PALE Y'S 
NATURAL THEOLOGY, 
WITH ILLUSTRATIVE NOTES, &C. 
BY HENRY LORD BROUGHAM, F.R.S., 
AND 
SIR CHARLES BELL, K.G.H., F.R.S., L. & E. 
WITH NUMEROUS WOODCUTS. 
TO WHICH ARE ADDED, 
PRELIMINARY OBSERVATIONS AND NOTES. 
BY A. POTTER, D.D., 
PROFESSOR OF MORAL PHILOSOPHY IN UNION COLLEGE. 
IN TWO VOLUMES 
VOL. I. 
NE W-YO RK: 
.HARPER <& BROTHERS, 82 CLIFF-STREET. 
1 84 0. Entered, according to Act of Congress, in the year 1839, by 
Harper & Brothers, 
In the Clerk's Office of the Southern District of New-York. TO 
THE KIGHT HONOURABLE AND RIGHT REVEREND 
SHUTE BARRINGTON, LL.D., 
LORD BISHOP OF DVRHAM. 
My Lord, 
The following work was undertaken at your lordship's rec- 
ommendation ; and, among other motives, for the purpose of 
making the most acceptable return I could make for a great and 
important benefit conferred upon me. 
It may be unnecessary, yet not, perhaps, quite impertinent, 
to state to your lordship and to the reader the several induce- 
ments that have led me once more to the press. The favour 
of my first and ever honoured patron had put me in possession 
of so liberal a provision in the church as abundantly to satisfy 
my wants and much to exceed my pretensions. Your lord- 
ship's munificence, in conjunction with that of some other ex- 
cellent prelates, who regarded my services with the partiality 
with which your lordship was pleased to consider them, hath 
since placed me in ecclesiastical situations more than adequate 
to every object of reasonable ambition. In the mean time, a 
weak, and, of late, a painful state of health, deprived me of the 
power of discharging the duties of my station in a manner at 
all suitable either to my sense of those duties, or to my most 
anxious wishes concerning them. My inability for the public 
functions of my profession, among other consequences, left me 
much at leisure. That leisure was not to be lost. It was only 
in my study that I could repair my deficiencies in the church. 
It was only through the press that I could speak. These circum- 
stances, in particular, entitled your lordship to call upon me for 
the only species of exertion of which I was capable, and dis- 
posed me, without hesitation, to obey the call in the best man- 
ner that I could. In the choice of a subject I had no place DEDICATION. 
left for doubt; in saying which, I do not so much refer, either 
to the supreme importance of the subject, or to any skepticism 
concerning it with which the present times are charged, as I do 
to its connexion with the subjects treated of in my former pub- 
lications. The following discussion alone was wanted to make 
up my works into a system : in which works, such as they are, 
the public have now before them the evidences of natural reli- 
gion, the evidences of revealed religion, and an account of the 
duties that result from both. It is of small importance that 
they have been written in an order the very reverse of that in 
which they ought to be read. I commend, therefore, the present 
volume to your lordship's protection, not only as, in all proba- 
bility, my last labour, but as the completion of a consistent and 
comprehensive design. 
Hitherto, my lord, I have been speaking of myself and not of 
my patron. Your lordship wants not the testimony of a dedica- 
tion, nor any testimony from me; I consult, therefore, the im- 
pulse of my own mind alone when I declare, that in no respect 
has my intercourse with your lordship been more gratifying to me 
than in the opportunities which it has afforded me of observing 
your earnest, active, and unwearied solicitude for the advance- 
ment of substantial Christianity : a solicitude, nevertheless, ac- 
companied with that candour of mind which suffers no subor- 
dinate differences of opinion, when there is a coincidence in the 
main intention and object, to produce an alienation of esteem 
or diminution of favour. It is fortunate for a country, and 
honourable to its government, when qualities and dispositions 
like these are placed in high and influential stations. Such is 
the sincere judgment which I have formed of your lordship's 
character and of its public value ; my personal obligations I can 
never forget. Under a due sense of both these considerations, 
I beg leave to subscribe myself, with great respect and gratitude, 
My lord, your lordship's faithful 
And most devoted servant, 
WILLIAM PALEY. 
Bishop- Wearmouth, July, 1802. ADVERTISEMENT 
TO THE AMERICAN EDITION. 
In this edition the illustrative woodcuts and most 
of the notes of the English edition are retained. 
It was thought best, however, in a work intended 
for popular reading, to omit some of the extended 
and learned dissertations subjoined by the English 
editors, and to substitute short notes, imbodying 
the most valuable facts noticed in the Physiologi- 
cal Dissertations of Sir C. Bell. In addition to 
these notes, which, being expressed for the most 
part in the language of the present editor, are marked 
(.Am. Ed.), original ones of a critical and explana- 
tory nature have been added by the same hand, and 
a few selected from Paxton, which are duly speci- 
fied. Where the authorship is not specified, the 
notes are from the pen of Lord Brougham or Sir 
Charles Bell, with the exception of the botanical 
notes to the twentieth chapter, which were furnished 
for the English edition by Professor Lindley of the 
London University, and the entomological notes to 
the nineteenth chapter, which were prepared by 
Mr. Waterhouse, Curator of the Zoological Museum 
of London CONTENTS 
OF 
THE FIRST VOLUME. 
CHAPTER I. 
STATE OF THE ARGUMENT. 
Watch, page 37 ; Eight cases, 37-42. 
Note 1, On the analogy of the argument, 37; 2, That the stone 
has not been framed without purpose, ib.; 3, Object of the re- 
mainder of the chapter, 40; On " laws" of nature, &c., note, 
42. 
CHAPTER II. 
STATE OF THE ARGUMENT CONTINUED. 
Note 4, View of design from geological organization, 47; On the 
management and tendency of the argument in Chapter II., 
note, 49. 
CHAPTER HI. 
APPLICATION OF THE ARGUMENT. 
Eye and telescope, 50; Light-distance, 56; Eyes of birds, 60; 
Eyes of fishes, ib.; Minuteness of picture, 63; Socket-eye- 
brow-eyelid-tears, ib.; Nictitating membrane-muscle, 65; 
Expedients, 67; Why means used, 68; Ears, 69. 
Note 5, On refraction of light, 50; 6, Adaptation of the eyes of 
fishes to the medium in which they live, 51 ; 7, On the len- 
ses of the eye, 53 ; 8, Analogy between the lenses of the tele- 
scope and the humours of the eye, 54; 9, On refraction and 
dispersion of light, ib.; 10, On the contraction and dilation 
of the pupil, 56; 11, On mechanical alteration in the eye, 57 ; 
12, On the power of vision in birds of prey, 58 ; 13, On the 
pressure of the sea at great depths, and on the structure of the 
eyes of fishes in order to resist that pressure, 61; 14, Provis X 
ions of the eyelid indicative of design, 64; 15, Provision in 
the mud-crab for cleansing the eye, 65; 16, On the membrana 
nictitans, 67 ; 17, Air not the only vehicle of sound, 73. 
CHAPTER IV. 
ON THE SUCCESSION OF PLANTS AND ANIMALS. 
No account hereby of contrivance, 76; Plants, 77 ; Oviparous an- 
imals, ib.; Viviparous-rational animals, 79; Instance from 
Gardener, ib. 
Note 18, On the propagation of plants, 78; 19, On the limits of the 
term of existence and on reproduction, 80. 
CHAPTER V. 
APPLICATION OF THE ARGUMENT CONTINUED. 
Repetition from Chapter I., 82; Imperfection, ib.; Superfluous 
parts, 83 ; Atheistic argument, 85 ; Remains of possible forms, 
88; Use arising out of the parts, 91; A principle of order, 
93; Of our ignorance, 94. 
Note 20, On the suspension of respiration, 83 ; 21, On parts of an- 
imals said to be superfluous, 85; 22, On the reflection of light 
in the eyes of animals, 86 ; 23, On results supposed to arise 
from chance, 87; 24, On the supposition of animals having 
been produced by chance, 89 ; 25, On the dexterity which 
man acquires by practice as distinguishing him from other 
animals, 92 ; 26, Illustration from Boyle, 96. 
CHAPTER VI. 
THE ARGUMENT CUMULATIVE. 
CHAPTER VII. 
THE MECHANICAL AND IMMECHANICAL PARTS AND FUNCTIONS 
OF ANIMALS AND VEGETABLES. 
Imperfection of knowledge no proof of want of contrivance, 99 ; 
On chymistry, 102; Secretion, 104. 
Note 27, On the perfection of the immechanical parts of animals, 
99; 28, On the gastric juice as not acting upon the stomach 
of the living animal, 104. 
'CHAPTER VIII. 
MECHANICAL ARRANGEMENT IN THE HUMAN FRAME. 
Of bones, 110 ; Neck,i5.; Forearm, 112 ; Spine, 114 ; Chest, 122; 
Kneepan, 123; Shoulder blade, 124; Joints, 125; Ball and sock- 
et, 126; Ginglymus, 128; Knee, ib.; Ankle, ib.; Shoulder, 129 
CONTENTS. CONTENTS. 
XI 
Passage of bloodvessels, 130; Gristle, 131; Moveable carti- 
lages, 132; Synovia, 133; How well the joints wear, 134 ; Im- 
moveable joints, 135. 
Note 29, On the meaning of the terms tenon and mortise, 111 ; 30, 
On the admirable structure of the spine, 117; 31, On varia- 
tions of structure to suit the peculiar condition or varieties 
of different animals, 120; 32, Additional illustration of the 
motion of the ribs, 123 ; 33, On the enlargement of the Lone 
at the articulations, 124 ; 34, On the shoulder blade and col- 
lar bone, 125 ; 35, On the absence in the orang-outang of the 
ligament in the head of the thighbone, 128; 36, On the an- 
kle joint, 129 ; 37, On the cartilage which covers the ends 
of the bones, 132; 38, On the manner in which the thigh- 
bone rests upon the shinbone, and the use of the cartilage be- 
tween them, 133 ; 39, On absorption in a case of inflamma- 
tion of a joint, 134 ; On the bones of the scull, note, 135. 
CHAPTER IX. 
OF THE MUSCLES. 
Suitableness to the joints, 136 ; Antagonist muscles, 138 ; Not ob- 
structing one another, 139 ; Action wanted where their situ- 
ation would be inconvenient, 140; Variety of figure, ib.; How 
many things must be right for health, 142; Variety, quickness, 
and precision of muscular motion, 143; Tongue, ib.; Mouth, 
144 ; Nose, 146; Music-writing, 147; Sphincters, ib. ; Combi- 
nation of muscles, 148 ; Delicacy of small muscles, ib.; Me- 
chanical disadvantages, 149; Single muscles, 150; Lower 
jaw, ib.; Slit tendons, 151; Bandage at the ankles, 152; Hy- 
pothesis from appetency repelled, ib.; Keill's enumeration of 
muscles, 153; Why mechanism is not more striking, ib.; De- 
scription inferior to inspection, ib.; Quotation from Steno, ib. 
Note 40, On the balance of action between the antagonist mus- 
cles, 137; On the necessity and utility of the tendons, note, 
140; 41, On the sacrifice of power in certain muscles in order 
to acquire velocity, 141; 42, On the complexity of structure in 
the tongue, 146. 
CHAPTER X. 
OF THE VESSELS OF ANIMAL BODIES. 
I. The circulation of the blood, 154; Disposition of the bloodves- 
sels, 156; Arteries and veins, ib.; II. Heart, as receiving and 
returning the blood, 158; Heart, as referable to the lungs, 160; 
valves of the heart, 165 ; Vital motions involuntary, 169; Per- 
icardium, ib.; III. Alimentary system, 170; Passage of the 
food through the stomach to the intestines, ib.; Passage of 
the chyle through the lacteals and thoracic duct to the blood, 
171; Length of intestines, 172; Peristaltic motion, ib.; Tenu- XII 
ity of the lacteals, ib.; Valves of the thoracic duct, 173; En- 
trance at the neck, ib.; Digestion, 174; IV. Gall-bladder, 176; 
Oblique insertion of the biliary duct into the intestines, 177; 
V. Parotid gland, 178; VI. Larynx, ib. ; Trachea-gullet-ep- 
iglottis, 179, 180; Rings of the trachea, 180; Sensibility, ib.; 
Musical instrument, 181; Lifting the hand to the head, 182. 
Note 43, On the circulation of fluids, 156; 44, On the action of the 
muscles in the circulation of blood, 158; 45, On the analogy 
between the flow of blood in the system and of water from a 
fire-engine, 159; 46, On the composition of the atmosphere, 
160; 47, On the necessity of exposing the venous blood to the 
air, 161; 48, On the valves of the veins and arteries, 167; 49, 
Instance of the process of digestion in man having been dis- 
played to the eye, 171; 50, On the use of saliva in the diges- 
tion of food, 174 ; 51, On digestion, ib.; 52, On the germina- 
tion of seeds which have passed unbroken through the stom- 
achs of animals, 175; 53, On digestion in the stomach of a 
horse, 177; 54, On breathing, 181; 55, On the necessity of 
certain sensibilities in the body, ib. 
CHAPTER XL 
OF THE ANIMAL STRUCTURE REGARDED AS A MASS. 
I. Correspondence of sides, 184; Not belonging to the separate 
limbs, 185; Nor to the internal contents, 186 ; Nor to the feed- 
ing vessels, ib.; II. Package, 187; Heart, 188; Lungs, ib.; 
Liver, 189; Bladder, ib. ; Kidneys, ib. ; Pancreas, ib. ; Spleen, 
ib.; Omentum, 190; Septa of the brain, ib.; Guts, ib.; III. 
Beauty, 191; In animals, 192 ; In flowers, 193; Whether any 
natural sense of beauty, ib.; IV. Concealment, 194; V. Stand- 
ing, 195; VI. Interrupted analogies, 198; Periosteum at the 
teeth, ib.; Early skin at the nails, 199; Soft integuments at 
the scull, 200. 
Note 56, On the spleen, 190; 57, On the sensibility by which we 
are enabled to balance the body, 197; 58, On the provision for 
the preservation of the teeth, 199; 59, On the use of the nails 
of the fingers, 200. 
CHAPTER XII. 
COMPARATIVE ANATOMY. 
I. Covering of animals, 202; Of man, 203 ; Of birds, ib.; Struc- 
ture of feathers, 204; Black down, 207; II. Mouths of ani- 
mals, 208; Bills of birds, ib.; Serrated bills, 211; Affinity of 
mouths, 212; III. Gullets of animals, 213 ; IV. Intestines of 
animals, 214; Valves or plates, ib.; Length, 215; V. Bones 
of animals, ib.; Bones of birds, ib.; VI. Lungs of animals, 
217 ; Lungs of birds, ib.; VII. Birds oviparous, ib.; VIII. In- 
struments of motion, 2)8; Wings of birds, ib.; Fins of fish, 
220 •. Webfeet of waterfowl, 223; IX. Senses of animals, 224. 
CONTENTS CONTENTS. 
XIII 
Note 60, On the coverings of birds and other animals with refer- 
ence to warmth, 207; 61, On the adaptation of the bills of 
birds to the habits of each kind, 210 ; 62, On the connexion 
of the fifth nerve of the brain with the organ of touch, 212; 
63, On the adaptation of the teeth of fish to enable them to 
retain their prey, 213 ; On the use of the valvula conniventes, 
note, 215; 64, On the form and composition of the bones of 
different animals, ib.; 65, On the strength of the hollow form 
of a cylinder, 216; 66, On the construction of amphibious ani- 
mals, 21J ; 67, On the necessity of birds being oviparous in or- 
der to retain the power of flying, and on lightness of birds of 
flight, ib.; 68, On the analogy in principle between the wings 
of birds and the sails of a windmill, 219; 69, On the similarity 
of the system of bones in all vertebrated animals, 220; 70, 
On the uses and muscular power of the fins of fishes, 221. 
CHAPTER XIII. 
PECULIAR ORGANIZATIONS. 
Pax-wax of quadrupeds, 226; Oil of birds, 227; Air-bladder of 
fish, 228 ; Fang of viper, 230 ; Bag of opossum, ib.; Claw of 
heron, 231; Stomach of camel, 232; Tongue of woodpecker, 
ib. ; babyroussa, 236. 
Note 71, On the ligaments of the neck, 227; 72, On the air-blad- 
der of fishes, 229 ; 73, On the use of the pouch of the kan- 
garoo, 231; 74, On the habits and tongue of the woodpecker, 
233 ; 75, On the erroneous notion of the babyroussa sleeping 
standing, 236. 
CHAPTER XIV. 
PROSPECTIVE CONTRIVANCES. 
Teeth, 237; Milk, 239; Eye of the foetus, 240; Lungs of the 
foetus-foramen ovale, &c., 241. 
Note 76, On the means by which the second set of teeth are made 
to succeed the first, 239; 77, On the provision for the first 
nourishment of plants and animals, 240 ; 78, On the gradual 
development of animal bodies, 243. 
CHAPTER XV. 
RELATIONS. 
Alimentary system, 245; Kidneys, ureters, and bladder, 247; Eyes, 
hands, feet, 248 ; Sexes, 249; Teats and mouths, ib; Partic 
ular relations, ib ; Swan, ib ; Mole, 250. 
Note 79, On the springs of a watch, 244; 80, On the gizzard of 
gallinaceous birds, 246 ; 81, On bringing carnivorous birds to 
live on grains, and granivorous birds to live on meat, 247. XIV 
CONTENTS. 
CHAPTER XVI. 
COMPENSATION. 
Elephant's proboscis, 252 ; Hook in the bat's wing, 254; Crane's 
neck, ib; Parrot's bill, ii; Spider's web, 255; Multiplying 
eyes of insects, 256; Eyelid of the chameleon, 257; Intes- 
tines of the alopecias, 258 ; Snail-muscle-cockle-lobster, 
259 ; Sloth-sheep, 260 ; More general compensations, 261; 
Want of fore-teeth-rumination, ib; In birds, want of teeth 
and gizzard, 263 ; Reptiles, 264. 
Note 82, On the unreasonableness of the notion of a change in the 
original structure of animal organs, 253; 83, Interesting par 
ticulars concerning the powers and habits of the spider, 255 
84, On the wisdom displayed in the constitution of the sloth 
260; 85, On the digestive organs, with reference to the dif 
ferent kinds of food, 262; 86, On the relation between the 
mouths and stomachs of animals, 263; 87, On the variety of 
the instruments of motion of different animals, 265. ILLUSTRATIVE WOODCUTS.-VOL. I. 
No. • Page 
1. Works of a watch, horizontal view of the ... 39 
2. The form of the eye 50 
3. Section of the anterior part of the human eye, to show 
the manner in which the images of objects are im- 
pressed upon the retina 55 
4 The iris separated from the eye, and laid out flat . . 56 
5. Head of the eel, showing the form of the eye . . 61 
6. Plan of the human ear 70 
7. Bones of the ear 72 
8. Bones of the ear separated 72 
9. Drum of the ear 74 
10. The eye, showing the transmission of the images of objects 97 
11. A muscle 100 
12. The lower surface or base of the scull .... 109 
13. Uppermost vertebra? or atlas 110 
14. Articulation of the first and second vertebrae of the neck 111 
15. Section of the three lower vertebrae . . . .115 
16. Three views of the knee joints 123 
17. Muscle with tendons on different sides .... 141 
18. Figure showing how velocity is acquired by pulling ob- 
liquely 142 
19. Figure of the arm, showing the action of the biceps muscle 149 
20. The heart and great bloodvessels 155 
21 The two sides of the heart separated .... 162 
22. Section of the ventricle and the artery .... 164 
23. Valve of the great artery . . . . ■ . . 167 
24. Bones of the human foot 196 
25. Heads of birds, showing the form of the bills . . 209 
26. Head and neck of the heron . . . . • . . 210 
27. Head of the spoon-bill 211 
28. Feet of birds, with and without web .... 223 
29. Heads of the wolf and hare, showing the different man- 
ner in which the ears are turned .... 224 
30. Iris of the lion's eye 225 
31. Dissected head of the woodpecker .... 235 
32. Scull of the babyroussa 235 
33. Spider suspended from a twig 256 PRELIMINARY OBSERVATIONS 
The term Natural Theology usually comprehends 
all that knowledge of religion which can be gath- 
ered from a survey of Nature and Providence. 
Taken in a stricter sense, it may denote a syste- 
matic exposition of the proofs to be derived from 
these sources (more especially from the former), 
in regard to the being of God; his attributes of 
power, wisdom, goodness, and justice; our rela- 
tions to him as dependant and accountable crea- 
tures, and the probability that after death we shall 
pass into another and retributory state of being. 
It has long been a subject of doubt how far we 
are able to gather evidence on these questions, ei- 
ther from Nature alone, or from Nature and Prov- 
idence. On the one hand, we are prone, in con- 
sidering this point, to regard with some suspicion 
(and not, perhaps, without reason) any discussion 
of the evidences of natural religion by a believer in 
revelation, or, indeed, by any one who has had ac- 
cess to the Scriptures; since such a one, instead 
of proceeding as a judge, who weighs without par- 
tiality various, and, it may be, conflicting testimony, 
is apt to act as an advocate, collecting evidence on 
but one side, and with reference to a foregone con- 
clusion. Even if not a believer in the Bible, he 18 
PRELIMINARY OBSERVATIONS. 
is still liable to mistake its teachings for those of 
Nature, and to claim for reason what has been 
borrowed from inspiration. At the same time, 
we are not to assume the average proficiency 
in religious knowledge which has been made by 
unevangelized or pagan nations, as a fair index of 
the utmost that unaided reason can accomplish. 
On this, as on many other subjects, the native con- 
victions of the human heart may be obscured or 
altogether perverted by means of hereditary cus- 
toms and prejudices. We are rather to inquire 
what conclusions have been reached by minds on 
the one hand unenlightened by revelation, and on 
the other unsophisticated by prejudice or passion; 
minds that have been disposed to consult the still 
small voice of nature and conscience, and to con- 
sider with calmness the most momentous questions 
that can be weighed by man. It will be found that 
in such cases the educated and uneducated alike, 
the philosopher in the grove and the wanderer in 
the desert, are conducted to one and the same con- 
clusion. 
" How do you know," said a traveller to a poor 
Arab of the desert, " that there is a God ?" " In 
the same manner," he replied, " that I trace the 
footsteps of an animal, by the prints which it leaves 
upon the sand." 
" Which seems to you most worthy of admira- 
tion, Aristodemus," said Socrates, " the artist who 
forms images void of motion and intelligence, or 
one who hath the skill to produce animals, that are 
endued not only with activity, but with under- 
standing ?" 
"The latter, there can be no doubt," replied PRELIMINARY OBSERVATIONS. 
19 
Aristodemus, " provided the production was not the 
effect of chance, but of wisdom and contrivance." 
" But since there are many things, some of which 
we can easily see the use of, while we cannot say 
of others to what purpose they were produced, 
which of these, Aristodemus, do you suppose the 
work of wisdom ?" 
" It should seem the most reasonable to affirm 
it of those whose fitness and utility are so evidently 
apparent." 
" But it is evidently apparent, that He who at the 
beginning made man, endued him with senses be- 
cause they were good for him ; eyes wherewith to 
behold whatever was visible, and ears to hear what- 
ever was to be heard. For say, Aristodemus, to 
what purpose should odours be prepared, if the sense 
of smelling had been denied ? Or why the distinc- 
tion of bitter and sweet, of savoury and unsavoury, 
unless a palate had been likewise given, conve- 
niently placed, to arbitrate between them and de- 
clare the difference ? Is not that Providence, Aris- 
todemus, in a most eminent manner conspicuous, 
which, because the eye of man is so delicate in its 
contexture, hath therefore prepared eyelids, like 
doors, whereby to secure it, which extend of them- 
selves whenever it is needful, and again close when 
sleep approaches ? Are not those eyelids provided, 
as it were, with a fence on the edge of them to 
keep off the wind and guard the eye ? Even the 
eyebrow itself is not without its office; but, as a 
penthouse, is prepared to turn off the sweat, which, 
falling from the forehead, might enter and annoy 
that no less tender than astonishing part of us? 
Is it not to be admired that the ears should take in 20 
PRELIMINARY OBSERVATIONS. 
sounds of every sort, and yet are not too much filled 
by them. That the fore teeth of the animal should 
be formed in such a manner as is evidently best 
suited for the cutting of its food, as those on the side 
for grinding it in pieces ? That the mouth, through 
which this food is conveyed, should be placed so 
near the nose and eyes as to prevent the passing 
unnoticed whatever is unfit for nourishment; while 
Nature, on the contrary, hath set at a distance, and 
concealed from the senses, all that might disgust or 
any way offend them ? And canst thou still doubt, 
Aristodemus, whether a disposition of parts like 
this should be the work of chance, or of wisdom 
and contrivance ?" 
" I have no longer any doubt," replied Aristode- 
mus ; " and, indeed, the more I consider it, the 
more evident it appears to me, that man must be 
the master-piece of some great artificer, carrying 
along with it infinite marks of the love and favour 
of him who hath thus formed it." * * "Be as- 
sured," said Aristodemus, " if I once could be per- 
suaded the gods took care of man, I should want 
no monitor to remind me of my duty." 
" And canst thou doubt, Aristodemus, if the gods 
take care of man'! Consider that the soul, which 
resides in thy body, can govern it at pleasure. 
Why, then, may not the soul of the universe which 
pervades and animates every part of it, govern it 
in like manner? If thine eye hath the power to 
take in many objects, and these placed at no small 
distance from it, marvel not if the eye of the Deity 
can at one glance comprehend the whole! And 
as thou perceivest it not beyond thy ability to ex- 
tend thy care, at the same time, to the concern of PRELIMINARY OBSERVATIONS. 
21 
Athens, Egypt, Sicily, why thinkest thou, my Aris- 
todemus, that the providence of God may not easily 
extend itself throughout the whole universe 1 As, 
therefore, among men, we make the best trial of 
the affection and gratitude of our neighbour by 
showing him kindness, and discover his wisdom 
by consulting him in our distress, do thou, in like 
manner, behave towards the gods. And if thou 
wouldst experience what their wisdom and what 
their love, render thyself deserving of the communi- 
cation of some of those divine secrets which may 
not be penetrated by man, and are imparted to 
those alone who consult, who adore, who obey the 
Deity. Then shalt thou, my Anstodemus, under- 
stand there is a Being whose eye pierceth through- 
out all nature, and whose ear is open to every 
sound; extended to all place; extended through 
all time ; and whose bounty and care can know no 
other bounds than those fixed by his own creation!" 
" By this discourse, and others of the like nature, 
Socrates taught his friends that they were not only 
to forbear whatever was impious, unjust, and unbe- 
coming before men; but even when alone they 
ought to have a regard to all their actions, since 
the gods have their eyes continually upon us, and 
none of our designs can be concealed from them."* 
Here, then, are views of God which seem to have 
been formed by minds unenlightened by revelation, 
and which may unfold themselves, therefore, to any 
one who peruses with observing eye the books of 
Nature and Providence. They are substantially 
* Xenophon's Memorabilia of Socrates. Translated by Sarah 
Fielding. Vide Stewart's Phil, of the Active and Moral Powers 
of Man. 22 
PRELIMINARY OBSERVATIONS. 
the same views that are presented in the following 
treatise of Dr. Paley; who, though a Christian di- 
vine, endeavoured to close his eyes upon the 
Scriptures, that he might the better show how 
clearly and impressively the " invisible things of 
God" are made known by " the things which are 
seen." Nor are we to suppose that, in taking this 
course, he treats the Bible with disrespect. To 
show that Nature teaches the existence and per- 
fections of the Deity is to strengthen our confidence 
in a volume which unfolds the same truths, but with 
unspeakably greater precision and power. And if 
men are unbelievers, he who draws them to a can- 
did and thoughtful consideration of the proofs to be 
derived from Nature, of God's eternal power and 
wisdom, best prepares them (as we have seen in 
the case of Butler's Analogy) for a consideration 
of the Evidences of Revealed Religion, indeed, 
whether believer or unbeliever, no one, it is to be 
presumed, can examine, without profit, arguments 
which have been employed in substance by God 
himself, when condescending to reason with men. 
" He that planted the ear, shall he not hear ? He 
that formed the eye, shall he not see ? He that 
teacheth man knowledge, shall he not know ?" 
Here is the vei'y argument for Divine Wisdom 
deduced by Paley from the structure of the eye 
and ear, and which might have been most use- 
fully enlarged by a survey of the functions and pow- 
ers of the mind. In like manner, when Christ 
would vindicate the kind care of Providence, he ap- 
peals not only to his own authority, but to the touch- 
ing evidence afforded by " the fowls of the air" and 
" the lilies of the field just as Paul refers to " rain PRELIMINARY OBSERVATIONS. 
23 
from Heaven and fruitful seasons" as witness of 
God's benignity/and to the seed " not quickened 
except it die," as proof even from Nature that it is 
not " a thing incredible that God should raise the 
dead." And thus every analogy, which can be es- 
tablished between the teaching of Nature and rev- 
elation, must serve to impart new interest and au- 
thority to both. 
It should also be considered, that Revelation as- 
sumes the existence of God, and that he, therefore, 
who would vindicate his faith in this fundamental 
truth, and be ready "to give a reason" for it to 
others, must be able to show how that truth can be 
made manifest from Nature, or how the reception of 
it has been provided for, in the very constitution of 
our minds. Some good men admonish us that the 
Bible is the only proper guide in relation to God. 
To this it might, and, indeed, it ought to be replied, 
that the being, truth, and wisdom of God cannot 
be learned in the first instance from revelation, 
since revelation owes its own authority, its claims 
to our implicit belief, to the previous assumption 
that there is a God, clothed with these attributes, 
who superintended the composition of the sacred 
volume, and whose communications can contain no 
error. To employ the Bible, therefore, in proving 
the existence or perfections of the Deity, is to beg 
the very point in debate. It is that form of petitio 
principii which logicians usually term the circle; 
first assuming that there is a God of infinite wis- 
dom and veracity; from thence inferring the Divine 
authority of the Scriptures, and then proceeding 
from this last to conclude that there is a God !* 
* It may be proper to add, that the writer refers here to the 24 
PRELIMINARY OBSERVATIONS. 
