ESSAYS 
ON 
MUSCULAR ACTION, 
WRITTEN IN 
1843 AND 1844, 
BY 
LOUIS MACKALL, M. D. 
WASHINGTON: 
THOMAS McGILL, PRINTER, 
1860. ADVERTISEMENT. 
The subject of muscular action is one of the first magnitude in the science 
of physiology, and, as such, has been laboriously investigated for many years 
past by the Scientists of Europe. It is at this time exciting among them more 
than usual interest. 
Since the discovery of electricity—from observing the effect of this agent 
on the muscles of recently killed animals—the impression has very generally 
prevailed that this difficult subject was destined to be fully elucidated by means 
of electrical experiments. Accordingly, all the investigations referred to 
above have been directed to this end. 
The anticipations resulting from this general impression have not been real- 
ized ; nor is this surprising, when it is considered that it has been attempted 
to establish, or to reason out a law of nature that belongs to one department of 
science, by making use of instances or phenomena that belong to another and 
very distinct department. The law of muscular action is a vital law, its 
operation is confined to the living body, and is observable nowhere else in 
nature. Electrical phenomena belong to Physics, and perhaps to Chemistry, but 
have no place in Physiology. 
For the last twenty-six years I have been engaged in investigating this sub- 
ject of muscular action, but have reasoned solely from instances derived from 
vital phenomena, or such as are observable in the living body. The following 
is a succinct account of my proceedings in this investigation: 
From often observing, in the practice of medicine, the inadequacy of reme- 
dial means made use of, and from frequently experiencing disappointment in 
my anticipation of the results of the operation of such means, I became con- 
vinced that there was something wrong—some great error in the theory or in 
the principles of medicine in which I had been taught. 
This eonviction was brought forcibly home to my mind by the death of my 
wife, from uterine hemorrhage, notwithstanding the use of all the remedial 
means known to myself and a very skilful medical friend who was present. 
Under the influence of grief, consequent on this bereavement, I resolved that 
I would devote the residue of my life to the task of endeavoring to discover, if 
possible, the error in the theory of medicine that I had before suspected, and 
in which suspicion I was confirmed by my late experience. 
While studying this theory in the books, for the above purpose, a case of 
whitlow (paronychia) was presented for treatment. Prompted by the resolve 
mentioned, I carefully noted the prominent facts of the case. I particularly 
noticed the pulsation of the arteries at the diseased point, and at the wrist; and 
my attention was forcibly arrested by observing the remarkable difference in 4 
that pulsation at the two points; that in the finger was full and strong, while 
the pulsation of the artery at the wrist was comparatively calm. 
Reflecting on the above fact, I arrived at the conclusion that there must be 
some agency in the arteries of the finger, that were throbbing so violently, to 
produce this result, that was independent of that in the general circulation ; 
and, in casting about in my mind for some suggestion as to what that agency 
could be, it occurred to me that the throbbing or distension of the arteries was 
occasioned by the action of their muscular fibres. The correctness of this ex- 
planation of the phenomenon in question, was confirmed by running over in 
my mind, as I did at the moment, a number of instances wherein irritation was 
attended with the distension or dilatation of the tubes or hollow organs, when 
such organs were supplied with muscular fibres—as in the oesophagus, in the 
stomach, intestines, in the uterus in pregnancy, &c. 
I had now arrived at a definite proposition; and in the year 1834, in Novem- 
ber, I wrote down that proposition in the following words: “All the tubes of 
the animal body which are supplied with muscular fibres, have their calibres 
increased by the action of those fibres.” This was shown and explained to 
four medical gentlemen at the time mentioned, and signed by them, witnessing 
that it was so shown. Three of these gentlemen, namely, Drs. J. H. Skinner, 
B. B. Hodges, and Wm. Ghiselin, are now (1860) living. One of them, the 
late Dr. Henry Brooke, died a few years since. 
In 1836 I forwarded a paper,setting forth the above idea by an application of 
it to a number of vital phenomena, to the Professor of Anatomy in the Uni- 
versity of Maryland, requesting him to advise me as to the best mode of bring- 
ing the subject to the notice of the medical profession. My communication was 
treated with contempt, as were also several papers written on the same subject 
and shown to members of the medical profession. 
Although I was fully convinced, from the period mentioned above, that the 
calibres of the tubes and hollow organs were increased by the action of their 
muscular fibres, I did not fully comprehend how this occurred until the spring 
of 1842. At that time, being in conversation with a gentleman who was fond 
of gesticulating, he, in derision of something that was said, thrust out his 
tongue over his under lip. This sudden elongation of the tongue instantly 
suggested that which I had been in search of for eight years—a rational ex- 
planation of the action of the fibres about the tubes. The truth flashed on my 
mind, that the fibres of muscles are actively elongated by innervation.'" 
In 1843, February 24th, I wrote the following “Essay on Muscular Action,” 
embracing the idea just mentioned—applying it to the action of all the muscles 
in the animal body, and showing its application by a number of experiments 
on living domestic animals and on my own person. This essay is certified by 
me, under oath before a magistrate, as having been written at the time at which 
it bears date. 
In 1844 I wrote another essay on the same subject, and illustrated my views 
by a reference to a large number of instances taken from Natural History. 
This essay is also included in this pamphlet. 
In 1848 I published a small pamphlet, entitled “Outlines of a New System 
of Physiology,” and at the same time a circular, to be enclosed with it, referring 
to instances in Natural History in corroboration of the correctness of my views 5 
of muscular action. This pamphlet and circular were gratuitously distributed 
the same year to all the most distinguished physiologists and physicians in 
Europe and in this country of whom I had any account. 
In 1850, having carefully reflected on and retraced the mental process by 
which I had been enabled to arrive at and to apprehend the law of muscular 
action, I wrote and published an essay, entitled “ An Account of the Seasoning 
Process,” and instanced this process in the discovery of this law. 
