, and that the air receives the vibrations, whence * Opera Lib. ii. Problemat. § xi. t Opera, de Larynge, Lib. vii. X The flute, here alluded to, is the common flute or flute a bee, in which the embouchure is at one extremity. § De Locutione, &c. in Oper. Lugd. Bat. 1737. || Physiology by Elliotson, 4th edit. p. 140. Lond. 1828. t Icones organorum gustus et vocis. Francof. 1808, and Corp. Human. Fabric, vi. 93. ** Journal de Physiologie, v. 367. \\ Memoir, de l'Acad. Royale des Sciences, 1700, p. 244, and 1707, p. 409. XX Ibid, for 1741, p. 409, and Haller. Elem. Phys. ix. 3. l\ Lectures on Natural Philos. I. 400, and Philos. Trans.for 1800, p. 141. |)|| Mr. Willis, in Cambridge Philosophical Transactions, vol. iv. VOICE—INTENSITY AND TONE. 403 sound results.* The process is, however, very complex. Before a single word can be uttered, a series of actions must be executed: these, according to Sir C. Bell,f consist in the compression of the chest, the adjustment of the glottis, the elevation and depression of the larynx, and the contraction of the pharynx,—actions which will be readily understood after what has been already said on the me- chanism of phonation. Intensity or strength of the voice.—The strength of a sound depends upon the extent of the vibrations of the body producing it. In the case of the voice, it is partly dependent upon the force with which the air is sent from the lungs, and partly on the size of the larynx. A strong, active person, with a capacious chest and prominent pomum adami,—in other words, with a large larynx,—is of an or- ganization the most favourable for a strong voice. But if this same individual, thus favourably organized, be reduced in strength by sickness, his voice is enfeebled; because, although the formation of his larynx may be favourable, he is incapable of sending the air through it with sufficient force to excite extensive vibrations of the vocal ligaments. The voice of the male is much stronger than that of the female, of the eunuch, or of the child. This is greatly owing to his larynx being more developed. The change of the voice in the male at puberty is owing to the same cause; the prominence of the pomum adami, which is first observed at this age, indicating the elongation, which has supervened in the lips of the glottis. As voice is com- monly produced, both ligaments of the glottis participate; but if one should Jose its power of vibrating, from any cause, as from paralysis of one-half the body, the voice loses, cceteris paribus, one-half its intensity. MagendieJ affirms, that this is manifested by cutting one of the recurrents on a dog. Tone of the voice.—Nothing can exceed the human organ of voice in variety and execution. Dr. Barclay^ has endeavoured to calcu- late the different changes of which it is susceptible, proceeding on the principle, that where a number of movable parts constitute an organ destined to some particular function, and where this function is varied and modified by every change in the relative situation of the movable parts, the number of changes, producible in the organ, must at least equal the number of muscles employed, together with all the combinations of which they are capable. The muscles, pro- per to the five cartilages of the larynx, are, at least, seven pairs; and fourteen muscles, that can act separately or in pairs, in combi- nation with the whole or with any two or more of the rest, are estimated to be capable of producing upwards of sixteen thousand different movements—not reckoning as changes the various degrees * Adelon, Physiologie, edit. cit. ii. 228; also, Elliotson's Human Physiology, p. 505, and Mailer's Handbuch der Physiologie des Menschen, P. iii. Coblenz, 1837; and Baly's Translation. Lond. 1837-8. t Philos. Transact, for 1832, p. 299; and Nervous System, 3d edit. Lond. 1837. X Precis, &c. I. 245. § The Muscular Motions of the Human Body. Edinb. 1808. 404 MUSCULAR MOTION. of force and velocity, with which they are occasionally brought into action. These muscles, too, are only the proper muscles of the larynx, or the muscles restricted in their attachments to its five car- tilages. They are but a few of the muscles of voice. In speaking, we use a great many more. Fifteen pairs of different muscles, at- tached to the cartilages, or to the os hyoides, and acting as agents, antagonists, or directors, are constantly employed in keeping the cartilages steady, in regulating their situation, and moving them as occasion requires—upwards and downwards, backwards and for- wards, and in every intermediate direction, according to the course of the muscular fibres, or in the diagonal between different fibres. These muscles, independently of the former, are susceptible, it is calculated, of upwards of 1073,841,800 different combinations; and, when they co-operate with the seven pairs of the larynx, of 17592186,044,415; exclusive of the changes, which must arise from the different degrees of force, velocity, &c. with which they may be brought into action. But these muscles are not the whole that co-operate with the larynx, in the production of the voice. The diaphragm, the abdo- minal muscles, the intercostals, and all, that directly or indirectly act on the air, or on the parts to which the muscles of the glottis or os hyoides are attached,—in short, all the muscles that receive nerves from the respiratory system of Sir Charles Bell,—contribute their share. The numerical estimate would, consequently, require to be largely augmented. Mr. Bishop computes the number of mus- cles brought into action at the same time in the ordinary modula- tions of the voice to be one hundred.* Such calculations are, of course, only approximate, but they show the inconceivable variety of movement of which the vocal apparatus is directly or indirectly susceptible. The tone of the voice has been a great stumbling block to the physiologist and natural philosopher. The mode, in which it is produced, and the parts, more immediately concerned in the func- tion, have been the object of the various theories or hypotheses, from time to time enunciated regarding the voice. Galen, under his theory, that the larynx is a wind instrument of the flute kind, of which the glottis is the beak and the trachea the body of the flute, ascribed the variety of tones to two causes—to variation in the length of the musical instrument and in the embou- chure. In the theory of Dodart, in which the human vocal instru- ment was likened to a horn, the inferior ligaments of.the glottis being compared to the lips of the performer, no importance was attached to variation in the length of the instrument. He attributed the variety of tones to simple alteration in the embouchure or mouth- piece ; in other words, to changes in the size of the glottis, by the action of its approximate muscles, and the rising and falling of the larynx, he regarded as serving no other purpose than that of influ- * The London and Edinburgh Philosoph. Magazine, &c, for Sept. 1836, p. 209, VOICE.—TONE 405 encing, mechanically, the size of the aperture of the glottis; whilst Ferrein, who regarded the larynx as a stringed instrument, ac- counted for the variety of tones by the different degrees of tension and length of the inferior ligaments of the glottis or of the vocal cords. In the production of acute tones, these chords were stretched and shortened. For grave tones, they were relaxed, and, conse- quently, longer. He was of opinion, that the length of the vocal tube had no influence on the tone. Of late years, several new views have been propounded on this subject, and chiefly by Cuvier, Dutrochet, Magendie, Biot, Savart, &c.—men of the highest eminence in various departments of physi- cal science. Cuvier* attributes the variety of tones, in the first place, to the varied length of the vocal tube, and to differences in the size of the aperture of the glottis; and, secondly, to the shape and condition of the external aperture of the tube—that is, of the lips and nose. The larynx he regards as a wind instrument, in which the inferior liga- ments act, not as cords, but like the reed of a clarionet, or the lame of an organ pipe. The lungs and their external muscular apparatus constitute the reservoir of air and the bellows; the trachea conducts this air, and the glottis is the embouchure with its reed; the mouth and the whole of the space, comprised between the glottis and the opening of the lips, being the body of the instrument; whilst the openings of the nostrils are lateral holes, which permit the size of the instrument to be varied. The tones are changed by three causes, of a similar character to those that modify them in musical instruments;—the length of the body of the instrument, the variable- ness of the embouchure, and of the aperture at the lower extremity of the instrument. The condition of the external aperture of the vocal tube has, doubtless, much to do with the character of the tone produced by the glottis; but its influence appears to be greatly limited to giving it rotundity, volume, or the contrary, as will be seen hereafter; although analogy would seem to show, that the tone may be varied by more or less closure of the aperture. Many different notes can be produced in the first joint of a flute, if we modify the size of the opening at its extremity by passing the thumb more or less within it. It is doubtful, however, whether in man the altered size of the external aperture or the elongation or decurtation of the tube exerts as much influence on the production of acute or grave sounds as Cuvier imagines. Dutrochet,f again, believes, that the vocal tube has no influence in the production of tones, and that the larynx is a simple vibrating instrument, uncomplicated with a tube, the vocal sound being caused by the vibrations into which the vocal cords are thrown, by the im- pulse of the expired air. In his experiments, he saw the inferior * Lemons d'Anatomie Compared, torn. iv. 445. t Mem. pour servir a l'histoire anat. et physiol. des vegetaux et des animaux, T. ii. Paris, 1837; and Adelon, 6dit. cit. ii. 239. 406 MUSCULAR MOTION. ligaments vibrate; and he concludes, that the tone of the voice depends upon the number of vibrations of these ligaments in a given time, and that the number will necessarily vary considerably, as the dimensions of the ligaments,—that is, their length, and thickness,— and their elasticity are susceptible of incessant changes, by the con- traction of the thyro-arytenoid muscle of which they are essentially composed,—the ligament, covering the muscle, serving only " to prevent the collisions of the muscles at the time of vibration,"—as well as by that of the other intrinsic muscles of the larynx. MM. Biot and Magendie* dissent from Dutrochet in some impor- tant points. Like him, they do not consider the human larynx to constitute a stringed instrument. They regard it as a variety of reed instrument, but they consider the vocal tube to be of moment in the production of the voice. The objections they urge, against the view of its resembling a stringed instrument, are,—not only the kind of articulation between the arytenoid and cricoid cartilages, which admits of motion inwards and outwards only; but they ask how the vocal cords can retain the length they would require for the production of grave tones; and how these cords could elicit sounds of a volume so considerable as those of the human voice. They esteem it, consequently, as a reed instrument—of such nature as to be capable of affording very grave tones with a pipe of little length ; and such that the same tube, almost without varying its length, is susceptible, not only of furnishing a certain series of sounds in har- monic progression, but all the imaginable sounds and shades of sounds, in the compass of the musical scale which each voice embraces. The theory of the reed instrument MM. Biot and Magendie apply to the human vocal apparatus. The lips of the glottis are the reed and the thyro-arytenoid muscles render them fit for vibrating. In his experiments, made on living dogs, Magendie saw, that when grave sounds were produced, the ligaments of the glottis vibrated in their whole extent, and the expired air issued through the whole of the glottis. In acute sound, on the other hand, they vibrated only at their posterior part, and the air passed out through the part only that vibrated, the aperture being, consequently, diminished; and, when the sounds became very acute, the ligaments vibrated only at their arytenoid extremity, and scarcely any air issued; so that tones beyond a certain degree of acuteness, cannot be pro- duced in consequence of the complete closure of the glottis. The arytenoid muscle, whose chief use is to close the glottis by its pos- terior extremity, he conceives to be the principal agent in the pro- duction of acute sounds, and this idea was confirmed by the section of the two laryngeal nerves, that give motion to this muscle, which was followed by the loss of the power of producing almost all the acute tones; the voice, at the same time, acquiring a degree of habitual graveness, which it did not previously possess. The influence of contraction of the thyro-arytenoid muscles on the tones, he properly • Precis, &c. i. 248. VOICE.—TONE. 407 considers, is exerted in increasing or diminishing the elasticity of the ligaments, and, thus, in modifying the rapidity of the vibrations, so as to favour the production of acute or grave tones. He thinks, too, that the contraction of these muscles concurs greatly in closing, in part, the glottis, particularly its anterior half; although the course of its fibres, it appears to us, ought rather to widen the aperture. The trachea or porte-vent has usually been thought to exert no influence on the nature of the sound produced. It has been con- ceived, however, by Grenie and others, that its elongation or decur- tation may occasion some modification. Thus much for the reed:—MM. Biot and Magendie, however, include, in their theory of the voice, the action of the vocal tube, likewise. This tube, being capable of elongation and decurtation, of being dilated or contracted, and susceptible of assuming an infi- nite number of shapes, they think it well adapted for fulfilling the functions of the body of a reed instrument,—that is, if placed in har- monic relation with the larynx,—and thus of favouring the produc- tion of the numerous tones of which the voice is capable; of aug- menting the intensity of the vocal sound by assuming a conical shape with a wide external aperture; of giving rotundity and sweetness by the proper arrangement of its external outlet, or of entirely subduing it, by the closure of the outlet. The larynx rises in the production of acute sounds; and falls in that of grave. The vocal tube is, con- sequently, shortened in the former case; elongated in the latter. It experiences also a simultaneous change in its width. When the larynx descends,—in other words, when the vocal tube is elongated, the thyroid cartilage is depressed and separated from the os hyoides by the whole height of the thyro-hyoid membrane. By this separa- tion, the epiglottic gland is carried forwards, and lodged in the con- cavity at the posterior surface of the os hyoides. The gland drags after it the epiglottis; and a considerable enlargement in width occurs at the inferior part of the vocal tube. The opposite effect results, when the larynx rises. The use of the ventricles of the larynx, Magendie* considers to be, to isolate the inferior ligaments, so that they may vibrate freely in the air. Lastly, in this theory the epi- glottis has a use assigned to it which is novel. In certain experi- ments, instituted by Grenie^ for the improvement of reed instru- ments—being desirous of increasing the intensity of sound without changing the reed in any respect, he found, that to succeed in it he was compelled to augment gradually the strength of the current of air; but this augmentation, by rendering the sounds stronger, made them rise. To remedy this inconvenience, Grenie found no means answer, except that of placing obliquely in the tube, immediately below the reed, a supple, elastic tongue, nearly as we see the epi- glottis above the glottis. From this, Magendie| infers, that the epiglottis may assist in giving to man the faculty of increasing or * PrCcis, &c. i. 252; and Sir C. Bell, Philos. Transact, for 1832; and Nervous Sys- tem, 3d edit. p. 484. Lond. 1837. t Biot's Precis Elementaire de Physique, p. 399. X Ibid. i. 252. 408 MUSCULAR MOTION. inflating the vocal sound, without its mounting; but, as Mr. Bishop* properly remarks, neither the elevation nor depression of the epi- glottis can affect or regulate the vibrations of the glottis. Such are the main propositions of the theory of the voice by Biot, and Magendie. The larynx represents a reed with a double tongue; the tones of which are acute, in proportion to the decurtation of the laminae; and grave in proportion to their length. They admit, how- ever, that, although the analogy between the organ of voice and the reed is just, the identity is not complete. The ordinary reeds are composed of rectangular laminae; fixed at one side, but loose on the three others; whilst, in the larynx, the vibrating laminae, which are likewise nearly rectangular, are fixed by three sides and free by one only. Moreover, the tones of the ordinary reed can be made to rise or to descend by varying its length, whilst in the laminae of the larynx the width varies. Lastly, say they, in musical instruments reeds are never employed, whose movable laminae can vary in thickness and elasticity every moment, as is the case with the liga- ments of the glottis; so that, although we may conceive that the larynx can produce the voice and vary its tones, in the manner of a reed instrument, we are unable to demonstrate the particulars of its mode of action. All the more modern theories—which we have detailed at more or less length—agree, then, in considering the larynx to be a wind instrument and of the reed kind: they differ, chiefly, in the part which they assign to the vocal tube in causing the variation of tones. M. Savartf has propounded a theory of the human voice, in which he differs from Cuvier, Dutrochet and Magendie;—denying, that the mechanism of the voice resembles that of the reed instrument, and returning to the old idea, which referred the vocal organs to an instrument of the flute kind. The sounds of the human voice have, he remarks, a peculiar character, which no musical instrument can imitate; and this must necessarily be the case, as they are produced by a mechanism founded on principles, which do not serve as a basis for any of our instruments. He conceives, that the production of the voice is analogous to that of the sound in the tube of a flute, and that the small column of air, contained in the larynx and mouth, by the nature of the elastic parietes which bound them, as well as by the mode in which it is thrown into vibrations, is susceptible of ren- dering sounds of a particular nature, and at the same time, of a much more grave character than the dimensions would seem to admit. In the tube of a flute the column of air, within, is the sonorous body. A sound is first produced at the embouchure of the instrument, by the division, which the air experiences when blown into it; and this sound excites similar sonorous undulations in the column of air, * London and Edinburgh Philosophical Magazine, p. 205, for Sept. 1836. t Magendie's Journal de Physiologie, v. 367, Paris, 1825; Annales de Physique et de Chimie, xxx. 64; and xxxii. kVOICE.