Another reason which ought to recommend the 
study of Natural Religion is to be found in the pres- 
ent state of science. Our age is distinguished for 
its growing acquaintance with the great laws which 
regulate the operations of the physical world, and 
for the successful application of these laws to useful 
purposes, in the arts of life. Occupied with these 
discoveries and applications, it is not unnatural, that 
men should sometimes lose sight of the higher and 
more inspiring lessons which such laws are fitted 
to suggest. When, by patient observation and in- 
duction, we succeed in grouping a vast number of 
apparently incongruous facts under one simple prin- 
ciple, it is evident that the view of this principle 
ought to raise our thoughts to that Presiding Intel- 
ligence which has thus spread harmony over all his 
ways, and connected, by indissoluble bonds, bodies 
and changes the most remote and dissimilar. And 
when, from the contemplation of the law, we turn 
to the uses to which it may be applied, it is equal- 
ly clear that, instead of resting upon some single 
use, such as the construction of a machine, or the 
perfecting of a process in the arts, we should en- 
deavour to embrace those larger purposes which 
are all the while accomplishing, throughout the 
natural world, without the intervention of artisan 
or philosopher. As these various purposes rise 
into view, and we see how all things are made to 
work together for the promotion of happiness or 
virtue, ought such reflections to be attended with 
no adoring thoughts of Him who originally ordered 
argument for Divine Existence which is founded on the authority 
of the Bible. An argument founded on the character of the Bible 
would be very different, and would be unexceptionable. PRELIMINARY OBSERVATIONS. 
25 
and now sustains a system so fraught with blessing ? 
But here science is often and sadly at fault. When 
she reaches the eminence where visions of some- 
thing higher than sequences and generalizations 
are ready to break upon her, suddenly she be- 
comes mute. Often, indeed, she dwells with such 
zeal upon the constancy of these laws, upon the 
stability of worlds and systems, that she would 
seem to intimate (if not directly teach) that here is 
an order of things resulting, not from will and wis- 
dom, but from necessity. Nature is substituted 
for God, and an unalterable succession for the ever- 
present agency of the Creator and Ruler of the 
universe. Thus has science been robbed of half 
its glory ; its views have been narrowed and often 
obscured; and truths which ought to have roused 
a world to the admiration of Eternal Power and 
Goodness, have been employed to lull the soul into 
a practical atheism. Many causes have doubtless 
conspired to this result. One of them is, that man 
" does not like to retain God in his knowledge 
another is, that the habit of contemplating fixed 
laws, and tracing out their innumerable and multi- 
farious consequences, tends to engender a feeling 
that these laws are not only constant, but essential, 
and that they contain within themselves a guarantee 
for the perpetuity of the present order of things. 
And a third cause, which has had a great influence, 
ought not be omitted. Previous to the time of 
Bacon, philosophers were in the habit of confound- 
ing physical and final causes ; or, in other words, 
were accustomed to mistake the ends or uses of a 
phenomenon for its cause or principle. This con- 
fusion is still prevalent in Moral Science, where 
Vol. I.-C 26 
PRELIMINARY OBSERVATIONS. 
the fact, for example, that virtue subserves our 
happiness is constantly assumed as the ground or 
cause of our obligation to reverence and practise it. 
But this confusion has been excluded from the de- 
partment of Physical Science by the vigorous pro- 
test of Bacon. " The handling of final causes," 
says he, " mixed with the rest in physical inquiries, 
hath intercepted the severe and diligent inquiries 
of all real and physical causes, and given men the 
occasion to stay upon these satisfactory and spe- 
cious causes, to the great arrest and prejudice of 
farther discoveries." He adds, by way of illustra- 
tion, that we are not to think it a sufficient account 
of the clouds that they are for the watering of the 
earth, " or that the solidness of the earth is for the 
station and mansion of living creatures." It is 
rather the province of the natural philosopher to 
trace clouds to the laws of evaporation and con- 
densationand to determine the modeof action of those 
forces by which the materials of the earth are made 
solid and firm. 
Now we have here a most important caution ; 
but it is a caution which, like many more of Ba- 
con's, has been greatly misapprehended and abused. 
A careful perusal of his remarks will show, that he 
objected to the investigation of final causes, not as 
a speculation which ought to be omitted, but as one 
which is generally introduced out of its proper 
place, by being connected with physical researches ; 
by being, to use his own words, " made to invade 
and overrun the appropriate province of physics, 
so that it is likely to lay waste and ruin it." 
Had he lived in our age, when the proper method 
of philosophizing is generally understood, and when PRELIMINARY OBSERVATIONS. 
27 
philosophers, instead of intruding the notice of 
final causes, seem bent on the entire exclusion of 
them, it is likely that this caution would have been 
conceived in a widely different spirit. He would 
have reminded us, in his own pregnant language, 
that, though " it is true, a little philosophy inclineth 
man's mind to atheism, yet depth in philosophy 
bringeth men's minds about to religion ; for while 
the mind of man looketh upon second causes scat- 
tered, it may sometimes rest in them, and go no 
farther : but when it beholdeth the chain of them 
confederate and linked together, it must needs fly 
to Providence and to Deity." To the enlightened 
and reflecting man, this world must appear as it 
appeared to Boyle, " the temple of God ; and man 
as born the priest of nature, ordained (by being 
qualified) to celebrate divine service not only in it, 
but for it." If, then, science will not, in her ap- 
propriate tieatises, afford forms wherewith to cele- 
brate this service, let works in Natural Theology 
be furnished for the purpose. If La Place refuses 
to speak of aught save laws of Nature, let Paley 
be allowed to show how such laws indicate the 
wisdom and goodness of Nature's God ! 
There is another reason why views, such as those 
contained in this work, should have currency. I 
pity the man, says Sterne, who can go from Dan to 
Beersheba, and say it is all barren. How much 
more is he an object of pity who can look abroad 
upon the face of nature, and hear the voice which 
comes from the depths of his own heart, and yet 
think not of God ; the God who has spread out the 
one to be a never-failing source of good, and im- 
planted in the other such capacities for glory, hon- 28 
PRELIMINARY OBSERVATIONS. 
our, and immortality. Yet it is melancholy truth, 
that to the mass of mankind all this display of the 
Godhead is as a sealed book. Though they admit 
that there is a God, they neglect to observe the 
manifold traces of his handiwork which have been 
drawn around them on every side. They have be- 
come accustomed to look upon the material world 
as a self-subsisting system, rather than as a work 
evincing design, and continually evolving results 
which proclaim its Maker's power and skill. The 
human artist is seen ; all his operations and mate- 
rials are in view, no less than the works which he 
constructs ; and hence they find it difficult to con. 
ceive of Him " who works unseen, and by means 
which may seem, to philosophic eyes, trivial and 
worthy of disdain." 
" It is with difficulty," said Aristodemus, in reply 
to Socrates, " that I can suppose this universe to 
have been framed by intelligence, for I behold none 
of those gods whom you speak of as making and 
governing all things ; whereas I see the artists 
when at their work here among us." The fallacy 
of this remark, as exposed by Socrates, is sufficiently 
obvious, but it is none the less true that it is a fal. 
lacy which imposes, insensibly, upon many a mind. 
God is forgotten, because unseen. Is not he doing 
a good work, then, who endeavours to break this 
spell ? who would accustom the mind to see God in 
everything; to regard every fact, and especially 
every principle, as an expression of his wisdom 
and power, as a mode by which he manifests him- 
self even to our senses, and would impress us with 
a conviction of his ever-present agency ? What 
greater service can be rendered to the young and PRELIMINARY OBSERVATIONS. 
29 
inquiring mind, than to teach it early to connect 
every attainment in human knowledge with the con- 
templation of God ? Thus the true end of all knowl- 
edge will be kept in view. Science will no longer 
present itself as a system of vague generalities, or 
as a means of multiplying merely physical accom- 
modations. The philosophy of dead matter will 
become a living philosophy. It will speak to the 
heart as well as to the understanding; and, while it 
serves as the handmaid of religion, will invest, with 
new and immeasurably higher interest, its own spec- 
ulations. 
It may be proper, before closing these remarks, 
to call attention to the proper province of Natural 
Theology. So many extended treatises have ap- 
peared on this subject, that we are prone to suppose, 
either that their authors have undertaken a useless 
labour, or else that the existence of God is a truth 
which can be established only by a long course of 
consecutive reasoning, starting from a certain point, 
and advancing step by step to a remote conclusion. 
Either opinion is equally erroneous. To have a 
truth so interesting and important to mankind veiled 
in such obscurity, that nothing but a lengthened 
and elaborate argument could make it clear, is wholly 
unlike the usual order of the Divine procedure, and 
would preclude a large proportion of mankind from 
the intelligent recognition of God. Hence a belief 
in this first and most essential truth seems to have 
been provided for in the very constitution of our 
minds. Conscience cannot act without awakening 
in us awe of an unseen world and an unseen Pow- 
er. Our various intellectual faculties and moral 
susceptibilities, the moment we become conscious 30 
PRELIMINARY OBSERVATIONS. 
of them, suggest the idea of a personal and intelli- 
gent First Cause, endowed with similar but incom- 
parably nobler attributes. And what is, perhaps, 
more to the purpose, that principle of our nature 
which instantly prompts us, on perceiving, in the 
works of art any nice adaptation of means to an 
end, to ascribe such adaptation to intelligence and 
design ; this same principle constrains us, when 
from art we turn to nature, to attribute to a similar 
but still higher Intelligence, the manifold instances 
of adaptation which are seen in all her works. 
" Sooner," says Bacon, " would I believe all the fa- 
bles of the Legend, and the Talmud, and the Alcoran, 
than that this universal frame is without a mind." 
An instinctive and instantaneous sympathy seems 
to carry us from the consciousness of power and 
skill in our own souls, to the recognition of corre- 
sponding attributes in Him who is styled by Socra- 
tes the " Soul of the universe." This instinct is so 
strong, that a belief in God, if not absolutely intui- 
tive, is yet forced upon the consent of every mind 
of ordinary powers. It has been, in some shape, 
the universal faith of mankind. Superstition may 
have perverted and deformed it; but even super, 
stition, though in her wildest vagaries, never yet 
dreamed of dispensing with it. It is worthy of re- 
mark, that in all the vicissitudes of human opinion 
and of popular delusion, no nation ever yet wrought 
out for itself a system of atheism. That work 
was reserved for philosophy ; and even she has al- 
ways found her doubts so abhorrent to the popular 
mind, that she never aspired, except in one instance, 
to make the people atheists. No stronger evidence 
eould be afforded, not only that this faith is conge. preliminary observations. 
31 
nial with our natural sentiments, but that its ele- 
ments lie among the first principles of all knowl- 
edge, and that it is reached by a road so plain, that 
the wayfaring man, though a fool, need not err 
therein. 
But, if this be so, why such massive volumes of 
argument to prove what is'all but self-evident? 
To this we reply, that the object of these volumes 
is not so much to prove the existence of God, as to 
render it palpable and impressive. They abound 
in examples rather than arguments; examples se- 
lected in such a manner as to impress the mind 
with the reality and present value of the truth which 
they illustrate. A single instance properly applied 
-the wing of an insect, a blade of grass, considered 
in reference to the uses it subserves-contains 
nearly all the argument which we find expanded in 
volumes of Natural Theology. But it is evident that 
one such example of Divine wisdom and goodness 
is not fitted to affect the mind so deeply as many. 
The more we see of the benevolence and wisdom 
of another, the more deeply we are impressed with 
a sense of his worth; the better disposed to offer 
him our heartfelt homage. We may at all times ad- 
mire the sagacity of a Newton or the philanthropy 
of a Howard: but never is this admiration so fervent 
as when we trace the one in the history of his dis- 
coveries, or the other in his visits of mercy and self- 
denial to the abodes of guilt. So each new speci- 
men of God's handiwork will, if properly consider- 
ed, have the effect of bringing us into nearer con- 
tact with Infinite Perfection, and making us eye- 
witnesses, as it were, of his eternal power and God- 
head. It is in this way, too, that we may cultivate 32 
PRELIMINARY OBSERVATIONS. 
a habit of tracing design in the works of creation, 
and thus not only fortify our minds against the ap- 
proaches of skepticism, but cherish sentiments 
which lie at the foundation of personal religion. 
To him who has formed such a habit, " the world," 
to borrow our author's language, " becomes thence- 
forth a temple, and life itself one continued act of 
adoration. Whereas, formerly, God was seldom in 
our thoughts, we can now scarcely look upon any- 
thing without perceiving its relation to him." 
The account which we have here given of the 
proper province of Natural Theology, corresponds 
sufficiently well with the views of Paley. He seems 
to regard the existence of God as nearly, if not 
quite, self-evident; as a truth which will suggest it- 
self, at once, to a mind that considers the works of 
creation. He multiplies examples, not so much to 
prove, as to make proof impressive. To use his 
own language, "Were there no example in the 
world, of contrivance except that of the eye, it 
would be alone sufficient to support the conclusion 
which we draw from it as to the necessity of an 
Intelligent Creator." " The proof is not a conclu- 
sion which lies at the end of a chain of reasoning, 
of which chain each instance of contrivance is only 
a link, and of which, if one link fails, the whole falls; 
but it is an argument separately supplied by every 
separate example. An error in stating an exam- 
ple affects only that example. The argument is 
cumulative in the fullest sense." (Seech, vi.) And 
in the concluding chapter he defends the propriety 
of thus accumulating examples ; because it is by 
such means alone that the truths of Natural Reli- 
gion can be placed in different points of view, and, PRELIMINARY OBSERVATIONS. 
33 
by being often the subject of meditation, can impart 
their appropriate influence, as principles of conduct. 
To borrow his own illustration, " There is a great 
deal of difference between taking a medicine and 
the medicine getting into the constitution. It is 
one thing to assent to a proposition, and another, 
and a very different thing, to have imbibed its in- 
fluence." 
But though the author's views in this respect 
seem to be, in the main, correct; it is not to be de- 
nied that he sometimes uses language, which is 
scarcely consistent with a clear apprehension of 
the process by which the mind reaches the first 
truths of Natural Religion. " Contrivance proves 
design." "There can be no design without a de- 
signer." These, which are stated by Paley as fun- 
damental and all-important propositions, evidently 
belong to the class usually known as identical prop- 
ositions, and which, in effect, prove nothing. Con- 
trivance necessarily involves or supposes design, 
and design is inconceivable except as the act of an 
Intelligent Mind. The real question at issue is 
whether there be design in the natural world ; i. e., 
whether that adaptation of means to specific ends 
which we see around us in the natural world, can 
be accounted for without design ; and on this ques- 
tion the truth seems to be, that when we see such 
instances of adaptation, we instinctively refer them 
to an Intelligent or designing Cause. We do it, 
not because we have reasoned out the connexion, 
nor because we have learned it by experience. It 
has been aptly compared to our instinctive inter- 
pretation of natural signs. As the passions of 
others are immediately and intuitively evident from 34 
PRELIMINARY OBSERVATIONS. 
their looks and gestures, so we read in these ex- 
amples of adaptation so many natural and signifi- 
cant tokens of a Creating Mind. 
Having alluded to this defect in our author's lan- 
guage, the result, perhaps, of inadvertence rather 
than of misapprehension, it may be proper to no- 
tice some other respects in which his work is lia- 
ble to criticism, without entering, however, on de- 
tails which belong, more properly, to the follow- 
ing notes. In order to exhibit evidences of design, 
Paley relies principally, as he tells us, upon the 
mechanism of the frame. This he had an unques- 
tionable right to do, since it is impossible to pre- 
sent, in one volume, all the proofs of design discov- 
erable in the universe ; and every writer, therefore, 
should confine himself to those which he thinks he 
can render most clear and impressive. But, in his 
zeal to enforce this argument, our author loses 
sight of the fact that there is something about man 
higher than mere mechanism, even the functions 
of life and sensation ; and something incomparably 
nobler still, even mind, with all its glorious pow- 
ers and aspirations ; and that these, though not so 
easily analyzed, still furnish the most impressive 
evidence of Divine wisdom and benevolence. He 
omits to notice even our moral constitution, and 
thus deprives himself of the most cogent arguments 
in favour of the intrinsic and essential righteous-" 
ness of God's government. The consequence is, 
that he offers no proof from nature to show that 
God is just, and refers to none except incidental 
proof that there is a future state. These omissions 
are much to be regretted. Every friend of sound 
learning and religion must long, therefore, for the PRELIMINARY OBSERVATIONS. 
35 
appearance of another Paley, who, with equal tact 
in selecting and equal felicity in exhibiting exam- 
ples, shall imbody, within a moderate compass, this 
portion of the argument, and thus vindicate the 
highest perfections of the Deity. 
To offer any commendation of the style or gen- 
eral mode of discussion adopted by Paley in this 
work, would be presumption. He has invested his 
subject with an indescribable charm. His exam- 
pies are so apt, his descriptions of the mechanism 
of the frame so clear and vivid, his matter so con- 
densed and yet so striking, that this treatise may 
claim the distinction of being the people's text-look in 
Natural Theology. As such, it takes its place in 
the People's Library, and is commended, not with- 
out prayer, to the attention of the public and the 
blessing of the Most High. 
A. P. NATURAL THEOLOGY. 
CHAPTER I. 
STATE OF THE ARGUMENT.1 
In crossing a heath, suppose I pitched my foot 
against a stone, and were asked how the stone came 
to be there, I might possibly answer, that, for any- 
thing I knew to the contrary, it had lain there for 
ever; nor would it, perhaps, be very easy to show 
the absurdity of this answer. But suppose I had 
found a watch upon the ground, and it should be in- 
quired how the watch happened to be in that place, 
1 should hardly think of the answer which I had be- 
fore given, that, for anything I knew, the watch 
might Ifave always been there. Yet why should not 
this answer serve for the watch as well as for the 
stone ? why is it not as admissible in the second case 
as in the first? For this reason, and for no other, 
viz., that, when we come to inspect the watch, we 
perceive (what we could not discover in the stone)2 
that its several parts are framed and put together for 
a purpose, e. g., that they are so formed and adjusted 
as to produce motion, and that motion so regulated 
1 The argument is analogical; applying to man and other or- 
ganized beings, the reasoning which any one would apply to a 
watch. If the one must have had a maker, so must the other.- 
Am. Ed. 
2 Not that the parts of the stone have been framed and put 
together without purpose, but that this purpose is much less ob- 
vious than in the case of the watch. Dr. Buckland, in the last 
chapter of his Bridgewater Treatise, has some valuable reflections 
on the proofs of design apparent in the structure and composition 
of unorganized mineral bodies, to which the reader is referred.- 
Am. Ed. 
Vol. I.-D 38 
NATURAL THEOLOGY. 
as to point out the hour of the day; that, if the differ- 
ent parts had been differently shaped from what they 
are, of a different size from what they are, or placed 
after any other manner, or in any other order than 
that in which they are placed, either no motion at 
all would have been carried on in the machine, or 
none which would have answered the use that is 
now served by it. To reckon up a few of the plain- 
est of these parts, and of their offices, all tending to 
one result: We see a cylindrical box (a) contain- 
ing a coiled elastic spring, which, by its endeavour 
to relax itself, turns round the box. We next ob- 
serve a flexible chain (b) (artificially wrought for the 
sake of flexure) communicating the action of the 
spring from the box to the fusee (b). We then find 
a series of wheels, the teeth of which catch in, and 
apply to, each other, conducting the motion from the 
fusee to the balance (l), and from the balance to the 
pointer, and, at the same time, by the size and shape 
of those wheels, so regulating that motion as to ter- 
minate in causing an index, by an equable and meas- 
ured progression, to pass over a given space in a 
given time. We take notice that the wheels are 
made of brass, in order to keep them from rust; the 
springs of steel, no other metal being so elastic ; that 
over the face of the watch there is placed a glass, a 
material employed in no other part of the work ; but 
in the room of which, if there had been any other 
than a transparent substance, the hour could not be 
seen without opening the case. This mechanism 
being observed (it requires, indeed, an examination of 
the instrument, and, perhaps, some previous knowl- 
edge of the subject, to perceive and understand it; 
but being once, as we have said, observed and under- 
stood), the inference, we think, is inevitable, that the 
watch had a maker : that there must have existed, 
at some time, and at some place or other, an artificer 
or artificers who formed it for the purpose which we 
find it actually to answer: who comprehended its 
construction and designed its use. 
I. Nor wotiio it, I apprehend, weaken the conclu- NATURAL THEOLOGY 
39 
Description of the Engraving. 
A, the barrel: B, the fusee ; b, a flexible steel chain which communicates the motion of the barrel to the 
fusee ; C, the great wheel; D, the pinion (called the cannon pinion) of the second or centre wheel, de- 
signed to revolve once in an hour; E, the centre wheel, containing sixty-four teeth; F, pinion of the third 
wheel, containing eight leaves ; G, third wheel, containing sixty teeth ; H, pinion of fourth wheel, contain- 
ing eight leaves ; I, fourth wheel, containing sixty teeth ; K, pinion of the balance wheel (sometimes called 
the scapement wheel), containing six leaves ; L, the balance wheel, containing fifteen teeth, which oper- 
ate upon the pallets of the balance, and give to it its oscillating motion ; a a, the pallets; M, the balance; 
b, the hair spring ; c d ef, minute wheels ; e, pinion of ten teeth, revolving once in an hour; d, wheel of 
forty teeth, revolving once in four hours ; e, pinion of twelve leaves ; f, wheel of thirty-six teeth, revolving 
once in twelve hours ; g, the end of the axis of the centre wheel, upon which the minute-hand, h, revolves; 
i, the axis of the hour wheel, upon which the hour-hand goes round once in twelve hours. 40 
NATURAL THEOLOGY. 
sion, that we had never seen a watch made ;3 that 
we had never known an artist capable of making 
one; that we are altogether incapable of executing 
such a piece of workmanship ourselves, or of under- 
standing in what manner it was performed; all this 
being no more than what is true of some exquisite re- 
mains of ancient art, of some lost arts, and, to the 
generality of mankind, of the more curious produc- 
tions of modern manufacture. Does one man in 
a million know how oval frames are turned 7 Ig- 
norance of this kind exalts our opinion of the un- 
seen and unknown artist's skill, if he be unseen and 
unknown, but raises no doubt in our minds of the ex- 
istence and agency of such an artist, at some former 
time, and in some place or other. Nor can I per- 
ceive that it varies at all the inference, whether the 
question arise concerning a human agent, or concern- 
ing an agent of a different species, or an agent pos- 
sessing, in some respect, a different nature. 
II. Neither, secondly, would it invalidate our con- 
clusion, that the watch sometimes went wrong, or 
that it seldom went exactly right. The purpose of 
the machinery, the design, and the designer, might be 
evident, and, in the case supposed, would be evident, 
in whatever way we accounted for the irregularity of 
the movement, or whether we could account for it or 
not. It is not necessary that a machine be perfect in 
order to show with what design it was made: still 
less necessary where the only question is whether it 
were made with any design at all. 
III. Nor, thirdly, would it bring any uncertainty 
into the argument, if there were a few parts of the 
watch, concerning which we could not discover, or 
had not yet discovered, in what manner they condu- 
ced to the general effect; or even some parts, con- 
cerning which we could not ascertain whether they 
conduced to that effect in any For, 
3 Through the remainder of this chapter the author discusses 
various objections which have been advanced against the argu- 
ment from design, bjT showing that, if applied to the watch, they 
would appear frivolous.-Am. Ed. 41 
as to the first branch of the case, if by the loss, or 
disorder, or decay of the parts in question, the move- 
ment of the watch were found in fact to be stopped, 
or disturbed, or retarded, no doubt would remain in 
our minds as to the utility or intention of these parts, 
although we should be unable to investigate the man- 
ner accordimg to which, or the connexion by which, 
the ultimate effect depended upon their action or as- 
sistance ; and the more complex is the machine, the 
more likely is this obscurity to arise. Then, as to 
the second thing supposed, namely, that there were 
parts which might be spared without prejudice to the 
movement of the watch, and that he had proved this 
by experiment, these superfluous parts, even if we 
were completely assured that they were such, would 
not vacate the reasoning which we had instituted con- 
cerning other parts. The indication of contrivance 
remained, with respect to them, nearly as it was be- 
fore. 
IV. Nor, fourthly, would any man in his senses 
think the existence of the watch, with its various 
machinery, accounted for by being told that it was 
one out of possible combinations of material forms; 
that whatever he had found in the place where he 
found the watch, must have contained some internal 
configuration or other; and that this configuration 
might be the structure now exhibited, viz., of the 
works of a watch, as well as a different structure. 
V. Nor, fifthly, would it yield his inquiry more sat- 
isfaction to be answered that there existed in things 
a principle of order, which had disposed the parts of 
the watch into their present form and situation. He 
never knew a watch made by the principle of order; 
nor can he even form to himself an idea of what is 
meant by a principle of order, distinct from the intel- 
ligence of the watchmaker. 
VI. Sixthly, Utt would be surprised to hear that the 
mechanism of the watch was no proof of contrivance, 
only a motive to induce the mind to think so: 
VII. And not less surprised to be informed that the 
watch in his hand was nothing more than the result 
NATURAL THEOLOGY. 42 
NATURAL THEOLOGY. 
of the laws of metallic nature. It is a perversion of 
language to assign any law as the efficient operative 
cause of anything. A law presupposes an agent; for 
it is only the mode according to which an agent pro- 
ceeds: it implies a power ; for it is the order accord- 
ing to which that power acts. Without this agent, 
without this power, which are both distinct from it- 
self, the law does nothing, is nothing. The expres- 
sion, " the law of metallic nature," may sound strange 
and harsh to a philosophic ear; but it seems quite as 
justifiable as some others which are more familiar to 
him, such as " the law of vegetable nature," " the law 
of animal nature," or, indeed, as " the law of nature" 
in general, when assigned as the cause of phenome- 
na, in exclusion of agency and power, or when it is 
substituted into the place of these.* 
VIII. Neither, lastly, would our observer be driven 
out of his conclusion, or from his confidence in its 
truth, by being told that he knew nothing at all about 
the matter. He knows enough for his argument: he 
knows the utility of the end : he knows the subser- 
viency and adaptation of the means to the end. These 
points being known, his ignorance of other points, his 
doubts concerning other points, affect not the certain- 
ty of his reasoning. The consciousness of knowing 
little need not beget a distrust of that which he does 
know. 
* When philosophers and naturalists observe a certain succes- 
sion in the phenomena of the universe, they consider the uniform- 
ity to exist through a law of nature. If they discover the order of 
events, or phenomena, they say they have discovered the law : for 
example, the law of affinities, of gravitation, &c. It is a loose 
expression ; for to obey a law supposes an understanding and a 
will tc comply. The phrase also implies that we know the nature 
of the governing power which is in operation, and in the present 
case both conditions are wanting. 
The " law" is the mode in which the power acts, and the term 
should infer not only an acquiescence in the existence of the 
power, but of Him who has bestowed the power and enforced the 
law. 
The term " force" is generally used instead of power, when the 
intensities are measurable in their mechanical results. NATURAL THEOLOGY. 
43 
CHAPTER II. 
STATE OF THE ARGUMENT CONTINUED. 
Suppose, in the next place, that the person who 
found the watch should, after some time, discover 
that, in addition to all the properties which he had 
hitherto observed in it, it possessed the unexpected 
property of producing, in the course of its move- 
ment, another watch like itself (the thing is con- 
ceivable) ; that it contained within it a mechanism, 
a system of parts, a mould, for instance, or a com- 
plex adjustment of lathes, files, and other tools, evi- 
dently and separately calculated for this purpose ; let 
us inquire what effect ought such a discovery to have 
upon his former conclusion. 
I. The first effect would be to increase his admi- 
ration of the contrivance, and his conviction of the 
consummate skill of the contriver. Whether he re- 
garded the object of the contrivance, the distinct ap- 
paratus, the intricate, yet in many parts intelligible 
mechanism by which it was carried on, he would per- 
ceive, in this new observation, nothing but an addi- 
tional reason for doing what he had already done; 
for referring the construction of the watch to design 
and to supreme art. If that construction without this 
property, or, which is the same thing, before this 
property had been noticed, proved intention and art 
to have been employed about it, still more strong 
would the proof appear when he came to the knowl- 
edge of this farther property, the crown and perfec- 
tion of all the rest. 
II. He would reflect, that though the watch be- 
fore him were, in some sense, the maker of the watch 
which was fabricated in the course of its movements, 
yet it was in a very different sense from that in which 
a carpenter, for instance, is the maker of a chair : the 
author of its contrivance, the cause of the relation of 44 
NATURAL THEOLOGY. 
its parts to their use. With regard to,these, the first 
watch was no cause at all to the second; in no such 
sense as this was it the author of the constitution and 
order, either of the parts which the new watch con- 
tained, or of the parts by the aid and instrumentality of 
which it was produced. We might possibly say, but 
with great latitude of expression, that a stream of 
water ground corn; but no latitude of expression 
would allow us to say, no stretch of conjecture could 
lead us to think, that the stream of water built the 
mill, though it were too ancient for us to know who 
the builder was. What the stream of water does in 
the affair is neither more nor less than this; by the 
application of an unintelligent impulse to a mechan- 
ism previously arranged-arranged independently of 
it, and arranged by intelligence-an effect is produ- 
ced, viz., the corn is ground. But the effect results 
from the arrangement. The force of the stream can- 
not be said to be the cause or the author of the effect, 
still less of the arrangement. Understanding and 
plan in the formation of the mill were not the less 
necessary for any share which the water has in grind- 
ingthe corn; yet is this share the same as that which 
the watch would have contributed to the production 
of the new watch, upon the supposition assumed in 
the last section. Therefore, 
III. Though it be now no longer probable that the 
individual watch which our observer had found was 
made immediately by the hand of an artificer, yet 
doth not this alteration in anywise affect the infer- 
ence, that an artificer had been originally employed 
and concerned in the production. The argument from 
design remains as it was. Marks of design and con- 
trivance are no more accounted for now than they 
were before. In the same thing, we may ask for the 
cause of different properties. We may ask for the 
cause of the colour of a body, of its hardness, of its 
heat; and these causes maybe all different. We are 
now asking for the cause of that subserviency to a 
use, that relation to an end, which we have remark- 
ed in the watch before us. No answer is given to 
this question by telling us that a preceding watch produced it. There cannot be design without a de- 
signer ; contrivance without a contriver; order with- 
out choice; arrangement without anything capable of 
arranging; subserviency and relation to a purpose 
without that which could intend a purpose; means 
suited to an end, and executing their office in accom- 
plishing that end, without the end ever having been 
contemplated, or the means accommodated to it. Ar- 
rangement, disposition of parts, subserviency of means 
to an end, relation of instruments to a use, imply the 
presence of intelligence and mind. No one, there- 
fore, can rationally believe that the insensible, inani- 
mate watch, from which the watch before us issued, 
was the proper cause of the mechanism we so much 
admire in it; could be truly said to have constructed 
the instrument, disposed its parts, assigned their of- 
fice, determined their order, action, and mutual de- 
pendence, combined their several notions into one 
result, and that also a result connected with the util- 
ities of other beings. All these properties, therefore, 
are as much unaccounted for as they were before. 