In 1852 was published my “Notes on Carpenter’s Human Physiology;” and, 
In 1857, the first forty pages of “ Principles of General Physiology”—merely 
as a record of conclusions at which I had arrived, but which I had not had 
time to arrange in any order. 
In 1859, in May or June, my Essay on the Law of Muscular Action was 
printed. 
Most of the above publications have been distributed freely and gratuitously, 
wherever it was thought probable they might awaken an interest. 
LOUIS MACKALL, M. D. 
Georgetown Heights, 
January, 1860. AN ESSAY ON MUSCULAR ACTION. 
“ Non alius fere sit aditus ad regnum hominum ut fundatur in scientiis, quam 
ad regnum colorum ; * in quod, nisi sub persona iufantis, intrare non datur.’ ” 
It is assumed by physiologists that there is a certain subtle 
fluid, termed the nervous fluid, transmitted through the nerves 
to the muscles. This transmission of the nervous fluid to the 
muscular fibre is termed innervation. 
It has always been thought, and is thought at the present 
time, by physiologists, that the effect of innervation is contraction 
of the muscular fibre. This is not considered an abstract propo- 
sition, laid upon the shelf as one of those the truth or the fallacy 
of which is immaterial. No; it is taken as one of the funda- 
mental principles—one of the main axioms of the Science of 
physiology. In explaining locomotion, the circulation of the 
blood, digestion ; in short, in explaining all the functions of ani- 
mal life, there is a constant recurrence to this principle ; and in 
any process of reasoning on physiological subjects, the mind 
must continually recur to this axiom. The proposition, that 
innervation causes muscular contraction, bears the same relation 
to the science of physiology, as the proposition, that “ things 
which are equal to the same are equal to each other,” bears to 
the science of geometry. 
Having studiously examined and closely observed the phe- 
nomena of life connected with this subject, and having made some 
careful experiments on the same, I am prepared to assert that 
this axiom, adopted by physiologists, is false—totally false. I 
declare boldly, that innervation does not cause muscular con- 
traction, but a state diametically the opposite of contraction— 
elongation. 
We will take an instance—the most familiar—the tongue. 
For the sake of elucidation, we will consider the tongue as one 
muscle. Here, then, is the point at issue. We can elongate or 
shorten the tongue at will. Physiologists assert, that by deter- 
mining a flow of nervous fluid to this organ or muscle, wre cause 
its contraction, and by withdrawing or diverting elsewhere the 
nervous fluid, we cause its relaxation or elongation. I maintain 
that, by determining nervous fluid to this muscle, we cause its 
elongation; and that elongation is exactly in proportion to the 8 
power we possess of innervating this organ. The contraction of 
the tongue is caused, I contend, simply by a withdrawal of the 
nervous fluid. Man possesses the faculty of elongating or of 
shortening his tongue to a limited extent, but this faculty is pos- 
sessed to a remarkable degree by some of the lower orders of 
animals, as lizards, serpents, &c. It may be suggested that the 
elongation or protrusion of the tongue may be attributed to the 
contraction of the muscles attached to it, but I confidently 
defy physiologists to show any muscles, the contraction of which 
could produce the state of the tongue referred to above, and 
particularly that observed in the lower animals. 
I have said that the opinion that innervation causes muscular 
contraction was erroneous, and to show that it is, let us attend 
more particularly to the phenomenon alluded to above. A rat- 
tlesnake* is confined in a cage; we scrape harshly on the side of 
the cage ; it becomes violently excited; it shakes its rattles, erects 
its head, and protrudes its tongue to the extent of several inches. 
The tongue of this animal, as that of every other animal, is mus- 
cular. It is evidently in a state of action. The cause of this 
action must be derived from its nerves, for there is no way of 
operating on the muscles except through the medium of the 
nerves The operation of the nerves in the instance before us 
could not be that of withdrawing the nervous fluid from this 
muscle or organ. It would be absurd to say that the state of 
this organ which we are contemplating is that of relaxation. 
The only mode, then, in which the nerves could operate on the 
organ in question, is that of innervation. 
Innervation, then, causes elongation in this instance, and I 
proceed to show that it produces the same effect in other in- 
stances. We will take the ciliary processes. This is one of 
those muscles which, like the tongue, is attached by one of its 
extremities, whilst the other extremity is free. Let us observe 
the muscle in the eye of this horse. He is withdrawn from the 
light into the stable ; the ciliary processes are contracted ; the 
pupil is enlarged. He is led slowly to the door of the stable; as 
he approaches the light, the ciliary processes are elongated; and 
now that he is in the full light of day, they are so much elon- 
gated as to have reduced the pupil to a small opening. The 
horse is again withdrawn slowly from the light and returned to 
his stall. As he recedes from the light, the ciliary processes 
become gradually shortened, until the pupil is enlarged to the 
* The instance here alluded to had been observed a day or two before writing 
this essay at the U. S. Patent Office; where, among other subjects of natural 
history, a rattlesnake confined in a wire cage, was exhibited, and where I made 
the experiment referred to. size it was when we first noticed it. In this instance, again, the 
muscle is in a state of action or of innervation from the exciting 
cause—light—and the effect is elongation, and not contraction. 
I might adduce another familiar instance* of the same character 
as those mentioned, which would furnish arguments still more 
conclusive on this point, hut I forbear. What has been written is 
sufficient to explain the position I have taken, and I make no 
doubt that, as we proceed, the truth of that position will be 
made apparent. 