—TONE. 409 ?1iii)iiii.iiiiii uniiuiiiiii which fills the tube. The sound, resulting in this way, is more grave in proportion to the length of the tube; and it is in order to vary its tones, that the instrument has apertures in its sides, by means of which the length may be modified. In assimilating the human vocal apparatus to a flute, the great difficulty has been to explain how, with so short a tube as the vocal tube in man, and one so little variable in length, tones so different, and especially so grave, can be produced. To explain this, Savart establishes the existence of a number of physical facts, previously unknown or unnoticed. In organ pipes of great length the velocity of the current of air, which acts as a motor, has but little influence on the number of oscil- lations. When the length of the pipe is, for instance, twelve or fifteen times greater than its diameter, it is difficult to vary the sound a semitone. When the air is forcibly driven in, it rises an octave; and, when the velocity is diminished, the sound merely becomes more feeble; but is depressed an almost imperceptible quantity. In short pipes, on the contrary, the influence of the velocity of the current of air is much greater, and several tones can be elicited. The bird-call, used by sportsmen, is illustrative of this principle. It is a small instrument, employed for imitating the notes p. 8«. of certain birds; consisting of a cylindrical tube, about three-fourths of an inch in diameter, and a third of an inch high; closed at each end by a thin, flat plate, which is pierced, at its centre, by a hole about the sixth of an inch in diameter. Sometimes, it has the shape re- presented in the lower of the marginal figures. By placing this instrument between the teeth and lips, and forcing „. air, with more or less strength, through the two apertures, different sounds can be produced. This is more certainly effected, by attaching a porte- vent to the whistle, as A A, Fig. 88, when it is capable of producing all the sounds comprised in an extent of from an octave and a half to two octaves. M. Savart found, that, other things -A- being equal, the diameter of the apertures has an appreciable influence on the acuteness or grave- ness of the sounds, which are more grave when the orifices are larger. The nature of the pa- rietes of the instrument appeared, also, to exert some effect on the number of oscillations, and on the quality of the sounds; and if, in the hemispherical whistle, Fig. 88, the plain plate was replaced by a thin leaf of some extensible substance, as parchment, the sounds issued more rapidly, and were usually more grave, full, and agree- able, than when they were formed of a more solid substance. It is an opinion, generally admitted, that the material, which com- poses an organ pipe, has no influence on the number of vibrations, which the column of air, contained in it, is capable of executing. This is true as regards long pipes; but, according to Savart, it is vol. i. 35 iA 410 MUSCULAR MOTION. not so with the short, and the nature of the biseau* he conceives, may have a great influence, even on the sound of long pipes. For instance, if we substitute, for the stiff lamina, which forms the biseau of an organ pipe two feet long and two inches on the side, a lamina, formed of some elastic substance, as skin or parchment, and so arranged as to admit of being stretched at pleasure,—by gradually increasing the tension of the membrane, at the same time that we increase the velocity of the current of air, the tone may be made to vary a fourth, and even a fifth. In still shorter tubes, the much greater influence of the velocity of the current of air being united to that of the tension of the biseau, the result is still more evident. Thus, the sound of a cubical tube may easily be lowered an octave, when the parietes of the biseau are susceptible of different degrees of tension; but when all the parietes, which compose a short pipe, are of a nature to enter into vibration along with the air they con- tain, and when their degree of tension can be, moreover, varied, they have such an influence on the number of vibrations, that the sound may be greatly modified. Short tubes, open at both extremities, and formed of elastic parietes, are also susceptible of producing a great number of sounds, even when they are only partly mem- branous, and the quality of the sound of membranous tubes is said to be somewhat peculiar; partaking of that of the flute, and of the free reed. Again, in order that a mass of air shall enter into vibration, a sound must be produced in some part of it. In an organ pipe, for example, a sound is first excited at the embouchure, and this throws the column of air, within the instrument, into vibration. Every sound, indeed, produced at the orifice of a column of air, throws it into vibration, provided its dimensions are adapted to the length of the waves produced directly;—hence, the utility of a musical pipe having parietes susceptible of varying in dimension and in tension, whatever may be the character of its embouchure. Lastly.—The fundamental note of a tube, closed at one end, and whose diameter is every where the same, is an octave lower than the sound of the same tube, when open at both extremities. But this is not the case with tubes that are of unequal diameter, conical, pyramidal, &c, when made to vibrate at their narrowest part. The tone, produced in such case, will increase in graveness, according to the difference between its narrow and expanded portions. These different physical conditions Savart invokes to account for the different tone of the human voice,—under the theory, that the vocal organ—composed of the larynx, pharynx, and mouth—forms a conical tube, in which the air is set in vibration by a movement similar to that which prevails in organ pipes. The trachea is ter- minated above by a cleft—the glottis—which is the inferior aperture of the vocal instrument. This cleft, which is capable of being ren- dered more or less narrow, plays the same part as the lumiere des tuyaux a bouche, or the narrow space in the organ pipe, at the edge * The biseau or languette is the diaphragm, placed between the body of an organ pipe and its foot. VOICE.-TONE. 4U of the biseau or languette, along which the air passes. The air clears it, traverses the ventricles of the larynx, or the cavity of the instrument, and strikes the superior ligaments. These surround the upper aperture of the instrument, and fulfil the same function as the biseau of the organ pipe. The air, contained if) the interior of the larynx, now vibrates, and sound is produced. This sound acquires intensity, because the waves, that constitute it, are extended into the vocal tube situated above the larynx, and excite, in the column of air filling it, a movement similar to that occasioned in the tube of a flute; except, that the tone can be much varied, because the larynx, being a short tube, can give rise to various tones by simple modifi- cation in the velocity of the air sent through it; and, moreover, the vocal tube has the same power, its parietes being membranous, of a vibratory nature, and capable of different degrees of tension. The inferior or outer part of the vocal tube is equally constituted of elastic parietes, susceptible of varied tension; and the mouth, by modifying the dimensions of the column of air within the vocal tube, exerts an influence on the number of vibrations which the column is capable of experiencing; whilst the lips can convert the channel at pleasure into an open or closed conical tube. Certain sounds, Sa- vart affirms, are produced altogether in the ventricles of the larynx —those of pain and the falsetto voice, for example. They can be elicited, even when the vocal tube has been removed; and there are animals, in which the vocal organ is reduced to the ventricles of the larynx—frogs for instance. Savart, consequently, considers, that the human vocal organ has, in its essential parts, C C, B B, Fig. 86, a striking analogy to the action of the bird-call; and, in this way, he explains the use of the superior ligaments C C, which are en- tirely overlooked in the different theories of the voice previously propounded. We have given Savart's view at some length, in consequence of its ingenuity, and of its seeming to explain as well as any other theory the varied tones of which the human voice is susceptible. It cannot, however, be esteemed established, inasmuch as it is diametrically opposed, in many of its points, to the observations and vivisections of distinguished physiologists; who, it has been seen, affirm, that voice is produced solely by the inferior ligaments; that all the parts above these may be destroyed, and yet voice may continue; and that a wound in the ventricles, which permits the exit of air through the parietes of the larynx, does not destroy the function. Our notions on this point must not, therefore, be con- sidered definite. Farther experiments are necessary; and, in all deductions from them, great importance will have to be attached to the vital action of the organs, especially of the intrinsic muscles, which are capable of modifying the situation of parts, and the cha- racter of the function, in myriads of inappreciable ways.* * See, on the whole subject of the "Mechanism of Phonation," Adelon's Physiolo- gie de PHomme, 2de. edit. ii. 224. Paris, 1829 ; and Richerand's Elemens de Phy- siologic, 13eme, edit, par M Berard aine, p. 294, edit. Beige. Bruxelles, 1837; and Sir C. Bell, Philos. Transact, for 1832, and Nervous System, 3d edit. p. 479. Lond, 1837. 412 MUSCULAR MOTION: 3. Timbre, or Quality of the Voice. In the preliminary essay on sound, attached to the physiology of audition, it was remarked, that the cause of the different timbres of sound, in the various musical instruments, had hitherto remained unexplained. The same remark is applicable to the timbre of the voice. Each individual has his own, by which he is distinguished from those around him; and it is the same with each sex and period of life. In this, the larynx is, doubtless, concerned; but in what manner is not clear. The feminine timbre or stamp, which charac- terizes the voice of the child and of the eunuch, would appear to be generally connected with the cartilaginous condition of the larynx; whilst the masculine voice, which is sometimes met with in the female, is connected with the osseous condition of these parts, and especially of the thyroid cartilage. An infinity of modifications may also be produced by changes in the thickness, elasticity, and size of the lips of the glottis. The vocal tube probably exerts great influence in this respect, by its shape as well as by the nature of the material composing it. Such conditions, at least, appear to modify the timbre of our wind instruments. The timbre of a flute, made of glass or brass, is very different from that of one formed of wood, although the instruments may resemble each other in every other respect. The form of the body of the instrument has, also, considerable effect. If it be conical, and wider towards its outlet, as in the cla- rionet, or hautboy, the quality of the sound is shrill. If it be entirely cylindrical, as in the flute, we have the soft quality, which charac- terizes that instrument; and on the other hand, if the tube be ex- panded at its middle portion, the quality of the sound is raucous and dull. It is probable, therefore, that we must reckon, amongst the elements of the varying character of the timbre or stamp of the voice, the different conditions of the vocal tube, as to length, width, and form ; and that we must likewise include the position and shape of the tongue, of the velum palati, and of the mouth and nose, the presence or want of teeth, &c. all of which circumstances modify the voice considerably. The first modification takes place, probably, in the ventricles of the larynx, in which the voice requires more rotundity and expansion. By the generality of physiologists, it is conceived, that the voice enters the different nasal fossae, and, by resounding in them, a timbre or character is given to it, which it would not otherwise possess. According to this belief, when the voice is prevented from passing through the nose, from any cause, it acquires the nasal twang; or, by a singular inaccuracy of language, we are said " to talk through the nose." Magendie,* however, considers, that, whenever the sound passes through the nasal fossae, the voice becomes disagree- able and nasal. Simple experiment, by holding the nose, exhibits, * Precis elementaire, I. 254. VOICE.—TIMBRE. 413 that, in the enunciation of the true vocal sound, unmodified by the action of the organs of articulation, the timbre or quality is materially altered; and we shall see, hereafter, that there are cer- tain letters, which do not admit of enunciation, unless the nasal fossae be pervious—the m and the n, and the ng, for example. It would seem that, under ordinary circumstances, the sound, after it is produced in the larynx, flows out by both channels; and that, if we either shut off the passage through the nose altogether, or attempt to pass the sound more than usually through the nasal fossae, the voice becomes nasal. The fine, sharp voice prior to puberty is especially owing to the narrowness of the glottis, to the shortness of the ligaments, and, ac- cording to Malgaigne,* to want of developement of the nasal cavities. At puberty the size of the opening of the larynx is doubled: the ligaments enlarge, and the passages of the nose are augmented. The timbre now becomes raucous, dull and coarse, and for a time its harmony is lost. M. Bennati,f himself an excellent theoretical and practical musician, whose voice marks three octaves, advises, that the voice should not be much exerted during this revolution. He has known perseverance in singing at this time completely destroy the voice in several instances. Not only does the voice, when produced in the larynx, pass out by the vocal tube, but it resounds along the tracheal and bronchial tubes, giving rise to the resonance or thrill, which is audible in certain parts of the chest more especially, when the ear or the stethoscope is placed over them; and, when cavities exist in the lungs, in per- sons labouring under pulmonary consumption, if the ear be placed upon the chest, immediately over one of those cavities, the voice will appear to come directly up to the ear. The same thing hap- pens, if the stethoscope be used. In this case, the voice will appear to pass directly through the tube to the ear, when the extremity of the instrument is applied over the vomica, so as to give rise to what Laennec terms pectoriloquy. AdelonJ conceives, that this distribu- tion of the sound, along the trachea or porte-vent and the lungs, may induce a belief, that the condition of these organs has some effect on the timbre of the voice. In speaking of the timbre of the voice in different individuals, we have had in view the natural quality, not that which is the result of imitative action, and which can be maintained for a time only. Many of the conditions, which have been described, as regulating the timbre, are voluntary, especially that of the shape of the vocal tube. In this way, we can modify the timbre and imitate voices very different from our own. The table d'hote of many of the * Archives generates de Medecine, p. 201 and 214, Fevrier, 1831. t Recherches sur le Mecanisme de la voix Humaine. Paris, 1832. I Physiologie de I'Homme, edit. cit. ii. 204. 35* 414 MUSCULAR MOTION. hotels of continental Europe is enlivened by the presence of indivi- duals, capable of not only imitating various kinds of birds, but the timbres of different musical instruments; and the success which has attended the personation of the different voices of public speakers, by Matthews, Yates, and others, is sufficient evidence of the fidelity of their representatiqns. We see the difference between the natural and imitative voice strongly exemplified in one of the feathered songsters of our forests, the turdus polyglottis or mocking bird, which is capable of imitating, not only the voices of other birds, but sounds of other character, which cannot be regarded in the light of accomplishments. There is a singular variety of the imitative voice, now employed only for purposes of amusement—but, of old, perhaps, used in the Pagan temples, by the priests, to infuse confidence in the oracular dicta of the gods*—which requires some notice; it is engastrimism or ventriloquism. Both these terms, by their derivation, indicate the views,, at one time entertained, of its physiology, namely, that the voice of the ventriloquist is made to resound in the abdomen, in some inexplicable manner, so as to give rise to the peculiarity it exhibits. This singular view seems to have been once embraced by M. Ri- cherand.f .", At first," says he, " I had conjectured, that a great par,t of- the air expelled by expiration did not pass out by the mouth and nostrils, but was swallowed and carried into the stomach; and, being reflected in some part of the digestive canal, gave rise to a real echo"; but, having afterwards more attentively observed this curious phenomenon on Mr. Fitzjames, who exhibits it in its greatest perfection, I was soon convinced, that the name of ventriloquism is by no means applicable."