IY. Nor is anything gained by running the difficulty 
farther back, i. e., by supposing the watch before us 
to have been produced from another watch, that from 
a former, and so on indefinitely. Our going back ever 
so far brings us no nearer to the least degree of 
satisfaction upon the subject. Contrivance is still 
unaccounted for. We still want a contriver. A de- 
signing mind is neither supplied by this supposition, 
nor dispensed with. If the difficulty were diminished 
the farther we went back, by going back indefinitely we 
might exhaust it. And this is the only case to which 
this sort of reasoning applies. Where there is a ten- 
dency, or, as we increase the number of terms, a con- 
tinual approach towards a limit, there, by supposing 
the number of terms to be what is called infinite, we 
may conceive the limit to be attained; but where 
there is no such tendency or approach, nothing is ef- 
fected by lengthening the series. There is no differ- 
ence as to the point in question (whatever there may 
be as to many points), between one series and an- 
NATURAL THEOLOGY: 
45 46 
NATURAL THEOLOGY. 
other; between a series which is finite and a series 
which is infinite. A chain, composed of an infinite 
number of links, can no more support itself than a 
chain composed of a finite number of links. And of 
this we are assured (though we never can have tried 
the experiment), because, by increasing the number 
of links from ten, for instance, to a hundred, from a 
hundred to a thousand, &c., we make not the smallest 
approach, we observe not the smallest tendency to- 
wards self-support. There is no difference in this 
respect (yet there may be a great difference in many 
respects) between a chain of greater or less length, 
between one chain and another, between one that is 
finite and one that is infinite. This very much re- 
sembles the case before us. The machine which we 
are inspecting demonstrates, by its construction, con- 
trivance and design. Contrivance must have had 
a contriver, design a designer, whether the ma- 
chine immediately proceeded from another or not. 
That circumstance alters not the case. That other 
machine may, in like manner, have proceeded from 
a former machine : nor does that alter the case ; the 
contrivance must have had a contriver. That former 
one from one preceding it: no alteration still; a con- 
triver is still necessary. No tendency is perceived, 
no approach towards a diminution of this necessity. 
It is the same with any and every succession of these 
machines; a succession of ten, of a hundred, of a 
thousand ; with one series as with another; a series 
which is finite as with a series which is infinite. In 
whatever other respects they may differ, in this they 
do not. In all, equally, contrivance and design are 
unaccounted for. 
The question is not simply, How came the first 
watch into existence 1 which question, it may be pre- 
tended, is done away by supposing the series of 
watches thus produced from one another to have 
been infinite, and, consequently, to have had no such 
first, for which it was necessary to provide a cause. 
This, perhaps, would have been nearly the state of 
the question, if nothing had been before us but an NATURAL THEOLOGY. 
47 
unorganized, unmechanized substance, without mark 
or indication of contrivance. It might be difficult to 
show that such substance could not have existed from 
eternity, either in succession (if it were possible, 
which 1 think it is not, for organized bodies to spring 
from one another), or by individual perpetuity. But 
that is not the question now. To suppose it to be 
so is to suppose that it made no difference whether 
he had found a watch or a stone. As it is, the meta- 
physics of that question have no place: for, in the 
watch which we are examining, are seen contrivance, 
design ; an end, a purpose ; means for the end, adap- 
tation for the purpose. And the question which ir- 
resistibly presses upon our thoughts is, Whence this 
contrivance and design 1 The thing required is the 
intending mind, the adapted hand, the intelligence by 
which that hand was directed. This question, this 
demand, is not shaken off by increasing a number or 
succession of substances, destitute of these proper- 
ties ; nor the more by increasing that number to in- 
finity. If it be said that, upon the supposition of one 
watch being produced from another, in the course of 
that other's movements, and by means of the mech- 
anism within it, we have a cause for the watch in 
my hand, viz., the watch from which it proceeded, 
I deny that for the design, the contrivance, the suit- 
ableness of means to an end, the adaptation of instru- 
ments to a use (all of which we discover in the watch), 
we have any cause whatever. It is in vain, therefore, 
to assign a series of such causes, or to allege that a 
series may be carried back to infinity; for I do not 
admit that we have yet any cause at all for the phe- 
nomena, still less any series of causes either finite 
or infinite. Here is contrivance, but no contriver; 
proofs of design, but no designer.4 
4 There is another view of this matter furnished by geology. 
Says Dr. Buckland, " It has been the refuge of speculative phi- 
losophers to refer the origin of existing organizations either to an 
eternal succession of the same species, or to the formation of more 
recent from more ancient species by successive developments, 
without the interposition of direct and repeated acts of creation, 48 
NATURAL THEOLOGY. 
V. Our observer would farther also reflect, that the 
maker of the watch before him was in truth and real- 
ity the maker of every watch produced from it: there 
being no difference (except that the latter manifests 
a more exquisite skill) between the making of an- 
other watch with his own hands, by the mediation of 
files, lathes, chisels, &c., and the disposing, fixing, 
and inserting of these instruments, or of others equiv- 
alent to them, in the body of the watch already made 
in such a manner as to form a new watch in the 
course of the movements which he had given to 
the old one. It is only working by one set of tools 
instead of another. 
The conclusion which the first examination of the 
watch, of its works, construction, and movement, sug- 
gested, was, that it must have had, for cause and au- 
thor of that construction, an artificer who understood 
its mechanism, and designed its use. This conclu- 
sion is invincible. A second examination presents us 
with a new discovery. The watch is found, in the 
course of its movement, to produce another watch 
similar to itself; and not only so, but we perceive in 
it a system or organization separately calculated for 
that purpose. What effect would this discovery have, 
or ought it to have, upon our former inference ? 
What, as hath already been said, but to increase, be- 
yond measure, our admiration of the skill which had 
been employed in the formation of such a machine 1 
Or shall it, instead of this, all at once turn us round 
to an opposite conclusion, viz., that no art or skill 
and thus to deny the existence of any first term in the infinite se- 
ries of succession which this hypothesis assumes. Against this 
theory no decisive evidence has been accessible, until the modern 
discoveries of geology had established two conclusions of the 
highest value in relation to this long-disputed question ; the first 
proving that existing species have had a beginning, and this at a 
period comparatively recent; the second showing that they were 
preceded by several other systems of animal and vegetable life; 
respecting each of which it may no less be proved, that there was 
a time when, their existence had not commenced, and that to 
these systems also the doctrine of eternal succession, both retro- 
spective and prospective, is equally inapplicable."-Am. Ed. NATURAL THEOLOGY. 
49 
whatever has been concerned in the business, al- 
though all other evidences of art and skill remain as 
they were, and this last and supreme piece of art be 
nowr added to the rest! Can this be maintained with- 
out absurdity! Yet this is atheism.* 
CHAPTER III. 
APPLICATION OF THE ARGUMENT. 
This is atheism : for every indication of contri- 
vance, every manifestation of design, which existed 
in the watch, exists in the works of nature; with the 
difference, on the side of nature, of being greater and 
more, and that in a degree which exceeds all compu- 
tation. I mean that the contrivances of nature surpass 
the contrivances of art in the complexity, subtilty, 
and curiosity of the mechanism; and still more, if 
possible, do they go beyond them in number and va- 
riety ; yet, in a multitude of cases, are not less evi- 
dently mechanical, not less evidently contrivances, 
not less evidently accommodated to their end, or 
suited to their office, than are the most perfect pro- 
ductions of human ingenuity. 
* We must leave this logical and satisfactory argument un- 
touched. In this chapter our author is laying the foundation for 
a course of reasoning on the mechanism displayed in the animal 
body. The argument in favour of a creating and presiding In- 
telligence may be drawn from the study of the laws of physical 
agency: such as the properties of heat, light, and sound; of 
gravitation and chymical combination ; the structure of the globe, 
the divisions of land and sea, the distribution of temperature ; nay, 
the mind may rise to the contemplation of the sun and planets, 
their mutual dependence, and their revolutions ; but, as affording 
proofs obvious not only to cultivated reason, but to plain sense, 
almost to ignorance, there is nothing to be compared with that for 
which our author is preparing the reader in this chapter, the mech- 
anism of the animal body, and the adaptations which affect the 
well-being of living creatures. 
Vol, I.-E 50 
NATURAL THEOLOGY 
[The right-hand figure represents the human eye, the left-hand 
figure the eye of a fish. The human eye is nearly spherical, ex- 
cept in front, where the transparent part, called the cornea (c), pro- 
jects. Within the cornea lies a transparent humour, called, from 
its resemblance to water, the aqueous humour (d), and in this 
is suspended the curious curtain called the iris. Back of the 
aqueous lies the crystalline humour or lens (F), which is the 
most important refracting instrument in the eye ; the remainder 
of the cavity is occupied by the vitreous humour (G), so called 
from its resemblance to melted glass. The optic nerve is at O, 
and an expansion of it, called the retina, is spread over the back 
part of the eye contiguous to the vitreous humour. On this 
membrane images of external objects are formed by means of 
light, and these images are the cause of vision.-Am. Ed.] 
I know no better method of introducing so large a 
subject, than that of comparing a single thing with a 
single thing: an eye, for example, with a telescope. 
As far as the examination of the instrument goes, 
there is precisely the same proof that the eye was 
made for vision, as there is that the telescope was 
made for assisting it. They are made upon the 
same principles; both being adjusted to the laws by 
which the transmission and refraction5 of rays of 
5 When light passes obliquely from one medium into another 
of different density (as from air into water, or the reverse), it is 
turned from its straight course (i. e., refracted) towards the denser 
medium ; this refraction will be greater in proportion as the 
media differ more in density (hence greater in passing from air 
into glass than from air into water), and also in proportion as the 
aght passes more obliquely in respect to the surface that divides 
hese media. Now if this surface is made round, as is the case 
with the eye and with the object-glass of a telescope, the light, in 
passing, will be drawn in on all sides towards the central parts of 
the medium, and thus will be brought to a focus somewhere back 
of the surface. Separate pencils of light, coming from different NATURAL THEOLOGY. 
51 
light are regulated. I speak not of the origin of the 
laws themselves; but such laws being fixed, the con- 
struction in both cases is adapted to them. For in- 
stance • these laws require, in order to produce the 
same effect, that the rays of light, in passing from 
water into the eye, should be refracted by a more 
convex surface than when it passes out of air into 
the eye. Accordingly, we find that the eye of a fish, 
in that part of it called the crystalline lens, is much 
rounder than the eye of terrestrial animals.6 What 
plainer manifestation of design can there be in this 
difference 1 What could a mathematical instrument 
maker have done more to show his knowledge of his 
principle, his application of that knowledge, his suit- 
ing of his means to his end; I will not say to display 
the compass or excellence of his skill and art, for in 
these all comparison is indecorous, but to testify 
counsel, choice, consideration, purpose 1 
To some it may appear a difference sufficient to de- 
stroy all similitude between the eye and the telescope, 
that the one is a perceiving organ, the other an unper- 
ceiving instrument. The fact is that they are both in- 
struments. And as to the mechanism, at least as to 
mechanism being employed, and even as to the kind of 
it, this circumstance varies not the analogy at all. 
For observe what the constitution of the eye is. It is 
necessary, in order to produce distinct vision, that an 
points in the object, will form foci corresponding to the points 
from which they proceeded, and thus form an image of the ob- 
ject. In a telescope this image is formed within the tube of the 
instrument, and is then viewed by the eye through a magnifying- 
glass called the eyeglass. In the eye the image is formed on a 
membrane on the back part of the eye called the retina, and is 
then viewed by the mind. See figure and description on page 97. 
•-Am. Ed. 
6 Water being almost as dense as the humours of the eye, light 
would undergo but little refraction on entering a fish's eye, were 
it not for this provision, by which the light is made to fall more 
obliquely on the lens, and thus be more bent out of its course. 
The greater convexity of the lens makes up for the slight differ- 
ence in the density of the media. See the left-hand figure, where 
the crystalline lens is a sphere, and where, as might be antici- 
pated, the aqueous humour is deficient.-Am. Ed. 52 
NATURAL THEOLOGY. 
image or picture of the object be formed at the bot- 
tom of the eye. Whence this necessity arises, or 
how the picture is connected with the sensation, or 
contributes to it, it may be difficult, nay, we will con- 
fess, if you please, impossible for us to search out. 
But the present question is not concerned in the in- 
quiry. It may be true that, in this and in other in- 
stances, we trace mechanical contrivance a certain 
way; and that then we come to something which is 
not mechanical, or which is inscrutable. But this 
affects not the certainty of our investigation as far 
as we have gone. The difference between an ani- 
mal and an automatic statue consists in this: that in 
the animal we trace the mechanism to a certain 
point, and then we are stopped; either the mecha- 
nism being too subtile for our discernment, or some- 
thing else besides the known laws of mechanism 
taking place; whereas, in the automaton, for the 
comparatively few motions of which it is capable, we 
trace the mechanism throughout. But, up to the 
limit, the reasoning is as clear and certain in the one 
case as in the other. In the example before us, it is 
a matter of certainty, because it is a matter which 
experience and observation demonstrate, that the 
formation of an image at the bottom of the eye is 
necessary to perfect vision. The image itself can 
be shown. Whatever affects the distinctness of the 
image, affects the distinctness of the vision. The 
formation, then, of such an image being necessary (no 
matter how) to the sense of sight, and to the exer- 
cise of that sense, the apparatus by which it is 
formed is constructed and put together, not only 
with infinitely more art, but upon the selfsame prin- 
ciples of art, as in the telescope or the camera ob- 
scura. The perception arising from the image may 
be laid out of the question; for the production of 
the image, these are instruments of the same kind. 
The end is the same, the means are the same. The 
purpose in both is alike; the contrivance for accom- 
plishing that purpose is in both alike. The lenses of 
the telescopes and the humours of the eye bear a NATURAL THEOLOGY. 
53 
complete resemblance to one another7 in their figure, 
their position, and in their power over the rays of 
light, viz., in bringing each pencil to a point at the 
right distance from the lens; namely, in the eye, at 
the exact place where the membrane is spread to re- 
ceive it. How is it possible, under circumstances of 
such close affinity, and under the operation of equal 
evidence, to exclude contrivance from the one, yet 
to acknowledge the proof of contrivance having been 
employed, as the plainest and clearest of all proposi- 
tibns, in the other 1 
The resemblance between the two cases is still 
more accurate, and obtains in more points than we 
have yet represented, or than we are, on the first 
view of the subject, aware of. In dioptric telescopes 
there is an imperfection of this nature. Pencils of 
light, in passing through glass lenses, are separated 
into different colours, thereby tinging the object, es- 
pecially the edges of it, as if it were viewed through 
a prism. To correct this inconvenience had been 
long a desideratum in the art. At last it came into 
the mind of a sagacious optician to inquire how this 
matter was managed in the eye : in which there was 
exactly the same difficulty to contend with as in the 
telescope. His observation taught him, that in the 
eye the evil was cured by combining lenses compo- 
sed of different substances, i. e., of substances which 
7 Except that in the eye the contrivance is much more per- 
fect. For example, in the eye the lens is not, as in the telescope, 
of uniform density, but is composed of concentric layers, increas- 
ing in density towards the centre. There are two advantages in 
this ; first, a certain irregularity in the refraction, produced by the 
spherical form of the lens, is corrected, and the image formed is 
more distinct than it could be if formed by the lens of a telescope; 
secondly, the light, as it advances within the eye, is not opposed by 
a sudden increase of density, the effect of which would be to dis- 
pose it to reflection, and prevent its proceeding through the lens, 
and thus the image is rendered brighter or more luminous. The 
whole eye, indeed, seems to be constructed with reference to this 
last effect; the humour which is least dense being placed in the 
front part of the eye, and the density gradually increasing till we 
reach the centre of the crystalline lens, from which it diminishes. 
-Am. Ed. 54 
NATURAL THEOLOGY. 
possessed different refracting powers. Our artist bor- 
rowed thence his hint,8 and produced a correction of 
the defect by imitating, in glasses made from differ 
ent materials, the effects of the different humours 
through which the rays of light pass before they 
reach the bottom of the eye. Could this be in the 
eye without purpose, which suggested to the optician 
the only effectual means of attaining this purpose 19 
But farther; there are other points, not so much, 
perhaps, of strict resemblance between the two, as ot 
superiority of the eye over the telescope; yet of a 
superiority which, being founded in the laws that reg- 
ulate both, may furnish topics of fair and just com- 
parison. Two things were wanted to the eye, which 
were not wanted (at least in the same degree) to the 
telescope; and these were the adaptation of the or- 
gan, first,to different degrees of light; and, secondly, 
to the vast diversity of distance at which objects are 
viewed by the naked eye, viz., from a few inches to 
as many miles. These difficulties present not them- 
selves to the maker of the telescope. He wants all 
the light he can get; and he never directs his instru- 
ment to objects near at hand. In the eye both these 
cases were to be provided for; and for the purpose 
of providing for them, a subtile and appropriate mech- 
anism is introduced. 
8 It is not known that Dollond was led to this invention by an 
examination of the eye. The analogy in question, however, is 
none the less striking. It has recently been rendered still more 
complete by an invention of Dr. Blair. The best of Dollond's ob- 
ject-glasses, compounded of two or more lenses, do not render 
the image perfectly colourless. This Dr. B. has accomplished by 
combining solid and fluid lenses, i. e., by constructing an instru- 
ment still more like the human eye. The only difference is, that 
his is composed of one fluid between two solid lenses; whereas 
the eye has one solid between two fluid lenses.-Am. Ed. 
9 It is not, accurately speaking, " glasses of different refracting 
powers" which are required. Refraction is the new direction 
which the ray takes in passing from one transparent body into an- 
other of different density. Dispersion is the separation of the 
beam of light into differently coloured rays. A piece of glass 
may differ from another in its power of refracting, and also in its 
property of dispersing. It is by duly arranging these different 
properties that the achromatic telescope is formed. NATURAL THEOLOGY. 
55 
[The above figure represents a section of the anterior part of the 
human eye ; A, A, the iris ; B, the object, from which the rays 
strike off in all directions : a pencil of these enters at the pupil; 
a portion is intercepted by the iris A, A. The pencil which enters 
the eye, passing through the lens, converges to form the image. 
But the spaces C, C are deprived of rays by the intervention of 
the iris A, A. Yet this in no measure affects the size of the image, 
but only diminishes the intensity of its illumination. By the con- 
traction of the iris, and consequent enlargement of the pupil, a 
larger pencil of rays is admitted. It is remarkable that the image 
formed on the retina must always be inverted, and yet such is the 
constitution of our frames that we see things as they are in real- 
ity-] 
I. In order to exclude excess of light when it is 
excessive, and to render objects visible under obscu- 
rer degrees of it, when no more can be had, the hole 
or aperture in the eye through which the light enters 
is so formed as to contract or dilate itself for the pur- 
pose of admitting a greater or less number of rays at 
the same time. The chamber of the eye is a came- 
ra obscura, which, when the light is too small, can 
enlarge its opening; when too strong, can again con- 
tract it; and that without any other assistance than 
that of its own exquisite machinery. It is farther 
also, in the human subject, to be observed, that this 
hole in the eye, which we call the pupil, under all its 
different dimensions, retains its exact circular shape. 
This is a structure extremely artificial. Let an artist 
only try to execute the same; he will find that his 
threads and strings must be disposed with great con- 
sideration and contrivance, to make a circle which 
shall continually change its diameter yet preserve its 56 
NATURAL THEOLOGY. 
form. This is done in the eye by an application of 
fibres, t. e., of strings similar in their position and ac- 
tion to what an artist would and must employ if he 
had the same piece ofSvorkmanship to perform.10 
[This figure represents the iris separated from the eye and laid 
out fiat. We perceive the straight fibres passing towards the in- 
ner margin, and the circular fibres running round the margin.] 
II. The second difficulty which has been stated was 
the suiting of the same organ to the perception of ob- 
jects that lie near at hand, within a few inches, we 
will suppose, of the eye, and of objects which are pla- 
ced at a considerable distance from it, that, for exam- 
ple, of as many furlongs (I speak in both cases of the 
distance at which distinct vision can be exercised). 
Now this, according to the principles of optics, that 
is, according to the laws by which the transmission 
of light is regulated (and these laws are fixed), could 
not be done without the organ itself undergoing an 
alteration, and receiving an adjustment that might 
correspond with the exigency of the case, that is to 
say, with the different inclination to one another un- 
der which the rays of light reached it. Rays issuing 
from points placed at a small distance from the eye, 
and which, consequently, must enter the eye in a 
10 This contraction and dilatation of the pupil is involuntary, 
and results from the sensibility of the retina, which, being awa- 
kened by the action of the light, excites the iris to the necessary 
motions.-Am. Ed. NATURAL THEOLOGY. 
57 
spreading or diverging order, cannot, by the same op- 
tical instrument in the same state, be brought to a 
point, i. <?., be made to form an image in the same 
place with rays proceeding from objects situated at a 
much greater distance, and which rays arrive at the 
eye in directions nearly (and, physically speaking) 
parallel. It requires a rounder lens to do it. The 
point of concourse behind the lens must fall critically 
upon the retina, or the vision is confused; yet, other 
things remaining the same, this point, by the immu- 
table properties of light, is carried farther back when 
the rays proceed from a near object than when they 
are sent from one that is remote. A person who was 
using an optical instrument would manage this mat- 
ter by changing, as the occasion required, his lens or 
his telescope, or by adjusting the distance of his glass- 
es with his hand or his screw: but how is this to be 
managed in the eye 1 What the alteration was, or in 
what part of the eye it took place, or by what means 
it was effected (for if the known laws which govern 
the refraction of light be maintained, some alteration 
in the state of the organ there must be), had long 
formed a subject of inquiry and conjecture. The 
change, though sufficient for the purpose, is so minute 
as to elude ordinary observation. Some very late 
discoveries, deduced from a laborious and most accu- 
rate inspection of the structure and operation of the 
organ, seem at length11 to have ascertained the me- 
chanical alteration which the parts of the eye under- 
go. It is found that by the action of certain muscles, 
called the straight muscles, and which action is the 
most advantageous that could be imagined for the 
purpose, it is found, I say, that whenever the eye is 
directed to a near object, three changes are produced 
in it at the same time, all severally contributing to 
the adjustment required. The cornea, or outermost 
coat of the eye, is rendered more round and pro mi- 
11 Philosophers are by no means agreed, even yet, as to the 
means by which this adjustment in the eye is produced. The 
first and last of the three changes mentioned in the text are not 
well ascertained.-Am. Ed. 58 
NATURAL THEOLOGY. 
nent; the crystalline lens underneath is pushed for- 
ward ; and the axis of vision, as the depth of the eye 
is called, is elongated. These changes in the eye 
vary its power over the rays of light in such a man- 
ner and degree as to produce exactly the effect which 
is wanted, viz., the formation of an image upon the 
retina, whether the rays come to the eye in a state of 
divergency, which is the case when the object is near 
to the eye, or come parallel to one another, which is 
the case when the object is placed at a distance. Can 
anything be more decisive of contrivance than this is! 
The most secret laws of optics must have been known 
to the author of a structure endowed with such a ca- 
pacity of change. It is as though an optician, when 
he had a nearer object to view, should rectify his in- 
strument by putting in another glass, at the same time 
drawing out also his tube to a different length.12 
Observe a newborn child first lifting up its eye- 
lids. What does the opening of the curtain discov- 
er ? The anterior part of two pellucid globes, which, 
when they come to be examined, are found to be 
constructed upon strict optical principles; the self- 
12 However difficult it may be to account for the mode of ad- 
justment, yet the property is not denied, and, therefore, the argu- 
ment in the text remains. That there is something in the sensi- 
bility of the nerve and in the power of attention, there seems no 
doubt. Birds of prey, it has been noticed, possess a power ot 
vision of which we can hardly form a conception. Where it is 
the object to snare the falcon, a pigeon is tied in an exposed situ- 
ation, with a cord so attached that a person concealed can flutter 
the bird, or make it extend its wings; and, although no bird of 
prey be visible in the whole sky, presently the hawk will be seen 
descending to pounce upon the pigeon. The endowment of the 
bird's eye must be different from ours, else the bird of prey could 
not see the most minute object when hovering at a great height; 
nor, in sweeping down upon his quarry, could he strike it with 
precision. Nothing of the nature of mere mechanical provision 
can account for the possession of this superior power. One in- 
stance of the power of adjustment which the eye has under the 
influence of the will, seems to be this. Let a person who cannot 
read distinctly, or at all, without spectacles, at a given distance, 
look at a word through a very small aperture, and he will see 
what he before could not without spectacles. This can hardly be 
explained by the removal of the lateral light, or by inflexion. NATURAL THEOLOGY. 
59 
same principles upon which we ourselves construct 
optical instruments. We find them perfect for the 
purpose of forming an image by refraction, composed 
of parts executing different offices; one part having 
fulfilled its office upon the pencil of light, delivering 
it over to the action of another part, that to a third, 
and so onward ; the progressive action depending for 
its success upon the nicest and minutest adjustment 
of the parts concerned: yet these parts so in fact 
adjusted as to produce, not by a simple action or ef- 
fect, but by a combination of actions and effects, the 
tesult which is ultimately wanted. And forasmuch 
as this organ would have to operate under different 
circumstances, with strong degrees of light and with 
weak degrees, upon near objects and upon remote 
ones, and these differences demanded, according to 
the laws by which the transmission of light is regu- 
lated, a corresponding diversity of structure ; that the 
aperture, for example, through which the light passes 
should be larger or less, the lenses rounder or flatter, 
or that their distance from the tablet upon which the 
picture is delineated should be shortened or length- 
ened ; this, I say, being the case, and the difficulty 
to which the eye was to be adapted, we find its sev- 
eral parts capable of being occasionally changed, and 
a most artificial apparatus provided to produce that 
change. This is far beyond the common regulator 
of a watch, which requires the touch of a foreign 
hand to set it; but it is not altogether unlike Harri- 
son's contrivance for making a watch regulate itself, 
by inserting within it a machinery which, by the art- 
ful use of the different expansion of metals, preserves 
the equability of the motion under all the various 
temperatures of heat and cold in which the instru- 
ment may happen to be placed. The ingenuity of 
this last contrivance has been justly praised. Shall, 
therefore, a structure which differs from it chiefly by 
surpassing it, be accounted no contrivance at all ? or, 
if it be a contrivance, that it is without a contriver1? 
But this, though much, is not the whole: by dif- 
ferent species of animals the faculty we are descri- 60 
NATURAL THEOLOGY. 
bing is possessed in degrees suited to the different 
range of vision which their mode of life and of pro- 
curing their food requires. Birds, for instance, in 
general, procure their food by means of their beak; 
and, the distance between the eye and the point of 
the beak being small, it becomes necessary that they 
should have the power of seeing very near objects 
distinctly. On the other hand, from being often ele- 
vated much above the ground, living in the air, and 
moving through it with great velocity, they require 
for their safety, as well as for assisting them in de- 
scrying their prey, a power of seeing at a great dis- 
tance; a power of which, in birds of rapine, surpri- 
sing examples are given. The fact accordingly is, 
that two peculiarities are found in the eyes of birds, 
both tending to facilitate the change upon which the 
adjustment of the eye to different distances depends. 
The one is a bony, yet, in most species, a flexible 
rim or hoop, surrounding the broadest part of the 
eye, which, confining the action of the muscles to 
that part, increases the effect of their lateral pres- 
sure upon the orb, by which pressure its axis is elon- 
gated for the purpose of looking at very near ob- 
jects. The other is an additional muscle, called the 
marsupium, to draw, on occasion, the crystalline lens 
lack, and to fit the same eye for the viewing of very 
distant objects. By these means, the eyes of birds 
can pass from one extreme to another of their scale 
of adjustment, with more ease and readiness than 
the eyes of other animals. 
The eyes of fishes also, compared with those of 
terrestrial animals, exhibit certain distinctions of 
structure adapted to their state and element. We 
have already observed upon the figure of the crys- 
talline compensating by its roundness the density of 
the medium through which their light passes. To 
which we have to add, that the eyes of fish, in their 
natural and indolent state, appear to be adjusted to 
near objects, in this respect differing from the human 
eye, as well as those of quadrupeds and birds. The 
ordinary shape of the fish's eye being in a much higher degree convex than that of land animals, a 
corresponding difference attends its muscular con- 
formation, viz., that it is throughout calculated for 
flattening the eye. 
The iris also in the eyes of fish does not admit of 
contraction. This is a great difference, of which the 
probable reason is, that the diminished light in water 
is never too strong for the retina. 
NATURAL THEOLOGY. 
61 
In the eel, which has to work its head through sand 
and gravel, the roughest and harshest substances, there 
is placed before the eye, and at some distance from it, 
a transparent, horny, convex case or covering, which, 
without obstructing the sight, defends the organ. To 
such an animal could anything be more wanted or 
more useful 1 
Thus, in comparing the eyes of different kinds of 
animals, we see in their resemblances and distinctions 
one general plan laid down, and that plan varied with 
the varying exigencies to which it is to be applied.13 
13 In viewing the structure of the eye as adjusted to the con- 
dition of fishes, we may remark the peculiar thickness of the scle- 
rotic* coat in the whale. Although he breathes the atmosphere, 
and lies out on the surface of the water, to escape his enemies he 
will plunge some hundred fathoms deep. The pressure, there- 
fore, must be very great upon his surface and on the surface ot 
the eye. If a cork be knocked into the mouth of a bottle so that 
it resists all farther pressure that we can make upon it, and if this 
bottle be carried, by being attached to the sounding-lead, to a great 
depth in the sea, the pressure of the water will force in the cork 
* I. e., the outer coat or covering usually called the white of the 
eye. It is thick and tough, serving to defend the organ from in- 
jury, and to preserve its spherical form.-Am. Ed. 
You I.-F 62 
There is one property, however, common, I believe, 
to all eyes, at least to all which have been examined,* 
namely, that the optic nerve enters the bottom of the 
eye, not in the centre or middle, but a little on one 
side : not in the point where the axis of the eye meets 
the retina, but between that point and the nose. The 
difference which this makes is, that no part of an ob- 
ject is unperceived by both eyes at the same time. 