Having noticed the physiological action of some of those mus- 
cles having one of their extremities attached, we will proceed to 
notice briefly the action of some having both extremities at- 
tached. We will take the flexors and extensors of the fingers, 
and, to render the subject more simple, and to make our remarks 
more easily understood, we will assume that all the flexors of the 
fingers are one muscle, and all the extensors of the same, one. I 
grasp in my hand this rule lying on my table—the flexor muscle 
is contracted, that portion of the muscular fibres near the wrist, 
which, before the contraction, gave a rotundity and fulness to 
that part of my arm, is so contracted as to cause a hollowness 
there. Physiologists assert that this state of the muscle is caused 
by innervation; that is, by a determination of nervous fluid to the 
muscle. It was probably in observing this very phenomenon we 
are now contemplating, that the false inference was drawn, that 
innervation causes muscular contraction. There is no evidence 
before us that there is an innervation of this flexor muscle. We 
have no reason for such a supposition. It is true, my attention is 
turned to this muscle while in a state of contraction, and there 
is an effort to continue or increase the contraction; but may not 
that effort consist in withdrawing nervous fluid from this muscle 
instead of determining to it ? I grasp the rule still more firmly. 
What do I observe ? The flexor muscle is, indeed, still more 
contracted, but the extensor muscle is considerably developed. 
The portion of this muscle, which, before this effort of contracting 
the fingers, was not observable, is now palpably enlarged, and 
that, too, in proportion as I increase my present effort. Having 
shown in the instances before enumerated, that innervation causes 
elongation of the muscular fibre, I infer from this fact that the 
extensor muscle is innervated in the act of grasping, and that 
the nervous fluid is withdrawn from the flexor muscle during 
that operation. Again, my fingers are moderately flexed, and 
the back of them placed against a resisting body—the table. 
An effort is made to extend or straighten them. The extensor 
* My allusion here was to the male organ of generation. 10 
muscle is contracted, and evidently diminished in size, but the 
flexor muscle is becoming larger and more developed. If the 
effort is increased, instead of the hollowness remarked in the 
former experiment, there is considerable fulness and enlarge* 
ment of the muscle near the wrist. From this experiment I 
draw the same inference as from the former, viz: that the ner- 
vous fluid is withdrawn from the contracted muscles, and deter- 
mined to the muscle which was elongated or enlarged. Another 
inference from these experiments is, that where there are antagon- 
izing muscles, motion is not the result of the action of either set 
of muscles exclusively, but the result of the motion of both sets. 
Thus, in grasping the rule, the action of the extensor muscle 
contributed to that act as well as the contraction of the flexor. 
Another inference may be, that the tendons are not, as laid down 
in all our works of physiology, mere ropes or pulleys, but are 
parts of muscles as important as the fleshy portion ; that they 
are supplied with nerves, and are acted upon by the nervous 
fluid in the same manner as the fleshy parts of the muscles are. 
Thus, that the flexor muscle has its tendon shortened as much as 
its fleshy portion, and the extensor has its tendon elongated in 
the first of the above experiments, &c. 
Let us dwell awhile on the phenomena before us. I have said 
that it was from probably observing the contraction of muscles, 
that the erroneous conclusion was adopted that contraction was 
caused by innervation. I say further, that from observing mus- 
cular contraction, physiologists draw this still more absurd 
inference, that muscular action and muscular contraction were 
one and the same thing, and the terms used to express those 
states, are synonymous and convertible terms. Whereas, those 
two states of a muscle, so far from being identical, are opposite. 
Why is it that physiologists have not endowed animals with 
the power of producing muscular contraction by withdrawing 
nervous fluid from the muscle, when that muscle notoriously has 
its size diminished, or occupies a less space, in consequence ot 
being contracted ? Is it not more reasonable to suppose, that a 
body could be lessened by taking somewhat from it than by 
adding to it ? 
I have attempted to show, in a very brief and cursory manner, 
that the physiological axiom, that innervation causes muscular 
contraction, is false, when applied to the explanation of the action 
of two classes of muscles; and it remains for me to show that 
this axiom cannot be admitted in explaining the action of the 
muscles constituting the tubes or hollow organs. This principle 
is not only tacitly allowed by physiologists in explaining the 
functions of the hollow organs, but, at the very outset of such 
explanations, we are gravely informed that the tendency of the 11 
action of the muscular fibres placed around such organs is, to 
obliterate their cavity. But the truth is, that the tendency of 
such action is exactly the reverse, namely, to enlarge the cavities of 
the tubes. I repeat, that in every instance that has come under 
my observation, where there has been innervation or determina- 
tion of nervous fluid to a living animal tube, it has caused a 
dilatation or enlargement of its cavity, and not an obliteration. 
It appears strange that the ancient physiologists should have 
thought the arteries did not contain blood, but only animal 
spirits, when they must have had so many opportunities of 
observing the arteries pouring out blood. But it is passing 
strange that physiologists even of the present day should shut 
their eyes against so glaring a fact as that we are now treating of. 
I can account for so strange an oversight only by supposing 
that the axiom, that innervation causes muscular contraction, had 
been adopted before the muscular fibres about the tubes were ob- 
served or demonstrated. Some of those fibres are semi-circular 
and some longitudinal. If we admit that innervation contracts 
those fibres, we must admit the conclusion that innervation oblit- 
erates the cavity of tubes. But I assert that this conclusion is 
utterly false, and I am borne out in this assertion by the phenom- 
ena constantly before our eyes. If the conclusion is false, as I 
shall presently proceed to show, then the premise, the above axiom, 
must be false. We will take an instance of a muscular tube, the 
oesophagus. As this tube is very muscular and highly sensitive, it 
will be easy to cause innervation, by irritating it. I expose the 
oesophagus of this living rabbit by carefully dissecting the integ- 
uments so as not to injure the nerves. I introduce a feather into 
• its mouth, and gently irritate the upper portion of the oesophagus. 
What do I observe ? There is suddenly a dilatation of the part of 
the tube irritated—not a contraction—but a palpable dilatation. 
This dilatation is confined to a small portion of the tube at a 
time, say to the extent of four lines. After having taken place 
in one portion, it ceases there, and is transferred to the adjoining 
portion of the tube of the same extent, and thus proceeds alter- 
nately and regularly from one end of the tube to the other. This 
operation is repeated as often as I cause an act of deglutition by 
irritating the fauces. 