—M. Richerand was probably the last remnant of the ancient vague hypothesis, and his views soon under- went a conversion. Another, equally unfounded notion, at one time entertained, was, that the ventriloquist possesses a double or triple larynx. It is now universally admitted, that the voice is produced at the ordinary place, and that it is modified in its intensity and quality by actions of the larynx and of the vocal tube, so as to give rise to the deceptions we experience. It is 'known, that our appreciation of the distance and nature of a sonorous .body is formed from the intensity and quality of the sound proceeding from it. We instinctively believe, that a loud sound proceeds from a near object, and a feeble sound from one more re- mote; accordingly, if the intensity and quality of the sound, from a known body, be such as to impress us with the idea, that it is more » Purkinje, Art. Bauchreden, in Encyclopad. Worterb. der Medicinisch.Wissenschaft. v. 97. Berlin, 1830—Pierer, Art. Bauchredner, und Bauchsprecher, in Anat. Phys. Real. Worterb., I. 667. Leipz. und Allenb. 1816; and Rullier, Art. Engastrimysme, in Diet, de Medecine, leme edit. viii. 105. Paris, 1823. t Elemens de Physiologie, edit. 13eme, par M. Berard aine, edit, Beige, exciv. p. 300 Bruxelles, 1837. VOICE.—VENTRILOaUISM. 415 remote than it really is, we incur an acoustic illusion. The ventri- loquist takes advantage of this source of illusion; and, by skilfully regulating the force and timbre of his voice, irresistibly leads us into error. Mr. Dugald Stewart* gives some striking examples of this kind of illusion. He mentions having seen a person, who, by counterfeiting the actions of a performer on the violin, whilst he imitated the music by his voice, riveted the eyes of the audience on the instrument, although every sound they heard proceeded from his own mouth. Mr. Savile Carey, who imitated the whistling of the wind through a narrow chink, told Mr. Stewart, that he had fre- quently practised the deception in the corner of a coffee-house, and that he seldom failed to see some of the company rise to examine the tightness of the windows, whilst others, more intent on the news- papers, contented themselves with putting on their hats, and button- ing their coats.f It is to account for the mode in which this is effected, that dif- ferent hypotheses have been, from time to time, entertained. Haller, Nollet, Mayer,J and others, believed, that the voice is formed during inspiration; but this does not seem to be the case. Voice can cer- tainly be effected during inspiration; but it is raucous, unequal, and of trifling extent only. Dumas and Lauth§ consider ventriloquism to be a kind of rumination of sounds; the voice, formed in the larynx, being sent into the interior of the chest, attaining there a peculiar timbre, and issuing of a dull character. Richerand is of opinion, that the whole mechanism consists in a slow, gradual expira- tion, which is always preceded by a deep inspiration. By means of this, the ventriloquist introduces into his lungs a considerable quan- tity of air, the exit of which he carefully regulates. Mr. Gough|| attempts to explain the phenomenon upon the prin- ciple of echoes;—the ventriloquist, he conceives, selecting a room, well disposed for echoes in various parts of it, and producing false voices, by directing his natural voice in a straight line towards such echoing parts, instead of in a straight line towards the audience, who are supposed, by Mr. Gough, to be placed designedly by the ventriloquist on one or both sides of him. A sufficient answer to this is, that the practised ventriloquist is careless about the room chosen for his exhibitions; and that he habitually performs in rooms, where this system of echoes would be totally impracticable. But let us'see what the ventriloquists themselves have said of the mechanism of their art. We pass over the explanation of Baron von Mengen, an Austrian colonel, who forms a kind of vocal organ between his tongue and * Elements of the Philosophy of the Human Mind, 3d edit. Lond. 1808. Amer. edit. Brattleborough, (Vermont) 1813. t Brewster, Natural Magic. Amer. edit., p. 158. New York, 1832. , X Haller, Element. Physiol., torn, ix.; and Lepelletier, Physiologie Medicale, &c, iv. 213. Paris, 1833. § Memoir, de la Societe des Sciences Agricol. de Strasbourg, I. 4^7. U Manchester Memoirs, 2d edit. v. 622. Lond. 1789. 416 MUSCULAR MOTION. his left cheek, if we understand his description correctly, and keeps a reservoir of air in his throat to throw the organ into vibration. His object must evidently have been to mislead. In 1811, M. L'Espagnol, a young physician, maintained a thesis on this subject before the Faculte de Medecine of Paris, which may be regarded, as at least, an honest exposition of his belief, regarding the mode in which the phenomenon was effected in his own person. According to him, the whole is dependent upon the action of the velum pendulum palati. In the ordinary voice, he remarks, a part of the sound passes directly through the mouth, whilst another re- sounds in the nasal fossae. If we are near the person who is speak- ing, these two sounds strike equally and almost synchronously upon the ear; but if we are at a distance, we hear only the first of the two sounds, when the voice appears more feeble, and, especially, has another timbre, which experience makes us judge to be that of the voice at a distance. The difference, says L'Espagnol, between the voice that proceeds from a near, and that from a more distant object is, that in the former we hear the mixture of the two sounds; whilst in the latter we hear that sound only, which issues directly from the mouth. Now, the secret of the ventriloquist is, to permit this direct sound only to pass to the ear, to prevent the nasal sound from being produced, or at least from being heard; and this is done by the elevation of the velum pendulum palati; the vocal sound does not then resound in the nasal fossae; the direct sound is alone produced; the voice has the feebleness and timbre that belong to the distant voice, and is judged to proceed from a distance; and if, during the performance, the voice seems to come from any determinate place, it is owing to the ventriloquist attracting attention to it; the voice itself need only appear to proceed from a distance; and this it does more or less, according as the pendulous veil has more or less completely prevented the vocal sound from issuing by the nasal fossae. The ventriloquist, thus, according to M. L'Espagnol, makes the voice nearer or more remote at pleasure, by raising or depressing the velum palati. He denies that he speaks with his mouth closed; and affirms, that he articulates, but to a trifling extent only. M. Comte, another ventriloquist, and of some celebrity, who has endeavoured to explain the physiology of his art, affirms, that the voice takes place as usual in the larynx; but that it is modified by the action of other parts of the apparatus; inspiration directing it into the thorax, where it resounds; and that both strength and flexibility are required in the organ to produce this effect. This, however, is no explanation. It is now universally admitted, that the voice of the ventriloquist is produced in the larynx; and that its character and intensity are modified by the action of other parts of the apparatus, but the particular action 'that produces it is not elucidated by any of these attempted explanations of the ventriloquist. About twenty-five years ago, Dr. John Mason Good,* in some lee- * Book of Nature, ii. p. 261. Lond. 1826; and Study of Medicine, Physiological Proem to Class, ii. VOICE.—VENTRILOaUISM. 417 tures delivered before the Surry Institution of London, suggested that the larynx alone, by long and dexterous practice, and, perhaps, by a peculiar modification in some of its muscles or cartilages, may be capable of answering the purpose, and of supplying the place, of the associate organs of the mouth. In confirmation of this view, he remarks, that, in singing, the glottis is the only organ made use of, except where the notes are articulated ; and it is apparently the sole organ employed in the mock articulations of the parrot and other imitative birds; some of which have exhibited unusual powers. A parrot, belonging to a Colonel O'Kelly, could repeat twenty of the most popular English songs, and sing them to their proper tunes.* The larynx, too, is the sole organ of all the natural cries; and hence, it has been imagined, by Lord Monboddo,f to have been the chief organ of articulate language in its rudest and most barbarous state. " As all natural cries," he observes, " even though modulated by music, are from the throat and larynx, or knot of the throat, with little or no operation of the organs of the mouth, it is natural to suppose, that the first languages were, for the greater part, spoken from the throat; and that what consonants are used to vary the cries, were mostly gutturals; and that the organs of the mouth would at first be but very little employed." Certain it is, that privation of the tongue does not necessarily induce incapacity of articulation; whether the defect be congenital, or caused after speech has been ac- quired. Professor John Thomson found the speech but little impaired after bullets had carried away more or less of the tongue.J Under the sense of taste, several authentic cases were stated of individuals, who were deprived of this organ, who yet possessed the faculty of speech. To these we may add one other, which excited unusual interest at the time, and was examined under circumstances that could admit of no deception. The case forms the subject of various papers, by Dr. Parsons.§ A young woman, of the name of Margaret Cutting, of Wickham market, near Ipswich, in Suffolk, when only four years old, lost the whole of her tongue, together with the uvula, from a cancerous affection; but still retained the powers of speech, taste, and degluti- tion, without any imperfection; articulating as fluently and correctly as other persons; and even those syllables that commonly require the aid of the tip of the tongue for accurate enunciation. She also sang admirably; articulating her words whilst singing; and could form no conception of the use of a tongue in other people. Her teeth were few, and rose scarcely higher than the surface of the gums, owing to the injury to the sockets from the disease that had destroyed the tongue. The case, when first laid before the Royal Society, was attested by the minister of the parish; by a medical * Good's Book of Nature, ii. 248. t Origin and Progress of Language. Lond. 1774—1792. X Report of Observations made in the British Hospital, in Belgium, after the Battle of Waterloo. Edinb. 1816. § Philosoph. Transact, for 1742 and 1747. 418 MUSCULAR MOTION. practitioner of repute, and by another respectable individual. The society, however, were not satisfied, and they appointed commis- sioners to inquire into the case, whose report coincided minutely with the first; and, to set the matter completely at rest, the young woman was shortly afterwards conveyed to London, and examined, in person, before the Royal Society.* These cases are not so extraordinary as they appear to be at first sight; when we consider, that the tongue is not the sole organ of articulation, but that it shares the functions with the various parts that compose the vocal tube. In reality, of the twenty-four articu- late sounds, which our common alphabet comprises, there are but few in which the tongue takes a distinct lead, as the /, d, t, r, &c, though it is auxiliary to several others; but the guttural or palatine, g, h, k, q; the nasal, as m, and n ; the labial, as b, p,f v; and most of the dental, together with all the vowels, are but little indebted to its assistance. From these, and other concurrent facts, Dr. Goodf concludes, that ventriloquism appears to be an imitative art, founded on a close attention to the almost infinite variety of tones, articulations, and inflexions, which the glottis is capable of producing in its own region alone, when long and dexterously practised upon; and in a skilful modification of these vocal sounds, thus limited to the glottis, into mimic speech, passed, for the most part, and whenever necessary, through the cavity of the nostrils, instead of through the mouth. It is possible, he adds, though no opportunity has hitherto occurred of proving the fact by dissection, that those who learn this art with facility, and carry it to perfection, possess some peculiarity in the structure of the glottis, and particularly in respect to its muscles or cartilages. Magendie,J and Rullier,§ however, affirm, that the quiescence of the lips, observed in the practised ventriloquist when enunciating, is more apparent than real; and that, if he is capa- ble of pronouncing without moving his lips, it is because he is careful to make use of words in which there are no labial consonants, or which do not absolutely require the movement of the lips in their formation. Rullier, indeed, denies positively, that the ventriloquist can speak without opening his mouth and moving his lips; but he affirms, that he uses his jaws, mouth and lips, as little as possible in articulation; and he ascribes the common belief in their perfect quiescence to the habit, acquired by the ventriloquist, of restraining their movements, united to the care he takes in concealing them; and of giving to his face an impassive expression; or one very foreign to the verbal expression to which he is giving utterance. On the whole, the explanation of Dr. Good appears most satisfac- tory:—the larynx or glottis affording to some individuals a facility in acquiring the art, which others do not possess, in the same man- * Elliotson's Human Physiology, p. 507. fOp. citat. ii. 259. t Precis, I. 265. § Art. Engastrimysme, in Diet, de Medecine, torn. viii. Paris, 1823. VOICE.—NATURAL LANGUAGE. 419 ner as it makes some capable of singing, whilst others are ever inca- pacitated. It is probable, however, that there may be a greater degree of obscure action about the parts composing the vocal tube, than Dr. Good is disposed to admit; and that this maybe materially concerned in giving the voice its peculiar quality and intensity: and in eliciting some of the sounds which might not be so easily produced by the action of the glottis alone. Sir David Brewster* observes that when the ventriloquist utters sounds from the larynx without moving the muscles of his face, he gives them strength by a power- ful action of the abdominal muscles: and Bennati affirms that the ventriloquist uses chiefly the pharyngeal voice, of which mention will be made under the head of Singing. Such is the history of the simple voice, as effected in the larynx. Articulate sounds may, however, be produced in the vocal tube alone. Whistling, for example, is caused by the expired air being broken or divided by the lips; which act the part of the lips of the larynx in the production of voice. Whispering consists in the articulation of the air of expiration. It is wholly accomplished in the vocal tube; and, hence, the im- practicability of singing in a whisper ; singing being produced in the glottis. The sound of sighing is produced by the rushing of the air along the air passages, and especially along the vocal tube. In laughing, crying, and yawning, the voice is likewise concerned; but the phy- siology of these functions of expression will fall more appropriately under the head of respiration. Having described the different views, that have been entertained, with regard to the production of voice, we shall now inquire into the function in connexion with expression. In this respect it admits of division into the natural or inarticulate voice, and into the artifi- cial or articulate. 4. Of Natural or Inarticulate Language. This, which is sometimes termed the cry or native voice, is an inappreciable sound, entirely produced in the larynx, requiring few or none of the organs of articulation to aid in its formation. As, however, it is caused by different degrees of contraction of the intrinsic muscles of the larynx, it is susceptible of a thousand differ- ent tones. It is elicited independently of all experience or education; seems to be inseparably allied to organization; and, consequently, occurs in the new-born infant, in the idiot, in the deaf from birth, and in the wild man, if any such there be, as well as in the civilized individual. The natural voice differs as much as the sentiments it is employed to express. Each moral affection has its appropriate cry;—the cry * Letters on Natural Magic, p. 169, Amer. edit. New York, 1832. 