NATURAL THEOLOGY. 
and fill the bottle; for the cork is pressed with a force equal to 
the weight of the column of water above it, of which it is the 
base. It is pressed in all directions equally, so that a common- 
sized cork is reduced to the size of that of a vial bottle. 
" A creature living at the depth of 100 feet would sustain a pres- 
sure, including that of the atmosphere, of about 60 pounds on the 
square inch; while one at 4000 feet, a depth by no means consid- 
erable, would be exposed to a pressure of about 1830 pounds upon 
the square inch."-De la Beche,Theor. Geol., p. 243. 
We can therefore comprehend how it shall happen, that on the 
foundering of a ship at sea, though its timbers part, not a spar 
floats to the surface ; everything is swallowed up; for, if the hull 
has sunk to a great depth, all that is porous is penetrated with wa- 
ter, or compressed, and consequently remains where it sunk. So 
it happened, and the fact goes directly to our purpose, that when, 
by the entangling of the line of the harpoon, the boat was carried 
down with the whale, and, being recovered, it required two boats 
to keep it at the surface.-Scoresby. 
We may easily conceive, therefore, the pressure which the eye 
of the whale sustains when it dives, and why it is formed with the 
provisions which we are about to describe. When we make a sec- 
tion of the whole eye, cutting through the cornea, the sclerotic 
coat, which is dense as tanned leather, increases in thickness to- 
wards the back part, and is full five times the thickness behind 
that it is at the anterior part. The anterior part of the eye sustains 
the pressure from without, and requires no additional support; but 
were the back part to yield, the globe would be then distended in 
that direction, and the whole interior of the eye consequently suf- 
fer derangement. We perceive, therefore, the necessity of the 
coats being thus so remarkably strengthened behind. The natu- 
ral enemies of the whale are the swordfish and the shark ; and it 
is stated, with some show of reason, that this huge creature, being 
without means of defence of any kind, carries his enemies that 
have fixed upon him to a depth of water, and consequently to a 
pressure, which subdues them, as their bodies are not constituted 
for such depths. It is under this instinct that when the whale re- 
ceives the harpoon, he dives to the bottom. 
* The eye of the seal or seacalf, I understand, is an exception. 
Mem. Acad. Paris, 1710, p. 123.-Paley. NATURAL THEOLOGY. 
63 
In considering vision as achieved by the means of 
an image formed at the bottom of the eye, we can 
never reflect without wonder upon the smallness yet 
correctness of the picture, the subtilty of the touch, 
the fineness of the lines. • A landscape of five or six 
square leagues is brought into a space of half an inch 
diameter; yet the multitude of objects which it con- 
tains are all preserved, are all discriminated in their 
magnitudes, positions, figures, colours. The pros- 
pect from Hampstead Hill is compressed into the 
compass of a sixpence, yet circumstantially repre- 
sented. A stagecoach, travelling at an ordinary 
speed for half an hour, passes, in the eye, only over 
one twelfth of an inch, yet is this change of place in 
the image distinctly perceived throughout its whole 
progress; for it is only by means of that perception 
that the motion of the coach itself is made sensible 
to the eve. If anything can abate our admiration of 
the smallness of the visual tablet compared with the 
extent of vision, it is a reflection which the view of 
nature leads up every hour to make, viz., that in the 
hands of the Creator great and little are nothing. 
Sturmius held, that the examination of the eye 
was a cure for atheism. Besides that conformity to 
optical principles which its internal constitution dis- 
plays, and which alone amounts to a manifestation 
of intelligence having been exerted in the structure; 
besides this, which forms, no doubt, the leading char- 
acter of the organ, there is to be seen, in everything 
belonging to it and about it, an extraordinary degree 
of care, an anxiety for its preservation, due, if we 
may so speak, to its value and its tenderness. It is 
lodged in a strong, deep, bony socket, composed by 
the junction of seven different bones,* hollowed out 
at their edges. In some few species, as that of the 
coatimondi,f the orbit is not bony throughout; but, 
whenever this is the case, the upper, which is the 
deficient part, is supplied by a cartilaginous ligament; 
a substitution which shows the same care. Within 
* Heister, sect. 89. f Mem. R. Ac. Paris, p. 117.-Paley. 64 
NATURAL THEOLOGY. 
this socket it is imbedded in fat, of all animal sub- 
stances the best adapted both to its repose and mo- 
tion. It is sheltered by the eyebrows; an arch of 
hair, which, like a thatched penthouse, prevents the 
sweat and moisture of the forehead from running 
down into it. 
But it is still better protected by its lid. Of the 
superficial parts of the animal frame, I know none 
which, in its office and structure, is more deserving 
of attention than the eyelid. It defends the eye; it 
wipes it; it closes it in sleep. Are there, in any 
work of art whatever, purposes more evident than 
those which this organ fulfils I or an apparatus for 
executing those purposes more intelligible, more ap- 
propriate, or more mechanical 114 If it be overlooked 
by the observer of nature, it can only be because it 
is obvious and familiar. This is a tendency to be 
guarded against. We pass by the plainest instances, 
while we are exploring those which are rare and cu- 
rious ; by which conduct of the understanding we 
sometimes neglect the strongest observations, being 
taken up with others which, though more recondite 
and scientific, are, as solid arguments, entitled to 
much less consideration. 
In order to keep the eye moist and clean (which 
qualities are necessary to its brightness and its use), 
a wash is constantly supplied by a secretion for the 
purpose; and the superfluous brine is conveyed to 
the nose, through a perforation in the bone as large as 
14 Sir C. Bell notices other provisions about the lid which are 
beautifully indicative of design. For example, when the eyelids 
meet, they touch only at their outer edges, so that, when closed, 
there is a gutter left between them and the cornea. If the eye- 
ball, then, were to remain without motion when the lids are closed, 
there would be a certain portion of the cornea left uncleansed, 
because untouched. To prevent this, the instant the eyelids are 
closed, the eyeball makes a movement which raises the cornea 
under the upper eyelid. 
Another provision worthy of notice is, that while the upper eye- 
lid falls, the lower eyelid is moved towards the nose. This is a 
part of the curious mechanism for collecting offensive particles 
towards the inner corner of the eye.-Am. Ed. NATURAL THEOLOGY. 
65 
a goose-quill. When once the fluid has entered the 
nose, it spreads itself upon the inside of the nostril, 
and is evaporated by the current of warm air which, 
in the course of respiration, is continually passing 
over it. Can any pipe or outlet for carrying off the 
waste liquor from a dye-house or a distillery be more 
mechanical than this is 1 It is easily perceived that 
the eye must want moisture: but could the want of 
the eye generate the gland which produces the tear, 
or bore the hole by which it is discharged; a hole 
through a bone 1 
It is observable that this provision is not found in 
fish, the element in which they live supplying a con- 
stant lotion to the eye.13 
It were, however, injustice to dismiss the eye as a 
piece of mechanism, without noticing that most ex- 
quisite of all contrivances, the nictitating membrane, 
which is found in the eyes of birds and of many 
quadrupeds. Its use is to sweep the eye, which it 
does in an instant; to spread over it the lachrymal hu- 
mour; to defend it also from sudden injuries; yet not 
totally, when drawn upon the pupil, to shut out the 
light. The commodiousness with which it lies folded 
up in the upper corner of the eye, ready for use and 
action, and the quickness with which it executes its 
purpose, are properties known and obvious to every 
observer; but what is equally admirable, though not 
quite so obvious, is the combination of two kinds of 
substance, muscular and elastic, and of two different 
kinds of action, by which the motion of this mem- 
brane is performed. It is not, as in ordinary cases, 
by the action of two antagonist muscles, the one pull- 
15 To enable them to use this lotion, muscles seem to have been 
provided by which they can move their eyes backward and for- 
ward with great rapidity, as it were to rinse them. In the mud 
crab, an animal which, like the eel, seeks it3 food in mud and tur- 
bid water, a most striking provision is seen for this cleansing of 
the eye. To remove the slime which covers the eye when if 
emerges from the mud, a little brush is placed near, to which it 
raises itself, and " against which," to use the words of Sir C. Bell, 
it is wiped with an action as intelligible as a man wiping his 
spectacles."-Am. Ed. 66 
NATURAL THEOLOGY. 
ing forward and the other backward, that a recipro- 
cal change is effected ; but it is thus: the membrane 
itself is an elastic substance, capable of being drawn 
out by force, like a piece of elastic gum, and by its 
own elasticity returning, when the force is removed, 
to its former position. Such being its nature, in order 
to fit it up for its office, it is connected by a tendon or 
thread, with a muscle in the back part of the eye: 
this tendon or thread, though strong, is so fine as not 
to obstruct the sight, even when it passes across it; 
and the muscle itself, being placed in the back part of 
the eye, derives from its situation the advantage not 
only of being secure, but of being out of the way; 
which it would hardly have been in any position that 
could be assigned to it in the anterior part of the orb, 
where its function lies. When the muscle behind the 
eye contracts, the membrane, by means of the com- 
municating thread, is instantly drawn over the fore- 
part of it. When the muscular contraction (which is a 
positive and, most probably, a voluntary effort) ceases 
to be exerted, the elasticity alone of the membrane 
brings it back again to its position.* Does not this, 
if anything can do it, bespeak an artist, master of his 
work, acquainted with his materials ? " Of a thou- 
sand other things," say the French Academicians, 
" we perceive not the contrivance, because we under- 
stand them only by their effects, of which we know 
not the causes; but we here treat of a machine, all 
the parts whereof are visible, and which need only be 
looked upon to discover the reasons of its motion and 
action."! 
In the configuration of the muscle which, though 
placed behind the eye, draws the nictitating membrane 
over the eye, there is what the authors just now quo- 
ted deservedly call a marvellous mechanism. I sup- 
pose this structure to be found in other animals; but, 
in the memoirs from which this account is taken, it is 
* Phil. Trans., 1796. 
t Memoirs for a Natural History of Animals, by the Royal 
Academy of Sciences at Paris, done into English by order of the 
Royal Society, 1701, p. 249.-Paley. NATURAL THEOLOGY. 
67 
tnatomically demonstrated only in the cassowary. 
The muscle is passed through a loop formed by another 
muscle; and is there inflected as if it were round a 
pulley. This is a peculiarity, and observe the advan- 
tage of it. A single muscle with a straight tendon, 
which is the common muscular form, would have been 
sufficient if it had had power to draw far enough. But 
the contraction necessary to draw the membrane over 
the whole eye, required a longer muscle than could 
lie straight at the bottom of the eye. Therefore, in 
order to have a greater length in a less compass, the 
chord of the main muscle makes an angle. This so 
far answers the end; but, still farther, it makes an 
angle, not round a fixed pivot, but round a loop form- 
ed by another muscle, which second muscle, when- 
ever it contracts, of course twitches the first muscle 
at the point of inflection, and thereby assists the ac- 
tion designed by both.16 
One question may possibly have dwelt in the read- 
er's mind during the perusal of these observations, 
namely, why should not the Deity have given to the 
animal the faculty of vision at once ? Why this cir- 
cuitous perception; the ministry of so many means; 
an element provided for the purpose; reflected from 
opaque substances, refracted through transparent 
ones, and both according to precise laws; then a 
complex organ, an intricate and artificial apparatus, in 
16 There is one effect, however, of this apparatus, which our 
author has omitted to notice; that is, the rapidity of motion in 
the membrana nictitans, produced by the oblique direction and junc- 
tion of the tendons of these muscles. 
The membrana nictitans is peculiar to birds : the term is not ap- 
plicable to the corresponding structure in quadrupeds, the object 
being there obtained by a very different mechanism. The haw is 
a thin cartilage, which, lying between the eyeball and the inner 
part of the orbit, flies rapidly out, and sweeps the surface of the 
eye in a manner much more perfect than can be performed by the 
outer eyelids. Every one who has ridden a horse in a dusty road 
must have been struck with the superior provision in the horse's 
eye : he never suffers from the dust, because this cartilage, being 
bedewed by the secretion of a peculiar gland, not tears, but a mat- 
ter more glutinous, sweeps across the eye, and collects and re- 
moves every particle of dust. 68 
NATURAL THEOLOGY. 
order, by the operation of this element, and in con- 
formity with the restriction of these laws, to produce 
an image upon a membrane communicating with the 
brain 1 Wherefore all this 1 Why make the diffi- 
culty in order to surmount it 1 If to perceive objects 
by some other mode than that of touch, or objects 
which lay out of the reach of that sense, were the 
thing proposed, could not a simple volition of the 
Creator have communicated the capacity ? Why re- 
sort to contrivance where power is omnipotent 1 
Contrivance, by its very definition and nature, is the 
refuge of imperfection. To have recourse to expe- 
dients implies difficulty, impediment, restraint, defect 
of power. This question belongs to the other senses 
as well as to sight; to the general functions of ani- 
mal life, as nutrition, secretion, respiration; to the 
economy of vegetables; and, indeed, to almost all the 
operations of nature. The question, therefore, is 
of very wide extent, and among other answers which 
may be given to it, besides reasons of which proba- 
bly we are ignorant, one answer is this : It is only 
by the display of contrivance that the existence, the 
agency, the wisdom of the Deity could be testified to 
his rational creatures. This is the scale by which 
we ascend to all the knowledge of our Creator which 
we possess, so far as it depends upon the phenomena 
or the works of nature. Take away this, and you 
take away from us every subject of observation and 
ground of reasoning; I mean as our rational facul- 
ties are formed at present. Whatever is done, God 
could have done without the intervention of instru- 
ments or means; but it is in the construction of in- 
struments, in the choice and adaptations of means, 
that a creative intelligence is seen. It is this which 
constitutes the order and beauty of the universe. 
God, therefore, has been pleased to prescribe limits to 
liis own power, and to work his ends within those 
limits. The general laws of matter have, perhaps, 
prescribed the nature of these limits, its inertia, its 
reactipn, the laws which govern the communication 
of motion, the refraction and reflection of light, and NATURAL THEOLOGY. 
69 
the constitution of fluids non-elastic and elastic, the 
transmission of soupd through the latter, the laws of 
magnetism, of electricity, and probably others yet un- 
discovered. These are general laws; and when a 
particular purpose is to be effected, it is not by ma- 
king a new law, nor by the suspension of the old 
ones, nor by making them wind, and bend, and yield 
to the occasion (for nature, with great steadiness, ad- 
heres to and supports them), but it is, as we have 
seen in the eye, by the interposition of an apparatus 
corresponding with these laws, and suited to the ex- 
igency which results from them, that the purpose is 
at length attained. As we have said, therefore, God 
prescribes limits to his power, that he may let in the 
exercise, and thereby exhibit demonstrations of his 
wisdom. For then, i. e., such laws and limitations 
being laid down, it is as though one being should 
have fixed certain rules, and, if we may so speak, pro- 
vided certain materials, and afterward have commit- 
ted to another being, out of these materials, and in sub- 
ordination to these rules, the task of drawing forth a 
creation; a supposition which evidently leaves room, 
and induces, indeed, a necessity for contrivance. 
Nay, there may be many such agents, and many 
ranks of these. We do not advance this as a doc- 
trine either of philosophy or of religion; but we say 
that the subject may safely be represented under this 
view, because the Deity, acting himself by general 
laws, will have the same consequences upon our 
reasoning as if he had prescribed these laws to an- 
other. It has been said, that the problem of crea- 
tion was " attraction and matter being given to make 
a world out of themand, as above explained, this 
statement, perhaps, does not convey a false idea. 
We have made choice of the eye as an instance 
upon which to rest the argument of this chapter. 
Some single example was to be proposed; and the 
eye offered itself under the advantage of admitting of 
a strict comparison with optical instruments. The 
ear, it is probable, is no less artificially and mechan- 
ically adapted to its office than the eye. But we 70 
NATURAL THEOLOGY. 
know less about it; we do not so well understand 
the action, the use, or the mutual dependance of its 
Explanation of the Plan of the Ear.-A, the tube of the ear, hav- 
ing little glands to secrete the wax, and hairs standing across it 
to exclude insects, without impeding the vibrations of the atmo- 
sphere ; B, the membrane of the tympanun drawn into the form of 
a funnel by the attachment of the malleus ; C, the chain of four 
bones lying in the irregular cavity of the tympanum, and commu 
nicating the vibrations of the membrane B to the fluid in the laby 
rinth; 1), Eustachian tube, which forms a communication be 
tween the throat and the tympanum, so as to preserve an equilibrium 
of the air in the cavity of the tympanum and the atmosphere ; E, 
F, the labyrinth, consisting of a central cavity, the vestibule, the 
three semicircular canals, E, and the cochlea, F. 
Beginning from the left hand, we have the malleus, or hammer, 
the first of the chain of bones; we see the long handle or process 
which is attached to the membrane of the tympanum, and which 
moves with the vibrations of that membrane ; the other end is en- 
larged, and has a groove upon it which is articulated with the 
next bone. The second bone is the incus, or anvil, to the grooved 
surface of which the malleus is attached. A long process extends 
from this bone, which has upon it the os orbiculare; and to this NATURAL THEOLOGY. 
71 
third bone there is attached a fourth, the stapes, which is in shape 
like a stirrup iron. The base of this bone is of an oval shape, and 
rests upon a membrane which closes the hole leading into the 
labyrinth. This hole is called foramen ovale. The plan of the 
cochlea shows that one of its spiral passages, beginning in the ves- 
tibule, winds round the pillar till it meets in a point with another 
tube. If the eye follow this second spiral tube it will be found to 
lead, not into the vestibule, but into the irregular cavity of the 
tympanum. 
internal parts. Its general form, however, both ex- 
ternal and internal, is sufficient to show that it is an 
instrument adapted to the reception of sound; that is 
to say, already knowing that sound consists in pulses 
of the air, we perceive in the structure of the ear a 
suitableness to receive impressions from this species 
of action, and to propagate these impressions to the 
brain. For of what does this structure consist 1 An 
external ear (the concha), calculated, like an ear- 
trumpet, to catch and collect the pulses of which we 
have spoken ; in large quadrupeds turning to the sound, 
and possessing a configuration, as well as motion, 
evidently fitted for the office; of a tube which leads 
into the head, lying at the root of this outward ear, 
the folds and sinuses thereof tending and conducting 
the air towards it; of a thin membrane, like the pelt 
of a drum, stretched across this passage upon a bony 
rim; of a chain of movable and infinitely curious 
bones, forming a communication, and the only com- 
munication that can be observed, between the mem- 
brane last mentioned and the interior channels and 
recesses of the scull; of cavities, similar in shape 
and form to wind instruments of music, being spiral 
or portions of circles ; of the Eustachian tube, like 
the hole in a drum, to let the air pass freely into and 
out of the barrel of the ear, as the covering mem- 
brane vibrates, or as the temperature may be altered; 
the whole labyrinth hewn out of a rock; that is, 
wrought into the substance of the hardest bone of 
the body. This assemblage of connected parts con- 
stitute together an apparatus plainly enough relative 
to the transmission of sound, or of the impulses re- 
ceived from sound, and only to be lamented in not 
being better understood. 72 
NATURAL THEOLOGY* 
The communication within, formed by the small 
bones of the ear, is, to look upon, more like what we 
are accustomed to call machinery than anything I 
am acquainted with in animal bodies. It seems evi- 
dently designed to continue towards the sensorium 
the tremulous motions which are excited in the mem- 
brane of the tympanum, or what is better known by 
the name of the " drum of the ear." The compages 
of bones consists of four, which are so disposed, and 
[This figure represents the bones which form the chain.} 
so hinge upon one another, as that if the membrane, 
the drum of the ear, vibrate, all the four are put in 
motion together; and, by the result of their action, 
work the base of that which is the last in the series, 
upon an aperture which it closes, and upon which it 
plays, and which aperture opens into the tortuous ca- 
nals that lead to the brain. This last bone of the four 
is called the stapes. The office of the drum of the 
ear is to spread out an extended surface, capable of 
receiving the impressions of sound, and of being put 
by them into a state of vibration. The office of the 
stapes is to repeat these vibrations. It is a repeating 
frigate, stationed more within the line. From which 
account of its action may be understood how the 
sensation of sound will be excited by anything which 
communicates a vibratory motion to the stapes, 73 
though not, as in all ordinary cases, through the in- 
tervention of the membrana tympani. This is done 
by solid bodies applied to the bones of the scull, as 
by a metal bar holden at one end between the teeth, 
and touching at the other end a tremulous body. It 
likewise appears to be done, in a considerable degree, 
by the air itself, even when this membrane, the drum 
of the ear, is greatly damaged. Either in the natural 
or preternatural state of the organ, the use of the 
chain of bones is to propagate the impulse in a direc- 
tion towards the brain, and to propagate it with the 
advantage of a lever; which advantage consists in 
increasing the force and strength of the vibration, 
and, at the same time, diminishing the space through 
which it oscillates; both of which changes may aug- 
ment or facilitate the still deeper action of the audi- 
tory nerves.17 
The benefit of the Eustachian tube to the organ 
may be made out upon pneumatic principles. Be- 
hind the drum of the ear is a second cavity or barrel, 
called the tympanum. The Eustachian tube is a slen- 
der pipe, but sufficient for the passage of air leading 
from this cavity into the back part of the mouth. 
Now it would not have done to have had a vacuum 
in this cavity; for, in that case, the pressure of the 
atmosphere from without would have burst the mem- 
brane which covered it. Nor would it have done to 
have filled the cavity with lymph or any other secre- 
tion; which would necessarily have obstructed both 
the vibration of the membrane and the play of the 
small bones. Nor, lastly, would it have done to have 
occupied the space with confined air, because the ex- 
pansion of that air by heat, or its contraction by cold, 
NATURAL THEOLOGY. 
17 It should be observed here, that air is not the only vehicle 
of sound. Both solids and fluids answer the same purpose, and 
in a higher degree. The exterior ear, and the complex apparatus 
of bones within, described above, are rendered necessary, in truth, 
by the rarity and elasticity of the atmosphere, and hence are not 
found except in animals that breathe the air. In fishes there is 
neither exterior ear nor opening even for collecting sound-water 
being an excellent conductor-and the solid bones of the head an- 
swer the purpose of the chain of bones in the human ear.-Am. Ed. 
Vol. I.-G 74 
would have distended or relaxed the covering mem- 
brane, in a degree inconsistent with the purpose 
which it was assigned to execute. The only remain- 
ing expedient, and that for which the Eustachian tube 
serves, is to open to this cavity a communication 
with the external air. In one word, it exactly an- 
swers the purpose of the hole in a drum. 
The membrana tympani itself, likewise, deserves 
all the examination which can be made of it. It is 
not found in the ears of fish; which furnishes an ad- 
ditional proof of what, indeed, is indicated by every- 
thing about it, that it is appropriated to the action of 
air, or of an elastic medium. It bears an obvious re- 
semblance to the pelt or head of a drum, from which 
it takes its name. It resembles also a drum-head in 
this principal property, that its use depends upon its 
NATURAL THEOLOGY. 
[This figure represents the membrane of the tympanum of a 
larger size than natural. It is represented as tucked in by the 
Handle of the malleus. The description of Sir Everard Home, re- 
ferred to in the text, is altogether fanciful. There is no proof 
that these fibres are muscular : they are drawn tight by the small 
muscle attached to the malleus called taisor tympani: and it would 
appear that these cords are necessary to produce that variety of 
motion in the membrane suited to all the variety of sounds which 
are conveyed through it to the seat of the sense. Sir Everard 
played to the elephant on the piano-forte. That the animal took 
some notice of the extraordinary sound cannot surprise us; but 
the inferences drawn by Sir Everard were equally ingenious and 
groundless. He supposed that the musical ear was owing to the 
membrane of the tympanum.] NATURAL THEOLOGY. 
75 
tension. Tension is the state essential to it. Now 
we know that, in a drum, the pelt is carried over a 
hoop, and braced, as occasion requires, by the means 
of strings attached to its circumference. In the 
membrane of the ear, the same purpose is provided 
for more simply, but not less mechanically nor less 
successfully, by a different expedient, viz., by the end 
of a bone (the handle of the malleus) pressing upon 
its centre. It is only in very large animals that the 
texture of this membrane can be discerned. In the 
Philosophical Transactions for the year 1800 (vol. i.), 
Mr. Everard Home has given some curious observa- 
tions upon the ear, and the drum of the ear of an 
elephant. He discovered in it what he calls a radia- 
ted muscle; that is, straight muscular fibres passing 
along the membrane from the circumference to the 
centre; from the bony rim which surrounds it towards 
the handle of the malleus, to which the central part 
is attached. This muscle he supposes to be design- 
ed to bring the membrane into unison with different 
sounds: but then he also discovered that this mus- 
cle itself cannot act unless the membrane be drawn 
to a stretch, and kept in a due state of tightness by 
what may be called a foreign force, viz., the action 
of the muscles of the malleus. Supposing his expla- 
nation of the use of the parts to be just, our author is 
well-founded in the reflection which he makes upon 
it: "that this mode of adapting the ear to different 
sounds is one of the most beautiful applications of 
muscles in the body; the mechanism is so simple, and 
the variety of effects so great." 
In another volume of the Transactions above re- 
ferred to, and of the same year, two most curious 
cases are related, of persons who retained the sense 
of hearing, not in a perfect, but in a very considerable 
degree, notwithstanding the almost total loss of the 
membrane we have been describing. In one of these 
cases, the use here assigned to that membrane, of 
modifying the impressions of sound by change of ten- 
sion, was attempted to be supplied by straining the 
muscles of the outward ear. " The external ear," 76 
NATURAL THEOLOGY. 
we are told, "had acquired a distinct motion upward 
and backward, which was observable whenever the 
patient listened to anything which he did not dis- 
tinctly hear; when he was addressed in a whisper, 
the ear was seen immediately to move; when the 
tone of voice was louder, it then remained altogether 
motionless." 
It appears probable, from both these cases, that a 
collateral, if not principal, use of the membrane is to 
cover and protect the barrel of the ear which lies be- 
hind it. Both the patients suffered from cold : one, 
" a great increase of deafness from catching cold 
the other, " very considerable pain from exposure to 
a stream of cold air." Bad effects therefore follow- 
ed from this cavity being left open to the external 
air; yet, had the Author of Nature shut it up by any 
other cover than what was capable, by its texture, of 
receiving vibrations from sound, and, by its connex- 
ion with the interior parts, of transmitting those vi- 
brations to the brain, the use of the organ, so far as 
we can judge, must have been entirely obstructed. 
CHAPTER IV. 
ON THE SUCCESSION OF PLANTS AND ANIMALS. 
The generation of the animal no more accounts for 
the contrivance of the eye or ear, than, upon the sup- 
position stated in the preceding chapter, the produc- 
tion of a watch by the motion and mechanism of a 
former watch, would account for the skill and atten- 
tion evidenced in the watch so produced, than it 
would account for the disposition of the wheels, the 
catching of their teeth, the relation of the several 
parts of the works to one another and to their com- 
mon end; for the suitableness of their forms and 
places to their offices, for their connexion, their oper- 
ation, and the useful result of that operation. I do 77 
insist most strenuously upon the correctness of this 
comparison; that it holds as to every mode of specif- 
ic propagation; and that, whatever was true of the 
watch under the hypothesis above mentioned, is true 
of plants and animals. 
I. To begin with the fructification of plants. Can 
it be doubted but that the seed contains a particular 
organization! Whether a latent plantale* with the 
means of temporary nutrition, or whatever else it be, 
4 encloses an organization suited to the germination 
of a new plant. Has the plant which produced the 
seed anything more to do with that organization, 
than the watch would have had to do with the struc- 
ture of the watch which was produced in the course 
of its mechanical movement! I mean, Has it any- 
thing at all to do with the contrivance 1 The maker 
and contriver of the watch, when he inserted within 
it a mechanism suited to the production of another 
watch, was, in truth, the maker and contriver of that 
other watch. All the properties of the new watch 
were to be referred to his agency: the design man- 
ifested in it, to his intention: the art, to him as 
the artist; the collocation of each part, to his pla- 
cing : the action, effect, and use, to his counsel, intel- 
ligence, and workmanship. In producing it by the 
intervention of a former watch, he was only working 
by one set of tools instead of another. So it is with 
the plant, and the seed produced by it. Can any dis- 
tinction be assigned between the two eases; between 
the producing watch and the producing plant; both 
passive, unconscious substances; both, by the organ- 
ization which was given to them, producing their like, 
without understanding or design; both, that is, in- 
struments ! 
II. From plants we may proceed to oviparous an- 
imals : from seeds to eggs. Now I say that the bird 
has the same concern in the formation of the egg 
which she lays, as the plant has in that of the seed 
which it drops; and no other nor greater. The in- 
NATURAL THEOLOGY. 
* i. e., a little plant, the part which first sprouts from the seed 
when it begins to grow.-Am. Ed. 78 
ternal constitution of the egg is as much a secret to 
the hen as if the hen were inanimate. Her will can- 
not alter it, or change a single feather of the chick. 
She can neither foresee nor determine of which sex 
her brood shall be, or how many of either; yet the 
thing produced shall be, from the first, very dif- 
ferent in its make according to the sex which it 
bears. So far, therefore, from adapting the means, 
she is not beforehand apprized of the effect. If 
there be concealed within that smooth shell a provis- 
ion and a preparation for the production and nourish- 
ment of a new animal, they are not of her providing 
or preparing; if there be contrivance, it is none of 
hers. Although, therefore, there be the difference of 
life and perceptivity between the animal plant, it is a 
difference which enters not into the account; it is a 
foreign circumstance ; it is a difference of properties 
not employed. The animal function and the vegeta- 
ble function are alike destitute of any design which 
can operate upon the form of the thing produced. 
The plant has no design in producing the seed; no 
comprehension of the nature or use of what it pro- 
duces : the bird, with respect to its egg, is not above 
the plant with respect to its seed. Neither the one nor 
the other bears that sort of relation to what proceeds 
from them which a joiner does to the chair which he 
makes. Now a cause which bears this relation to 
the effect, is what we want, in order to account for 
the suitableness of means to an end, the fitness and 
fitting of one thing to another; and this cause the 
parent plant or animaj does not supply. 
It is farther observable, concerning the propagation 
of plants and animals, that the apparatus employed 
exhibits no resemblance to the thing produced ; in 
this respect holding an analogy with instruments and 
tools of art. The filaments, antherae, and stigmata of 
flow'ers,i8 bear no more resemblance to the young 
NATURAL THEOLOGY. 