We will make the experiment on another animal, in which in- 
nervation may be more readily effected. Let us take the game 
cock. We expose the oesophagus, as in the case of the rabbit. I 
make the same experiment with the same result. I have a solution of 
tartarized antimony by me, into which I dip the end of the feather, 
and again apply it to the fauces. The dilatation is greater than 
before, and passes from one extremity of the tube to the other. 
Since using the tartarized antimony, the whole tube is sensibly 12 
enlarged. Now, the dilatation commences at the other extremity 
of the oesophagus, that next the crop, and proceeds towards the 
fauces—the same action as before, but only its course reversed. 
It might be imagined that this dilatation was caused by something 
contained; but it was evident that the tube contained nothing. 
However, to make the thing certain, I pass two ligatures under 
the oesophagus at such distance from each other as just to include 
the portion which is dilated. A single tie is made on the liga- 
tures, but they are left loose. An act of deglutition is caused. 
When the dilatation reaches the space between the two ligatures, 
these are suddenly tightened ; the dilatation of the portion inclu- 
ded by the ligatures ceases as before, and nothing is found in the 
tube. A grain of corn is introduced into the upper portion of 
the oesophagus—that tube is momentarily dilated—it then begins 
to contract; as the first portion of the tube contracts, the adjoin- 
ing portion dilates, and when sufficiently dilated, the grain of corn 
passes into it. This operation is repeated until the grain has 
passed the whole length of the tube. I press the use of the tar- 
tarized antimony, and now the contents of the crop passes into 
the oesophagus and is ejected by the mouth—vomiting is produced. 
I observe that in the passage of any body through this tube 
there never appears to be any pressure of its walls on the body 
that is passing; but the motion of the body passing, appears to be 
the effect of the dilatation as well as of the subsequent contrac- 
tion of the tube. When contraction takes place after every act 
of dilatation, it is carried, momentarily, beyond the natural state, 
or its state of rest, and then immediately returns to that state. 
The fallacy of the principle I have been combating, is, I conceive, 
clearly shown in the phenomena observed in the above experiment. . 
Irritation or innervation does not cause contraction or an obliteration 
of the cavity of the oesophagus but manifestly an opposite state, dila- 
tation. Nor is this a solitary instance. Nature is uniform in her 
operations. When the stomach is irritated or innervated by taking 
stimulating articles of food, &c., is there not a sensation of dis- 
tension ? When the intestines are innervated, is there not the 
same sensation ? The uterus is innervated in pregnancy, and in 
consequence of that innervation, is dilated or enlarged. In con- 
nection with the latter remark I will mention a case : Shortly 
after adopting my present view of muscular action, I was called 
to visit a woman in labour. She was of about the middle age, 
was healthy and robust; there was considerable general excite- 
ment of the system, but the pulse not remarkably full. She had 
been in labour twenty-four hours or more. At first, parturient 
efforts were tolerably strong, but for twelve hours immediately 
preceding my visit the pains had subsided ; and when I saw her 
there appeared to be no disposition in the uterus to contract. I 13 
determined to try if I could not cause uterine contraction by di- 
minishing the general excitement and by lessening the powers of 
life. For this purpose a bowl of pounded ice was procured, and 
the patient made to swallow the ice freely ; in a minute or two, 
or as soon as the system was brought under the influence of ice, 
the uterus contracted forcibly and the fetus was expelled. This 
occurred, I find by reference to my books, on the 26th day of May, 
in the year eighteen hundred and thirty-five. 
Soon after this occurrence I relinquished the practice of medi- 
cine, in which I had been engaged in Maryland, but mentioned 
the circumstance to several of my medical acquaintances in the 
vicinity. I have been since informed by them that the practice 
has been very generally adopted in that neighborhood, and with 
great success.* I have in one case, recently, in Georgetown, 
very similar to the one mentioned above, advised the use of this 
agent, and with the same successful result. 
But to return to our experiment. What is termed peristaltic 
action is here, I think, fairly explained. The first stage in that 
action is, as we have seen, dilatation ; and the second stage, that 
of contraction, is merely the consequence of the expenditure of 
innervation in the first stage. What has been observed in the 
o # 
action of the oesophagus may be observed in all other animal 
tubes, differing only in the extent of their action ; thus the 
stomach has an extent of action greater than the oesophagus ; 
the intestines greater than the stomach; the arteries greater 
than the intestines; for the action of all the arteries in the ani- 
mal body is synchronous, and alternates with that of the heart. 
But let us apply the principle in question to the action of blood- 
vessels. I strip up my sleeve, and apply a small sinapism on 
the forepart of the wrist—irritation and consequently innerva- 
tion is caused. The bloodvessels are not contracted, but, on the 
contrary, are enlarged, and the part appears red from the en- 
largement of those vessels. They evidently contain more blood 
than before the experiment. After what has been written, is it 
not more satisfactory to attribute this increased quantity of blood 
to the dilatation of those vessels caused by innervation, than to 
attribute this dilatation to the increased flow of blood to the 
part ? The importance of the subject we are treating is so great 
that I shall be excused for introducing the following instance to 
show the fallacy of the principle 1 have been combating, by show- 
ing the extremly ridiculous conclusion to which it must inevita- 
bly lead. I refer to the condition of the organs of reproduction 
* See letters from some of these gentlemen at the end of my little pamphlet 
entitled •• Outlines of a New System of Physiology,” published in 1848. 14 
in the act of copulation. The male organ, the penis, is clearly 
muscular ; the female organ, the vagina, is surrounded by mus- 
cular fibres. In the venereal orgasm these organs are highly 
innervated. If it is true that innervation causes muscular con- 
traction, and that the tendency of the action of the muscular 
fibres about tubes is to an obliteration of their cavity, then, in 
this condition of things, ***** 
LOUIS MACKALL, M. D, 
Georgetown Heights, 
February 24, 1843. AN ESSAY ON MUSCULAR ACTION. 