420 MUSCULAR MOTION. of joy is very distinct from that of grief;—of surprise from that of fear, &c.; and the pathologist finds, in the diseases of children more especially, that he can occasionally judge of the seat of a disease by the character of the cry, to which the little sufferer gives utter- ance ; in other words, that there is, in the language of Broussais, a cry peculiar to the suffering organ. By the cry, our vivid sensations are expressed, whether they are of the external or internal kind; or are agreeable or painful; and, by it we exhibit all our natural passions, and most simple instinctive desires. Generally, the most intense sounds to which the organ of voice can give utterance, are embraced in the natural cry: and, in its character, there is frequently something, which annoys the ear and produces more or less effect on those within its sphere. It is, indeed, by its agency, that sympathetic relations are established between man and his fellows; and between animals of the same kind. The language, possessed by the greater part of animals, is, as we have already remarked, this natural voice, differing according to varying organization, and, therefore, instinctive; hence the various notes of birds; and the different ranges, which we find the voice to possess in the different species. Yet each species has one, by which it is distinguished, and which it possesses, even when brought up in the same cage with one of another species; or hatched, and at- tended to, by a foster mother, endowed with very different vocal powers. In the case of a goldfinch and chaffinch, this has heen put directly to the proof; and it is well known, that the cuckoo, which is never hatched or nurtured by its own parent, still retains the note, which has acquired it its name in almost every language of the globe. It is, probably, by this natural cry, and not from any signs addressed to the eye, that the process of pairing is effected and that the female is induced to select her mate. The vocabulary of the common cock and hen is quoted as per- haps the most extensive of that of any tribe of birds, with which we are acquainted: or rather, as Dr. Good remarks,* we are better acquainted with the extent of its range than with that of any other. The cock has his watch-word for announcing the morning; his love-speech and his terms of defiance. The voice of the hen, when leaving her nest, after laying, is far different from that which she assumes, when the brood is hatched, and both are very different from her cries, when her young are placed in jeopardy. Even the chick exhibits a variety in its voice, according to the precise emo. tion it experiences. All these sounds are such as the larynx of the animal permits alone to be produced: and hence we can understand why,, so far, they should be mere modifications of the natural voice; but it is more than probable, that the chick learns the adoption of a particular sound by the parent, to express a particuar emotion, as an affair * Book of Nature, ii. 277. Lond. 1826. VOICE.-ARTICULATE LANGUAGE. 421 of education. It can scarcely, indeed, be conceived, that the cluck- ing of the hen, when she meets with food proper for her offspring, can be understood at first by the chick. But as soon as it traces the connexion between the sound produced and the object of such sound, it comprehends the signification ever afterwards. There are sounds, which, from their discordant and harsh cha- racter, affect most animals perhaps, independently of all experience. The cry of terror or of pain, appears to occasion, sympathetically, disagreeable effects in all that are within its sphere. 5. Artificial or Articulate Language. Speech is, likewise, a vocal sound; but it is articulated, in its pas- sage through the vocal tube; and is always employed to convey ideas, which have been attached to it by the mind. It is a succes- sion of articulate sounds, duly regulated by volition, and having determinate significations attached to them. The faculty of speech has been assigned, by some philosophers, chiefly to the organ of hearing. It is manifest, however, that this, like the musical ear, is referable to a higher organ. The brain must attach an idea to the impression, made upon it by the sound that impinges upon the organ of hearing; the sound, thus, becomes the sign of such idea, and is reproduced in the larynx, at the will of the individual. Of the intellectual character of the process, we have the most decisive evidence. The infant, of tender age, has the ear and the voice well developed, yet it is long before he is capable of speech; this does not happen, indeed, until he discovers the meaning of the sounds addressed to him, and finds his own larynx capable of producing similar sounds, which can be made subservient to his wishes. It is thus, by imitation, that he acquires the faculty of speech. Again, the idiot, notwithstanding his hearing may be acute, and his voice strong, is incapable of speech; whilst, in the maniacal and delirious, the language participates in the derangement and irregularity of the ideas. The brain must, therefore, be regarded as the organ of the faculty of language, and the ear, larynx, and vocal tube as its instru- ments. Man, who is endowed with the most commanding intellect, has the vocal apparatus most happily organized for expressing its various combinations; and, according to Gall, if the ourang-outang and other animals are incapable of speech, it is because they have not the intellectual faculty of language. In proof that it is not to the vocal organ that this deficiency must be ascribed, he remarks, that animals may be made to enunciate several of the words of human speech, and to repeat them to music. The case of the far-famed parrot of Colonel O'Kelly has already been referred to. Mr. Her- bert* saw this parrot, about the year 1799: it then sang perfectly about fifty different tunes, solemn psalms, and humorous or low bal- lads, articulating every word as distinctly as a man, without a single * In a note to the Rev. Gilbert White's Natural History of Selborne, p. 227. VOL. I. 36 422 MUSCULAR MOTION. mistake, beating time with its foot, turning round upon its perch, and marking the time as it turned. If a person sang part of a song it would take it up where he left off; and when moulting and unwill- ing to sing, turned its back and said, " Poll's sick." Gall, amongst other cases, cites that of the dog mentioned by Leib- nitz, which could articulate some German and French words. This dog, of which Leibnitz was an "eye-witness," was at Zeitz, in Misnia. A young child had heard it utter some sounds, which he thought resembled German, and this led him to teach it to speak. At the end of about eight years, it had learned thirty words, some of which were, tea, coffee, chocolate, assembly. It spoke only after its master had pronounced the word, and appeared to do so only on compul- sion, although it was not ill used.* In the " Dumfries Journal," Scotland, for January, 1829, mention is made of a dog, then living in that city, which could utter, distinctly, the word " William," the name of the young man to whom it was much attached.f There is no doubt, however, that, in numerous animals, speech would be im- practicable, owing to defective organization, even were they gifted with adequate intellect. It is difficult—perhaps impossible—to say, how man came to select certain sounds as the types of certain intelfectual acts; nor is it a matter, which strictly concerns the physiologist. We may remark, however, that whilst some contend, that speech is a science which was determined upon, and inculcated, at an early period of the world, by one or more superior persons, acting in concert, and inducing those around them to adopt their articulate and arbitrary sounds; others affirm, that it has grown progressively out of the natural language, as the increasing knowledge and increasing wants of mankind have demanded a more extensive vocabulary .J The first view is that of Pythagoras and Plato; but it was opposed by Lucretius, and the Epicureans, on the ground, that it must have been impossible for any one person or synod of persons to invent the most difficult and abstruse of all human sciences, with the pau- city of ideas, and of the means of communicating ihem which they must have possessed; and that even allowing they could have in- vented such a science, it must still have been utterly impossible for them to teach it to the barbarians around them. The opinions of those philosophers, who confine themselves to the phenomena of nature, and hold themselves uncontrolled by other authority, accord with those of the Epicureans. In the origin of language, it is probable, that words were sug- gested to mankind by the sounds, which were heard around them:— by the cries of quadrupeds ;—the notes of the birds of the forest;— the noises emitted by the insect tribe;—the audible indications from the elements, ; Latin, ululare; German, heulen; Dutch, huilen; Spanish, aullar; French, hurler, &c. Hence the word owl. Neighing of the horse.—Latin, hinnire; French, hennir; German, wiehern ; Saxon, hncegan, &c. Clocking, or clucking of hens.—Latin, glocire; French, glousser; Greek, Kaxiceigtiv; German, glucken; Dutch, klokken; Saxon, cloccan, &c. To crow, like a cock.—Greek, Kfct?a>; German, krahen; Dutch, kraayen; Saxon, craw, &.c. whence the word crow, the bird. * Glossarium Germanicum. Lips. 1737. 424 MUSCULAR MOTION. The Latin words tinnimentum, tinnitus, tintinnabulum, &c. from tinnio, I ring, are all from the radical tin; imitating the sound ren- dered on striking a metallic vessel. The gurgling of water, the clanging of arms, the crash of falling ruins, are of the same charac- ter; and the game trictrac, formerly tictac, seems to have been so called, from the noise made in putting down the men or dice. In whatever manner langauage was first formed, it is manifest, that the different sounds could make but a transient impression, until they were reduced to legible characters, which could bring them back to the mind. On our continent, the fact has often been noticed of a tribe of Indians, separating themselves into two parties, and re- maining distinct for years. In such case, the language has become so much modified, that after the lapse of a considerable period they have scarcely been able to comprehend each other. Hence, the importance of the art of WTiting,—certainly the most valuable of human inventions. Of this, there have been two kinds,—the imita- tive or alphabetical,—and the symbolical, allegorical, or emblematic, which latter consists of hieroglyphics, or designs representing ex- ternal objects, or of symbolical allegories. The former or the written representation of spoken sounds alone concerns us. To attain this, every compound sound has been re- duced to certain elementary sounds, which are represented by signs, called letters. These elementary sounds, by combination, form sylla- bles; and the syllables, by combination, words. The number of elementary sounds, admitted in each language, constitutes its alphabet, which differs more or less in certain languages; but as it is entirely a matter of human invention, and as the elementary sounds, of which the human voice is capable, are alike in the different races of man- kind, we see readily, that the alphabets of the different languages must strikingly correspond, although the combinations of the letters constituting syllables and words, may vary essentially. Into the origin of the written legible language, it is not necessary for us to inquire. We may remark, however, that the invention has been considered so signally wonderful as to transcend the human powers; and hence St. Cyril, Clement of Alexandria, Eusebius, Isidore, and, in more modern times, Messrs. Bryant, Costard, &c. have been of opinion, that the knowledge of letters was first com- municated to Moses by the Almighty himself, and that the decalogue was the earliest specimen of alphabetic writing. Many passages, however, in the writings of Moses, show unequivocally, that written records must have existed prior to his time. In the passage in which writing is first mentioned in the sacred volume, the art is alluded to as one of standing:—" And the Lord said unto Moses, < Write this for a memorial in a book or table;'" and in a subsequent chapter— " And thou shalt make a plate of pure gold, and grave upon it, like the engravings of a signet, Holiness to the Lord."* The English alphabet is considered to consist of twenty-six letters. • Good, Op. citat. ii. 304. VOICE.—ARTICULATE LANGUAGE. 425 It may, however, by ultimate analysis, be reduced to twenty-four simple sounds—A, B, D, E, F, G, H, I, J, K, L, M, N, O, P, R, S, T, U, V, Z, Ch, Sh, and Th. To these letters arbitrary names have been assigned, as Bee (B,) See, (C) Dee, (D,) &c. which express very different sounds from those that belong to the letter when it forms part of a word or syllable. The word bad is not pronounced bee-a- dee; as the child, just escaped from learning his alphabet, must ima- gine ; hence, he has to unlearn all that he has acquired, or to ima- gine, that the different letters have very different sounds, according to the situation in wThich they may be placed. To obviate this incon- venience, many individuals are in the habit of teaching their children syllabically from the very first, by which they acquire the true sound, attached to each letter of the alphabet. In the preceding enumeration of the simple sounds, which consti- tute the alphabet, C, Q, W, X, and Y, have been excluded, for the following reasons. C has always the sound of either S or K, as in cistern or consonant. Q has the sound of koo, as in quart, (kooart;) W of oo, as in word, (oourd;) X of ks, or Z, as in vex, (vecks,) or Xerxes, (zerkses;) whilst Y has the sound of I or E, as in wry or yard, (ivri or eeard.) Ch, Sh, and Th, have been added, as being true alphabetic or simple sounds. Letters have been usually divided into two classes,—vowels and consonants. The vowels or vocal sounds are so called, because they appear to be simple modifications of the voice, formed in the larynx, unin- terrupted by the tongue and lips, and passing entirely through the mouth. Such at least is the case with those that are reckoned pure vowels. These, in the English alphabet, are five in number,—A, E, I, O, and U. W and Y are, likewise, vowel sounds in all situations. In enunciating A, as in fate, the tongue is drawn backwards and slightly upwards, so as to contract the passage immediately above the larynx. In sounding E, the tongue and lips are in their most natural position, without exertion. I is formed by bringing the tongue nearly into contact with the bony palate. O, by the con- traction of the mouth being greatest immediately under the uvula, the lips being also somewhat contracted. In the production of U, the contraction is prolonged beneath the whole of the soft palate. From these principal vowels, all the other vowel sounds of the language may be formed, by considering them as partaking more or less of the nature of each. These are, in our language, thirteen in number; besides compound sounds, as in oil and pound. Of these thirteen, three belong to A; two to E ; two to I; three to O; and three to U. i Fate. i No. A, as in - - - < Fat. O, as in * . . < Move. Fall. (Not, „ 5 Me. I Tune, E'asln " * " {Met. U.asio - - - < Tub. T SPine. (Bull, I, as in . - - jpin 36* 426 MUSCULAR MOTION. The vowels are more easy of pronunciation than the consonants. They merely require the mouth to be opened; and, however it may be arranged in the enunciation of the different vowels, the vocal tube is simply modified, to vary the impression, which has to be made on the organ of hearing. The shape of the cavity is altered, but the passage of the air continues free, and the voice, conse- quently, issues in an unrestrained manner. Hence, perhaps, the physiological origin of the Danish word Aa, " a river"—a generic term, which became afterwards applied to three rivers in the Low Countries, three in Switzerland, and five in Westphalia—the sound of the two broad As flowing without obstacle, like a river. Time passes away in a similar manner; hence, for a like reason, the Greek usi which signifies " always, perpetually;" and the German j e, which has the same signification. The consonants are more difficult of enunciation than the vowels; as they require different, and sometimes complex, and delicate move- ments of the vocal tube; and, on this account, are not acquired so early by children. The term consonant is derived from one of its uses,—that of binding together the vowels, and being sounded with them; but it may be defined, an interruption to the sound, effected in the larynx, by the application of the organs of articulation to each other. By most, and according to Mr. Walker,* by the best, gramma- rians, w and y are consonants, when they begin a word ; and vowels when they end one. Dr. Lowth,f however, a man of learning and judgment, who certainly would not suffer in a comparison with any of his opponents, regards them, as we have, to be always vowels. Physiologically it is impossible to look upon them in any other light. Yet Mr. Walker exclaims,—" how so accurate a gram- marian as Dr. Lowth could pronounce so definitely on the nature of y, and insist on its being always a vowel, can only be accounted for by considering the small attention which is generally paid to this part of grammar." No stronger argument, however, could be used against the useless expenditure of time on this subject, than the con- clusion to which Mr. Walker himself, has arrived; and for which he can find no stronger reasons, than that if w and y have every property of a vowel, and not one of a consonant; why, when they begin a word, do they not admit of the euphonic article an before them? The consonants are usually divided into mutes, semi-vowels, and liquids. The mutes are such as emit no sound without a vowel; as, b, p, t, d, k, and c and g hard. The semi-vowels are such as emit a sound, without the concur- rence of a vowel, as/, v, s, z, x, g soft or ;. The liquids are such as flow into, or unite easily with, the mutes, as I, m, n, r. These letters issue without much obstacle; and hence perhaps their name. * Preface to his Dictionary. t Introduction to English Grammar, p. 3. VOICE.—ARTICULATE LANGUAGE. 427 In tracing the mode in which the different consonants are ar- ticulated, we find, that certain of them are produced by an analo- gous action of the vocal tube; so that the physiology of one will suffice for the other also. For instance, the following nearly cor- respond ;— p f t s k ch &&&&&& b v d x g j. B and P are produced when the lips, previously closed, are sud- denly opened. B differs from P in the absence, in the latter, of an accompanying vocal sound. F and V are formed by pressing the upper incisor teeth upon the lower lip. They are, consequently, not well enunciated by the aged, who have lost their teeth. F differs from V only in the absence of an accompanying vocal sound. T and D are formed by pressing the tip of the tongue against the gums behind the upper incisor teeth : D is accompanied by a vocal sound; T not. S and Z are produced by bringing the point of the tongue nearly in contact with the upper teeth, and forcing the air against the edges of the teeth with violence. S differs from Z in the ab- sence of the vocal sound. K and G are formed by pressing the middle of the tongue against the roof of the mouth, near the throat ; and separating the parts a little more rapidly to form the first, and more gently to form the last of those letters. In K, the accompa- nying vocal sound is absent. Ch and J are formed by pressing t to sh; and d to zh. In Ch, there is no accompanying vocal sound. SH and ZH are formed in the same part of the tube as s and z. TH is formed by protruding the tongue between the incisor teeth, and pressing it against the upper incisors to produce its sound in think. Its sound in that, is effected by pressing the tongue behind the upper incisor teeth. In the former case, it is unaccompanied by a vocal sound. In M, the lips are closed, as in B and P, and the voice issues by the nose. N is formed by resting the tongue against the gums, as in the enunciation of t and d; and breathing through the nose with the mouth open. In L, the tip of the tongue is pressed against the palate, the sound escaping laterally. In forming the letter K, the middle and point of the tongue strikes the palate with a vibratory motion; the tip being drawn back. Lastly, in the formation of H, the breath is forced through the mouth, which is every where a little contracted. It need hardly be said, that the enunciation of these letters requires, that the vocal tube, or the parts concerned in the function, shall be in a sound con- dition.