18 Plants are propagated by means of seed, and the seed is 
fructified or made productive by means of a fertilizing dust called 
pollen, which is formed on the extremities of the little upright fila- 
ments in a flower, usually called stamens, and which, in order to 79 
plant, or even to the seed which is formed by their in- 
tervention, than a chisel or a plane does to a table 
or chair. What, then, are the filaments, antherae, and 
stigmata of plants, but instruments, strictly so called 1 
III. We may advance from animals which bring 
forth eggs to animals which bring forth their young 
alive; and of this latter class, from the lowest to the 
highest; from irrational to rational life, from brutes 
to the human species; without perceiving, as we pro- 
ceed, any alteration whatever in the terms of the com- 
parison. The rational animal does not produce its 
offspring with more certainty or success than the ir- 
rational animal : a man than a quadruped, a quadru- 
ped than a bird; nor (for we may follow the grada 
tion through its whole scale), a bird than a plant; nor 
a plant than a watch, a piece of dead mechanism, 
would do, upon the supposition which has already so 
often been repeated. Rationality, therefore, has no- 
thing to do in the business. If an account must be 
given of the contrivance which we observe; if it be 
demanded whence arose either the contrivance by 
which the young animal is produced, or the contri- 
vance manifested in the young animal itself, it is not 
from the reason of the parent that any such account 
can be drawn. He is the cause of his offspring in the 
same sense as that in which a gardener is the cause 
of the tulip which grows upon his parterre, and in no 
other. We admire the flower; we examine the plant; 
we perceive the conduciveness of many of its parts to 
their end and office; we observe a provision for its 
nourishment, growth, protection, and fecundity; but 
we never think of the gardener in all this. We attrib- 
ute nothing of this to his agency: yet it may still be 
true, that without the gardener we should not have 
NATURAL THEOLOGY. 
act upon the embryo seed, is by some means brought into con 
tact with the fluid covering the extremity of the pistil. This pis 
til stands in the middle of the stamens, and, being hollow, allows 
this fluid mixed with pollen to communicate with the germen or 
embryo at its base. The antherat are the extremities of the sta- 
mens, and contain the pollen. The stigmata are the extremities of 
the pistils.-See chap. xx.-Am. Ed. 80 
NATURAL THEOLOGY. 
had the tulip. Just so it is with the succession of 
animals even of the highest order. For the contri- 
vance discovered in the structure of the thing produ- 
ced, we want a contriver. The parent is not that 
contriver: his consciousness decides that question. 
He is in total ignorance why that which is produced 
took its present form rather than any other. It is for 
him only to be astonished by the effect. We can no 
more look, therefore, to the intelligence of the parent 
animal for what we are in search of (a cause of rela- 
tion, and of subserviency of parts to their use, w hich 
relation and subserviency we see in the procreated 
body), than we can refer the internal conformation ol 
an acorn to the intelligence of the oak from which it 
dropped, or the structure of the watch to the intelli- 
gence of the watch which produced it: there being no 
difference, as far as argument is concerned, between 
an intelligence which is not exerted, and an intelli- 
gence which does not exist.19 
is When we have in some measure comprehended the system 
of an animal body, how the different organs are related to each 
other, and how the whole exists through a mutual influence of its 
parts, the wonder is renewed how another creature should grow 
out of that, which, as far as we have seen, has no tendency to 
multiply itself. Authors who treat of reproduction, even to the 
very last, affirm, that with the germe of life in all organized struc- 
tures are conjoined the seeds of decay and of death: they tell us 
that the powers of life are finite, and that the time must come 
when they shall be expended. Now there are no seeds of decay ; 
and although, according to the law of animal existence, the indi- 
vidual perishes, it is incorrect to say that it is the result of the 
exhaustion of the powers of vitality, or the deterioration of the 
material which enters into its composition. We gain nothing by 
adapting the language of one science to explain another : it is of 
no advantage, in treating of life and death, to adopt a chymical 
nomenclature. The term of life in every creature, from the ele- 
phant to the ephemeral fly, has its limit; but it is wrong to say 
that it is by the defect of the material, or of the energy of life ; it 
is a better philosophy to admit that it is in accordance with the 
system which the Deity has ordained. 
Life, in the sense in which it is used here, is continued in the 
germe that rises from the parent; since out of the old body, that is 
described as a deteriorated and useless material, a new creation is 
produced, it suffices to show that there is no necessary decay from NATURAL THEOLOGY. 
81 
the material itself. A leaf or twig of an old tree will strike root 
into the ground, and vegetate and exhibit youthful vigour. So will 
the fresh-water polypus furnish a portion which, being cut off, 
will grow with a perfect resemblance to the original stock. In 
the reproduction of the higher and the more complex organized 
bodies there is much that is obscure ; but in the simpler, and, as 
it is termed, the lower examples (vegetables, zoophytes, and in- 
fusory animals), we have abundant proofs that the result doesnot 
proceed from the exhausted or deteriorated nature of the material. 
Among the infusoria, the animals called Monads, of which there 
is a great variety, exhibit very curious phenomena. They are of 
a globular form, and this globe is seen first to contract and then 
divide, each becoming a distinct animal And something like this 
may be done artificially by the division of the fresh-water polypus 
or hydra ; and what is deficient in the divided portion is supplied 
by a new growth, be it head or tail. The thing, however, is not 
so remarkable, if we consider that those lower animals have abun- 
dant resemblance to vegetables ; and that, in cutting off portions, 
the experimenter is cutting off buds. These buds or tubercles, if 
left to undergo their natural changes, acquire independent motion, 
produce tentacula, or feelers, to procure food, and, thus prepared 
to be independent, fall off from the parent stock. 
The microscope exhibits another instance in the Volvox. It is 
a transparent globule, within which smallerglobules may be seen; 
and, when matured, the parent bursts, discloses the offspring, and 
dies. 
In all these examples, we see that there is no reason to speak 
of exhausted or deteriorated matter, or debility in the powers of 
life. 
So in the higher and the more complex animals we find one set 
of organs decaying and another rising into existence. Contem- 
plating the one, we would say that the powers were decaying; 
contemplating the other, that they were fresh and vigorous. We 
must come to the conclusion, then, that the growth of parts, or 
the period of their development, the decay of the animal or of 
the parts of the animal, is by an ordinance which is very inaccu- 
rately expressed by the terms exhaustion of life or imperfection 
of the material. Imperfection, in truth, is a relative term, and 
means failure or insufficiency towards the accomplishment of cer- 
tain purposes. If the object in view were the duration of animal 
bodies for a great length of time, we might be justified in saying 
that the materials they are made of are imperfect; but this is 
clearly not the design with which they are formed. 82 
NATURAL THEOLOGY. 
CHAPTER V. 
APPLICATION OF THE ARGUMENT CONTINUED. 
Every observation which was made in our first 
chapter concerning the watch, may be repeated with 
strict {Jropriety concerning the eye; concerning ani- 
mals ; concerning plants ; concerning, indeed, all the 
organized parts of the works of nature. As, 
I. When we are inquiring simply after the existence 
of an intelligent Creator, imperfection, inaccuracy, 
liability to disorder, occasional irregularities, may 
subsist in a considerable degree, without inducing 
any doubt into the question : just as a watch may fre- 
quently go wrong, seldom perhaps exactly right, may 
be faulty in some parts, defective in some, without 
the smallest ground of suspicion from thence arising 
that it was not a watch, or not made for the purpose 
ascribed to it. When faults are pointed out, and 
when a question is started concerning the skill of 
the artist, or dexterity with which the work ;s exe- 
cuted, then, indeed, in order to defend these qualities 
from accusation, we must be able, either to expose 
some intractableness and imperfection in the materi- 
als, or point out some invincible difficulty in the exe- 
cution, into which imperfection and difficulty the 
matter of complaint may be resolved ; or, if we can- 
not do this, we must adduce such specimens of con- 
summate art and contrivance proceeding from the 
same hand as may convince the ihquirer of the ex- 
istence, in the case before him, of impediments like 
those which we have mentioned, although, what 
from the nature of the case is very likely to happen, 
they be unknown and unperceived by him. This we 
must do in order to vindicate the artist's skill, or, at 
least, the perfection of it; as we must also judge of 
his intention, and of the provisions employed in ful- 
filling that intention, not from an instance in which NATURAL THEOLOGY. 
83 
they fail, but from the great plurality of instances in 
which they succeed. But, after all, these are differ- 
ent questions from the question of the artist's exist- 
ence : or, which is the same, whether the thing be- 
fore us be a work of art or not; and the questions 
ought always to be kept separate in the mind. So 
likewise it is in the works of nature. Irregularities 
and imperfections are of little or no weight in the 
consideration, when that consideration relates simply 
to the existence of a Creator. When the argument 
respects his attributes, they are of weight; but are 
then to be taken in conjunction (the attention is not 
to rest upon them, but they are to be taken in con- 
junction) with the unexceptionable evidences which 
we possess of skill, power, and benevolence display- 
ed in other instances; which evidences may, in 
strength, number, and variety, be such, and may so 
overpower apparent blemishes, as to induce us, upon 
the most reasonable ground, to believe that these last 
ought to be referred to some cause, though we be ig- 
norant of it, other than defect of knowledge or of 
benevolence in the author. 
II. There may be also parts of plants and animals, 
as there were supposed to be of the watch, of which, 
in some instances the operation, in others the use, is 
unknown. These form different cases ; for the oper- 
ation may be unknown, yet the use be certain. 
Thus it is with the lungs of animals. It does not, I 
think, appear, that we are acquainted with the action 
of the air upon the blood, or in what manner that ac- 
tion is communicated by the lungs ; yet we find that 
a very short suspension of their office destroys the 
life of the animal.20 In this case, therefore, we may 
be said to know the use, nay, we experience the ne- 
20 Undoubtedly the exposure of the blood to the atmosphere, in 
the circulation through the lungs, and the throwing off of carbon, 
are essential to life. But the pain and alarm excited when there 
is danger of suffocation are not so much a direct consequence of 
the interruption of the function, as an instance of the manner in 
which the sensibility is bestowed to guard the important actions 
of life. 84 
cessity, of the organ, though we be ignorant of its 
operation. Nearly the same thing may be observed 
of what is called the lymphatic system. We suffer 
grievous inconveniences from its disorder, without 
being informed of the office which it sustains in the 
economy of our bodies. There may possibly also 
be some few examples of the second class, in which 
not only the operation is unknown, but in which ex- 
periments may seem to prove that the part is not ne- 
cessary, or may leave a doubt how far it is even 
useful to the plant or animal in which it is found. 
This is said to be the case with the spleen, which has 
been extracted from dogs without any sensibly inju- 
ry to their vital functions. Instances of the former 
kind, namely, in which we cannot explain the opera- 
tion, may be numerous; for they will be so in pro- 
portion to our ignorance. They will be more or 
fewer to different persons, and in different stages of 
science. Every improvement of knowledge dimin- 
ishes their number. There is hardly, perhaps, a year 
passes that does not, in the works of nature, bring 
some operation, or some mode of operation, to light, 
which was before undiscovered, probably unsuspect- 
ed. Instances of the second kind, namely, where 
the part appears to be totally useless, I believe to be 
extremely rare; compared with the number of those 
of which the use is evident, they are beneath any as- 
signable proportion, and, perhaps, have been never 
submitted to a trial and examination sufficiently ac- 
curate, long enough continued, or often enough re- 
peated. No accounts which I have seen are satisfac- 
tory. The mutilated animal may live and grow fat 
(as was the case of the dog deprived of its spleen), 
yet may be defective in some other of its functions, 
which, whether they can all, or in what degree of 
vigour and perfection, be performed, or how long 
preserved without the extirpated organ, does not 
seem to be ascertained by experiment. But to this 
case, even were it fully made out, may be applied the 
consideration which we suggested concerning the 
watch, viz., that these superfluous parts do not nega- 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
85 
tive the reasoning which we instituted concerning 
those parts which are useful, and of which we know 
the use ; the indication of contrivance, with respect 
to them, remains as it was before.21 
III. One atheistic way of replying to our observa- 
tions upon the works of nature, and to the proofs of 
a Deity which we think that we perceive in them, is 
to tell us that all which we see must necessarily 
have had some form, and that it might as well be its 
present form as any other. Let us now apply this 
answer to the eye, as we did before to the watch. 
Something or other must have occupied that place in 
the animal's head; must have filled up, we will say, 
that socket: we will say, also, that it must have been 
of that sort of substance which we call animal sub- 
stance, as flesh, bone, membrane, or cartilage, &c. 
But that it should have been an eye, knowing, as we 
do, what an eye comprehends; viz., that it should 
have consisted, first, of a series of transparent lenses 
(very different, by-the-by, even in their substance, 
from the opaque materials of which the rest of the 
body is, in general at least, composed, and with which 
the whole of its surface, this single portion of it ex- 
cepted, is covered): secondly, of a black cloth or 
canvass (the only membrane of the body which is 
2' In the higher animals there is a great complication of organs. 
Yet in the lower animals the functions of digestion, respiration, 
assimilation, secretion, and growth proceed by means of an ap- 
paratus comparatively simple. We must not be surprised, then, 
that certain parts may be removed from the higher animals with- 
out destroying life. But this does not imply that those parts are 
useless, since they are structures superadded for the finer adjust- 
ment of the different functions one to the other, belonging to a 
higher condition of the economy. 
With regard to parts which are thus called useless, we must 
remember that the varieties of created animals belong to one 
type. As we have just said, the essential functions are the same 
in all; and there is much of the structure common to all : when 
an animal of a particular class has its organization adjusted to a 
certain condition of existence, we may see the rudiments of parts 
which, not being in action, are imperfect, and we must look to the 
individuals 01 another species or variety to discover them in their 
full development. 
Vol. I.-H 86 
black22) spread out behind these lenses, so as to re- 
ceive the image formed by pencils of light transmit- 
ted through them, and placed at the precise geomet- 
rical distance at which, and at which alone, a distinct 
image could be formed, namely, at the concourse of 
the refracted rays: thirdly, of a large nerve commu- 
nicating between this membrane and the brain, with- 
out which the action of light upon the membrane, 
however modified by the organ, would be lost to the 
purposes of sensation; that this fortunate conforma- 
tion of parts should have been the lot, not of one in- 
dividual out of many thousand individuals, like the 
great prize in a lottery, or like some singularity in 
nature, but the happy chance of a whole species : nor 
of one species out of many thousand species with 
which we are acquainted, but of by far the greatest 
number of all that exist; and that under varieties not 
casual or capricious, but bearing marks of being suit- 
ed to their respective exigencies ; that all this should 
have taken place, merely because something must 
have occupied these points on every animal's fore- 
head ; or that all this should be thought to be ac- 
counted for by the short answer, " that whatever was 
there must have had some form or other," is too ab- 
surd to be made more so by any augmentation. We 
are not contented with this answer; we find no sat- 
isfaction in it by way of accounting for appearances 
of organization far short of those of the eye, such 
as we observe in fossil shells, petrified bones, or 
other substances which bear the vestiges of animal 
or vegetable recrements, but which, either in respect 
to utility or of the situation in which they are dis- 
covered, may seem accidental enough. It is no way 
of accounting even for these things to say, that the 
NATURAL THEOLOGY. 
22 This membrane is not black in all animals. In one that 
prowls by night, the eye, besides being large and having a very 
dilatable pupil, has a bright coating back of the retina which, like 
the silver on the back of a mirror, reflects the light, and thus 
gives a second or double impulse to the nerve. The membrane 
itself is transparent; but in man and other animals that move by 
day, and are liable to have too much light, this coating is black, 
and thus serves to absorb instead of reflecting.-Am. Ed. NATURAL THEOLOGY. 
87 
stone, for instance, which is shown to us (supposing 
the question to be concerning a petrification) must 
have contained some internal conformation or other. 
Nor does it mend the answer to add, with respect to 
the singularity of the conformation, that, after the 
event, it is no longer to be computed what the chan- 
ces were against it. This is always to be computed 
when the question is whether a useful or imitative 
conformation be the produce of chance or not: I de- 
sire no greater certainty in reasoning than that by 
which chance is excluded from the present disposi- 
tion of the natural world. Universal experience is 
against it. What does chance ever do for us 1 In 
the human body, for instance, chance, i. e., the oper- 
ation of causes without design, may produce a wen, 
a wart, a mole, a pimple, but never an eye. Among 
inanimate substances, a clod, a pebble, a liquid drop 
might be; but never was a watch, a telescope, an or- 
ganized body of any kind, answering a valuable pur- 
pose by a complicated mechanism, the effect of 
chance.23 In no assignable instance hath such a thing 
existed without intention somewhere. 
23 There is great inaccuracy, and, indeed, a very unphilosophical 
and superficial view of the subject in these observations upon 
" chance." Chance is merely an abridged form of expressing our 
ignorance of the cause or preceding event to which any given 
event may be traced ; and nothing can be more inaccurate, or, in- 
deed, more productive of serious errors in this very branch of sci- 
ence than to speak of chance as a substantive thing or power. 
To take the most obvious instance : we say, in common parlance, 
that the dice being shaken together, it is a matter of chance what 
faces they will turn up; but, if we could accurately observe their 
position in the box before the shaking, the direction of the force 
applied, its quantity, the number of turns of the box, and the 
curve in which the motion was made, the manner of stopping the 
motion, and the line in which the dice were thrown out, the faces 
turned up would be a matter of certain prediction, after a suffi- 
cient number of experiments had been made to correct the theory. 
It is only because we take no heed of all these things that we are 
ignorant what will be the event; and the darkness in which we 
are respecting the circumstances which regulate it, is called by 
the name of chance. Nor is it correct to say that this or any- 
thing else is done without design. All we can mean by the ex- 
pression is, that our design stops short at a certain point, and leaves 88 
NATURAL THEOLOGY. 
IV. There is another answer which has the same 
effect as the resolving of things into chance; which 
answer would persuade us to believe that the eye, 
the animal to which it belongs, every other animal, 
every plant, indeed every organized body which we 
see, are only so many out of the possible varieties 
and combinations of being which the lapse of infinite 
ages has brought into existence; that the present 
world is the relic of that variety; millions of other 
bodily forms and other species having perished, be- 
ing, by the defect of their constitution, incapable of 
preservation, or of continuance by generation. Now 
there is no foundation whatever for this conjecture 
in anything which we observe in the works of na- 
ture ; no such experiments are going on at present; 
no such energy operates as that which is here sup- 
posed, and which should be constantly pushing into 
existence new varieties of beings. Nor are there 
any appearances to support an opinion, that every 
possible combination of vegetable or animal struc- 
ture has formerly been tried. Multitudes of confor- 
mations, both of vegetables and animals, may be con- 
ceived capable of existence and succession, which 
yet do not exist. Perhaps almost as many forms of 
plants might have been found in the fields as figures 
the laws of nature to guide the rest of the operation. But such 
a position is manifestly quite inapplicable to the operations of na- 
ture. 
Equally inaccurate is it, if not more so, to speak of a wen or a 
pimple, <"tc., as the result of any cause in the least degree differ- 
ent from that which produced the eye. These are possibly al- 
ways, certainly sometimes, diseases; but they are the result of 
contrivance as clearly as the eye itself. The functions of the an- 
imal system, though acting in an unusual manner, yet acting ac- 
cording to rule, produce these phenomena. Indeed, one of them, 
a pimple, is, in part at least, the result of the provision made for 
restoring the interrupted continuity of the skin, by a slight sup- 
puration from which the granulation, or production of new animal 
fibre takes place. The like remark applies to the cases of a clod, 
pebble, or liquid drop, also put in this passage. We have already 
adverted to the first two in a former note; the formation of a 
drop is in truth one of the phenomena of gravitation, and a very 
remarkable one. NATURAL THEOLOGY. 
89 
of plants can be delineated upon paper. A count- 
less variety of animals might have existed which do 
not exist. Upon the supposition here stated, we 
should see unicorns and mermaids, sylphs and cen- 
taurs, the fancies of painters and the fables of poets, 
realized by examples. Or, if it be alleged that these 
may transgress the bounds of possible life and prop- 
agation, we might at least have nations of human be- 
ings without nails upon their fingers, with more or 
fewer fingers and toes than ten, some with one eye, 
others with one ear, with one nostril, or without the 
sense of smelling at all. All these, and a thousand 
other imaginable varieties, might live and propagate. 
We may modify any one species many different 
ways, all consistent with life, and with the actions 
necessary to preservation, although affording differ- 
ent degrees of convenience and enjoyment to the 
animal. And, if we carry these modifications through 
the different species which are known to subsist, 
their number would be incalculable. No reason can 
be given why, if these deperdits ever existed, they 
have now disappeared. Yet, if all possible exist- 
ences have been tried, they must have formed part 
of the catalogue.24 
24 No doubt men in different ages have asserted the possibility 
of all we see being made by chance; but we are not uncharitable 
when we say that no man ever believed it. It is easily shown, 
that, of all the varieties of fabulous animals which have been bred 
in the fertile imagination of the poet, not one could have lived. 
They want that relation and balance of the different organs, that 
provision running through the whole texture of the frame of the 
animal, which we see in the natural productions. The sphinx 
has wings, but no constitution of body to give these strength. 
The griffin, with its hooked bill, has no feathers to prin, and no 
substitute for teeth. The centaur has the body of the horse, but 
no mouth to gather appropriate food. 
We may conclude, then, that these products of the imagina- 
tion are altogether abortive, and only tend to prove how exact the 
relation must be of all the parts, and especially of the vital organs 
of an animal, in order that it may live. 
As to the second position, that the animals which exist are the 
happy results of chance when thousands have perished by imper- 
fection, the supposition is contradicted by the perfect and harmo- 90 
NATURAL THEOLOGY. 
But, moreover, the division of organized substances 
into animals and vegetables, and the distribution and 
sub-distribution of each into genera and species, which 
distribution is not an arbitrary act of the mind, but 
founded in the order which prevails in external na- 
ture, appear to me to contradict the supposition of 
the present world being the remains of an indefinite 
variety of existences; of a variety which rejects all 
plan. The hypothesis teaches that every possible 
variety of being hath, at one time or other, found its 
■way into existence (by what cause or in what man- 
ner is not said), and that those which were badly 
formed perished ; but how, or why those which sur- 
vived should be cast, as we see that plants and ani- 
mals are cast, into regular classes, the hypothesis 
does not explain; or, rather, the hypothesis is incon- 
sistent with this phenomenon. 
The hypothesis, indeed, is hardly deserving of the 
consideration which we have given to it. Whafshould 
we think of a man who, because we had never our- 
selves seen watches, telescopes, stocking-mills, steam- 
engines, &c., made, knew not how they were made, 
nor could prove by testimony when they were made, 
or by whom, would have us believe that these ma- 
chines, instead of deriving their curious structures 
from the thought and design of their inventors and 
contrivers, in truth derive them from no other origin 
than this, viz., that a mass of metals and other mate- 
rials having run, when melted, into all possible fig- 
ures, and combined themselves in all possible forms, 
and shapes, and proportions, these things which we 
see are what were left from the accident, as best 
worth preserving, and, as such, are become the re- 
maining stock of a magazine, which, at one time or 
other, has by this means contained every mecha- 
nism, useful and useless, convenient and inconve- 
nient, into which such like materials could be thrown ? 
I cannot distinguish the hypothesis, as applied to the 
nious chain of beings forming the animal kingdom, in which there 
is no link interrupted, no interval implying the loss of any spe- 
cies. NATURAL THEOLOGY. 
91 
works of nature, from this solution, which no one 
would accept as applied to a collection of machines. 
V. To the marks of contrivance discoverable in 
animal bodies, and to the argument deduced from 
them in proof of design and of a designing Creator, 
this turn is sometimes attempted to be given, namely, 
that the parts were not intended for the use, but that 
the use arose out of the parts. This distinction is in- 
telligible. A cabinet-maker rubs his mahogany with 
fishskin ; yet it would be too much to assert that the 
skin of the dogfish was made rough and granulated 
on purpose for the polishing of wood and the use of 
cabinet-makers. Therefore the distinction is intelli- 
gible. But I think that there is very little place for 
it in the works of nature. When roundly and gener- 
ally affirmed of them, as it hath sometimes been, it 
amounts to such another stretch of assertion as it 
would be to say that all the implements of the cabi- 
net-maker's workshop, as well as his fishskin, were 
substances accidentally configurated, which he had 
picked up and converted to his use; that his adzes, 
saws, planes, and gimlets were not made, as we sup- 
pose, to hew, cut, smooth, shape out, or bore wood 
with; but that, these things being made, no matter 
with what design, or whether with any, the cabinet- 
maker perceived that they were applicable to his pur- 
pose, and turned them to account. 
But, again. So far as this solution is attempted to 
be applied to those parts of animals the action of which 
does not depend upon the will of the animal, it is 
fraught with still more evident absurdity. Is it pos- 
sible to believe that the eye was formed without any 
regard to vision ; that it was the animal itself which 
found out that, though formed with no such intention, 
it would serve to see with; and that the use of the 
eye as an organ of sight resulted from this discovery, 
and the animal's application of it 1 The same ques- 
tion may be asked of the ear; the same of all the 
senses. None of the senses fundamentally depend 
upon the election of the animal; consequently, nei- 
ther upon his sagacity nor his experience. It is the 92 
impression which objects make upon them that con- 
stitutes their use. Under that impression he is pass- 
ive. He may bring objects to the sense or within 
its reach; he may select these objects; but over the 
impression itself he has no power, or very little ; and 
that properly is the sense. 
Secondly; there are many parts of animal bodies 
which seem to depend upon the will of the animal in 
a greater degree than the senses do, and yet with re- 
spect to which this solution is equally unsatisfactory. 
If we apply the solution to the human body, for in- 
stance, it forms itself into questions upon which no 
reasonable mind can doubt; such as, whether the 
teeth were made expressly for the mastication of 
food, the feet for walking, the hands for holding 1 or 
whether, these things being as they are, being, in fact, 
in the animal's possession, his own ingenuity taught 
him that they were convertible to these purposes, 
though no such purposes were contemplated in their 
formation 1 
All that there is of the appearance of reason in this 
way of considering the subject, is, that in some cases 
the organization seems to determine the habits of the 
animal and its choice to a particular mode of life, 
which, in a certain sense, may be called " the use 
arising out of the part."25 Now, to all the instances 
NATURAL THEOLOGY. 
25 We deceive ourselves in this matter: the dexterity which 
use gives makes us apt to believe that the faculty is gained through 
the accidental possession of the instrument. But the difficulty is 
removed if we make due comparison between man and other ani- 
mals. In the former it is intended that the faculty should be 
gradually developed ; and the slowness with which perfection is 
attained leaves us in some doubt of the relation between the ef- 
fort and the instrument used. But in the latter all obscurity is 
removed : their propensities and instincts, and the use of their in- 
struments, are so perfect from the beginning as to admit of no 
improvement. The fly-catcher requires no experience to adjust 
his eyes, no second effort of his bill to correct the first. Whether 
it be the horn, or the tooth, or the sting, the disposition is given 
with it, and the mode of its action is prescribed. The spider 
weaves his web without improvement or room for improvement. 
This subject is treated at some length in the " Bridgewater Trea- 
tise on the Hand," where the question is discussed, whether or 
not the possession of the hand is the source of man's superiority. NATURAL THEOLOGY. 
93 
in which there is any place for this suggestion, it may 
be replied, that the organization determines the ani- 
mal to habits beneficial and salutary to itself; and 
that this effect would not be seen so regularly to fol- 
low if the several organizations did not bear a con- 
certed and contrived relation to the substances by 
which the animal was surrounded. They would 
otherwise be capacities without objects, powers 
without employment. The web-foot determines, you 
say, the duck to swim; but what would that avail if 
there were no water to swim in 1 The strong hook- 
ed bill and sharp talons of one species of bird deter- 
mine it to prey upon animals; the soft straight bill 
and weak claws of another species determine it to 
pick up seed; but neither determination could take 
effect in providing for the sustenance of the birds, if 
animal bodies and vegetable seeds did not lie within 
their reach. The peculiar conformation of the bill, 
and tongue, and claws of the woodpecker, determines 
that bird to seek for his food among the insects 
lodged behind the bark or in the wood of decayed 
trees; but what would this profit him if there were 
no trees, no decayed trees, no insects lodged under 
their bark or in their trunk 1 The proboscis with 
which the bee is furnished determines him to seek 
for honey; but what would that signify if flowers 
supplied none 1 Faculties thrown down upon animals 
at random, and without reference to the objects 
amid which they are placed, would not produce to 
them the services and benefits which we see; and if 
there be that reference, then there is intention. 
Lastly; the solution fails entirely when applied to 
plants. The parts of plants answer their uses with- 
out any concurrence from the will or choice of the 
plant. 
VI. Others have chosen to refer everything to a 
principle of order in nature. A principle of order is the 
word; but what is meant by a principle of order, as 
different from an intelligent Creator, has not been ex- 
plained either by definition or example, and without 
such explanation it should seem to be a mere sub- 94 
NATURAL THEOLOGY. 
stitution of words for reasons, names for causes. 
Order itself is only the adaptation of means to an 
end : a principle of order, therefore, can only signify 
the mind and intention which so adapts them. Or, 
were it capable of being explained in any other sense, 
is there any experience, any analogy, to sustain it ? 
Was a watch ever produced by a principle of order? 
And why might not a watch be so produced as well 
as an eye ? 
Furthermore, a principle of order, acting blindly 
and without choice, is negatived by the observation 
that order is not universal, which it would be if it is- 
sued from a constant and necessary principle; nor in- 
discriminate, which it would be if it issued from an 
unintelligent principle. Where order is wanted, there 
we find it; where order is not wanted, i. e., where, if 
it prevailed, it would be useles, there do we not find 
it. In the structure of the eye (for we adhere to our 
example), in the figure and position of its several 
parts, the most exact order is maintained. In the 
forms of rocks and mountains, in the lines which 
bound the coasts of continents and islands, in the 
shape of bays and promontories, no order whatever 
is perceived, because it would have been superflu- 
ous. No useful purpose would have arisen from 
moulding rocks and mountains into regular solids, 
bounding the channel of the ocean by geometrical 
curves, or from the map of the world resembling a 
table of diagrams in Euclid's Elements or Simpson's 
Conic Sections. 
VII. Lastly, the confidence which we place in our 
observations upon the works of nature, in the marks 
which we discover of contrivance, choice, and de- 
sign, and in our reasoning upon the proofs afforded 
us, ought not to be shaken, as it is sometimes at- 
tempted to be done, by bringing forward to our view 
our own ignorance, or, rather, the general imperfec- 
tion of our knowledge of nature. Nor, in many ca- 
ses, ought this consideration to affect us, even when 
it respects some parts of the subject immediately 
under our notice. True fortitude of understanding NATURAL THEOLOGY. 