It is assumed bj physiologists that the transmission of the vital 
fluid to the muscular fibre, causes the globules of which that is 
composed to approach each other—causes the muscular fibre to be 
shortened or contracted. 
The very basis of physiological science, as it now exists, is foun- 
ded on the assumption that innervation causes contraction of the 
muscles; and, in all our systems of physiology, muscular action 
and muscular contraction are considered synonymous and con- 
vertible terms. 
The view I take of muscular action is, that the transmission or 
accession of the vital fluid separates the globules of which the 
single muscular fibre is composed, causing the extension or elonga- 
tion of the fibre.* The general law of the animal economy to 
which I wish to call the attention of the reader, is that innervation 
causes extension of the muscles. 
I will not now take the reader through the circuitous and devious 
route by which I arrived at this conclusion, but will apply the 
general law which I have proposed, in explaining a few phenom- 
ena mentioned in natural history; and thus the best proof that 
could be given of the truth of my position will be found in the 
facility and readiness with which it explains those phenomena. We 
will take, as the first instance, a phenomenon observed in the snail, 
(Helix Nemoralis.) The eyes of this singular animal, we are told 
by naturalists, is situated at the extremity of two muscular tubes 
projecting from the head, to the length of nearly an inch.f The 
muscular fibres surrounding these tubes are placed circularly. 
There are also distinct muscles arising from the lower part of its 
abdomen, traversing the body of the animal and these muscular 
tubes, and are inserted around the eyes at the extremity of the 
tubes.| The large optic nerves, enclosed in their own sheaths, 
accompany these muscles through the tubes. In a state of repose, 
* As the subtle fluid, heat, separates the particles of bodies, and causes ex- 
pansion, so the vital fluid separates the globules composing the fibres, and 
causes extension of the muscles; and as the abstraction of heat causes the con- 
traction of bodies, so the abstraction of the vital fluid causes the contraction of 
muscles. The means by which that abstraction is effected I propose to show 
hereafter. 
f Jones’ Animal Kingdom, fig. 195. JFig. 184, $430. 16 
the tubes are inverted, and the eyes are drawn within the body; 
hut when the animal is roused by the want of food or other cause, 
it protrudes these tubes so as to have the benefit of its eyes. If 
the reader understands the anatomy of the eye of the snail, which 
I have attempted to describe, he will understand at once, how this 
animal could, by an act of volition, determine the vital fluid to 
the longitudinal muscle I have mentioned—cause its extension, 
and thus cause the protrusion of the eye. A like determination 
of the vital fluid to the circular muscle constituting the tube, 
would enable it to act in concert with the former muscle to mod- 
erately enlarge the tube, and thus assist in protruding the eye. Thus, 
in the instance before us, the application of the general law I pro- 
pose, enables us clearly to understand the appearance presented. 
But let us advert to the explanation of this phenomenon given 
by physiologists—and it is the only explanation that can be given 
if we assume that innervation causes muscular contraction. They 
tell us that portion of the circular muscle or tube which happens 
to be immediately behind the position of the eye, begins to con- 
tract, and by continuing this action alternately to the extremity 
of the tube, overcomes the contraction of the longitudinal muscle, 
and protrudes the eye! Does not the reader perceive that if the 
eye of this animal were drawn within its body, and beyond the 
range of the tube, as it undoubtedly is very frequently, that the 
contraction of the tube at any point would only tend to prevent 
the protrusion of the eye. Again, if the eye could be protruded 
by the means referred to, would not a contraction of the circular 
muscle, carried to such an extent as to overcome the contraction 
of the longitudinal muscle, be sufficient to interrupt seriously, if 
not altogether, the function of sight, by compressing the optic 
nerve which lies by the side of this muscle ? 
But let us take another instance from natural history, some- 
what similar to the above, in which the explanation given by physi- 
ologists is still more unsatisfactory, and in which the assumption 
that innervation causes muscular contraction will appear still 
more absurd. Let us direct our attention to the tongue of the 
ant-eater, [Mynmeco-phaga.) 
Naturalists inform us that the tongue of this animal is formed 
of two muscles : one longitudinal, arising from the sternum or 
breast bone, and passing among the muscles of the neck, is in- 
serted in the end of the tongue; the other arises from the os hy- 
oides, and is placed spirally around the former.* The length of 
the longitudinal muscle, in an animal of middle size, would be 
about seven inches, in a state of repose; the length of this mus- 
*0p. Cit,, §751. 17 
cle, in a similar state, from the os hyoides to the extremity, would 
be between four and five inches. It is stated in natural history 
that this animal can protrude its tongue to the extent of seven- 
teen or eighteen inches ;* and we are gravely told by physiolo- 
gists that the protrusion of the tongue of the ant-eater is effected 
by the contraction of its spiral muscle ! The absurdity of such a 
supposition is monstrous. As there is no possible wray of ac- 
counting for the protrusion of the tongue in this animal by 
the contraction of any muscles attached to it, we are forced to 
admit the truth of my position, that innervation causes extension 
and not contraction of the muscles. 
I will refer to another instance out of many in which the same 
protrusion or elongation of the muscle is seen, but in which there 
is no spiral muscle by means of which that elongation could be 
effected—I mean the tongue of the frog. The tongue in this ani- 
mal is principally composed of longitudinal muscular fibres which 
arise from the anterior portion of the lower maoeilla.t The frog 
can protrude its tongue to the extent of several inches, seize a 
fly or other insect, and draw it into its mouth. This act it per- 
forms with wonderful celerity—with the speed of lightning. There 
is no way of explaining this phenomenon but by means )f the 
general law that innervation causes extension of muscles. 