* * See Mayo's Outlines of Human Physiology, 3d edit. p. 357. Lond. 1833. Also, Haller. Element. Physiol, ix. 4. 428 MUSCULAR MOTION. Wolfgang von Kempelen* in a work on the mechanism of human speech, &c. which is considered classical in Germany, divides the consonants into four classes. 1. Mutes, (g a n z s t u m m e,) as K, P, T. 2. Explosives, (w in d m it laut er,) as F, H, Ch, S, and Sh. 3. Vocal consonants, (s t i m m i 11 a u t e r,) as B, D, G, L, M, and N; and 4. Vocal explosives, (wind und stimmlauter,) asR, I, W,V,Z. Dr. Thomas Young has, likewise, divided the English consonants into classes; of which he enumerates five. 1. Pure semi-vowels, as L, R, V, Z, and J. 2. Nasal semi-vowels, as M and N. 3. Explo- sive letters, as B, D, and G. 4. Susurrant letters, as H, F, X, and S: and, 5. Mutes, as P, T, K. The most satisfactory classification, in a physiological, as well as philological point of view, is according to the parts of the vocal tube, more immediately concerned in their articulation. Labial. Dento-labial. Linguo-dental. Linguo-palatal. Guttural. B M P F V Th D JLN RSTZ Ch Sh Ng G K That this physiological arrangement has had much to do with the formation of congenerous tongues more especially is exhibited by the facts, connected with the permutation or change of letters; when a word passes, for example, from one of the Teutonic or Romanic languages to another. " The changes of vowels," says Mr. Lhuyd,f " whether by chance or affectation, are so very easy and so common in all languages, that in etymological observations, they need not, indeed, be much regarded; the consonants being the sinews of words, and their al- terations therefore the most perceptible. The changes of conso- nants also into others of the same class, (especially labials, palatals, and Unguals,) are such obvious mistakes, that there is no nation where the common people in one part or other of their country, do not fall into some of them." A few examples will show to what extent this permutation occurs between letters of the same class in different languages. In this view, we may regard the labials and dento-labials as belonging to the same class. P into B.—Greek, Levatores ani- * Lectures on Comparative Anatomy, I. 271. Lond. 1814. t Ibid. I. 293. DIGESTIVE ORGANS. 467 secretion to that of other membranes of the same class. The mus- cular coat is composed of the two planes of fibres, so united that they cannot be separated,—the innermost consisting of circular, and the outermost of longitudinal fibres, the arrangement of which dif- fers in the small and large intestines. The serous or peritoneal coat receives the intestine between two of its laminae, which, in their passage to it, form the mesentery. The serous coat only comes in direct contact with the intestine at the sides and forepart. Behind, or on the mesenteric side, is a vacant space, by which the vessels and nerves reach the intestine. These form their first net-work between the serous and muscular coats; their second between the muscular and mucous. Between the upper four-fifths of the intestinal canal, and the lower fifth, there is a well-marked distinction; not only as regards structure and magnitude, but function. This has given occasion to a division of the canal into the small intestine, and the large; and these, again, have been subdivided in the various modes, which will successively fall under consideration. As the small intestine fills so large a portion of the whole in- testinal canal, its convolutions occupy considerable space in the abdominal cavity,—in the middle, the umbilical, and the hypogastric regions,—and terminate—in the right iliac region—in the large in- testine, (see Fig. 103.) Its calibre differs in different parts; but it may be regarded on the average as about one inch. It is usually divided, arbitrarily, into three parts;—the duodenum, jejunum, and ileum. The duodenum is so called, in consequence of its length having been estimated at about twelve fingers' breadth. It is larger than the rest of the small intestine; and has hence received, also, the name of the second stomach, and of ventriculus succenturiatus. It is more firmly fixed to the body than the other intestines; and does not, like them, float loosely in the abdomen. In its course, until its termination in the jejunum, it describes a kind of Italic c, the con- cavity of which looks to the left. From this shape it has been sepa- rated into three portions;—the first situated horizontally beneath the liver: the second descending vertically in front of the right kidney; and the third in the transverse meso-colon. Its mucous membrane presents a number of circular folds, very near each other, which have been called valvulce conniventes. By some anatomists, however, this name is not given to the irregular rugae of its mucous coat; but to the folds of the lining membrane of the jejunum. The valvulae are not simple rugae, passively formed by the contraction of the muscular coat. They are dependent upon the original formation of the mucous membrane; and are not ef- faced, whatever may be the distention of the intestine. On and between these duplicatures, the different cxhalant and absorbent vessels are situated, forming, in part, the villi of the intes- tine. These villi give to the membrane a velvety appearance, and are not simply composed of exhalents and absorbents, but of nerves; 468 DIGESTION. all of which are distributed on a cellular and perhaps on an erectile tissue. The most obvious use of these villi, as Dr. Roget* and Dr. Hornerf have suggested, is to increase the surface from which the secretion is prepared. Within the membrane are numerous follicles, which, with the exhalants, secrete a mucous fluid, called by Haller succus intestindlis. Their entire number in the whole alimentary canal is estimated by Dr. Horner to be 46,896,000. At about four or five fingers' breadth from the pylorus, the duo- denum is perforated by the termination of the biliary and pancreatic ducts, which pour the bile and pancreatic fluids into it. Generally, these ducts enter the intestine by one opening; at times, they are distinct, and lie alongside each other. The structure of the duodenum is the same as that of the whole of the intestinal canal. The muscular coat is, however, thicker, and the peritoneal coat only covers its first portion, passes before the second, and is totally wanting in the third, which we have described as included in the transverse meso-colon. The other two portions of the small intestine are of considera- ble length; the jejunum commencing at the duodenum, and the ileum terminating, in the right iliac fossa, in the first of the great intestines—the caecum. They occupy the middle and almost the whole of the abdomen, being surrounded by the great intestine E F F F G H I, Fig. 103. The jejunum is so called, from being generally found empty; and the ileum, from its numerous windings. The line of demarcation, however, between the duodenum and jejunum, as well as between the latter and the ileum, is not fixed: it is an arbitrary division. The jejunum has, internally, the greatest number of valvulae conniventes and villi. The ileum is the lowest portion. It is of a paler colour, and has fewer valvulae conniventes. The jejunum is situated at the upper part of the umbilical region; the ileum at the lower part of it, extending as far as the hypogastric and iliac regions. The mucous membrane of the jejunum and ileum resembles, in essential respects, that of the duodenum; the valvulae conniventes are, however, more numerous in the jejunum than in the duodenum; and, in the course of the ileum, they gradually dis- appear, and are replaced by simple longitudinal rugae. The villi, too, which are chiefly destined for chylous absorption, abound in the jejunum, but gradually disappear in the ileum. The mucous membrane of both is largely supplied with follicles, called the glands of Peyer,J Brunner,§ and Lieberkuhn,|| which secrete the succus intestinalis,—a mucous fluid, to which Haller attached unnecessary importance in digestion. Lelutfl estimates the number of these glands, in the small intestine, at 40,000. The muscular coat is composed * Op. cit. ii. 246. t American Journal of the Medical Sciences, May, 1835, p. 62. X De Glandulis Intestinorum. Scaffhaus, 1677. § Glanduke Duodeni s. Pancreas Secundarium. Francof. 1715. H De Fabrica et Actione Villorum Intestinor. Hominis, Lugd. Bat. 1745. See, on the structure of these glands, Bohm, De Glandular. Intestinal. Structura Penitiori. Berol. 1835; and Brit, and For. Med. Review, April, 1836, p. 521. T Gazette Medicale, Juin, 1832. DIGESTIVE ORGANS. 469 of circular and longitudinal fibres; and the outer coat is formed by the prolongation of the peritoneum, which, after having surrounded the intestines, completes the mesentery, by which the gut floats, as it were, in the abdominal cavity. The large intestine terminates the intestinal canal. It is much shorter than the small, and considerably more capacious, being manifestly intended, in part, as a reservoir. It is less loose in the abdominal cavity than the portion of the tube which we have described. It commences at the right iliac fossa, (Fig. 103, E,) ascends along the right flank, as far as the under surface of the liver; crosses over the abdomen to gain the left flank, along which it descends into the left iliac region, and thence through the pelvis, along the hollow of the sacrum, to terminate at the anus. Like the small intestine it is divided into three portions; the caecum, the colon, and the rectum. The ccecum or blind gut is the part of the great intestine into which the ileum opens. It is about four fingers' breadth in length, and nearly double the diameter of the small intestine. It occupies the right iliac fossa, in which it is bound down, so as not to be able to change its position. The extremity of the ileum joins the caecum, at an angle; and if we examine the interior of the caecum, at the point of junction, we find a valvular arrangement, which has been called the valve of Tulpius, valve of Bauhin, ileo-ccecal valve, &c. Fig. 104. Commencement of the Large Intestines.— Valve of Tulpius. A C Small intestine.—B B. Large intestine.—D. Appendix vermiformis cseci. Fig. 104 exhibits the nature of this arrangement. At the point of union of the two intestines, a soft eminence exists, flattened from above to below, and elliptical transversely, which is divided into two lips. One of these seems to belong to the ileum and colon—hence called ileo-colic; the other to the ileum and caecum, and termed, ileo-ccBcal. vol. i. 40 470 DIGESTION. From the disposition of these lips a valve results, so constituted, that the lips, which form it, separate when the faecal matters press from the small to the large intestine; whilst they approximate, cross, and completely prevent all retrogression, when the faeces tend to pass from the great intestine to the small. At the extremities of this valve are small tendons, which give it strength, and have been termed the frcena or retinacula of the valve of Bauhin. Although this valvular arrangement prevents the ready return of the excrementitious matter into the small intestine, we have many opportunities, in pathology, for discovering, that it is not effectual in all cases. In stricture of the large intestine, stercoraceous vomiting is a frequent concomitant, and there have been instances of substances, thrown into the rectum, having been evacuated by the mouth. At the posterior and left side of the caecum, a small process de- taches itself, called, from its resemblance to a worm, appendix ver- miformis; and, from its connexion with the caecum, appendix cceci. It is convoluted, variable in its length, and attached, by its sides, to the caecum. Its free extremity is impervious; the other opens into the back part of the caecum. This appendage to the caecum has all the characters of an intes- tine. Various hypotheses have been indulged regarding its uses. Some have conceived it to be a reservoir for the faeces, but its di- minutive size, in the human subject, precludes this idea; others have thought, that it secretes a ferment, necessary to faecal forma- tion ; and others, again, a mucus for preventing the induration, which might result from the detention of the faeces in the csecum. The opinion—that it is a mere vestige of the useful and double caeca, which exist in certain animals—is as philosophical as any. M. De Blainville,* indeed, regards it as the true caecum, and what is named the caecum as the commencement of the colon. It is manifestly of but little importance, as it has been found wanting or obliterated in many subjects, and has been extirpated repeatedly with impunity. The colon is by much the longest of the large intestines, (F F F G H, Fig. 103.) It is a continuation of the caecum, from which it cannot be distinguished; but is considered to commence at the termination of the ileum. From the right iliac fossa it ascends along the right lumbar region, over the kidney, to which it is con- nected. It is, in this part, called the colon dextrum,—ascending, or right lumbar colon. From the kidney it passes forwards and crosses the abdomen in the epigastric and hypochondriac regions, being connected to the duodenum. This portion is called the great arch of the colon or colon transversum. The right portion of the great arch is situated under the liver and gall-bladder; and hence is found after death tinged yellow, owing to the transudation of bile. The left portion of the arch is situated under the stomach; and, immediately below it, are the convolutions of the jejunum. In the * De l'Organisation des Animaux, &c. Paris, 1825. DIGESTIVE ORGANS. 471 left hypochondre, the colon turns backward under the spleen, and descends along the left lumbar region, anterior to the kidney to which it is closely connected. This portion is termed the colon sinistrum, descending, or left lumbar colon. In the left iliac region, it forms two convolutions, which have been compared to the Greek s, or to the Roman s; and hence this part of the intestine has been designated the sigmoid flexure, or Roman s, or iliac turn of the colon. This flexure varies greatly in length in different persons, extending frequently into the hypogastric region, and, in some instances, as far as the caecum. The colon, through its whole extent, is fixed to the body by the meso-colon. The coats of the great intestine are the same in number and structure with those of the small, but they are thinner, and not as easily separable by dissection. The mucous membrane is less villous and velvety. The most characteristic difference, however, in the general appearance of the great and small intestines, is the pouched or cellular aspect of the former. These pouches are reser- voirs for the excrement, and in them it becomes more indurated, by the absorption of the fluid portions. In torpor of this part of the intestinal canal, the faeces are, at times, retained so long, that they become hard balls or scybala; and are not unfrequently the occasion of the inflammation of the lining membrane of the large intestine, which constitutes dysentery. The longitudinal muscular fibres are concentrated into three ligamentous bands or fasciculi, which run the whole length of the intestine. These fasciculi, being shorter than the intestine, pucker it, and are the occasion of the pouched or saccated arrangement. The inner or circular muscular fibres are, like those of the small intestine, uniformly spread over the surface, and stronger than those of the latter. Lastly, in the great intestine, especially in the colon, are numerous processes of the peritoneum containing fat, and hence called appendicular epiploicce, or appendiculce pinguedinosce. These are seen in greatest abundance in the right and left lumbar portions of the colon. The rectum terminates the intestinal canal, and extends from the termination of the colon to the anus. It commences about the fifth lumbar vertebra, and descends vertically into the pelvis, following the concavities of the sacrum and coccyx; and, consequently, is not straight, as its name would import. At its upper part, there are a few appendiculae epiploi'cae; and a small duplicature of the mesen- tery, called meso-rectum, attaches it to the sacrum. It differs from the other intestines in becoming wider in its progress downwards, and in its parietes being thicker. The lower part of the mucous membrane exhibits several longitudinal folds or rugae, which have been considered as the effect of the contraction of the circular fibres of the muscular coat. The longitudinal fibres of this last coat have a different arrangement from that which prevails in the other portions of the large intestine. They are distributed over the whole surface, as in the small intestine—or rather, as in the oesophagus— 472 DIGESTION. excepting that, at the lower part of the rectum, they are wanting. On the other hand, the circular fibres are more and more marked, as they approach the outlet, and, by circumscribing the margin of the anus, they form the sphincter ani muscle. Immediately within the anus is the widest portion of the rectum; and, in this part, accu- mulations of indurated faeces sometimes take place in old people to a surprising extent, owing to torpor of the muscular powers, con- cerned in the expulsion of the faeces. Lastly, there are a few muscles, which are concerned in the act of expelling the faeces. These require a short reference. 