95 
consists in not suffering what we know to be disturb- 
ed by what we do not know. If we perceive a use- 
ful end and means adapted to that end, we perceive 
enough for our conclusion. If these things be clear, 
no matter what is obscure. The argument is finished. 
For instance, if the utility of vision to the animal 
which enjoys it, and the adaptation of the eye to this 
office, be evident and certain (and I can mention 
nothing which is more so), ought it to prejudice the 
inference which we draw from these premises, that 
we cannot explain the use of the spleen 1 Nay, more: 
if there be parts of the eye, viz., the cornea, the crys- 
talline, the retina, in their substance, figure, and po- 
sition, manifestly suited to the formation of an im- 
age by the refraction of rays of light, at least as man- 
ifestly as the glasses and tubes of a dioptric telescope 
are suited to that purpose, it concerns not the proof 
which these afford of design and of a designer, that 
there may, perhaps, be other parts, certain muscles, for 
instance, or nerves in the same eye, of the agency or 
effect of which we can give no account, any more than 
we should be inclined to doubt, or ought to doubt, 
about the construction of a telescope, viz., for what 
purpose it was constructed, or whether it were con- 
structed at all, because there belonged to it certain 
screws and pins, the use or action of which we did 
not comprehend. I take it to be a general way of 
infusing doubts and scruples into the mind, to recur 
to its own ignorance, its own imbecility; to tell us 
that upon these subjects we know little, that little 
imperfectly, or, rather, that we know nothing prop- 
erly about the matter. These suggestions so fall in 
with our consciousness as sometimes to produce a 
general distrust of our faculties and our conclusions. 
But this is an unfounded jealousy. The uncertainty 
of one thing does not necessarily affect the certainty 
of another thing. Our ignorance of many points 
need not suspend our assurance of a few. Before 
we yield, in any particular instance, to the skepticism 
which this sort of insinuation would induce, we 
ought accurately to ascertain whether our ignorance 96 
NATURAL THEOLOGY. 
or doubt concern those precise points upon which 
our conclusion rests. Other points are nothing. 
Our ignorance of other points may be of no conse- 
quence to these, though they be points, in various 
respects, of great importance. A just reasoner re- 
moves from his consideration not only what he 
knows, but what he does not know, touching mat- 
ters not strictly connected with his argument, i. e., 
not forming the very steps of his deduction ; beyond 
these, his knowledge and his ignorance are alike rel- 
ative.26 
CHAPTER VI. 
THE ARGUMENT CUMULATIVE. 
Were there no example in the world of contriv- 
ance except that of the eye, it would be alone suffi- 
cient to support the conclusion which we draw from 
it, as to the necessity of an intelligent Creator. It 
could never be got rid of; because it could not be 
26 This view is enforced by Boyle in an Essay on Final Causes. 
Among other remarks is the following: "Suppose that a coun- 
tryman, being, in a clear day, brought into the garden of some 
famous mathematician, should see there one of those curious 
gnomonic instruments that show at once the place of the sun in 
the zodiac, his declination from the equator, the day of the month, 
the length of the day,&c., &c. It would indeed be presumption 
in him, being unacquainted both with the mathematical disciplines 
and the several intentions of the artist, to pretend or think him- 
self able to discover all the ends for which so curious and elab- 
orate a piece was framed : but when he sees it furnished with a 
style, with horary lines and numbers, and manifestly perceives 
the shadow to mark, from time to time, the hour of the day, it 
would be no more a presumption than an error in him to conclude 
that (whatever other uses the instrument was fit or designed 
for) it is a sundial that was meant to show the hour of the day." 
See on this subject Stewart's Active and Moral Powers, sec. iv. 
-Am. Ed. NATURAL THEOLOGY. 
97 
accounted for by any other supposition, which did not 
contradict all the principles we possess of knowl- 
edge ; the principles according to which things do, as 
often as they can be brought to the test of experi- 
ence, turn out to be true or false. Its coats and hu- 
mours, constructed, as the lenses of a telescope are 
[The figure is introduced to remind the reader of the fine ad 
justment of the eye; a subject explained in the appendix: A B is 
the object, and the lines represent the light reflected from it into 
the eye. On the surface of the cornea, which is the transparent 
part of the eye, the rays are in a certain degree refracted. Pass 
ing through the coat called cornea, they enter the aqueous hu 
mour. In their transmission through it, they pass into the pupil. 
They enter the lens or crystalline humour, and by the greatei 
power of refraction in this humour, the rays are drawn to a point 
and impinge on the bottom of the eye at A B. It will be farther 
seen that the rays coining from B are refracted to a, those from 
A to b, and that the image is therefore represented inverted.] 
constructed, for the refraction of rays of light to a 
point, which forms the proper action of the organ; 
the provision in its muscular tendons for turning its 
pupil to the object, similar to that which is given to 
the telescope by screws, and upon which power of 
direction in the eye the exercise of its office as an 
optical instrument depends ; the farther provision for 
its defence, for its constant lubricity and moisture, 
which we see in its socket and its lids, in its glands 
for the secretion of the matter of tears, its outlet or 
communication with the nose for carrying off the 
liquid after the eye is washed with it; these provis- 
ions compose altogether an apparatus, a system of 
parts, a preparation of means, so manifest in their 
design, so exquisite in their contrivance, so success- 
ful in their issue, so precious, and so infinitely bene- 
Vol. I.-I 98 
NATURAL THEOLOGY. 
ficial in their use, as, in my opinion, to bear down all 
doubt that can be raised upon the subject. And what 
I wish, under the title of the present chapter, to ob- 
serve, is, that if other parts of nature were inacces- 
sible to our inquiries, or even if other parts of nature 
presented nothing to our examination but disorder 
and confusion, the validity of this example would re- 
main the same. If there were but one watch in the 
world, it would not be less certain that it had a ma- 
ker. If we had never in our lives seen any but one 
single kind of hydraulic machine, yet, if of that one 
kind we understood lhe mechanism and use, we 
should be as perfectly assured that it proceeded from 
the hand, and thought, and skill of a workman, as if 
we visited a museum of the arts, and saw collected 
there twenty different kinds of machines for drawing 
water, or a thousand different kinds of machines for 
other purposes. Of this point each machine is a 
proof independently of all the rest. So it is with the 
evidences of a Divine agency. The proof is not a 
conclusion which lies at the end of a chain of reason- 
ing, of which chain each instance of contrivance is 
only a link, and of which, if one link fail, the whole 
falls; but it is an argument separately supplied by 
every separate example. An error in stating an ex- 
ample affects only that example. The argument is 
cumulative, in the fullest sense of that term. The 
eye proves it without the ear; the ear without the 
eye. The proof in each example is complete ; for 
when the design of the part, and the conduciveness 
of its structure to that design is shown, the mind may 
set itself at rest; no future consideration can detract 
anything from the force of the example. NATURAL THEOLOGY. 
99 
CHAPTER VII. 
OS' THE MECHANICAL AND IMMECHANICAL PARTS AND FUNC- 
TIONS OF ANIMALS AND VEGETABLES. 
It is not that every part of an animal or vegetable 
has not proceeded from a contriving mind; or that 
every part is not constructed with a view to its proper 
end and purpose, according to the laws belonging to, 
and governing the substance or the action made use 
of in that part; or that each part is not so construct- 
ed as to effectuate its purpose while it operates ac- 
cording to these laws; but it is because these laws 
themselves are not in all cases equally understood; 
or, what amounts to nearly the same thing, are not 
equally exemplified in more simple processes and 
more simple machines, that we lay down the distinc- 
tion here proposed between the mechanical parts of 
animals and vegetables.27 
For instance: the principle of muscular motion, 
27 The observation here is most sensible. When we speak of 
an organ as peculiarly suited to exhibit design, we mean merely 
that we comprehend something of the object of the particular 
structure. But there is no part of an animal, if we fully compre- 
hended what was necessary to the performance of its functions, 
that would not raise our admiration. Were we to take a portion 
of the skin, and contemplate its exquisite sensibility, so finely ap- 
pnpriated; could we penetrate, as it were, into the pores, and 
duly estimate the power which regulates the secretions and ab- 
sorption ; could we fully understand the relations of this organ, 
either with the economy of the body within, or the constitution of 
the atmosphere without, we should have no occasion to draw 
our argument, for the twentieth time, from the structure of the 
eye or the ear. Were we to take one cell of the millions of that 
substance which, intervening between the more solid textures of 
the frame, gives elasticity to the whole, and permits circulation 
and muscular action, and all the various movements of the body, 
we should have in that one cell as much reason for wonder at the 
perfection of the contrivance as in any joint of the limb. 100 
NATURAL THEOLOGY. 
[The reader will not be easily convinced that the mass of flesh, 
with which he is familiar, is easily and almost spontaneously di- 
vided into distinct muscles. This figure represents a muscle. C 
is the belly of the muscle; A and B the tendons : A being the ten- 
dinous origin, as it is termed, attached to a fixed point of bone; 
B the tendinous insertion, being attached to a part moveable by 
the contraction of the muscle. The belly, C, consists of fibres, 
which are possessed of the power of contraction or irritability, and 
through the operation of which the various motions of the body 
are performed. We shall presently have to remark on the direc- 
tion of these fibres.] 
viz., upon what cause the swelling of the belly of the 
muscle, and consequent contraction of its tendons, 
either by an act of the will or by involuntary irrita- 
tion, depends, is wholly unknown to us. The sub- 
stance employed, whether it be fluid, gaseous, elec- 
trical, or none of these, or nothing resembling these, 
is also unknown to us: of course, the laws belong- 
ing to that substance, and which regulate its action, 
are unknown to us. We see nothing similar to this 
contraction in any machine which we can make, or 
any process which we can execute. So far (it is con- 
fessed) we are in ignorance, but no farther. This 
power and principle, from whatever cause it proceeds, 
being assumed, the collocation of the fibres to re- 
ceive the principle, the disposition of the muscles for 
the use and application of the power, is mechanical, 
and is as intelligible as the adjustment of the wires 
and strings by which a puppet is moved. We see, 
therefore, as far as respects the subject before us, 
what is not mechanical in the animal frame, and 
what is. The nervous influence (for we are often 
obliged to give names to things which we know little 
about), I say the nervous influence, by which the 
belly or middle of the muscle is swelled, is mechani- 
cal. The utility of the effect we perceive; the means, or the preparation of means, by which it is produced, 
we do not. But obscurity as to the origin of muscu- 
lar motion brings no doubtfulness into our observa- 
tions upon the sequel of the process: which obser- 
vations relate, 1st, to the constitution of the muscle, 
in consequence of which constitution the swelling of 
the belly or middle part is necessarily or mechanical- 
ly followed by a contraction of the tendons; 2dly, to 
the number and variety of the muscles, and the cor- 
responding number and variety of useful powers which 
they supply to the animal, which is astonishingly 
great; 3dly, to the judicious (if we maybe permitted 
to use that term in speaking of the Author or of the 
works of Nature), to the wise and well-contrived dis- 
position of each muscle for its specific purpose ; for 
moving the joint this way, and that way, and the 
other way; for pulling and drawing the part to which 
it is attached in a determinate and particular direc- 
tion : which is a mechanical operation exemplified in 
a multitude of instances. To mention only one : the 
tendon of the trochlear muscle of the eye, to the end 
that it may draw in the line required, is passed through 
a cartilaginous ring, at which it is reverted, exactly in 
the same manner as a rope in a ship is carried over 
a block, or round a stay, in order to make it pull in 
the direction which is wanted. All this, as we have 
said, is mechanical, and is as accessible to inspection, 
as capable of being ascertained, as the mechanism of 
the automaton in the Strand. Supposing the automa- 
ton to be put in motion by a magnet (which is prob- 
able), it will supply us with a comparison very apt 
for our present purpose. Of the magnetic effluvium 
we know, perhaps, as little as we do of the nervous 
fluid. But, magnetic attraction being assumed (it sig- 
nifies nothing from what cause it proceeds), we can 
trace, or there can be pointed out to us, with perfect 
clearness and certainty, the mechanism, viz., the steel 
bars, the wheels, the joints, the wires, by which the 
motion so much admired is communicated to the 
fingers of the image; and to make any obscurity, or 
difficulty, or controversy in the doctrine of magnet- 
NATURAL THEOLOGY. 
101 102 
NATURAL THEOLOGY. 
ism an objection to our knowledge or our certainty 
concerning the contrivance or the marks of contrivance 
displayed in the automaton, would be exactly the same 
thing as it is to make our ignorance (which we ac- 
knowledge) of the cause of nervous agency, or even of 
the substance and structure of the nerves themselves, 
a ground of question or suspicion as to the reasoning 
which we institute concerning the mechanical part of 
our frame. That an animal is a machine is a propo- 
sition neither correctly true nor wholly false. The dis- 
tinction which we have been discussing will serve to 
show how far the comparison, which this expression 
implies, holds; and wherein it fails. And whether 
the distinction be thought of importance or not, it is 
certainly of importance to remember that there is 
neither truth nor justice in endeavouring to bring a 
cloud over our understandings, or a distrust into our 
reasonings upon this subject, by suggesting that we 
know nothing of voluntary motion, of irritability, of 
the principle of life, of sensation, of animal heat, upon 
all which the animal functions depend; for our igno- 
rance of these parts of the animal frame concerns 
not at all our knowlege of the mechanical parts 
of the same frame. I contend, therefore, that there 
is mechanism in animals; that this mechanism is as 
properly such as it is in machines made by art: that 
this mechanism is intelligible and certain; that it is 
not the less so because it often begins or terminates 
with something which is not mechanical; that, when- 
ever it is intelligible and certain, it demonstrates in- 
tention and contrivance, as well in the works of na- 
ture as in those of art; and that it is the best demon- 
stration which either can afford. 
But, while I contend for these propositions, I do not 
exclude myself from asserting that there may be, and 
that there are, other cases in which, although we can- 
not exhibit mechanism, or prove, indeed, that mecha- 
nism is employed, we want not sufficient evidence to 
conduct us to the same conclusion. 
There is what may be called the chymical part of 
our frame; of which, by reason of the imperfection NATURAL THEOLOGY. 
103 
of our chymistry, we can attain to no distinct knowl- 
edge ; I mean not to a knowledge, either in degree 
or kind, similar to that which we possess of the me- 
chanical part of our frame. It does not, therefore, 
afford the same species of argument as that which 
mechanism affords; and yet it may afford an argu- 
ment in a high degree satisfactory. The gastric juice, 
or the liquor which digests the food in the stom- 
achs of animals, is of this class. Of all the menstrua* 
it is the most active, the most universal. In the hu- 
man stomach, for instance, consider what a variety 
of strange substances, and how widely different from 
one another, it in a few hours reduces to a uniform 
pulp, milk, or mucilage. It seizes upon everything; 
it dissolves the texture of almost everything that 
comes in its way. The flesh of, perhaps, all animals ; 
the seeds and fruits of the greatest number of plants; 
the roots, and stalks, and leaves of many, hard and 
tough as they are, yield to its powerful pervasion. 
The change wrought by it is different from any chym- 
ical solution which we can produce or with which 
we are acquainted, in this respect as well as in many 
others, that, in our chymistry, particular menstrua 
act only on particular substances. Consider, more- 
over, that this fluid, stronger in its influence than a 
caustic alkali, or mineral acid, than red precipitate or 
aquafortis itself, is nevertheless as mild, and bland, 
and inoffensive to the touch or taste as saliva or gum- 
water, which it much resembles. Consider, I say, 
these several properties of the digestive organ, and 
of the juice with which it is supplied, or, rather, with 
which it is made to supply itself, and you will con- 
fess it to be entitled to a name which it has some- 
times received, that of " the chymical wonder of ani- 
mal nature." 
Still we are ignorant of the composition of this fluid 
and of the mode of its action ; by which is meant that 
we are not capable, as we are in the mechanical part 
of our frame, of collating it with the operations of 
* i. e., fluids by which bodies are dissolved.-Am. Ed. art. And this I call the imperfection of our chym- 
istry; for, should the time ever arrive, which is not, 
perhaps, to be despaired of, when we can compound 
ingredients so as to form a solvent which will act in 
the manner in which the gastric juice acts, we may 
be able to ascertain the chymical principles upon 
which its efficacy depends, as well as from what part, 
and by what concoction in the human body, these 
principles are generated and derived. 
In the mean time, ought that, which is in truth the 
defect of our chymistry, to hinder us from acquiescing 
in the inference which a production of nature, by its 
place, its properties, its action, its surprising efficacy, 
its invaluable use, authorizes us to draw in respect of 
a creative design I28 
Another most subtle and curious function of animal 
bodies is secretion* This function is semi-chymical 
and semi-mechanical; and very important and diver- 
sified in its effects, but obscure in its process and in 
its apparatus. The importance of the secretory or- 
gans is but too well attested by the diseases which 
an excessive, a deficient, or a vitiated secretion is 
almost sure of producing. A single secretion being 
wrong is enough to make life miserable, or sometimes 
to destroy it. Nor is the variety less than the impor- 
tance. From one and the same blood (I speak of the 
104 
NATURAL THEOLOGY. 
28 After this enumeration of the things dissolved by the gastric 
juice, the most extraordinary fact remains to be stated, that the 
delicate surface of the stomach itself, softer and finer than the 
surface of the eye, remains untouched by this humour, which our 
author somewhat quaintly describes as more powerful to dissolve 
than aquafortis John Hunter showed us that it was the property 
of life that protected the coats of the stomach. This fact is a most 
singular proof of the power bestowed through life on the mem- 
branes and vessels ; and it is as important as it is curious: for as 
the stomach in the dead body no longer resists this menstruum, it 
may become dissolved, if the person has died with the fluid 
already secreted into the stomach. And so it has happened that 
persons have been supposed to be poisoned, and relations have 
been falsely accused, from the stomach being found eroded as if 
some acrid poison had been taken before death. 
* That function by which, from the blood, substances different 
from itself are produced.-Am. Ed. NATURAL THEOLOGY. 
105 
human body), about twenty different fluids are sep- 
arated ; in their sensible properties, in taste, smell, 
colour, and consistency, the most unlike one another 
that is possible; thick, thin, salt, bitter, sweet: and 
if from our own we pass to other species of animals, 
we find among their secretions not only the most 
various, but the most opposite properties; the most 
nutritious aliment, thedeadliest poison ; the sweetest 
perfumes, the most fetid odours. Of these the greater 
part, as the gastric juice, the saliva, the bile, the slip- 
pery mucilage which lubricates the joints, the tears 
which moisten the eye, the wax which defends the 
ear, are, after they are secreted, made use of in the 
animal economy, are evidently subservient, and are 
actually contributing to the utilities of the animal it- 
self. Other fluids seem to be separated only to be 
rejected. That this also is necessary (though why it 
was originally necessary we cannot tell), is shown by 
the consequence of the separation being long sus- 
pended, which consequence is disease and death. 
Akin to secretion, if not the same thing, is assimila- 
tion, by which one and the same blood is converted 
into bone, muscular flesh, nerves, membranes, ten- 
dons ; things as different as the wood and iron, can- 
vass and cordage, of which a ship with its furniture 
is composed. We have no operation of art where- 
with exactly to compare all this, for no other reason, 
perhaps, than that all operations of art are exceeded 
by it. No chymical election, no chymical analysis or 
resolution of a substance into its constituent parts, 
no mechanical sifting or division that we are acquaint- 
ed with, in perfection or variety come up to animal 
secretion. Nevertheless, the apparatus and process 
are obscure, not to say absolutely concealed from our 
inquiries. In a few, and only a few, instances, we 
can discern a little of the constitution of a gland. In 
the kidneys of large animals we can trace the emul- 
gent artery* dividing itself into an infinite number of 
branches; their extremities everywhere communica- 
* By which blood is earned to the kidneys.-Am. Ed. 106 
NATURAL THEOLOGY. 
ting with little round bodies, in the substance of which 
bodies the secret of the machinery seems to reside, 
for there the change is made. We can discern pipes 
laid from these round bodies to the pelvis, which is 
a basin within the solid of the kidney. We can dis- 
cern these pipes joining and collecting together into 
larger pipes; and, when so collected, ending in innu- 
merable papillae, through which the secreted fluid is 
continually oozing into its receptacle. This is all we 
know of the mechanism of a gland, even in the case in 
which it seems most capable of being investigated. 
Yet to pronounce that we know nothing of animal se- 
cretion, or nothing satisfactorily, and with that con- 
cise remark to dismiss the article from our argu- 
ment, would be to dispose of the subject very hast- 
ily and very irrationally. For the purpose which we 
want, that of evincing attention, we know a great 
deal. And what we know is this. We see the blood 
carried by a pipe, conduit, or duct, to the gland. We 
see an organized apparatus, be its construction what 
it will, which we call that gland. We see the blood, 
or part of the blood, after it has passed through and 
undergone the action of the gland, coming/ro/n it by 
an emulgent vein or artery, i. e., by another pipe or 
conduit. And we see also, at the same time, a new 
and specific fluid issuing from the same gland by its 
excretory duct, i. e., by a third pipe or conduit; which 
new fluid is in some cases discharged out of the body, 
in more cases retained within it, and there executing 
some important and intelligent office. Now suppo- 
sing, or admitting, that we know nothing of the proper 
internal constitution of a gland, or of the mode of its 
acting upon the blood, then our situation is precisely 
like that of an unmechanical looker on, who stands 
by a stocking-loom, a cornrinill, a carding-machine, 
or a thrashing-machine at work, the fabric and mech- 
anism of which, as well as all that passes within, is 
hidden from his sight by the outside case; or, if seen, 
would be too complicated for his uninformed, unin- 
structed understanding to comprehend. And what is 
that situation] This spectator, ignorant as he is, NATURAL THEOLOGY. 
107 
sees at one end a material enter the machine, as un- 
ground grain the mill, raw cotton the carding-ma- 
chine, sheaves of unthrashed corn the thrashing-ma- 
chine ; and when he casts his eye to the other end of 
the apparatus, he sees the material issuing from it in 
a new state; and, what is more, in a state manifestly 
adapted to future uses; the grain in meal fit for the 
making of bread, the wool in rovings ready for spin- 
ning into threads, the sheaf in corn dressed for the 
mill. Is it necessary that this man, in order to be 
convinced that design, that intention, that contrivance 
has been employed about the machine, should be 
allowed to pull it to pieces; should be enabled to ex- 
amine the parts separately; explore their action upon 
one another, or their operation, whether simultaneous 
or successive, upon the material which is presented 
to them 1 He may long to do this to gratify his cu- 
riosity; he may desire to do it to improve his theo- 
retic knowledge; or he may have a more substantial 
reason for requesting it if he happen, instead of a 
common visiter, to be a millwright by profession, or 
a person sometimes called in to repair such like ma- 
chines when out of order; but, for the purpose of as- 
certaining the existence of counsel and design in the 
formation of the machine, he wants no such intro- 
mission or privity. What he sees is sufficient. The 
effect upon the material, the change produced in it, 
the utility of that change for future applications, abun- 
dantly testify, be the concealed part of the machine or 
of its construction what it will, the hand and agency 
'of a contriver. 
If any confirmation were wanting to the evidence 
which the animal secretions afford of design, it may 
be derived, as has been already hinted, from their va- 
riety, and from their appropriation to their place and 
use. They all come from the same blood; they are 
all drawn off by glands; yet the produce is very dif- 
ferent, and the difference exactly adapted to the work 
which is to be done, or the end to be answered. No 
account can be given of this, without resorting to ap- 
pointment. Why, for instance, is the saliva, which 108 
NATURAL THEOLOGY. 
is diffused over the seat of taste, insipid, while so 
many others of the secretions, the urine, the tears, 
and the sweat, are salt! Why does the gland within 
the ear separate a viscid substance, which defends 
that passage 1 the gland in the upper angle of the 
eye a thin brine, which washes the ball ? Why is 
the synovia* of the joints mucilaginous; the bile bit- 
ter, stimulating, and soapy 1 Why does the juice 
which flows into the stomach contain powers which 
make that bowel the great laboratory, as it is by its 
situation the recipient, of the materials of future nu- 
trition 1 These are all fair questions; and no answer 
can be given to them but what calls in intelligence 
and intention. 
My object in the present chapter has been to teach 
three things: first, that it is a mistake to suppose 
that, in reasoning from the appearances of nature, 
the imperfection of our knowledge proportionably af- 
fects the certainty of our conclusion; for in many 
cases it does not affect it at all; secondly, that the 
different parts of the animal frame may be classed 
and distributed according to the degree of exactness 
with which we compare them with works of art; 
thirdly, that the mechanical parts of our frame, or 
those in which this comparison is most complete, al- 
though constituting, probably, the coarsest portions 
of nature's workmanship, are the most proper to be 
alleged as proofs and specimens of design. 
* i. e., a fluid between the joints.-Am. Ed. NATURAL THEOLOGY 
109 
CHAPTER VIII. 
OF MECHANICAL ARRANGEMENT IN THE HUMAN FRAME. 
[This figure represents the lower surface or base of the scull. 
The hole is the foramen magnum, through which the spinal mar- 
row descends into the spine; and on each side of the hole are 
the articulating processes, called the condyles.'] 
We proceed, therefore, to propose certain exam- 
ples taken out of this class, making choice of such 
as, among those which have come to our knowledge, 
appear to be the most striking and the best under- 
stood, but obliged, perhaps, to postpone both these 
recommendations to a third : that of the example be- 
ing capable of explanation without plates, or figures, 
or technical language. 
Vol. I.-K 110 
NATURAL THEOLOGY. 
Of the Bones. 
I. I challenge any man to produce in the joints and 
pivots of the most complicated or the most flexible 
machine that was ever contrived, a construction more 
artificial, or more evidently artificial, than that which 
is seen in the vertebrae of the human neck. Two 
things were to be done: the head was to have the 
power of bending forward and backward, as in the 
act of nodding, stooping, looking upward or down- 
ward, and, at the same time, of turning itself round 
upon the body to a certain extent; the quadrant, we 
will say, or rather, perhaps, a hundred and twenty 
degrees of a circle. For these two purposes, two 
distinct contrivances are employed: first, the head 
rests immediately upon the uppermost part of the 
vertebrae, and is united to it by a hinge-yomt, upon 
which joint the head plays freely forward and back- 
ward, as far either way as is necessary, or as the 
ligaments allow; which was the first thing required. 
But then the rotatory motion is unprovided for: 
therefore, secondly, to make the head capable of 
this, a farther mechanism is introduced; not between 
[This figure represents the uppermost vertebra, or atlas ; and 
the condyles, mentioned in the former figure, sink into the articu- 
lating surfaces of this vertebra, permitting the nodding motions. 
a and 6 are the articulating surfaces; c is a surface which re- 
ceives the tooth of the vertebra below ; d, the circle through which 
the spinal marrow passes.] 
the head and the uppermost bone of the neck, where 
the hinge is, but between that bone and the bone next 
underneath it. It is a mechanism resembling a tenon 
and mortise. This second, or uppermost bone but NATURAL THEOLOGY. 
111 
one, has what anatomists call a process, viz., a pro- 
jection somewhat similar in size and shape to a 
tooth ; which tooth, entering a corresponding hole or 
socket in the bone above it, forms a pivot or axle, 
upon which that upper bone, together with the head 
which it supports, turns freely in a circle, and as far 
in the circle as the attached muscles permit the head 
to turn. Thus are both motions perfect without in- 
terfering with each other. When we nod the head, 
we use the hinge-joint, which lies between the head 
and the neck. When we turn the head round, we 
use the tenon and mortise, which runs between the 
first bone of the neck and the second.29 
[Here the toothlike process of the second vertebra, which is 
called dentata, is passed through the ring of the first, and is held 
there by a transverse ligament, like a spindle in the bush. No 
doubt the object of this complexity is to permit the free motion 
of the head, without too great a laxity at any one joining, and 
thereby to protect the most vital organ of the body, the medulla 
oblongata, or spinal narrow, which passes from the head into the 
tube of the spine.] 
We see the same contrivance and the same prin- 
ciple employed in the frame or mounting of a tele- 
scope. It is occasionally requisite that the object-end 
29 The meaning of our author is obvious here; but the tenon 
and mortise are terms used for the firm joining of beams, as in 
the carpentry of a roof; not for rotatory motion. 112 
of the instrument be moved up and down, as well as 
horizontally or equatorially. For the vertical mo- 
tion there is a hinge, upon which the telescope plays; 
for the horizontal or equatorial motion, an axis upon 
which the telescope and the hinge turn round to- 
gether. And this is exactly the mechanism which is 
applied to the motion of the head; nor will any one 
here doubt of the existence of counsel and design, 
except it be by that debility of mind which can trust 
to its own reasonings in nothing. 
We may add that it was, on another account also, 
expedient that th$ motion of the head backward and 
forward should be performed upon the upper surface 
of the first vertebra; for, if the first vertebra itself 
had bent forward, it would have brought the spinal 
marrow, at the very beginning of its course, upon the 
point of the tooth. 
II. Another mechanical contrivance, not unlike 
the last in its object, but different and original in its 
means, is seen in what anatomists call the fore-arm; 
that is, in the arm between the elbow and the wrist. 
Here, for the perfect use of the limb, two motions 
are wanted: a motion at the elbow, backward and 
forward, which is called a reciprocal motion; and a 
rotatory motion, by which the palm of the hand, as 
occasion requires, may be turned upward. How is 
this managed 1 The fore-arm, it is well known, con- 
sists of two bones lying alongside each other, but 
touching only towards the ends. One, and only one, 
of these bones is joined to the cubit, or upper part 
of the arm, at the elbow ; the other alone to the hand 
at the wrist. The first, by means, at the elbow, of a 
hinge-joint (which allows only of motion in the same 
plane), swings backward and forward, carrying along 
with it the other bone and the whole fore-arm. In 
the mean time, as often as there is occasion to turn 
the palm upward, that other bone to which the hand 
is attached rolls upon the first, by the help of a 
groove or hollow near each end of one bone, to 
which is fitted a corresponding prominence in the 
other. If both bones had been joined to the cubit, or 
NATURAL THEOLOGY. NATURAL THEOLOGY 
113 
[Since it has been our author's pleasure to 
take this instance, the figure will illustrate 
his description. A is the lower part of the 
arm-bone, or humerus; B is the ulna, and C the 
radius, the two bones of the fore-arm. It will 
be understood how these bones, being tied 
together by ligaments, hinge and move upon 
the humerus A ; c being the process of the 
ulna, on which we rest when leaning on the 
elbow. By applying our hand to the arm, 
we at once feel the freedom with which the 
bone moves in bending and extending the 
arm. When we turn the key in a lock, or 
make the guards in fencing by the motion of 
the wrist, the ulna B is stationary, and the 
radius C turns round upon the head of the 
bone at d and e, carrying the hand with it. 