But in order to illustrate this law, I need not confine myself to 
instances taken fron natural history. I will take them nearer 
home. If the reader will protrude his own tongue to some extent, 
and continue it in that position for a moment, he may observe 
that the protrusion is mainly effected by extending or elongating 
the longitudinal fibres of his tongue ; and that he is actually de- 
termining to that organ a flow of vital fluid. Again, let the reader 
take a small mirror in his hand, and, standing in a part of the 
room where the light is partially excluded, let him observe the 
muscular fibres of his own iris placed around the pupil of his eye, 
then let him approach the light, and he will perceive that the 
muscular fibres of the iris are extended or elongated in proportion 
as the stimulus or cause of motion in the vital fluid is increased— 
light being the appropriate stimulus of this organ. 
I request the reader’s attention to another familiar phenome- 
non. I wish to show that the law I have been endeavoring to 
establish is not the only important object that has escaped the 
observation of physiologists. Let the reader place his arm on 
the table before him; let him strip up his sleeve, so that he may 
observe the action of the muscles of the forearm. In a state of 
*Cuvier’s Animal Kingdom, edited by Griffith, vol. 3, p. 300. 
fOp. Cit., Jones’ Animal Kingdom, §611 and 612. 18 
repose the fingers are slightly flexed; but let the reader shut 
his hand tightly—the muscles on the front of the forearm and 
in the palm of the hand are contracted; the fleshy fibres have 
their extremities drawn nearer together ; the upper portion or 
belly, as it is called, of those muscles is swollen or thickened. 
Physiologists have inferred—from the appearance of the muscles 
of the forearm and the palm of the hand, in the action we are 
now contemplating, and especially from their appearing enlarged 
or swollen—that those muscles were in a state of action ; and 
being entirely convinced of the correctness of this conclusion, 
they thought it useless to look any further. I now assure the 
reader that that conclusion was altogether erroneous—that it 
was a gross fallacy. Let us look a little further. What is the 
condition of those muscles called the extensors, during this act 
of shutting the hand ? These muscles are elongated—their 
fleshy fibres are extended; and hut a little attention will con- 
vince the reader that in the act before us the muscles, now re- 
garded as the extensors, are in a state of action; while those 
muscles, now regarded as the flexor muscles, are in a contrary 
state, or in a state of inaction—the shortening and consequent 
thickening or swelling of their fleshy portions being the effect of 
an abstraction of the vital fluid. Again, in the act of opening 
the hand, the muscles now termed flexors are in a state of action, 
and those termed extensors are in a state of inaction ; so that 
physiologists have made a grand mistake in their nomenclature. 
The view I have advanced of muscular action is confirmed by 
the fact that, when an individual has the tendon of the gastroc- 
nemius muscle ruptured, he is unable to raise his toes.* 
In connection with this subject, it may he observed that the 
tendons should not be regarded as mere ropes or pullies, by 
means of which the muscles are inserted in and move the bones. 
But, as recent anatomists have considered a muscle and its ten- 
don as constituting one organ, so they should be regarded as 
being influenced by the same cause of action. Thus, the tendinous 
portion of a muscle is elongated equally with the fleshy portion, 
when that organ is in a state of action ; and shortened, when in 
a contrary state. Ligaments, too, may be elongated or shorten- 
ed by the same cause. 
I need not remark that the view I have given of the action of 
the muscles employed in opening and shutting the hand will 
apply equally well to the action of all the muscles in the animal 
system. Thus, in locomotion—walking, running, leaping—the 
extensor muscles are in a state of action, &c. 
* This fact is stated by Mr. John Hunter, who suffered from a fracture of the 
tendo A chillis. 19 
But the most important application, in a physiological point 
of view, is to the muscular fibres placed around the tubes or 
hollow organs. Some of the fibres placed around those organs 
are semi-circular, some spiral, and others longitudinal. If it be 
assumed that innervation contracts those fibres, it must be ad- 
mitted that innervation causes the diminution of the calibre of 
those organs—causes their systole ; and this conclusion is actu- 
ally adopted by physiologists, and acted on by physicians. I 
assert here that this conclusion is utterly erroneous, and contra- 
dicted by all the phenomena of animal life in which such law 
is involved. The truth is, as I shall proceed to show, that in- 
nervation causes dilatation of the tubes or hollow organs. It 
was in observing the uniformity of this fact in nature that my 
attention was first drawn to our present subject. I observed 
many instances of the fact in question, and to convince myself 
of its reality, made many experiments. (My first step, was the 
discovery that this dilatation was effected by means of the mus- 
cular fibres. This fact was committed to writing by me, and 
attested by a number of the most respectable physicians of my 
acquaintance in the year eighteen hundred and thirty-four, 
1834.) 
But to proceed. I will here state only one of the experi- 
ments, out of many, as this one is perfectly conclusive. A 
barn-yard fowl was secured on his back to a board by ligatures 
passed through holes bored in the board; his neck was extended 
and'secured in the same way, by a ligature passed through the 
crest or comb. An incision was made through the integuments 
on the side of the neck, from the pharynx to the crop; the 
oesophagus was thus fairly brought into view. A feather was 
introduced into the mouth of the animal, and the fauces irritated, 
so as to cause an act of deglutition; the pharynx was instantly 
dilated, and the dilatation passed deliberately and regularly 
through the whole course of the oesophagus; the portion of the 
oesophagus dilated at any time did not exceed probably the length 
of three lines, or about a quarter of an inch, but this dilatation 
proceeded alternately from one portion of the tube to another, 
throughout its whole course, beginning at the pharynx and ter- 
minating at the crop; the dilatation was very palpable, being 
of twice the diameter of that part of the tube which was in a 
state of repose. To convince myself that the dilatation was not 
caused by any substance within the oesophagus, I passed two lig- 
atures under this tube, about the middle, at such a distance from 
each other as would include the dilated portion of the tube; the 
ligatures were tied by a single turn, but left perfectly loose. I 
held.the ends of the ligatures, and made an assistant cause an 
act of deglutition in the animal; when the dilated portion reached the space included between the two ligatures, I suddenly 
drew them tight—the dilatation between the ligatures ceased, 
and that part of the tube returned to its normal state or state 
of repose, showing that there was no substance contained within 
it that could cause its dilatation. I then dipped the feather in 
a strong solution of tartarized antimony, and applied it to the 
fauces—the dilatations were greater than before. After con- 
tinuing this irritant for some little time, the whole tube was 
somewhat enlarged, and then the action of the tube was reversed; 
the dilatation commenced at the extremity of the tube next the 
crop, and proceeded to the pharynx. 'Finally, some of the con- 
tents of the crop were ejected through the mouth. 