1. The sphincter ani or coccygeo-anal which keeps the anus constantly closed, except during defecation. 2. The levator ani or subpubio- coccygeus, which, with the next muscle, constitutes the floor of the pelvic and abdominal cavities. It restores the anus to its place, when pushed outwards during defecation. 3. The coccygeus or ischio-coccygeus, which assists the levator ani in supporting or rais- ing the lower extremity of the rectum; and 4. The transversus perinei or ischio-perineal, some fibres of which unite both with the bulbo-cavernosi and with the sphincter ani muscles; and, con- sequently, it is associated slightly with the action of both one and the other. In regard to the intestinal canal, again, we find, that man holds a medium place between the carnivorous and herbivorous animal, although approximating more to the latter. In the carnivorous ani- mal—for reasons more than once mentioned—it is unnecessary, that the food should remain long, and, accordingly, the canal is very short. In the herbivora, on the other hand, and for opposite reasons, the canal is long, and there is generally a large caecum and a pouched colon. Cuvier* has given tables of the length of the canal, compared with that of the body; but where the comparison has been applied to man, the length of the body has included that of the legs. Instead, therefore, of the canal, in man, being considered to bear the proportion of six to one, it ought to be doubled, or to be as twelve to one; a proportion somewhat greater than prevails in the simiae or ape tribe. It is not, however, in length always, that the canal of the herbivorous exceeds that of the omnivorous animal; but, as a general rule, it may be affirmed, that the capacity of the canal is much more considerable. 5. The abdomen, in which the principal digestive organs are situated, and whose parietes exert considerable influence on the di- gestive function, will require a brief description. It is that division of the body, which is betwixt the thorax and pelvis; and is bounded, above, by the arch of the diaphragm; behind, by the vertebral column; laterally, and anteriorly, by the abdominal muscles; and, below, by the ossa ilii, os pubis, and by the cavity of the pelvis. To connect the knowledge of the internal parts of the abdomen * Lemons d'Anatomie Comparee. Paris, 1799; and Roget's Animal and Vegetable Physiology, edit. cit. ii. 149. DIGESTIVE ORGANS. 473 with the externa], it is customary to mark certain arbitrary divisions on the surface, which have been called regions. The epigastric region, A, Fig. 105, is at the upper portion of the abdomen, under the point of the sternum, and in the angle formed by the cartilages of the ribs. The hypochondriac regions, B B, are covered by the cartilages of the ribs. These three regions—the epigastric and right and left hypochondre—constitute the upper division of the abdomen, in which are seated the stomach, liver, spleen, pancreas, duodenum, and part of the arch of the colon. The space, surrounding the umbilicus, between the epigastric region and a line drawn from the crest of one os ilii to the other, is the umbilical region, C. Here the small intestines are chiefly situated. This region is bound- Fig. 105. ed by lines, raised perpendicularly to the spine of the ilium; and the lateral por- tions, on the outside of these lines, form the iliac regions, JE E; behind which, again, are the lumbar regions, or the loins. In these, the colon and kidneys are chiefly situated. The hypogastric, D, is, likewise, divid- ed into three regions, —the pubic (a) in the middle, in which the bladder is situated; and an inguinal (b) on each side. The muscles, that constitute the abdo- minal parietes, are, first of all, above, the diaphragm, which is the boundary be- tween the thorax and abdomen; convex to- wards the chest, and considerably concave Regions of the abdomen. towards the abdomi- nal cavity. Below, if we add the pelvic cavity,—wbich, as it con- tains the rectum, and muscles, concerned in the evacuation of the faeces, it may be proper to do,—the cavity is bounded by the peri- neum, formed chiefly of the levatores ani and coccygei muscles. 40* 474 DIGESTION. Behind, laterally, and anteriorly, from the lumbar vertebrae round to the umbilicus, the parietes consist of planes of muscles, and aponeu- roses in superposition, and united at the median line, A D, Fig. 105, by a solid, aponeurotic band, extending from the cartilago ensiformis of the sternum to the pubis, called the linea alba. The abdominal muscles, properly so called, are,—reckoning the planes from within to without,—the greater oblique muscle, the lesser oblique, and the transversalis, which are situated chiefly at the sides of the abdomen; —and the rectus and pyramidalis, which occupy the anterior part. The greater oblique, obliquus externus or costo-abdominalis;—the lesser oblique, obliquus internus or ilio-abdominalis, and the transver- salis, transversus abdominis or lumbo-abdominalis, support and com- press the abdominal viscera; assist in the evacuation of the faeces and urine, and in the expulsion of the foetus; besides other uses, con- nected with respiration and the attitudes. The rectus, pubio-sternalis or sterno pubi- alis; and the pyramidalis or pubio-sub-umbilicalis, are more limited in their action, and compress the forepart of the abdomen; besides having other functions. Lastly, a serous membrane —the peritoneum—lines the abdomen, and gives a coat to most of the viscera. The mode, in which its various reflections are made, is sin- gular, but easily intelligible from the accompanying fi- gure. It has neither begin- ning nor end, constituting, like all the serous membranes, a shut sac, and, in reality, having no viscus within it. If we assume the diaphragm as the part at which it com- mences, we find it continued from the surface of that mus- cle over the abdominal mus- cles, D; then reflected, as ex- hibited by the dotted line, over the bladder, E; and, in the female, over the uterus, G; from thefce over the rectum, F; the kidney, H; enveloping the intestine, B, and constituting, by its two laminae, the mesentery, C; giving a coat to the liver, A; and receiving the sto- mach between its duplicatures. Fig. 106. Reflections of the peritoneum. FOOD OF MAN. 475 The use of this membrane is to fix and support the different viscera; to constitute, for each, a pedicle, along which the vessels and nerves may reach the intestine; and to secrete a fluid, which enables them to move readily upon each other. When we speak of the cavity of the peritoneum, we mean the inside of the sac; and when it is distended with fluid, as in ascites, the fluid is contained between the peritoneum lining the abdominal muscles, and that which forms the outer coat of the intestines. The omenta or epiploa are fatty membranes, which hang over the face of the bowels, and are reflections, formed by the peritoneum after it has covered the stomach and intestines. Their names will sufficiently indicate their situation:—the lesser epiploon or omentum, —the omentum hepato-gastricum; the greater or gastro-colic; and the appendices or appendiculce epiploicce, which last have already been referred to, and may be regarded as so many small epiploons. The abdomen is entirely filled by the contained viscera. There are several apertures into it; three, above, in the diaphragm, for the passage of the oesophagus, vena cava inferior, and aorta; one ante- riorly in the course of the linea alba, but which is closed after birth, —the umbilicus; and two anteriorly and inferiorly; the one—the abdominal, inguinal or supra-pubian ring—which gives passage to the vessels, nerves, &c. of the testicle; and the other—the crural arch—through which the vessels and nerves pass to the lower ex- tremity. Lastly, two others exist in the inferior paries, for the pas- sage of the obturator vessels and nerves, and of the sciatic arteries and nerves, respectively. Such is a brief view of the various organs concerned in digestion. To this might have been added the general anatomy of the liver and pancreas,—each of which organs furnishes a fluid, which is a material agent in the digestive process,—and of the spleen, which has been looked upon by some as inservient, in some manner, to the same function. As, however, the function of these organs will be considered in another place, we defer their anatomy for the present. 2. Of the Food of Man. The articles, inservient to the nourishment of man, have usually been considered to belong entirely to the animal and the vegetable kino-doms; but there seems to be no sufficient reason for excluding those articles of the mineral kingdom that are necessary for the due constitution of the different parts of the body. Generally, the term food or aliment, is applied to substances, which, when received into the digestive organs, are capable of being converted into chyle; but, from this class again, the products of the mineral kingdom cannot, with entire propriety, be excluded. Animals are often characterized by the kind of food on which they subsist. The carnivorous feed on flesh; the piscivorous on fish; the insectivorous on insects ; the phytivorous on vegetables; the gra- nivorous on seeds; the frugivorous on fruits; the graminivorous and 476 DIGESTION. herbivorous on the grasses; and the omnivorous on the products of both the animal and vegetable kingdoms. In antiquity, we find whole tribes designated according to the aliment they' chiefly used. Thus, there were the ^Ethiopian and Asiatic ichthyophagi or fish-eaters; the hylophagi, who fed on the young shoots of certain trees; the elephantophagi, and struthiophagi, the elephant and ostrich eaters, &c. &c. We have already shown, that the digestive apparatus of man is intermediate between that of the carnivorous and the herbivorous animal; that it partakes of both, and that man may, consequently, be regarded omnivorous ;'* that is, capable of subsisting on both the products of the animal and vegetable kingdoms;—an important capability, seeing, that he is destined to live in arctic regions, in which vegetable food is not to be met with, as well as in the torrid zone, which is more favourable for vegetable, than for animal, life. The nature of the country must, to a great extent, regulate the food of its inhabitants, for although commerce can furnish us with articles of luxury; and with many, which are looked upon as necessaries, no nation is entirely indebted to it for its supplies; be- sides, numerous extensive tribes of the human family are denied the advantages of commerce, and compelled to subsist on their own resources. This is the great cause, why the Esquimaux, the Sa- moiedes, &c. live wholly on animal food; and why the cocoa-nut, the plantain, the banana, the sago, the yam, the cassava, the maize and the millet, form the chief articles of diet with the natives of torrid regions. In certain countries, the scanty supply of the useful and edible animals has given occasion to certain prohibitory dietetic rules and regulations, which have been made to form a part of the religious creed, and, of course, are most scrupulously observed. Thus, in Hindusthan, animal food is not permitted to be eaten; but the milk of the cow is excepted. Accordingly, to ensure the necessary sup- ply of this fluid, the cow is made sacred; and its destruction a crime against religion. Amongst the laws of the Egyptians are similar edicts, but they seem to have been chiefly enacted for political pur- poses, and not in consequence of the unwholesome character of the interdicted articles. The same remark applies to many of the dietetic rules of Moses, for the regulation of the tables of the" Hebrews. Blood was forbidden, in consequence, probably, of the fear entertained, that it might ren- der the people too familiar with that fluid, and diminish the horror, which was inculcated against the shedding ofiblood: the parts of generation were excluded from the table, because the taste might interfere with the reproduction of the species, if it should become indulged, &c. &c. We have said, that, in his arrangement of the digestive organs, man is intermediate between the carnivorous, and the herbivorous' * Tiedemann's Physiologie des Menschen, iii. 91. Darmstadt, 1836. FOOD OF MAN. 477 animal. Not the slightest ground is afforded, by anatomy, for the opinion of Rousseau, that man was, originally, herbivorous; or for that of Helvetius* that he was exclusively carnivorous. Brous- sonet affirms, that he is more herbivorous than carnivorous; since, of his thirty-two teeth, twenty resemble those of the herbivorous, whilst twelve only resemble those of the carnivorous, animal. Ac- cordingly, he infers, that, in the origin of society, his diet must have been exclusively vegetable. Mr. Lawrence,f too, concludes, that, whether we consider the teeth and jaws, or the immediate instru- ments of digestion, the human structure closely resembles that of the simiae,—the great archetypes, according, to Lord MonboddoJ and Rousseau of the human race—all of which are, in their natural state, completely herbivorous.§ Again, we observe a wide discrepancy between man and ani- mals in the variety of their aliments. Whilst the latter are gene- rally restricted to either the animal or the vegetable kingdom ; and to but a small part of one or the other, man embraces an exten- sive range, and, by means of his culinary inventions, can convert a variety of articles from both kingdoms into materials of suste- nance. But it has been argued by those, who are sticklers for the natural, that man probably confined himself, primitively, like animals to one kind of food ; that he adhered to this whilst he re- mained in his natural state, and that his omnivorous practices are a proof of his degeneracy. Independently, however, of all argu- ments deduced from organization, experience sufficiently shows the inaccuracy of these assertions. If we trace back nations to their state of infancy, we find, that then, as in their more advanced con- dition, the diet was animal, or vegetable, or both, according to cir- cumstances. Of this fact we have some signal examples, in a part of the globe where the lights of civilization have penetrated to a less extent than in most others; and where the influence of circumstances, that prevailed in ancient periods, has continued, almost unmodified, until the present time. Agatharchides|| describes the rude tribes, who lived on the coast of the Red Sea, and subsisted on fish, under the name ichthyophagi. Along both banks of the Astaboras, which flows on one side of Meroe, dwelt another nation, who lived on the roots of reeds growing in the neighbouring swamps. These roots they cut to pieces with stones, formed them into a tenacious mass, and dried them in the sun. Close to them were the hylophagi, who lived on the fruits of trees, on vegetables growing in the valleys, &c. To the west of these were the hunting nations, who fed on wild beasts, which they killed with the arrow. There were, also, other * De I'Homme, ii. 17. t Lectures on Physiology, Zoology, &c. p. 221. Lond. 1819. t On the Ori -vet we have no proof, that these substances are obtained from any other source than the food; and some of them are, with diffi. « Elements of Chemistry, 9th edit., ii. 435, Lond. 1823. 46* 546 DIGESTION. culty, obtained any where. Every one of them is necessary for the constitution of the urine; and many must be formed by a chemical union of their elements under the vital agency. Some are met with in the animal body exclusively. Berzelius* found, in 100 parts of human faeces:—water, 73.3; un- altered residue of animal and vegetable substances, 7.0; bile, 0.9; albumen, 0.9; peculiar extractive matter, 2.7; substance, formed of altered bile, resin, animal matter, &c. 14; and salts, 1.2. Seventeen parts of these salts contained, carbonate of soda, 5; muriate of soda, 4; sulphate of soda, 2 ; ammoniaco-magnesian phosphate, 2; phos- phate of lime, 4. The excrements have likewise been examined by Leuret and Lassaigne, and others; but none of the analyses have shed much light on the physiology of digestion. In the large intestine, gases are also met with, along with the faeces. These were examined by Magendief and Chevreul, in the three criminals already referred to. In the first, 100 parts of the gas contained;—oxygen, 0.00; carbonic acid, 43.50; carburetted, and some traces of sulphuretted, hydrogen, 5.47 ; azote, 51.03. In the second, oxygen, 0.00; carbonic acid, 70.00; pure and carbu- retted hydrogen, 11.60 ; azote, 18.40. In the third, the gases, found in the caecum, were analyzed separately from that of the rectum. These were found to contain respectively in 100 parts:— Oxygen, - ....... Carburetted hydrogen, - - -Traces of sulphuretted hydrogen, Caecum. Rectum. 1 0.00 12.50 7.50 12.50 67.50 Some. 0.00 42.86 11.18 45.96 Some. 100.00 | 100.00 The results accord with those of Jurine,^ obtained long ago, as regards the nature of the gases: but they do not accord with what he says relating to the carbonic acid; the quantity of which, according to him, goes on decreasing from the stomach to the rec- tum. The analyses show that the proportion increases instead of decreasing. Concerning the origin of these gases, the remarks made on those . of the small intestine are equally applicable here. When the faecal matter has accumulated to the necessary extent in the rectum, its expulsion follows; and to this function the term defecation has been appropriated. The faeces collect gradually in the large intestine, without any consciousness on the part of the in- dividual. Sooner or later, the desire or want to evacuate them arises. This is usually classed among the internal sensations or de- * Traite de Chimie, trad, par Jourdan et Esslinger, torn. vii. t Precis, &c. ii. 126. X M6moir de la Soc. Royale de Med. x. 72. DEFECATION. 