The rest is abundantly well explained in the 
text.] 
upper arm, at the elbow, or both to the hand at the 
wrist, the thing could not have been done. The first 
was to be at liberty at one end, and the second at the 
other, by which means the two actions may be per- 114 
NATURAL THEOLOGY. 
formed together. The great bone which carries the 
fore-arm may be swinging upon its hinge at the el- 
bow, at the very time that the lesser bone, which 
carries the hand, may be turning round it in.the 
grooves. The management, also, of these grooves, 
or, rather, of the tubercles and grooves, is very ob- 
servable. The two bones are called the radius and 
the ulna. Above, i. e., towards the elbow, a tubercle 
of the radius plays into a socket of the ulna; while 
below, i. towards the wrist, the radius finds the 
socket, and the ulna the tubercle. A single bone in 
the fore-arm, with a ball and socket joint at the el- 
bow, which admits of motion in all directions, might, 
in some degree, have answered the purpose of both 
moving the arm and turning the hand. But how 
much better it is accomplished by the present mech- 
anism any person may convince himself who puts 
the ease and quickness with which he can shake his 
hand at the wrist circularly (moving likewise, if he 
pleases, his arm at the elbow at the same time), in 
competition with the comparatively slow and labori- 
ous motion with which his arm can be made to turn 
round at the shoulder by the aid of a ball and socket 
joint. 
III. The spine, or back-bone, is a chain of joints 
of very wonderful construction. Various, difficult, 
and almost inconsistent offices were to be executed 
by the same instrument. It was to be firm, yet flex- 
ible (now I know no chain marde by art which is both 
these ; for by firmness I mean not only strength, but 
stability): firm, to support the erect position of the 
body ;* fiexible, to allow of the bending of the trunk 
in all degrees of curvature. It was farther also 
(which is another and quite a distinct purpose from 
the rest) to become a pipe or conduit for the safe 
conveyance from the brain of the most important 
fluid of the animal frame, that, namely, upon which 
all voluntary motion depends, the spinal marrow; a 
substance not only of the first necessity to action, 
* And also tbe weight of the head. NATURAL THEOLOGY. 
115 
if not to life, but of a nature so delicate and tender, 
so susceptible and so impatient of injury, as that any 
unusual pressure upon it, or any considerable ob- 
struction of its course, is followed by paralysis or 
death. 
[This represents a section of three of the lower vertebrae. The 
subject being by no means exhausted in the text, the reader will 
find it taken up in the Appendix.] 
Now the spine was not only to furnish the main 
trunk for the passage of the medullary substance 
from the brain, but to give out, in the course of its 
progress, small pipes therefrom, which, being after- 
ward infinitely subdivided, might, under the name of 
nerves, distribute this exquisite supply to every part 
of the body. The same spine was also to serve an- 
other use, not less wanted than the preceding, viz., to 
afford a fulcrum, stay, or basis (or, more properly 
speaking, a series of these) for the insertion of the 
muscles which are spread over the trunk of the body; 
in which trunk there are not, as in the limbs, cylin- 
drical bones to which they can be fastened : and 116 
NATURAL THEOLOGY. 
likewise, which is a similar use, to furnish a support 
for the ends of the ribs to rest upon.* 
Bespeak of a workman a piece of mechanism 
which shall comprise all these purposes, and let him 
set about to contrive it; let him try his skill upon it; 
let him feel the difficulty of accomplishing the task, 
before he be told how the same thing is effected in 
the animal frame. Nothing will enable him to judge 
so well of the wisdom which has been employed; 
nothing will dispose him to think of it so truly. 
First, for the firmness, yet flexibility of the spine; 
it is composed of a great number of bones (in the hu- 
man subject of twenty-four), joined to one another, 
and compacted by broad bases. The breadth of the 
bases upon which the parts severally rest, and the 
closeness of the junction, give to the chain its firm- 
ness and stability; the number of parts and conse- 
quent frequency of joints, its flexibility. Which flex- 
ibility, we may also observe, varies in different parts 
of the chain; is least in the back, where strength 
more than flexure is wanted ; greater in the loins, 
which it was necessary should be more supple than 
the back; and greatest of all in the neck, for the free 
motion of the head. Then, secondly, in order to af- 
ford a passage for the descent of the medullary sub- 
stance, each of these bones is bored through in the 
middle, in such a manner as that, when put together, 
the hole in one bone falls into a line and corresponds 
with the holes in the two bones contiguous to it. 
By which means the perforated pieces, when joined, 
form an entire, close, uninterrupted channel, at least 
while the spine is upright and at rest. But as a set- 
tled posture is inconsistent with its use, a great diffi- 
culty still remained, which was to prevent the verte- 
brae from shifting upon one another, so as to break 
the line of the canal as often as the body moves or 
twists, or the joints gaping externally whenever the 
body is bent forward, and the spine thereupon made 
* See Bell's " Animal Mechanics" for a striking comparison 
between the spine and the masts of a ship.-Am. Ed. NATURAL THEOLOGY. 
117 
to take the form of a bow. These dangers, which are 
mechanical, are mechanically provided against. The 
vertebrae, by means of their processes and projec- 
tions, and of the articulations which some of these 
form with one another at their extremities, are so 
locked in and confined as to maintain, in what are 
called the bodies or broad surfaces of the bones, the 
relative position nearly unaltered, and to throw the 
change and the pressure produced by flexion al- 
most entirely upon the intervening cartilages,* the 
springiness and yielding nature of whose substance 
admits of all the motion which is necessary to be per- 
formed upon them, without any chasm being produ- 
ced by a separation of the parts. I say, of all the 
motion which is necessary; for although we bend 
our backs to every degree almost of inclination, the 
motion of each vertebrae is very small: such is the 
advantage we receive from the chain being composed 
of so many links, the spine of so many bones. Had 
it consisted of three or four bones only, the spine 
must have been bruised at every angle. The reader 
need not be told that these intervening cartilages are 
gristles, and he may see them in perfection in a loin 
of veal. Their form also favours the same intention. 
They are thicker before than behind; so that, when 
we stoop forward, the compressible substance of the 
cartilage, yielding in its thicker and anterior part to 
the force which squeezes it, brings the surface of the 
adjoining vertebrae nearer to the being parallel with 
one another than they were before, instead of increas- 
ing the inclination of their planes, which must, have oc- 
casioned a fissure or opening between them.30 Third- 
* Which are not only elastic, but so strong that they never 
break. The bone often breaks from violence, the cartilage never. 
-Am. Ed. 
30 Sir C. Bell notices another admirable thing in the spine. It is 
the manner in which the head is sustained on a column possess- 
ing elasticity, and in which the brain is thereby saved from undue 
concussion in the movements of the body This is owing to the 
general form of the spine, as well as to its elasticity. Had it been 
a strictly vertical column, the incumbent weight must have fallen 
on the centres of all the vertebrae, and they would have yielded 118 
NATURAL THEOLOGY. 
ly, for the medullary canal giving out in its course 
and in a convenient order, a supply of nerves to dif- 
ferent parts of the body, notches are made in the 
upper and lower edge of every vertebrae, two on 
each edge, equidistant on each side from the middle 
line of the back. When the vertebrae are put togeth- 
er, these notches, exactly fitting, form small holes, 
through which the nerves at each articulation issue 
out in pairs, in order to send their branches to every 
part of the body, and with an equal bounty to both 
sides of the body. The fourth purpose assigned to 
the same instrument is the insertion of the bases of 
the muscles, and the support of the ends of the ribs ; 
and for this fourth purpose, especially the former 
part of it, a figure specifically suited to the design, 
and unnecessary for the other purposes, is given to 
the constituent bones. While they are plain, and 
round, and smooth towards the front, where any 
roughness or projection might have wounded the ad- 
jacent viscera, they run out behind and on each side 
into long processes, to which processes the muscles 
necessary to the motions of the trunk are fixed, and 
fixed with such art that, while the vertebrae supply 
a basis for the muscles, the muscles help to keep 
these bones in their position, or by their tendons to 
tie them together. That most important, however, 
and general property, viz., the strength of the corn- 
pages * and the security against luxation, was to be 
much less. But the figure of the italic/being given to it, the pres- 
sure is directed on the margins of the vertebrae, so that they yield 
easily,thereby producing an increase of the curve, and a conse- 
quent shortening of the whole column, while they admit an easy 
return to their original places. " Suppose we rest the palm of the 
hand upon a walking cane which is elastic, but perfectly straight; 
it bears a considerable pressure without yielding, and when it does 
yield it is with a jerk; but if it is previously bent, however we 
may increase or diminish the pressure, there will be no shock, 
the hand will be supported, or the cane yield with an easy and 
uninterrupted resiliency. Such we conceive to be the end ob- 
tained through the double curvature of the spine, that the brain 
shall receive no shock in the motion of the body." 
* I.a system of parts united. NATURAL THEOLOGY. 
119 
still more specially consulted; for, where so many 
joints were concerned, and where, in every one, 
derangement would have been fatal, it became a sub- 
ject of studious precaution. For this purpose the 
vertebrae are articulated, that is, the moveable joints 
between them are formed by means of those pro- 
jections of their substance which we have mentioned 
under the name of processes, and these so lock in 
with and overwrap one another qs to secure the body 
of the vertebra not only from accidentally slipping, 
but even from being pushed out of its place by any 
violence short of that, which would break the bone. 
I have often remarked and admired this structure in 
the chine of a hare. In this, as in many instances, a 
plain observer of the animal economy may spare 
himself the disgust of being present at human dissec- 
tions, and yet learn enough for his information and 
satisfaction, by even examining the bones of the ani- 
mals which come upon his table. Let him take, for 
example, into his hands a piece of the clean-picked 
bone of a hare's back, consisting, we will suppose, of 
three vertebrae. He will find the middle bone of the 
three so implicated, by means of its projections or 
processes, with the bone on each side of it, that no 
pressure which he can use will force it out of its 
place between them. It will give way neither for- 
ward nor backward, nor on either side. In which- 
ever direction he pushes, he perceives, in the form, 
or junction, or overlapping of the bones, an impedi- 
ment opposed to his attempt, a check and guard 
against dislocation. In one part of the spine he will 
find a still farther fortifying expedient, in the mode 
according to which the vertebrae are annexed to the 
spine. Each rib rests upon two vertebrae. That is 
the thing to be remarked, and any one may remark it 
in carving a neck of mutton. The manner of it is 
this: the end of the rib is divided by a middle ridge 
into two surfaces, which surfaces are joined to the 
bodies of two contiguous vertebrae, the ridge apply- 
ing itself to the intervening cartilage. Now this is 
the very contrivance which is employed in the fa- 120 
mous iron bridge at my door at Bishop-Weannouth, 
and for the same purpose of stability, viz., the cheeks 
of the bars which pass between the arches ride across 
the joints by which the pieces composing each arch 
are united. Each crossbar rests upon two of these 
pieces at their place of junction, and by that position 
resists, at least in one direction, any tendency in either 
piece to slip out of its place. Thus perfectly, by one 
means or the other, is the danger of slipping lateral- 
ly, or of being drawn aside out of the line of the back, 
provided against; and, to withstand the bones being 
pulled asunder longitudinally, or in the direction of 
that line, a strong membrane runs from one end of 
the chain to the other, sufficient to resist any force 
which is ever likely to act in the direction of the 
back or parallel to it, and, consequently, to secure the 
whole combination in their places. The general re- 
sult is, that not only the motions of the human body 
necessary for the ordinary offices of life are perform- 
ed with safety, but that it is an acccident hardly ever 
heard of, that even the gesticulations of a harlequin 
distort his spine. 
Upon the whole, and as a guide to those who may 
be inclined to carry the consideration of this subject 
farther, there are three views under which the spine 
ought to be regarded, and in all which it cannot fail 
to excite our admiration. These views relate to its 
articulations, its ligaments, and its perforation; and 
to the corresponding advantages which the body de- 
rives from it, for action, for strength, and for that 
which is essential to every part, a secure communi- 
cation with the brain. 
The structure of the spine is not, in general, differ- 
ent in different animals.31 In the serpent tribe, how- 
NATURAL THEOLOGY. 
31 There is a notion entertained by the ingenious and somewhat 
fanciful physiologists of France, that the extremities of the body, 
the parts farthest removed from the centre, are most subject to 
change in their conformation, while the central parts of the sys- 
tem are the most unvarying. Entertaining such a view, we lose 
much of the interest that is attached to the subject; and the in- 
ference which it is important to draw is forgotten, the accommo- NATURAL THEOLOGY. 
121 
ever, it is considerably varied; but with a strict refer- 
ence to the convenience of the animal. For, whereas 
in quadrupeds the number of vertebrae is from thirty 
to forty, in the serpent it is nearly one hundred and 
fifty; whereas in men and quadrupeds the surfaces 
of the bones are flat, and those flat surfaces laid one 
against the other and bound tight by sinews, in the 
serpent the bones play one within another, like a ball 
and socket,* so that they have a free motion upon one 
another in every direction : that is to say, in men and 
quadrupeds, firmness is more consulted ; in serpents, 
dation, not of parts only, but of the whole framework of the ani- 
mal body, to the peculiar condition or necessities of the creature. 
The teeth vary because the food is different; the feet vary be- 
cause the mode of progression is different; the claws vary in con- 
nexion with the teeth, and the mode of procuring food, by digging 
or scraping, or by holding and tearing. So does the eye, and so 
does the ear. But with these adaptations of parts, we must not 
lose sight of the fact which is the most important to our conclu- 
sions : that the whole is accommodated, as well as the individual 
organs. 
The spine in all vertebrated animals holds its office in perpetu- 
ity ; it contains and protects the spinal marrow ; and, so far as its 
office is permanent, there will be a uniforrpity in its appearance 
in all creatures. But even in man it varies in its structure, in the 
different portions or divisions of it, as these portions are required 
to admit of more or less freedom of motion. In the hare, as men- 
tioned in the text, the spine is beautifully accommodated to the 
motion in running. In the cat kind, as the leopard or tiger, it has 
a lateral mobility,,quite different from its structure in the horse or 
the stag. In the hoar, the vertebra are unusually firm, and the 
processes enormously extended, to give strength to the union with 
the head, and to direct the action of the muscles upon the head, 
so that he may tear up strong roots and possess his defence in his 
powerful tusks. In short, as far as the spine is required to accom- 
modate itself to the motions of the trunk, it is varied with as fine 
an adjustment as the farthest bone of the toe or finger.* 
* Der. Phys. Theol., p. 396. 
* In fishes, where powerful and sudden action in the spine is re- 
quired (such as the sturgeon, lamprey, &c.), bone is dispensed with, 
and the spine consists of a cartilage made tough by ligamentous 
intermixture. This remarkable elasticity is more or less seen in 
all fishes; and we ascend some way in the scale of animals before 
we come to distinct vertebra of bone. This structure is always 
adapted to the condition and wants of the animal.-Am. Ed. 
Vol. L-L 122 
NATURAL THEOLOGY. 
pliancy. Yet even pliancy is not obtained at the ex- 
pense of safety. The backbone of a serpent, for co- 
herence and flexibility, is one of the most curious 
pieces of animal mechanism with which we are ac- 
quainted. The chain of a watch (I mean the chain 
which passes between the spring-barrel and the fusee), 
which aims at the same properties, is but a bungling 
piece of workmanship in comparison with that of 
which we speak. 
IV. The reciprocal enlargement and contraction of 
the chest, to allow for the play of the lungs, depends 
upon a simple yet beautiful mechanical contrivance, 
referable to the structure of the bones which enclose 
it. The ribs are articulated to the backbone, or, rather, 
to its side projections, obliquely: that is, in their nat- 
ural position they bend or slope from the place of ar- 
ticulation downward. But the basis upon which they 
rest at this end being fixed, the consequence of the 
obliquity, or the inclination downward, is, that when 
they come to move, whatever pulls the ribs upward, 
necessarily, at the same time, draws them out; and 
that, while the ribs are brought to a right angle with 
the spine behind, the sternum, or part of the chest to 
which they are attached in front, is thrust forward. 
The simple action, therefore, of the elevating muscles 
does the business ; whereas, if the ribs had been ar- 
ticulated with the bodies of the vertebrae at right an- 
gles, the cavity of the thorax could never have been 
farther enlarged by a change of their position. If 
each rib had been a rigid bone, articulated at both 
ends to fixed bases, the whole chest had been immo- 
vable. Keill has observed that the breastbone, in an 
easy inspiration, is thrust out one tenth of an inch; 
and he calculates that this, added to what is gained 
to the space within the chest by the flattening or de- 
scent of the diaphragm, leaves room for forty-two cu- 
bic inches of air to enter at every drawing in of the 
breath. When there is a necessity for a deeper and 
more laborious inspiration, the enlargement of the 
capacity of the chest may be so increased by effort, 
as that the lungs may be distended with seventy or & NATURAL THEOLOGY. 
123 
hundred such cubic inches.* The thorax, says Schel- 
hammer, forms a kind of bellows, such as never have 
been, nor probably will be, made by any artificer.32 
Y. The patella, or knee-pan, is a curious little bone: 
in its form and office unlike any other bone in the body. 
It is circular, the size of a crown piece, pretty thick, 
a little convex on both sides, and covered with a smooth 
cartilage. It lies upon the front of the knee : and the 
[Three views of the knee joints.] 
* Anat., p. 299. 
32 Sir C. Bell remarks, " Our author has omitted an essential 
part of this interesting subject. He has shown that the oblique 
position of the ribs is necessary to inspiration, and that, by the ri- 
sing of the anterior part of the rib, the breastbone is thrust for- 
ward, and the cavity enlarged. But the rib has a double motion. 
It has a motion on its own axis. Suppose a line drawn through 
the two extremities of a rib which would represent the string of a 
bow, that string is stationary, while the bow representing the rib 
revolves ; thus the rib, by having its anterior extremity depressed 
and revolving, as it is raised, enlarges the transverse diameter of 
the thorax as well as the anterior diameter. In this action, the 
cartilage in front is twisted,'' and this twisting is so adjusted that 
the elasticity acts to keep the thorax dilated even after a person 
has fainted, or is in any manner in danger of death. Thus the 
action of the lungs can be kept up for a time, at least, after the 
vital actions would have ceased through the muscles, and a prop- 
erty of dead matter, elasticity, is made the guard of life.-Am. 
Ed. 124 
NATURAL THEODOGY. 
powerful tendons, by which the leg is brought forward, 
pass through it (or, rather, it makes a part of their con- 
tinuation), from their origin in the thigh to their inser- 
tion in the tibia. It protects both the tendon and the 
joint from any injury which either might suffer by 
the rubbing of one against the other, or by the pres- 
sure of unequal surfaces. It also gives to the ten- 
dons a very considerable mechanical advantage, by 
altering the line of their direction, and by advancing 
it farther out from the centre of motion;* and this 
upon the principles of the resolution of force, upon 
which principles all machinery is founded. These 
are its uses. But what is most observable in it is, 
that it appears to be supplemental, as it were, to the 
frame: added, as it should almost seem, afterward; 
not quite necessary, but very convenient. It is sep- 
arate from the other bones: that is, it is not con- 
nected with any other bones by the common mode 
of union. It is soft or hardly formed in infancy, 
and produced by an ossification, of the inception or 
progress of which no account can be given from the 
structure or exercise of the part.33 
VI. The shoulder blade is, in some material respects, 
a very singular bone: appearing to be made so ex- 
pressly for its own purpose, and so independently of 
every other reason. In such quadrupeds as have no 
collar bones, which are by far the greater number, the 
shoulder blade.has no bony communication with the 
trunk, either by a joint, or process, or in any other 
way. It does not grow to, or out of, any other bone 
* In raising a weight by a lever, we do it more easily in propor- 
tion as we apply the moving power at a greater distance from the 
fulcrum or centre of motion.-Am. Ed. 
33 In connexion with the above figure, it may be well to notice 
the enlargement in the size of the bone, Which takes place not 
only at the knee joint, but at every other articulation. It adds to 
the power of the binding ligaments in the manner above stated; 
diminishes the danger of dislocation by an increase of surface and 
additional strength of ligament; and even lessens the friction, 
wherever, as is generally the case, the bones roll instead of sli- 
ding upon each other; for, the greater the diameter of the rolling 
bodies, the less the friction.-Am. Ed. NATURAL THEOLOGY. 
125 
of the trunk. It does not apply to any other bone of 
the trunk (I know not whether this be true of any 
second bone in the body, except, perhaps, the os hy- 
oides): in strictness, it forms no part of the skeleton. 
It is bedded in the flesh, attached only to the muscles. 
It is no other than a foundation bone for the arm, laid 
in, separate as it were, and distinct, from the general 
ossification. The lower limbs connect themselves at 
the hip with bones which form part of the skeleton; 
but this connexion in the upper limbs being wanting, 
a basis whereupon the arm might be articulated was 
to be supplied by a detached ossification for the pur- 
pose.34 
OF THE JOINTS. 
I. The above are a few examples of bones made 
remarkable by their configuration; but to almost all 
the bones belong joints; and in these, still more clear- 
ly than in the form or shape of the bones themselves, 
are seen both contrivance and contriving wisdom. 
Every joint is a curiosity, and is also strictly mechan- 
34 The shoulder blade undergoes many changes, as we view it in 
comparative anatomy. That bone which we feel running across 
the upper part of the chest and lower part of the neck, the collar 
bone, is properly a process of the shoulder blade. Its purpose is 
to hold the shoulders apart, and to give strength to the arms, by 
throwing upon the arm the action of the muscles of the chest 
Accordingly, we find it in climbing animals, in those which re- 
quire to swing themselves by the upper extremities, as the mon- 
keys ; but in animals that have a solid hoof, which implies that the 
anterior extremity is for the particular purpose of running or bound- 
ing upon the ground, not only is there no occasion for that variety 
in the motions of the extremity, which is produced by the introduc- 
ton of this bone into the skeleton of the arm, but it would be in- 
jurious ; it would deprive the animal of that elasticity with which 
it alights upon the ground. Where there is no clavicle-in the 
horse and deer, for example-the shoulder blade or scapula is at- 
tached to the trunk by muscles alone. Hence, when the animal 
makes a leap, it comes down upon the fore legs with an elastic re- 
bound, the trunk hanging upon the muscles, the muscles support- 
ed by the scapula, and the scapula sustained upon the bones of the 
extremity. There is no solid substance to receive the shock. 
Were the collar bone introduced here, it would be snapped across 
by the percussion, as happens to a man where he is thrown upon 
his shoulder. 126 
ical. There is the hinge joint, and the mortise and 
tenon joint; each as manifestly such, and as accurate- 
ly defined, as any which can be produced out of a cab- 
inet-maker's shop; and one or the other prevails, as 
either is adapted to the motion which is wanted ; 
e. g., a mortise and tenon, or ball and socket joint, is 
not required at the knee, the leg standing in need 
only of a motion backward and forward in the same 
plane, for which a hinge joint is sufficient; a mortise 
and tenon, or ball and socket joint, is wanted at the 
hip, that not only the progressive step may be provi- 
ded for, but the interval between the limbs may be 
enlarged or contracted at pleasure. Now observe 
what would have been the inconvenience, i. e., both 
the superfluity and the defect of articulation, if the 
case had been inverted: if the ball and socket joint 
had been at the knee, and the hinge joint at the hip. 
The thighs must have been kept constantly together, 
and the legs had been loose and straddling. There 
would have been no use, that we know of, in being 
able to turn the calves of the legs before; and there 
would have been great confinement by restraining the 
motion of the thighs to one plane. The disadvantage 
would not have been less if the joints at the hip and 
the knee had been both of the same sort; both balls 
and sockets, or both hinges : yet why, independently 
of utility, and of a Creator who consulted that utility, 
should the same bone (the thigh-bone) be rounded at 
one end and channelled at the other! 
The hinge joint is not formed by a bolt passing 
through the two parts of the hinge, and thus keeping 
them in their places, but by a different expedient. A 
strong, tough, parchment-like membrane, rising from 
the receiving bones, and inserted all round the receiv- 
ed bones a little below their heads, encloses the joint 
on every side. This membrane ties, confines, and 
holds the ends of the bones together, keeping the 
corresponding parts of the joints, i. e., the relative 
convexities and concavities, in close application to 
each other. 
For the ball and socket joint, besides the membrane 
natural theology. NATURAL THEOLOGY. 
127 
already described, there is in some important joints, 
as an additional security, a short, strong, yet flexible 
ligament, inserted by one end into the head of the 
ball, by the other into the bottom of the cup, which 
ligament keeps the two parts of the joint so firmly in 
their place, that none of the motions which the limb 
naturally performs; none of the jerks and twists to 
which it is ordinarily liable ; nothing less, indeed, than 
the utmost and the most unnatural violence, can pull 
them asunder. It is hardly imaginable how great a 
force is necessary, even to stretch, still more to break, 
this ligament: yet so flexible is it, as to oppose no 
impediment to the suppleness of the joint..* By its 
situation, also, it is inaccessible to injury from sharp 
edges. As it cannot be ruptured (such is its strength), 
so it cannot be cut, except by an accident which 
would sever the limb. If I had been permitted to 
frame a proof of contrivance, such as might satisfy 
the most distrustful inquirer, I know not whether I 
could have chosen an example of mechanism more 
unequivocal, or more free from objection, than this 
ligament. Nothing can be more mechanical; nothing, 
however subservient to the safety, less capable of 
being generated by the action of the joint. I would 
particularly solicit the reader's attention to this pro- 
vision, as it is found in the head of the thigh bone: to 
its strength, its structure, and its use. It is an in- 
stance upon which I lay my hand. One single fact, 
weighed by a mind in earnest, leaves oftentimes the 
deepest impression. For the purpose of addressing 
different understandings and different apprehensions, 
for the purpose of sentiment, for the purpose of ex- 
citing admiration of the Creator's works, we diversify 
our views, we multiply our examples: but for the 
purpose of strict argument, one clear instance is suf- 
ficient ; and not only sufficient, but capable, perhaps, 
* This ligament is also common to all quadrupeds, even in the 
more large and unwieldy, as the hippopotamus and rhinoceros; 
it is wanting in the elephant only, whose limbs, ill qualified for 
active movements, do not seem to require this security to the 
joint.-Paxton, 128 
NATURAL THEOLOGY. 
of generating a firmer assurance than what can arise 
from a divided attention.35 
The ginglymus, or hinge joint, does not, it is man- 
ifest, admit of a ligament of the same kind with that 
of the ball and socket joint; but it is always fortified 
by the species of ligament of which it does admit. 
The strong, firm, investing membrane above de- 
scribed, accompanies it in every part; and in particu- 
lar joints, this membrane, which is properly a liga- 
ment, is considerably stronger on the sides than ei- 
ther before or behind, in order that the convexities 
may play true in their concavities, and not be subject 
to slip sideways, which is the chief danger; for the 
muscular tendons generally restrain the parts from 
going farther than they ought to go in the plane of 
their motion. In the knee, which is a joint of this 
form, and of great importance, there are superadded 
to the common provisions for the stability of the joint, 
two strong ligaments, which cross each other, and 
cross each other in such a manner as to secure the 
joint from being displaced in any assignable direction. 
" I think," says Cheselden, " that the knee cannot be 
completely dislocated without breaking the cross lig- 
aments."* We can hardly help comparing this with 
the binding up of a fracture, where the fillet is al- 
most wholly strapped across, for the sake of giving 
firmness and strength to the bandage. 
Another no less important joint, and that also of 
the ginglymus sort, is the ankle; yet, though impor- 
tant (in order, perhaps, to preserve the symmetry and 
lightness of the limb), small, and on that account 
more liable to injury. Now this joint is strengthen- 
ed, i. e., is defended from dislocation, by two re- 
markable processes or prolongations of the bones of 
the leg, which processes form the protuberances that 
35 This ligament is absent in the orang-outang; and in the low- 
er extremity of this animal there are other points of resemblance 
to the structure of the arm; and certainly the use of the hinder 
extremity corresponds with this structure, since he grasps and 
swings equally well with either extremity. 
* Ches. Anat., ed. ?th, p. 45. NATURAL THEOLOGY. 
129 
we call the inner and outer ankle. It is part of each 
bone going down lower than the other part, and 
thereby overlapping the joint: so that, if the joint be 
in danger of slipping outward, it is curbed by the in- 
ner projection, i.'e., that of the tibia; if inward, by 
the outer projection, i. e., that of the fibula. Between 
both it is locked in its position. I know no account 
that can be given of this structure, except its utility.38 
Why should the tibia terminate at its lower extrem- 
ity with a double end, and the fibula the same, but to 
barricade the joint on both sides by a continuation of 
part of the thickest of the bone over it 1 The joint 
at the shoulder, compared with the joint at the hip, 
though both ball and socket joints, discovers a differ- 
ence in their form and proportions well suited to the 
different offices which the limbs have to execute. 
The cup or socket at the shoulder is much shallower 
and flatter than it is at the hip, and is also, in part, 
formed of cartilage set round the rim of the cup. 
The socket into which the head of the thigh bone is 
inserted is deeper, and made of more solid materi- 
als.* This agrees with the duties assigned to each 
part. The arm is an instrument of motion, princi- 
36 It is surprising, that among so many instances our author 
should omit to notice the perfection in the ankle joint. When we 
stand resting upon the foot, the joint is firm, and yields neither to 
the inside nor the outside; but when we move the foot forward, 
and point the toe in making the step, such is the happy form 
of the bones, that the foot is in this position thrown quite loose. 
The object here certainly is, that in walking on the irregular 
ground, we may have a freedom in directing the foot so as to plant 
it securely. But, before the weight of the body is brought per- 
pendicularly over the foot, there is no danger to the joint, because 
there is no strain upon it. Just in proportion as the advancing 
body begins to bear upon it, do the bones take that position, in 
■which they are as firm as in the knee joint itself, admitting only 
the motion of a hinge. 