I observed in this experiment that when the dilatation passed 
away from a portion of the tube, that that portion of the tube 
was immediately contracted to a smaller diameter than before its 
dilatation, and then instantly returned to its normal size. This 
appearance seems to have monopolized the attention of experi- 
mentalists ; but I conceive this contraction is owing to the cir- 
cumstance that the vital fluid had been expended in this portion 
of the tube by the previous act of dilatation. The above ex- 
periment has been repeated often by me, and with the same 
results. 
If the reader will examine carefully the above experiment, or 
will make others on this subject, he will be convinced with me 
that innervation causes dilatation of the tubes ; and consequent- 
ly that the general law is true which I have been endeavoring 
to establish, namely, that innervation causes the extension of the 
muscles. 
This truth is still more apparent when the law is applied to 
the explanation of the functions of animal organs. 
1st. Of the nervous function. We will assume that the brain 
and nerves are composed of tubes through which the vital fluid 
circulates. This circulation, I believe, is very similar to the 
circulation of the blood. The nerves have been divided into 
those of motion and those of sensation. The nerves of motion 
correspond with the arteries; the nerves of sensation with the 
veins. The brain and spinal cord, or the cerebro-spinal axis, 
correspond with the heart. This heart of the nervous system, 
in a state of action, dilates; in its opposite condition or state, 
it is contracted. When it dilates, it draws the vital fluid from 
the nerves of sensation and of motion; when it is contracted, 
that fluid is imparted to the nerves of motion. Thus the circle 
or circulation of the vital fluid is made. 
Before I proceed with this point, I will endeavor to give some 
general notion of what I mean by the vital fluid. I do not know 
that I can do this better than by comparing it to the fluid called 21 
lioat. I propose to call this fluid Life. It would serve to give 
a definite meaning to a word which is in everybody’s mouth—whose 
meaning now is extremely vague and indefinite. This fluid, Life, 
then, is the most important substance in the universe. It is 
possessed of ubiquity ; it enters as the principal ingredient into 
every object in creation. Take away this fluid, Life, from any 
object, and it immediately ceases to exist. Like heat, too, it 
may be considered as existing in bodies in different states. 
Bodies may be possessed of fixed life, or life of composition, and 
free life, or that which they are continually receiving from and 
imparting to the bodies around them. 
Every object in creation, animate and inanimate, is continually 
receiving or parting with a subtle fluid, Life, and—to proceed with 
the nervous function, this fluid is absorbed by the nerves of sen- 
sation of animals.* Animals receive this fluid, Life, through the 
medium of the nerves of the senses—those of respiration, diges- 
tion, &c. 
As there appears a design in nature that there should be a re- 
lation between the reception and expenditure of this vital fluid, 
animals expend it in muscular action, in extension of the long 
muscles, those of locomotion, &c., in dilating the tubes, but prin- 
cipally in the secretions. This last mentioned mode in which the 
vital fluid of animals is expended, is very apparent and very im- 
portant, in a practical point of view, though physicians seem not 
to have regarded it. The secretions of animals contain an excess 
of this vital fluid ; and the rapidity with which the vital fluid, or 
what is called the strength of an animal, is reduced by increasing 
the secretions, is very striking. The sounds caused by animals, 
the human voice, the singing of birds, the cries of other animals, 
the humming of insects, &c., seems to me the means provided by 
nature for the expenditure of the vital fluid. 
Having thus given a very rough outline of my views of the 
cause of muscular action, and of muscular action itself, we will 
proceed to apply the general law I have laid down to some par- 
ticular cases. Not to dwell on the instances in the lower classes 
of the animal kingdom, wherein elongation of the muscles is the 
result of acts of volition, we will only enumerate a few of them, 
and pass on to the higher classes of animals, in which the muscular 
and nervous systems are more fully developed. 
In Actinigef the tentacula having longitudinal muscular fibres 
can be elongated or contracted according to the will of the ani- 
mal. In the act of feeding, the tentacula are protruded or 
elongated ; in a state of repose, those organs are retracted. 
* I meant the afferent nerves. f Jones’ Animal Kingdom, fig. 11, § 54. 22 
The Physalus* is said to possess the power of elongating its 
tentacula to the extent of a fathom or more, when it wishes to 
attach itself to some object at the bottom of the water on which 
it is floating. 
The Beroef extends its tentacula in a remarkable manner in 
the act of feeding, and retracts them within its body in a state 
of repose-! 
Leaving the first division of the animal kingdom, (the acrita,) 
and entering upon the second division, (the nematoncura,) we 
will take the Stephanoceros Eichornii.§ This animal is enclosed 
in a horny case or tube attached at its base to some sub- 
marine object, and having its upper extremity open, through 
which the animal can, at will, protrude not only its tentacula, 
but its body to a ccrtaip extent. A muscle, composed of longi- 
tudinal fibres, arises from the bottom of its horny case, and is 
inserted into the membrane surrounding the body of the animal. 
The protrusion of the body is effected by the elongation of this 
muscle. 