547 sires. It is, however, properly, of a mixed character. That it is not always in a ratio with the quantity of faeces is shown by the fact, that occasionally the intestine will be filled without the want arising; and, if the faeces be unusually thin or irritating, the desire is developed, when an extremely small quantity of matter is present, —as in cases of tenesmus. The period, at which the desire returns, is variable, according to the quantity and character of the food em- ployed, as well as to the habit of the individual. Whilst the gene- rality of persons evacuate the bowels, at least once in the day,— and this usually at a period regulated by custom,—others will pass a week or two without any alvine discharge, and yet be in perfect health. Nay, some of the collectors of rare cases* have affirmed, on the authority of Rhodius, Panarolus, Salmuth, and others, that persons may continue in health, with the bowels moved not oflener than once a month, three months, half a year, two years, and even seven years, without serious mischief! Sir Everard Homef refers to the case of General Grose, who was in the Dutch service, under the Duke of Cumberland, in the Flanders war : for thirty years he never had a passage through the bowels. General Gage observed that he ate heartily ; but in two hours left the table and rejected his meal. He was healthy, and capable of exercise tike other men. HeberdenJ mentions the case of a person, who had naturally an evacuation once a month only, and another who had twelve evacua- tions every day during thirty years, and then seven every day for seven years, and rather grew fat than otherwise. A young lady re- ferred to by Pouteau,§ had no evacuation for upwards of eight years, although during the last year, she ate abundantly of fruit and drank coffee, milk, and tea, and broth with yolks of eggs; but she had copious greasy sweats.|| When the desire to evacuate has once ex- hibited itself, it generally persists until the faeces are expelled. Some- times, however, it disappears and recurs at an uncertain interval; and, if again resisted, it becomes the source of great pain, and ulti- mately commands implicit obedience. That the pressure and irrita- tion of the faeces develope the sensation is evidenced by the circum- stance, that the momentary relief at times experienced, when the desire is urgent, is usually accompanied by a manifest return of the faecal matters from the sigmoid flexure into the colon. In evacuating the faeces the object to be accomplished is,—that the contents of the large intestine shall be pressed upon with a force superior to the resistance, presented by the annulus or upper ex- tremity of the contracted rectum, and by the muscles of the anus. The contraction of the rectum is generally insufficient to effect this last object, notwithstanding the considerable thickness of its muscu- lar layer. In cases, however, of great irritability of the rectum, the sphincter is incapable of resisting the force developed by the proper muscular fibres of the rectum. Under ordinary circumstances, the * Art. Cas Rares, in Diet, des Sciences Medicales. t Lect. on Compar. Anat. v. 12. Lond. 1828. X Commentarii, p. 14. §Ouvres Postliumes, i. 27. Paris, 1783. II Elliotson's Human Physiology, p. 122. Lond. 1835. 548 DIGESTION aid of the diaphragm and abdominal muscles is invoked, and it is chiefly through these muscles, that volition influences the act of de- fecation,—suspending, deferring, or accelerating it as the case may be. After a full inspiration, the muscles, which close the glottis, and the expiratory muscles,—especially those on the anterior part of the abdomen,—contract simultaneously. The air cannot escape from the lungs; the diaphragm is depressed upon the abdominal viscera, and the whole thorax presents a resisting body; so that all the expiratory power of the abdominal muscles bears upon the vis- cera, and presses.them against the vertebral column. In this way, considerable force is exerted upon the contents of the colon and rectum ; the resistance of the sphincter,—already diminished by the direct exertion of volition,—is surmounted; it yields and the faeces are extruded. The levator ani and ischio-coccygeus, aided by the transversus perinei muscles, support the anus during the propulsory efforts, and restore it to its place, after these efforts have ceased. Whilst the straining is effected by the diaphragm and abdominal muscles, the longitudinal muscular fibres of the rectum contract, so as to shorten the intestines, and, consequently, the space over which the faeces have to pass. On the other hand, the circular fibres con- tract, from above to below, so as to propel the excrement down- wards, and to cause the mucous membrane to extrude, and form a ring or bourrelet, like that which occurs at the cardiac orifice of the stomach, when the food is passing from the oesophagus into that organ. If this extrusion occurs to a great extent it constitutes the disease, called prolapsus ani. Of late, Dr. O'Beirne,* has directed his attention to the subject of defecation; and, guided by the following facts and arguments;—that great irritation would be produced in the sphincter ani, and in the bladder, if the faeces descended readily into the rectum;—that the difficulty experienced in throwing up an injection is inconsistent with the idea of the rectum being open, and proves that it is firmly con- tracted and closed ;—that when the surgeon has occasion to pass his finger up the rectum, he rarely encounters either solid or fluid faeces; —that the two sphincter muscles of the anus are considerably weakened in certain diseases, and divided in certain operations, yet it rarely happens, that the power of retaining the faeces is destroyed; —that on passing a stomach tube to the height of half an inch up the rectum, in a number of healthy persons, it was found, that nothing escaped, and that it could be moved about freely in a space, which, on introducing the finger, was ascertained to be the pouch of the rectum; but that from the highest part of the pouch to the upper extremity of the gut—generally a distance of from six or seven to eight inches—the tube could not be passed upwards without meeting with considerable resistance, and using a degree of force to mecha- nically dilate the intestine, which was plainly felt to be contracted * New Views of the process of Defecation, &c. Dublin, 1833; reprinted in this country, Washington, 1834. OF LIQUIDS.-THIRST. 549 so as to leave no cavity for this extent;—that when the instrument reached, in this way, the highest point of the rectum, the resist- ance to its passage upward was felt to be sensibly increased, until, at length, by using a proportionate degree of pressure, it passed rapidly forward—as if through a ring—into a space in which its extremity could be moved with great freedom, and as instantly a rush of flatus, of fluid faeces, or of both, took place through the tube; ■—and that in every instance, where the tube presented the least ap- pearance of faeces after being removed, this appearance was con- fined to that portion, which had entered the sigmoid flexure.—Led by these and other facts, Dr. O'Beirne concludes, that, in the healthy and natural state, all that part of the rectum above its pouch, is at all times, with the single exception of a few minutes previous to the evacuation of the bowels, firmly contracted, and perfectly empty, at the same time that the pouch itself as well as the sigmoid flexure of the colon, are always more or less open, and pervious;—and that the sphincter ani muscles are merely subsidiary agents in retaining the faeces. When the faeces are firm, considerable muscular effort is necessary to expel them; but, when they are of a softer consis- tence, the contraction of the rectum is sufficient. The air, contained in the intestinal canal, readily moves about from place to place, and speedily reaches the rectum by the peris- taltic action alone. Its expulsion, however, is commonly accom- plished by the aid of the abdominal muscles, when it issues with noise. If discharged by the contraction of the rectum alone, it is generally in silence. Children are extremely subject to flatulence, but in the adult it is not common. Some kinds of diet favour its production more than others, especially in those of weak digestive powers, of which its undue evolution is, indeed, generally an indica- tion. The leguminous and the succulent vegetables, in general, belong to this class. Where digestion is tardily accomplished, they undergo fermentation, and the disengagement of gas is the conse- quence. Too often, however, the disgusting habit of constantly dis- charging air streperously from the bowels is encouraged, rather than repressed ; and there are those, who are capable of effecting the act almost as frequently as they attempt it. The noise, made by the air, as it passes backwards and forwards in the intestinal canal, constitutes the affection called borborygmus. So much for the digestion of solid food. 2. DIGESTION OF LIQUIDS. In examining into the digestion of liquids, we shall follow the same order as that observed in the digestion of solids; but as many of the acts are accomplished in precisely the same manner, it will not be necessary to dwell upon them. Thirst or the desire for drink is an internal sensation; in its essence resembling that of hunger, although not referred to pre- cisely the same organs. It arises from the necessities of the sys- tem, from the constant drain of the fluid portions of the blood, 550 DIGESTION and is instinctive or essentially allied to organization. The sensation differs in different individuals, and is rarely alike in the same person. Usually, it consists of a feeling of dryness, constriction, and heat in the back part of the mouth, pharynx, oesophagus, and occasionally in the stomach; and, if prolonged, redness and tumefaction of the parts supervene, with a clammy condition of the mucous and folli- cular—and diminution and viscidity of the salivary—secretions. These phenomena are described as being accompanied by restless- ness, general heat, injected eyes, disturbed mind, acceleration of the circulation, and short breathing, the mouth being frequently and largely open, so as to admit the air to come in contact with the irritated parts, and thus to afford momentary relief. Thirst is a very common symptom of febrile and inflammatory diseases, in which fluid is desired in consequence of the local relief it affords,—especially when cold,—to the parched and heated membrane of the alimentary canal. It is also developed by circum- stances exterior to us; as in summer, when the bodyT sustains con- siderable loss of fluid, as well as in those diseases—as dropsy, diabetes, &c.—which produce the same effect. There are many other circumstances, however, that excite it;—as long speaking or singing; certain kinds of diet—the saline and spicy, for example— and especially the habit, acquired by some, of frequently drinking. Whilst such individuals may need several gallons a day to satisfy their wants;—others, who have, by resistance, acquired the habit of using very little liquid, will be enjoying good health and not ex- periencing the slightest inconvenience from its privation; so com- pletely are we, as regards the character and quantity of our aliment, the creatures of habit. This privation, it is obvious, cannot be absolute or pushed beyond a certain extent. There must always be fluid enough taken to administer to the necessities of the system.* As in the production of every internal sensation, three acts are required in accomplishing that of thirst;—impression, conduction, and perception. The last, as in every similar case, is effected by the brain, and the second by the nerves passing between the part impressed and that organ. The act of impression—its seat and cause—will alone arrest our attention; we shall find, that we are still less instructed on these points, than on the physiology of hunger. Even with regard to the seat of the impression, we are in a state of uncertainty. It appears to be chiefly in the back part of the mouth and fauces; but whether primarily there, or produced by sympathy with the condition of the stomach, is by no means clear. The latter opinion, however, appears the more probable. In a remarkable case, published by Dr. Gairdner of Edinburgh, it was found imprac- ticable to allay the thirst, by merely supplying the mouth, tongue, and fauces with fluid. A man had cut through the oesophagus. An insatiable thirst arose; several pailfuls of water were swallowed o *,-Ru_!>Pohi' Art' Durst' in Enc.Vcl°Paa- Worterb. der Medicin. Wissensch. ix. 614. Berlin, 1833 ; and Tiedemann, Physiologie des Menschen, iii. 68. Darmstadt, 1836. OF LiaUIDS. 551 daily, and discharged through the wound without allaying the thirst; but, on injecting water, mixed with a little spirit, into the stomach, it was soon quenched. That the sensation is greatly dependent upon the quantity of fluid circulating in the vessels, is shown by the fact, mentioned by Dupuytren, that he succeeded in allaying the thirst of animals, by injecting milk, whey, water or other fluids into the veins; and Orfila states, that in his toxicological experiments, he frequently allayed, in this way, the excessive thirst of animals to which he had administered poison; and which were incapable of drinking, owing to the oesophagus having been tied. He found, also, in his experiments, that the blood of animals was more and more deprived of its watery portions, as the abstinence from liquids was more prolonged.* Like all other internal sensations, that of thirst arises from a mo- dification of the nerves of the organ, which is inappreciable: hence all the hypotheses, proposed to account for its cause, have been mere phantasies undeserving of enumeration. The prehension of liquids differs somewhat from that of solids. The fluid may be simply poured into the mouth, when it enters by its own gravity; or a vacuum may be formed in the cavity of the mouth, and the pressure of the atmosphere may force it in. When we drink from a vessel, the mouth is applied to the surface of the fluid; the chest is then dilated, so as to diminish the pressure of the atmosphere on the portion of the surface of the liquid, intercepted by the lips; and the atmospheric pressure on the surface of the fluid in the vessel forces it into the mouth, to replace the air, which has been removed from the mouth by the dilatation of the thorax. In sucking, the mouth may be compared to an ordinary syringe; the nozzle of which is represented by the lips; the body by the cheeks, palate, &c. and the piston by the tongue. To put this in action, the lips are accurately adjusted around the body, from which the liquid has to be extracted. The tongue is likewise applied, but it soon contracts, and is carried backwards; so that an approach to a vacuum is formed between its upper surface and the palate. The fluid,—now, no longer compressed equally by the atmosphere,—is deplaced, and enters the mouth. As neither mastication nor insalivation is required in the case of liquids, they do not remain long in the mouth, unless their tem- perature is too elevated to admit of their being passed down into the stomach immediately, or they be of such a luscious character, that their prolonged application to the organ of taste affords pleasure. The deglutition of liquids is effected by the same mechanism as that of solids ; and,—as they yield readily to the slightest pressure,— with less difficulty. Their accumulation in the stomach takes place in much the same manner. They arrive by successive mouthfuls; and, as they collect, the thirst disappears with all its local and gene- ral attendants. If, however, the organ be over-distended, a disposi- tion to vomiting is induced. * Adelon, Physiologie de I'Homme, 2d 6dit. ii. 525. Paris, 1829. 552 DIGESTION. The changes, which liquids undergo in the stomach, are of dif- ferent kinds. All acquire the temperature of that viscus, and become mixed with the secretions from its internal surface, as well as from that of the supra-diaphragmatic portion of the digestive tube. Some, however, undergo the operation of chymifieation ; others not. To the latter class belong,—water, weak alcoholic drinks, the vegetable acids, &c. Water experiences the admixture already mentioned; becomes turbid, and gradually disappears, without undergoing any transformation. Part passes into the small intestine; the other is directly absorbed. When any strong alcoholic liquor is taken, the effect is different. Its stimulation causes the stomach to contract, and augments the secretion from the mucous membrane; whilst, at the same time, it coagulates all the albuminous and mucous portions; mixes with the watery part of the mucous and salivary fluids, and rapidly disappears by absorption; hence, the speedy supervention of inebriety, or death after a large quantity of alcohol has been taken into the stomach. The substances, that have been coagulated by the action of the alcohol, are afterwards digested like solid food. We can thus understand the good effects of a small quantity of alco- hol, taken after a substance difficult of digestion,—a custom which has existed from high antiquity and has physiology in its favour. It is, in such cases,—to use the language of the eccentric Kitchener,*— a good " peristaltic persuader." Of the liquids, which are capable of being converted into chyme or chyle, some are so altogether; others in part only. Oil remains longer in the stomach than any other liquid, experiences little change there, but is probably altogether converted into chyle. Milk, as is well known, coagulates in the stomach, soon after it is swallowed, after which the clot is digested, and the whey absorbed. Yet the existence of coagula, in the stomach, is constantly regarded, by the unprofessional, as a pathological condition ! Where the liquid, aque- ous or spirituous, holds in suspension the immediate principles of animals or vegetables, as gelatine, albumen, osmazome, sugar, gum, fecula, colouring matter, &c, a separation occurs in the stomach between the water or alcohol and the substances combined with them. The latter remain in the stomach and undergo chymifieation; whilst the aqueous or spirituous portions are absorbed. The salts, united with these fluids, are taken up along with them. In soup, for example, the water and the salts are absorbed; and the gelatine, albumen, fat and osmazome are digested. Red wine, according to Magendie,f first becomes turbid by ad- mixture with the juices, formed in, or carried into, the stomach: the albumen of these fluids speedily undergoes coagulation, and becomes flocculent; and, subsequently, its colouring matter—entangled, per- haps, with the mucus and albumen—is deposited on the mucous * Directions for Invigorating and Prolonging Life: or the Invalid's Oracle, &c. Amer. edit, from the 6th London. By T. S. Barrett. New York 1831. t Precis, &c, ii. 143. ERUCTATION AND REGURGITATION. 