I refer the reader, for other instances in this division of the 
animal kingdom, to a paper on some species of bryozoa, pub- 
lished by Dr. Arthur Farre in the Philosophical Transactions 
for the year 1837. In this paper we have a clear and beautiful 
description of the phenomena presented by those animals, and 
also of their muscles. Application of the general law which 
I have proposed would furnish an easy and satisfactory explana- 
tion of those phenomena. 
In Echini and Asteri8e|| the extension of the longitudinal mus- 
cular fibres attached to their pedicles or suckers would explain 
the protrusion of those organs more readily than the mode now 
resorted to for that purpose. 
In the third division of the animal kingdom we will take 
as an instance the Leech. This animal** has a strong muscle 
composed of longitudinal fibres extending through the whole 
length of its body. It fixes itself by means of a sucking disc 
placed at the posterior extremity, and elongates its body to a 
considerable extent; that this elongation is not caused by the 
contraction of any circular fibres surrounding its body will be 
very manifest to any one who will closely observe the phenom- 
enon in question. The elongation of the body of the leech 
must be attributed to the extension of its longitudinal muscle. 
The Serpula Contuplicataff has a disc attached to longitudinal 
muscular fibres, with which it closes its external covering; when 
* Jones’ Animal Kingdom, Fig. 24, $ 96. 
+ Fig. 48, l 154. 
|| Figs. 64 and 65, § 190. ** § 234. 
f Fig. 22, 2 95. 
\ Sec. 105? 
ff Op. Cit., fig. 78, § 283. 23 
it wishes to protrude its tentacula it pushes up this disc by means 
of these muscular fibres. 
The trachem of insects* are lined with a delicate muscle 
placed spirally within the cavities of those trachea; throughout 
their whole extent. It is very evident that the elongation of 
the muscle thus situated would tend to dilate the trachea}, and 
thus cause an inspiration of air; and, per contra, the contrac- 
tion of this spiral muscle would tend to lessen the calibre of the 
trachese, and cause an expulsion of the air. 
The Onychoteuthis, in order to seize its prey, suddenly ex- 
tends its long brachial tentacula to a considerable distance.f 
The Tortoise has muscles arising from the dorsal vertebra}, by 
means of which it protrudes its head from beneath its shell or 
covering.! 
We have given some of the more striking out of innumerable 
instances of the extension or elongation of muscles when in a 
state of action, or under the influence of the will; but a still 
more important application of the general law I have proposed 
remains to be made; I mean its application to that portion of 
the muscular system placed about the tubes or hollow organs. 
We will take instances again from natural history. 
The Physalus, which we have already mentioned, has a bag or 
hollow organ on its upper surface which it can dilate at will. 
The Cuvieria Carisochroma, another species of physograda, has 
a number of similar organs arranged about the margin of its 
upper surface which it can dilate at pleasure. 
M. Lister published in the Philosophical Transactions for the 
year 1834 an account of the Tubularia indivisa, in which animal 
the act of dilating the upper portion of its body by a voluntary 
effort was very apparent. 
Certain classes of insects are possessed of a membranous bag 
called the sucking stomach, which Treviranus has seen dilated 
at the will of those insects, and thus by rarefying the air in their 
proboscides cause the fluids on which they feed to be drawn 
into their stomach. 
Do not the coecal appendages of the stomach of the leech per- 
form the same office in the economy of this animal ? 
The swimming bladder of fishes is said to be dilated at will. 
We have seen the oesophagus dilated under circumstances that 
could leave no doubt that the dilatation was owing to the elon- 
gation of its muscular fibres ; this dilatation of the oesophagus is 
very apparent in the deglutition of many animals, as in horses, 
cows, &c. We are sensible of a distension of the stomach on 
* Op. Cit,, Fig. 119, \ 308. f Fig. 203, § 476. % ’Fig. 265. 24 
taking exciting articles of food ; the same condition is observed 
in the intestines when the seat of irritation ; also in the urinary 
bladder. 
That the uterus in a state of pregnancy is not dilated by means 
of its contents is very evident to any one who has observed this 
viscus in this condition in the living animal. 
Dr. Marshall Hall, in a paper recently published, states that 
he has seen the heart elongated and actively dilated in its diastole, 
which condition he attributes to the injection of the arteries of 
this viscus. 
Any one whose mind is unprejudiced may, by placing his fin- 
ger on the artery at his wrist, be convinced that the arteries are 
dilated independently of the blood they contain. 
In the act of inspiration the chest is enlarged or dilated by the 
elongation of all the muscles of respiration, and has its calibre 
diminished by the contraction of those muscles. 
Having considered the above instances of the dilatation of 
tubes or hollow organs which could only be effected by the elon- 
gation of the muscular fibres placed about them, the reader will 
be prepared to understand the function of the nervous system to 
which I formerly adverted. Supposing the nerves and cerebro- 
spinal axis to be composed of tubes through which the vital fluid 
circulates, and those tubes to be surrounded by very delicate 
muscular fibres, we can readily conceive how a dilatation of those 
tubes would abstract the vital fluid from the muscles of the gen- 
eral system. 
Some confirmation of this view of the nervous function may 
be found in the fact that the brains of all animals possessed of 
this viscus are enclosed in a bony case, so that the dilatation of 
the brain could not be prevented by accidental external pressure. 
I have thus attempted in a very imperfect manner to generalize 
some of the facts of natural history, and to trace them up to a 
general law of the animal economy. I have carefully observed 
and considered the phenomena of muscular action not only in 
the human subject, but in other animals, and I can confidently 
assert that I have met with no fact at variance with the general 
law which I have proposed, namely, that innervation or the 
accession of the vital fluid causes elongation of the muscular 
fibre, and the contraction of the muscular fibre is caused by the 
abstraction of that fluid. I can further assert that in the above 
examination I have met with innumerable phenomena which are 
altogether inexplicable without the use of this general law. 
LOUIS MACKALL, M. D. 
Georgetown Heights, 
, 1841.