553 membrane of the stomach. The aqueous, and alcoholic portions soon disappear. Liquids reach the small intestine in two forms;—in the state of chyme; and in their unaltered condition. In the former case, they proceed like the chyme obtained from solid food. In the latter case, they undergo no essential change; being simply united with the fluids poured into the small intestine,—the mucous secretions, the bile, and the pancreatic juice. Their absorption goes on as they proceed: so that very little, if any, attains the large intestine. The mode in which liquids are expelled, is the same as in the case of solids. 4. Of Eructation, Regurgitation, and Rumination. Although the contraction of the oesophagus generally prevents the return of matters from the stomach; occasionally this occurs, giving rise to eructation, or regurgitation, or vomiting. a. Eructation. Eructation or belching is the escape of gas from the stomach. If air exists in that organ, it is necessarily situate as we have seen, near the cardiac orifice. When the aperture relaxes, it passes in, and, unless forced back by the contraction of the oesophagus, speed- ily reaches the pharynx, causing the edges to vibrate, and hence the sound by which it is accompanied. b. Regurgitation. If, instead of air, liquid or solid food ascends from the stomach into the mouth, the action is called regurgitation. Of this we have an instance in the puking of the infant at the breast; and in the adult, when the stomach is surcharged. Occasionally, too, it occurs when the stomach is empty; in the morning, for example, when it is frequently preceded by eructation, by which the air, contained in the organ, is got rid of. The mode, in which it takes place, is ana- logous to that of eructation. The substances, contained in the sto- mach become accidentally engaged in the cardiac orifice, during the open state of the orifice and the relaxation of the lower part of the oesophagus; owing to the direct pressure of the stomach on its contents, and the abdominal muscles contracting and compressing that viscus. When the food has once passed into the oesophagus, the latter contracts upon it, but inversely, or from below to above. In this way the food ascends into the pharynx, and ultimately into the mouth. Generally, regurgitation takes place in an involuntary manner; but there are some who are capable of effecting it at will; and can thus discharge the contents of their stomachs at pleasure. To ac- complish this,—a deep inspiration is taken, by which the diaphragm is forcibly depressed upon the stomach; the abdominal muscles are vol. i. 47 554 DIGESTION. then contracted, so as to compress the organ; and this effect is occasionally aided by pressing strongly with the hands on the epi- gastric region. When these efforts are simultaneous with the re- laxation of the lower third of the oesophagus, the alimentary matters pass into the oesophagus. This voluntary regurgitation seems to be what is called vomiting at pleasure. c. Rumination. Some individuals have taken advantage of this power to chew the food over again; and subject it to a second deglutition. The function of rumination is peculiar to certain animals. Yet man has, in this way occasionally possessed it. Peyer* has given numerous examples, as well as Percy and Laurent.f The wife of a frotteur or rubber of the floors, in the establish- ment of the then Duke of Orleans,—now king Louis Philip,—could bring up a glassful of water into her mouth immediately after she had swallowed it. Dr. Copland,;}; appears to have seen more than one instance of human rumination, and he describes it as an affection rather to be courted than shunned, so far as regards the feelings of the individual. Under usual circumstances, according to him, ru- mination commences from a quarter, to an hour and a half, after a meal. The process is never accompanied with the smallest degree of nausea, or with any pain or disagreeable sensation. The re- turned alimentary bolus is attended with no unpleasant flavour; is in no degree acidulous^]; is equally agreeable; and is masticated with additional pleasure, and with much greater deliberation than when first taken. The whole of the food swallowed at a meal is not returned, in order to undergo the process ; but chiefly the part that has been insufficiently masticated. The more fluid portions are sometimes, however, regurgitated along with the more solid: and when the stomach is distended by a copious meal, the fluid contents are frequently returned, and subjected to the process. d. Vomiting. This inverted action of the stomach, preceded, as it always is, by manifest local and general disturbance, cannot properly be regarded as within the domain of physiology.^ It is, however, so nearly al- lied to the phenomena we have just considered, and has engaged so much of the time of the physiologist, as well as of the pathologist, that it requires mention here. From regurgitation it differs essen- tially,—in the sensation that precedes, the retching that accompanies, and the fatigue, that generally succeeds it; in short, whilst in re- * Meryeologia, &c. Basil. 1685. t Art. Merycisme in Diet, des Sciences Medicales. See, also, Philos. Transact. abridgement, iii. 110. X Edition of De Lys's Translation of Richerand's Physiology. • m\urki?Je,'.in ArL Erbrechen, in Encyclopad, Worterbuch der Medic. Wissenchaft. vi. 214. Berlin, 1831. VOMITING. 555 gurgitation no indisposition may be felt, in vomiting it is always present, more or less. The sensation of the desire to vomit is termed nausea. It is an indescribable feeling of general indisposition; sometimes accompa- nied with a sensation of circumgyration, either in the head or epi- gastric region; trembling of the lower lip, and copious flow of the saliva: along with these signs, there is manifest diminution of the powers of the vascular and nervous systems ; and hence the utility of nauseating remedies when these systems are inordinately excited. The causes, which produce nausea, show that it may be either an external or internal sensation. Those, that occasion it directly or externally, are certain emetic substances; too great distention of the stomach, or the presence of food in it which disagrees by its quality; morbid secretions; the reflux of the bile from the duode- num, &c. All these are so many immediate irritants, which deve- lope the sensation, as the external sensations in general are developed. In other cases, however, the cause acts at a distance. Between the stomach and various organs of the body, such extensive sympa- thetic relations exist, that if one of these be long and painfully af- fected, the stomach sooner or later sympathizes, and nausea, or vomiting, or both are induced. In many instances, indeed, the cause is much more remote than this; the sight of a disgusting ob- ject, an offensive smell, or a nauseous taste will as certainly produce the sensation as any of the more direct agents. To this class of causes belongs the nausea, produced by riding in a carriage with the back to the horses, by swinging, and particularly by sailing on the ocean. How the motion, which obviously excites the nausea in these cases, acts, has been the subject of many specu- lations, especially as regards sea-sickness. Darwin* refers it to an association with sojue affection of the organs of vision, which, in the first instance, produces vertigo; and Bourru, in his French trans- lation of the work of Gilchrist,—" On the utility of sea voyages in the cure of different diseases,"—ascribes it to irritation of the optic nerves, caused by the impossibility of fixing the eyes on objects soon after embarking. The objection to these views is, that the sickness ought to be prevented by simply covering the eyes, and that the blind ought to be exempt from it, which is not the case. Wollastonf attempted to explain it, by some change in the distribution of the blood; the descending motion of the vessel causing an accumulation of blood in the brain, as it causes the mercury to rise in the tube of a barometer. But this explanation is too physical. The mercury, in an unyielding tube, is readily influenced by the motions of the vessel; but the blood in the living animal is situate far otherwise. It is under the influence of a vital force, which interferes greatly with the action of causes, that are purely physical. Were it other- wise we should be liable to alarming accidents, whenever the body is exposed to the slightest concussion. * Zoonomia, i. § 23. t Philos. Transact, for 1810. 556 DIGESTION. The generality of pathologists consider, that the first effect is upon the brain, "and that the sensation is produced consecutively, through the influence of that organ on the stomach ; and it is diffi- cult not to accord with this view; whilst we admit, that the precise manner, in which this is effected, is entirely beyond our cognizance, like every other phenomenon, indeed, of the nervous system. In the case of nausea, produced by the sight of a disgusting object, we have this catenation of actions somewhat more clearly evidenced. The impression must, manifestly, in this case, be conveyed to the brain by the optic nerves, and from that organ the sensation must emanate. It is probable, too, that when emetics are injected into the veins, the first effect takes place on the brain, and the stomach is affected secondarily. When the state of nausea, howsoever induced, continues for any length of time, it is usually followed by vomiting. The rejected matters are generally from the stomach, but if the retching, or violent contractile efforts of the muscles concerned, be long con- tinued, the contents of the small intestine also form part; hence, we account for the universality of the presence of bile in the rejected matters after an emetic has been taken, which is there- fore no evidence, in the generality of cases, of the person's being, what is termed bilious. The contents of the small intestine are returned into the stomach by an antiperistaltic action. The lon- gitudinal fibres take their fixed point below, and contract from above downwards; so that the chymous mass is forced towards the upper part of the canal, whilst the circular fibres contract from below to above. In cases of colica ileus, or the iliac passion, the inverted action extends through the whole intestinal canal; so that faecal matters, and even substances injected into the rectum, will force the ileo-caecal valve, and be discharged by the mouth. Of old, it was universally maintained, that vomiting is caused by the sudden and convulsive inverted contraction of the stomach ; and they, who admitted that the diaphragm and abdominal muscles take part in the action, looked upon them simply as accessories. Francis Bayle,* Professor in the University of Toulouse, in 1681, appears to have been the first, who suggested, that the stomach is nearly pas- sive in the act; and that vomiting is caused, almost exclusively, by the pressure, exerted upon that organ, by the diaphragm and abdo- minal muscles. His reason for this belief was founded on the fact, that, having introduced his finger into the abdomen of a living ani- ma'»'Whilst it was vomiting, he could not perceive any contraction of the stomach. In 1686, Chirac repeated the experiment with similar results; after which, the views of Bayle were embraced by many of the most eminent physiologists and pathologists,—by Senac, Van Swieten, Schulze, Schwartz,f and, at a later period, by the celebrated John Hunter,J who maintained, that the contraction of * Problemata Medico-physica et Medica. Hagce Comitis, 1678. 1 Haller. Elementa Physiol, lib. xix. § 14. X Observations on certain parts of the Animal Economy. Lond. 1786. VOMITING. 557 the muscular fibres of the stomach is not essential to the act. Many distinguished physiologists, however, ranged themselves on the op- posite side. Littre maintained, that the stomach is provided with considerable muscular bands, capable of powerful contraction; and that vomiting is often caused without the participation of the ab- dominal muscles, as in the case of ruminant animals. We have seen, however, that the rumination of animals more resembles re- gurgitation. Lieutaud* argued, that, according to Bayle's theory, vomiting ought to be a voluntary phenomenon; that the stomach is too deeply seated to be compressed by the neighbouring muscles, so as to empty it of its contents; and he details the singular case of a female, who, whilst labouring under an affection, for which eme- tics seemed to be required, resisted the action of the most power- ful substances of that nature. After her death, Lieutaud, feeling desirous to detect the cause of this resistance, had the body opened in his presence, when the stomach was found enormously dis- tended, but its structure unaffected. He, consequently, inferred, that the stomach had become paralyzed from over-distention, and that the effect produced was similar to that, so often met with in the bladder, when it has been long and largely distended. This case seemed to prove to him, that the stomach is the most concerned in the act of vomiting, as the abdominal muscles and diaphragm appeared healthy, and no obstacle existed to their contraction. It is singular, however, that the emetic substances should not have excited the contractions of the diaphragm and abdominal muscles; especially as there is reason for believing, that many of them at least, under ordinary circumstances, are taken into the blood, and affect the brain first, and through its agency the muscles concerned in the act of vomiting. The case seems to have been one of unusual resistance to the ordinary effects of nauseating substances, and cannot be looked upon as either favourable or unfavourable to the views of Bayle. We find, that vomiting does not follow the exhibition of the largest doses of the most powerful emetics, if the energy of the nervous system be suspended by the inordinate use of narcotics, or by violent injuries of the head. Lieutaud farther remarks, that, according to his theory, vomiting occurs at the time of inspiration; but this cannot be, as the lower part of the oesophagus is, at this time contracted, and if the vomited matters could reach the pha- rynx, they would pass into the larynx. Dr. Marshall Hallf has attempted, and successfully, to show, that the larynx is closed during vomiting; and has concluded, that the act is a modification of expiration, or that the muscles of expira- tion, by a sudden and violent contraction, press upon the contents of the stomach, and project them through the oesophagus. Haller} maintained the ancient doctrine, that the stomach, alone, is com- petent to the operation. His views were chiefly founded on hiss * Memoir, de 1'Acad. pour 1752, p. 223. t Journal of Science and Arts, xv, 388, X Op. citat, xix, 14 47* 558 DIGESTION. theory of irritability, which compelled him to admit the contraction, wherever there are muscular fibres; and on certain experiments of Wepfer,* who asserted, that when he produced vomiting by mine- ral substances, he observed the stornach contract. The Academie des Sciences of Paris, unsatisfied with the results of previous observa- tions, appointed Duverneyf to examine into the question, experi- mentally and otherwise; who, although he did not adopt the whole theory of Chirac, confirmed the accuracy of the facts on which it rested. He demonstrated that the stomach is but little concerned in the act; and that it is chiefly dependent upon the contraction of the diaphragm and abdominal muscles, which inclose the stomach as in a press, so that its contents are compelled to return by the oesophagus. On the other hand, in 1771, Portal,} in his lectures at the college of France, endeavoured to show, that the stomach is the great agent in vomiting. He administered to two dogs, arsenic, and nux vomica, which produced vomiting. The abdomen was immediately opened; and, according to Portal, the contractile movements of the stomach could be both seen and felt; and it was noticed, that instead of the vomiting being dependent upon the pressure of the diaphragm upon the stomach, it occurred at the lime of expiration; and was arrested during inspiration, because the depressed diaphragm then closes the inferior extremity of the oesophagus,—with such strength, indeed, that the contents cannot be forced into the oesophagus, when we press upon the organ with both hands. The views of Portal were confirmed by the experiments of Haighton.§ He opened several animals during the efforts of vomiting; and he states, that he distinctly saw the contractions of the stomach. In more recent times, the physiological world has been again agi- tated with this question. In 1813, Magendie|| presented to the French Institute the result of a series of experiments on dogs and cats,—ani- mals, which vomit with facility. Six grains of tartarized antimony were given to a dog; and, when he became affected with nausea, the linea alba was divided, and the finger introduced into the abdo men, to discover the state of the stomach. No contraction was felt; the organ appeared simply pressed upon by the liver and intestines! which the contracted diaphragm and abdominal muscles crowded upon it. Nor was any contraction perceptible to the eye; on the contrary, the stomach appeared full of air, and three times its usual size. This air manifestly came from the oesophagus, as a ligature, applied round the cardia, completely prevented its appearance! From this experiment Magendie inferred, that the stomach is pas- sive in vomiting. A solution of four grains of emetic tartar in two ounces of water was injected into the veins of a dog; and, as soon * Cicutro Aquaticas Historia, &c. Basil, 1679. t Memoir, de PAcadem. pour 1700, Hist. p. 27. t Cours d'Anatomie Medicale. Paris', 1804. § Memoirs of the Lond. Med. Society, vol. ii. ii MfmT fur *? yomiMement, P««, 1813; and Precis Elemental, edit. cit. ii. 15