* The socket for the head of the thigh bone is indeed deeper 
than that at the shoulder, but the " materials" which form the 
concavities are the same; both are solid bone covered by carti- 
lage, and have a rim of astrong fibro-cartilaginous texture, not 
only for the purpose of rendering the socket deeper, but for pre- 
venting fractures of the rim in robust exercises, to which, were it 
bony, it would be very liable.-Paxton. pally, if not solely. Accordingly, the shallowness of 
the socket at the shoulder, and the yieldingness of 
the cartilaginous substance with which its edge is 
set round, and which, in fact, composes a considerable 
part of its concavity, are excellently adapted for the 
allowance of a free motion and a wide range, both 
which the arm wants. Whereas, the lower limb, 
forming a part of the column of the body, having to 
support the body as well as to be the means of its 
locomotion, firmness was to be consulted as well as 
action. With a capacity for motion, in all directions, 
indeed, as at the shoulder, but not in any direction 
to the same extent as in th arm, was to be united 
stability, or resistance to dislocation. Hence the 
deeper excavation of the socket, and the presence of 
a less proportion of cartilage upon the edge. 
The suppleness and pliability of the joints we every 
moment experience; and the firmness of animai artic- 
ulation, the property we have hitherto been consid- 
ering, may be judged of from this single observation, 
that, at any given moment of time, there are millions 
of animal joints in complete repair and use for one 
that is dislocated, and this notwithstanding the con- 
tortions and wrenches to which the limbs of animals 
are continually subject. 
II. The joints, or, rather, the ends of the bones 
■which form them, display also, in their configuration, 
another use. The nerves, bloodvessels, and ten- 
dons, which are necessary to the life or for the mo- 
tion of the limbs, must, it is evident, in their way 
from the trunk of the body to the place of their des- 
tination, travel over the moveable joints; and it is 
no less evident that, in this part of their course, they 
will have, from sudden motions and from abrupt 
changes of curvature, to encounter the danger of 
compression, attrition, or laceration. To guard 
fibres so tender against consequences so injurious, 
their path is in those parts protected with peculiar 
care, and that by a provision in the figure of the 
bones themselves. The nerves which supply the 
fore-arm, especially the inferior cubital nerves, are at 
130 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
131 
the elbow conducted, by a kind of covered way, be- 
tween the condyls, or, rather, under the inner extu- 
berances of the bone which composes the upper part 
of the arm.* At the knee, the extremity of the thigh 
bone is divided by a sinus or cliff into two heads 
or protuberances ; and these heads on the back part 
stand out beyond the cylinder of the bone. Though 
the hollow which lies between the hind parts of these 
two heads, that is to say, under the ham, between 
the hamstrings, and within the concave recess of the 
bone formed by the extuberances on each side ; in a 
word, along a defile, between rocks, pass the great 
vessels and nerves which go to the leg.f Who led 
these vessels by a road so defended and secured! 
In the joint at the shoulder, in the edge of the cup 
which receives the head of the bone, is a notch, which 
is joined or covered at the top with a ligament. 
Through this hole, thus guarded, the bloodvessels 
steal to their destination in the arm instead of mount- 
ing over the edge of the concavity.| 
III. In all joints, the end of the bones, which work 
against each other, are tipped with gristle. In the 
ball and socket joint, the cup is lined and the ball 
capped with it. The smooth surface, the elastic and 
unfriable nature of cartilage, render it of all substan- 
ces the most proper for the place and purpose. I 
should, therefore, have pointed this out among the 
foremost of the provisions which have been made in 
the joints for the facilitating of their action, had it 
not been alleged that cartilage in truth is only nascent 
or imperfect bone ; and that the bone in these places 
is kept soft and imperfect, in consequence of a more 
complete and rigid ossification being prevented from 
taking place by the continual motion and rubbing of 
the surfaces; which being so, what we represent as 
a designed advantage is an unavoidable effect. I am 
far from being convinced that this is a true account 
of the fact; or that, if it were so, it answers the ar- 
* Ches. Anat., p. 255, ed. 7. f Ibid., p. 35. 
X Ibid., p. 30. 132 
NATURAL THEOLOGY. 
gument.31 To me the surmounting of the bones with 
gristle looks more like a plating with a different met- 
al, than like the same metal kept in a different state 
by the action to which it is exposed. At all events, 
we have a great particular benefit, though arising 
from a general constitution; but this last not being 
quite what my argument requires, lest I should seem, 
by applying the instance, to overrate its value, I have 
thought it fair to state the question which attends it. 
IV. In some joints, very particularly in the knees, 
there are loose cartilages or gristles between the 
bones, find within the joint, so that the ends of the 
bones, instead of working upon one another, work 
upon the intermediate cartilages. Cheselden has ob- 
served,* that the contrivance of a loose ring is prac- 
tised by mechanics where the friction of the joints of 
any of their machines is great, as between the parts 
of crook-hinges of large gates, or under the head of 
the male screw of large vices. The cartilages of 
which we speak have very much of the form of these 
rings. The comparison, moreover, shows the reason 
why we find them in the knees rather than in other 
joints. It is an expedient, we have seen, which a 
mechanic resorts to only when some strong and hea- 
vy work is to be done. So here the thigh bone has 
to achieve its motion at the knee, with the whole 
weight of the body pressing upon it, and often, as in 
rising from our seat, with the whole weight of the 
body to lift. It should seem also, from Cheselden's 
3' As the archdeacon had been a pupil of Dr. William Hunter, 
which we gather from the tenour of many of his observations, it 
is surprising that he has not spoken with more decision upon this 
point. The cartilage, which is the substitute for the bone in in- 
fancy, is very different from that which tips the ends of the artic- 
ulating extremities of the bones. In a valuable paper of Dr. Hunt- 
er's, it is shown that this articulating cartilage consists of fibres, 
placed together like the hairs of a brush, but more compactly and 
perpendicularly to the ends of the bones; and that on this ar- 
rangement chiefly depends the elasticity of the material. Its use 
is best proved by what takes place when it is deficient: for then 
the articulation creaks like an old hinge, and the patient suffers 
aches. 
'* Ches. Anat., p. 13, edit. 7. NATURAL THEOLOGY. 
133 
account, that the slipping and sliding of the loose car- 
tilages, though it be probably a small and obscure 
change, humoured the motion at the end of the thigh 
bone, under the particular configuration which was 
necessary to be given to it for the commodious action 
of the tendons (and which configuration requires what 
he calls a variable socket, that is, a concavity, the 
lines of which assume a different curvature in differ- 
ent inclinations of the bones.)38 
V. We have now done with the configuration : but 
there is also in the joints, and that common to them 
all, another exquisite provision manifestly adapted to 
their use, and concerning which there can, I think, be 
no dispute, namely, the regular supply of a mucilage, 
more emollient and slippery than oil itself, which is 
constantly softening and lubricating the parts that rub 
upon each other, and thereby diminishing the effect 
of attrition in the highest possible degree. For the 
continual secretion of this important liniment, and for 
the feeding of the cavities of the joint with it, glands 
are fixed near each joint, the excretory ducts of which 
glands, dripping with their balsamic contents, hang 
loose like fringes within the cavity of the joints. A 
late improvement in what are called friction wheels, 
which consist of a mechanism so ordered as to be 
regularly dropping oil into a box which encloses the 
axis, the nave, and certain balls upon which the nave 
38 This is not explained with our author's usual clearness. The 
lower head of the thigh bone, which rests upon the shin bone or 
tibia, is not the segment of a regular circle. When we stand with 
the knees straight, the thigh bone rests with a broad surface, and 
the convexity is principally on the back part. Such an irregulari- 
ty would make a very imperfect and jarring hinge joint on any 
configuration that could be given to the corresponding surface of 
the tibia. Therefore these cartilages intervene; and, being pos- 
sessed of considerable elasticity, and so connected with the bone 
as to shift their place a little, they accommodate themselves, 
whether the flatter end or the more convex part of the articula- 
ting surface of the bone be presented to them ; and there is this 
advantage, that, in standing, when the weight on the joint is 
greatest, the thigh bone has a more extensive, and, consequently, 
a more secure basis, at the same time that the motion of the joint 
as a hinge is perfect. 134 
revolves, may be said, in some sort, to represent the 
contrivance in the animal joint, with this superiority, 
however, on the part of the joint, viz., that here the 
oil is not only dropped, but made* 
In considering the joints, there is nothing, perhaps, 
which ought to move our gratitude more than the 
reflection how well they wear. A limb shall swing 
upon its hinge or play in its socket many hundred 
times in an hour, for sixty years together, without 
diminution of its agility, which is a long time for any- 
thing to last; anything so much worked and exerci- 
sed as the joints are.f This durability I should attrib- 
ute, in part, to the provision which is made for the 
preventing of wear and tear, first by the polish of 
the cartilaginous surfaces, secondly by the healing 
lubrication of the mucilage, and, in part, to that as- 
tonishing property of animal constitutions, assimila- 
tion, by which, in every portion of the body, let it 
consist of what it will, substance is restored and 
waste repaired.39 
NATURAL THEOLOGY. 
* This mucilage is termed synovia; vulgarly called joint oil, but 
it has no property of oil. It is very viscid, and, at the same time, 
smooth and slippery to the touch ; and, therefore, better adapted 
than any oil to lubricate the interior of the joints and prevent ill 
effects from friction.-Paxton. 
+ It is incorrect to compare the action of living parts upon each 
other with the wear and tear of machinery. The former are best 
preserved by being kept in use. When joints are kept at rest, the 
muscles, nerves, &c., begin to waste.-Am. Ed. 
39 We have said that exercise is necessary to the perfection of a 
joint. Suppose the knee joint to be inflamed: it is, of course, kept 
in perfect rest, because motion produces pain. The absolute rest, 
joined with inflammation, alters all the textures; the bone be- 
comes light and spongy ; the cartilage is absorbed ; the ligaments 
which ought to hold the bones together becomes loose and relax- 
ed ; and what the surgeon calls consecutive dislocation may take 
place ; that is, the bones will actually shift their place, from the 
defect of those attachments which ought to keep them together. 
Now let us suppose the inflammation to have subsided : by due 
attention all may be restored, and by no other mode than moving 
the joint; the only precaution necessary being, that it shall be 
moved with a care and gentleness corresponding to its weakened 
condition. By this simple means the ligaments will acquire firm- 
ness, the cartilages smoothness, and the synovia, or lubricating 
mucilage, will be again poured out: from all which we see that, NATURAL THEOLOGY. 
135 
Moveable joints, I think, compose the curiosity of 
bones; but their union, even where no motion is in- 
tended or wanted, carries marks of mechanism and of 
mechanical wisdom. The teeth, especially the front 
teeth, are one bone fixed in another, like a peg driven 
into a board. The sutures of the scull are like the 
edges of two saws, clapped together in such a man- 
ner as that the teeth of one enter the intervals of the 
other.* We have sometimes one bone lapping over 
another, and planed down at the edges ; sometimes, 
also, the thin lamella of one bone received into a nar- 
row furrow of another. In all which varieties we 
seem to discover the same design, viz., firmness of 
juncture without clumsiness in the seam. 
in the living animal textures, wear and tear do not take place upon 
continued motion; but, on the contrary, that exercise is made the 
stimulus to improvement. All other proofs of design, as adjust- 
ment, relation, compensation, prospective contrivance, are weak 
in comparison with this. 
* Most of the bones of the scull are composed of two plates or 
tablets, with an intermediate spongy, vascular substance ; the outer 
tablet is fibrous, having the edges curiously indented and united by 
a dovetailed suture ; the inner, from its brittleness, is called vitre- 
ous, and, therefore, merely joined together in a straight line; this 
mode of union is not accidental, not the result of chance, but de- 
sign. The author of the treatise on " Animal Mechanics" gives 
the following admirable illustration of the structure : 
"Suppose a carpenter employed upon his own material: he 
would join a box with regular indentations by dovetailing, be- 
cause he knows that the material on which he works, from its 
softness and toughness, admits of such adjustment of its edges. 
The processes of bone shoot into the opposite cavities with an ex- 
act resemblance to the foxtail wedge of the carpenter. 
" But if a workman in glass or marble were to join these ma- 
terials, he would smooth the edges and unite them by cement; 
for if he could succeed in indenting the line of union, he knows 
that his material would chip off on the slightest vibration. 
" Now apply this principle to the scull; the outer table, which 
resembles wood, is indented and dovetailed; the inner glassy 
table has its edges simply laid in contact."-Paxton. 136 
NATURAL THEOLOGY. 
CHAPTER IX. 
Muscles, with their tendons, are the instruments 
by which animal motion is performed. It will be our 
business to point out instances in which, and proper- 
ties with respect to which, the disposition of these 
muscles is as strictly mechanical as that of the wires 
and strings of a puppet. 
I. We may observe, what I believe is universal, an 
exact relation between the joint and the muscles 
which move it. Whatever motion the joint, by its 
mechanical construction, is capable of performing, 
that motion the annexed muscles, by their position, 
are capable of producing. For example, if there be, 
as at the knee and elbow, a hinge joint, capable of 
motion only in the same plane, the leaders, as they 
are called, *. e., the muscular tendons, are placed in 
directions parallel to the bone, so as, by the contrac- 
tion or relaxation of the muscles to which they be- 
long, to produce that motion and no other. If these 
joints were capable of a freer motion, there are no 
muscles to produce it. Whereas, at the shoulder and 
the hip, where the ball and socket joint allows, by its 
construction, of a rotary or sweeping motion, tendons 
are placed in such a position, and pull in such a direc- 
tion, as to produce the motion of which the joint 
admits. For instance, the sartorius or tailor's mus- 
cle, rising from the spine, running diagonally across 
the thigh, and taking hold of the inside of the main 
bone of the leg a little below the knee, enables us, by 
its contraction, to throw one leg and thigh over the 
other, giving effect, at the same time, to the ball and 
socket joint at the hip, and the hinge joint at the knee. 
There is, as we have seen, a specific mechanism in 
the bones for the rotatory motions of the head and 
hands : there is also, in the oblique direction of the 
muscles belonging to them, a specific provision for 
OF THE MUSCLES. NATURAL THEOLOGY. 
137 
the putting of this mechanism of the bones into ac- 
tion. And mark the consent of uses: the oblique 
muscles would have been inefficient without that par- 
ticular articulation; that particular articulation would 
have been lost without the oblique muscles. It may- 
be proper, however, to observe, without respect to 
the head, although I think it does not vary the case, 
that its oblique motions and inclinations are often 
motions in a diagonal produced by the joint action of 
muscles lying in straight directions. But whether the 
pull be single or combined, the articulation is always 
such as to be capable of obeying the action of the 
muscles. The oblique muscles attached to the head 
are likewise so disposed as to be capable of steady 
ing the globe as well as of moving it. The head of 
a newborn infant is often obliged to be filleted up. 
After death the head drops and rolls in every direc- 
tion. So that it is by the equilibre of the muscles, 
by the aid of a considerable and equipolent muscular 
force in constant exertion, that the head maintains 
its erect posture. The muscles here supply what 
would otherwise be a great defect in the articulation 
for the joint in the neck, although admirably adapted 
to the motion of the head, is insufficient for its sup- 
port. It is not only by the means of a most curious 
structure of the bones that a man turns his head, but 
by virtue of an adjusted muscular power that he even 
holds it up. 
As another example of what we are illustrating, 
viz., conformity of use between the bones and the 
muscles, it has been observed of the different verte- 
brae, that their processes are exactly proportioned to 
the quantity of motion which the other bones allow 
of, and which the respective muscles are capable of 
producing. 
II. A muscle acts only by contraction. Its force 
is exerted in no other way. When the exertion 
ceases, it relaxes itself; that is, it returns by relaxa- 
tion to its former state, but without energy.40 This 
40 Excellently well as this is put, there is something more admi- 
rable still in the condition of the muscular system. With respect 138 
NATURA.L THEOLOGY. 
is the nature of the muscular fibre ; and, being so, it 
is evident that the reciprocal energetic motion of the 
limbs, by which we mean motion with force in oppo- 
site directions, can only be produced by the instru- 
mentality of opposite or antagonist muscles ; of flex- 
ors and extensors answering to each other. For in- 
stance, the biceps and brachialis internus muscles, 
placed in the front part of the upper arm, by their 
contraction, bend the elbow, and with such degree 
of force as the case requires or the strength admits 
of. The relaxation of these muscles after the effort 
would merely let the forearm drop down. For the 
back stroke, therefore, and that, the arm may not only 
bend at the elbow, but also extend and straighten it- 
self with force, other muscles, the longus and brevis 
brachialis exlernus, and the anconseus, placed on the 
hinder part of the arms, by their contractile twitch, 
fetch back the forearm into a straight line with the 
cubit, with no less force than that with which it was 
bent out oT it. The same thing obtains in all the 
limbs, and in every moveable part of the body. A 
finger is not bent and straightened without the con- 
traction of two muscles taking place. It is evident, 
therefore, that the animal functions require that par- 
to the support of the head, as mentioned in the preceding page, 
and the instance embraces, of course, the erect position of the 
body as well as the equable poising of the head, the most extraor- 
dinary part of the phenomena is this, that we are sensible of the 
slightest inclination of the body or of any member, although it 
would be difficult to say to what order of acknowledged sensa- 
tions this belongs. Not only do we feel every degree of inclina- 
tion from the perpendicular in the poising of the body, but we act 
upon it with the most minute correspondence of the muscles. 
The muscles are antagonists certainly, but there is a fine combi- 
nation and adjustment in their action, which is not illustrated by 
the two sawyers dividing a log of wood. The muscle having fin- 
ished what we call its action or contraction, is not in the condition 
of a loose rope, but, on the contrary, there is always a perfect 
balance of action preserved between the extent of relaxation of 
the one class of muscles and the contraction of the other; and 
there is a tone in both by which the limb may be sustained, in any 
posture that is willed. This subject is treated in the Philosophical 
Transactions, and also in the Treatise on the Hand, under the 
head of the " Muscular Sense." NATURAL THEOLOGY. 
139 
ticular disposition of the muscles which we describe 
by the name of antagonist muscles. And they are 
accordingly so disposed. Every muscle is provided 
with an adversary. They act like two sawyers in a 
pit, by an opposite pull; and nothing, surely, can more 
strongly indicate design and attention to an end than 
their being thus stationed, than this collocation. The 
nature of the muscular fibre being what it is, the pur- 
poses of the animal could be answered by no other. 
And not only the capacity for motion, but the aspect 
and symmetry of the body is preserved by the mus- 
cles being marshalled according to this order: e. g., 
the mouth is holden in the middle of the face, and its 
angles kept in a state of exact correspondence, by 
two muscles drawing against and balancing each 
other. In a hemiplegia, when the muscle on one side 
is weakened, the muscle on the other side draws the 
mouth awry. 
III. Another property of the muscles, could 
only be the result of care, is their being almost uni- 
versally so disposed as not to obstruct or interfere 
with one another's action. I know but one instance 
in which this impediment is perceived. We cannot 
easily swallow while we gape. This, I understand, 
is owingto the muscles employed in the act of deglu- 
tition being so implicated with the muscles of the 
lower jaw, that, while these last are contracted, the 
former cannot act with freedom. The obstruction is, 
in this instance, attended with little inconvenience ; 
but it shows what the effect is where it does exist; 
and what loss of faculty there would be if it were 
more frequent. Now, when we reflect upon the num- 
ber of muscles, not fewer than four hundred and 
forty-six, in the human body, known and named,* 
how contiguous they lie to each other, in layers, as it 
were, over one another, crossing one another, some- 
times imbedded in one another, sometimes perfora- 
ting one another; an arrangement which leaves to 
* Keill's Anatomy, p. 295, ed. 3. More modern anatomists de- 
scribe five hundred and twenty-seven muscles.-Am. Ed. 140 
NATUItAL THEOLOGY. 
each its liberty and its full play, must necessarily re- 
quire meditation and counsel. 
IV. The following is oftentimes the case with the 
muscles. Their action is wanted where their situa- 
tion would be inconvenient. In which case the body 
of the muscle is placed in some commodious position 
at a distance, and made to communicate with the 
point of action by slender strings or wires. If the 
muscles which move the fingers had been placed in 
the palm or back of the hand, they would have 
swelled that part of the hand to an awkward and 
clumsy thickness. The beauty, the proportions of 
the part, would have been destroyed. They are 
therefore disposed in the arm, and even up to the el- 
bow', and act by long tendons strapped down at the 
wrist, and passing under the ligaments to the fingers, 
and to the joints of the fingers which they are sev- 
erally to move. In like manner, the muscles which 
move the toes and many of the joints of the foot, 
how gracefully are they disposed in the calf of the 
leg, instead of forming an unwieldy tumefaction in 
the foot itself! The observation may be repeated of 
the muscle which draws the nictitating membrane 
over the eye. Its office is in the front of the eye; 
Dut its body is lodged in the back part of the globe, 
where it lies safe, and where it encumbers nothing.* 
V. The .great mechanical variety in the figure of 
the muscles may be thus stated. It appears to be a 
fixed law, that the contraction of a muscle shall be 
towards its centre. Therefore, the subject for mech- 
* The convenience and beauty of the tendons seem only an 
ulterior object; their necessity and utility principally claim our at- 
tention. The force which a muscle possesses is as the number 
of the muscular fibres ; but a limited number of fibres only can be 
fixed to any certain point of a bone destined to be moved, there- 
fore the contrivapce is to attach them to a cord, called a sinew 
or tendon, which can be conveniently conducted and fixed to the 
bone. If we are desirous of moving a heavy weight, vve tie a 
•strong cord to it, that a greater number of men may apply their 
strength. Thus a similar effect is produced; the muscular fibres 
are the moving powers, the tendons are the cords attached to the 
point to be moved.-Paxton. NATURAL THEOLOGY. 
141 
anism on each occasion is so to modify the figure 
and adjust the position of the muscle as to produce 
the motion required agreeably with this law. This 
can only be done by giving to different muscles a di- 
versity of configuration suited to their several offices, 
and to their situation with respect to the work which 
they have to perform. On which account we find 
them under a multiplicity of forms and attitudes ; 
sometimes with double, sometimess with treble ten- 
dons, sometimes with none: sometimes one tendon 
to several muscles, at other times one muscle to 
several tendons. The shape of the organ is suscep- 
tible of an incalculable variety, while the original 
property of the muscle, the law and line of its con- 
traction, remains the same, and is simple. Herein 
the muscular system may be said to bear a perfect 
resemblance to our works of art. An artist does not 
alter the native quality of his materials or their laws 
of action. He takes these as he finds them. His 
skill and ingenuity are employed in turning them, 
such as they are, to his account, by giving to the 
parts of his machine a form and relation in which 
these unalterable properties may operate to the pro- 
duction of the effects intended.41 
41 In the figure of a muscle, given ip page 100, it maybe observ- 
ed that the tendons are on different sides of the muscle. 
If we were to apply their arrangement, it would be thus: A is 
the tendinous origin, and B the tendinous insertion ; and the 
muscular fibres run obliquely between them. This obliquity of 
the fibres is almost universal in the muscles of the limb, and the 
effect is very important. It needs no reference to mechanics to 
understand, that if we pull obliquely upon a weight we sacrifice 
a great deal of power. For what advantage, then, is power re- 
signed in the muscle'! " If you wish to draw a thing towards 
any place with the least force, you must pull directly in the line 142 
NATURAL THEOLOGY. 
VI. The ejaculations can never be too often re- 
peated, How many things must go right for us to be 
an hour at ease ! how many more for us to be vigor- 
ous and active ! Yet vigour and activity are, in a 
vast plurality of instances, preserved in human bod- 
ies, notwithstanding that they depend upon so great 
a number of instruments of motion, and notwithstand- 
between the thing and the place; if you wish to draw it as 
quickly as possible, and do not regard the loss of force, you must 
pull it obliquely, by drawing it in two directions at once. Tie a 
string to a stone, A, and draw it straight towards you at C with 
one hand ; then make a loop on another string, and, running the 
first through it, draw one string in each hand at B B, not towards 
you, in the line A C, but sideways, till both strings are stretched 
in a straight line : you will see how much swifter the stone 
moves than it did before when pulled straightforward. Now this 
is proved by mathematical reasoning to be the necessary conse- 
quence of forces applied obliquely ; there is a loss of power, but a 
great increase of velocity. The velocity is the thing required to 
be gained."* 
By the liberal employment of muscular power, quickness and 
variety of motion are obtained, and with the advantages which 
are so well described in the succeeding part of this chapter. 
* Preliminary treatise on the objects, advantages, and pleasures 
of science. (Library of Useful Knowledge.) NATURAL THEOLOGY. 
143 
ing that the defect or disorder sometimes of a very 
small instrument, of a single pair, for instance, out of 
the four hundred and forty-six muscles which are 
employed, may be attended with grievous inconve- 
nience. There is piety and good sense in the follow- 
ing observation, taken out of the " Religious Philoso- 
pher." "With much compassion," says this writer, 
" as well as astonishment at the goodness of our 
loving Creator, have I considered the state of a cer- 
tain gentleman, who, as to the rest, was in pretty 
good health, but only wanted the use of these two lit- 
tle muscles that serve to lift up the eyelids, and so had 
almost lost the use of his sight, being forced, as long 
as this defect lasted, to shove up his eyelids every 
moment with his own hands !" In general we may 
remark in how small a degree those who enjoy the- 
perfect use of their organs know the comprehensive- 
ness of the blessing, the variety of their obligation. 
They perceive a result, but they think little of the 
multitude of concurrences and rectitudes which go to- 
form it. 
Besides these observations, which belong to the 
muscular organ as such, we may notice some advan- 
tages of structure which are more conspicuous in 
muscles of a certain class or description than in oth- 
ers. Thus : 
I. The variety, quickness, and precision of which 
muscular motion is capable, are seen, I think, in no 
part so remarkably as in the tongue. It is worth any 
man's while to watch the agility of his tongue, the 
wonderful promptitude with which it executes changes 
of position, and the perfect exactness. Each sylla- 
ble of articulated sound requires for its utterance a 
specific action of the tongue and of the parts adja- 
cent to it. The disposition and configuration of the 
mouth appertaining to every letter and word is not 
only peculiar, but, if nicely and accurately attended 
to, perceptible to the sight; insomuch that curious 
persons have availed themselves of this circumstance 
to teach the deaf to speak, and to understand what is 
said by others. In the same person, and after his 144 
habit of speaking is formed, one, and only one, posi- 
tion of the parts will produce a given articulate sound 
correctly. How instantaneously are these positions 
assumed and dismissed! how numerous are the per- 
mutations, how various, yet how infallible! Arbi- 
trary and antic variety is not the thing we admire; 
but variety obeying a rule, conducing to an effect, and 
commensurate with exigencies infinitely diversified. 
I believe also that the anatomy of the tongue corre- 
sponds with these observations upon its activity. 
The muscles of the tongue are so numerous, and so 
implicated with one another, that they cannot be 
traced by the nicest dissection ; nevertheless (which 
is a greater perfection of the organ), neither the 
number, nor the complexity, nor what might seem to 
be the entanglement of its fibres, in anywise impede 
its motion, or render the determination or success of 
its efforts uncertain. 
I here entreat the reader's permission to step a 
little out of my way, to consider the parts of the mouth 
in some of their other properties. It has been said, 
and that by an eminent physiologist, that, whenever 
nature attempts to work two or more purposes by 
one instrument, she does both or all imperfectly. Is 
this true of the tongue, regarded as an instrument of 
speech and of taste, or regarded as an instrument of 
speech, of taste, and of deglutition 1 So much other- 
wise, that many persons, that is to say, nine hundred 
and ninety-nine persons out of a thousand, by the in- 
strumentality of this organ, talk, and taste, and swal- 
low very well. In fact, the constant warmth and 
moisture of the tongue, the thinness of the skin, the 
papillte upon its surface, qualify this organ for its of 
flee of tasting, as much as its inextricable multiplicity 
of fibres do for the rapid movements which are ne- 
cessary to speech. Animals which feed upon grass 
have their tongues covered with a perforated skin, so 
as to admit the dissolved food to the papillae* under- 
NATURAL THEOLOGY. 
* Papillae are small bodies situated on the surface and sides ol 
the tongue ; they are furnished by the extreme filaments of the 
gustatory nerve, through which medium we acquire the sense ol 
tasting. NATURAL THEOLOGY. 
145 
neath, which, in the mean time, remain defended 
from the rough action of the unbruised spiculae. 
There are brought together within the cavity of 
the mouth more distinct uses, and parts executing 
more distinct offices, than I think can be found lying 
so near to one another, or within the same compass, 
in any other portion of the body: viz., teeth of differ- 
ent shape, first for cutting, secondly for grinding; 
muscles, most artificially disposed for carrying on 
the compound motion of the lower jaw, half lateral 
and half vertical, by which the mill is worked : foun- 
tains of saliva, springing up in different parts of the 
cavity for the moistening of the food, while the mas- 
tication is going on: glands to feed the fountains; a 
muscular constriction of a very peculiar kind in the 
back part of the cavity, for the guiding of the pre- 
pared aliment into its passage towards the stomach, 
and, in many cases, for carrying it along that passage; 
for, although we may imagine this to be done simply 
by the weight of the food itself, it in truth is not so, 
even in the upright posture of the human neck; and 
most evidently is not the case with quadrupeds; with 
a horse, for instance, in which, when pasturing, the 
food is thrust upward by muscular strength instead of 
descending of its own accord. 
In the mean time, and within the same cavity, is 
going on another business, although different from 
what is here described, that of respiration and speech. 
In addition, therefore, to all that has been mentioned, 
we have a passage ppened from this cavity to the 
lungs, for the admission of air exclusively of every 
other substance: we have muscles, some in the 
larynx, and without number in the tongue, for the 
purpose of modulating that air in its passage, with a 
variety, a compass, and precision of which no other 
musical instrument is capable. And, lastly, which, in 
my opinion, crowns the whole as a piece of machine- 
ry, we have a specific contrivance for dividing the 
pneumatic part from the mechanical, and for pre- 
venting one set of actions interfering with the other. 
Where various functions are united, the difficulty is 
Vox,. L-N 146 
NATURAL THEOLOGY. 
to guard against the inconveniences of a too great 
complexity. In no apparatus put together by art and 
for the purposes of art, do I know such multifarious 
uses so aptly combined, as in the natural organiza- 
tion of the human mouth; or where the structure, 
compared with the uses, is so simple. The mouth, 
with all these intentions to serve, is a single cavity; 
is one machine; with its parts neither crowded nor 
confused, and each unembarrassed by the rest: each 
at least at liberty in a degree sufficient for the end to 
be attained. If we cannot eat and sing at the same 
moment, we can eat one moment and sing the next: 
the respiration proceeding freely all the while. 
There is one case, however, of this double office, 
and that of the earliest necessity, which the mouth 
alone could not perform; and that is, carrying on to- 
gether the two actions of sucking and breathing. An- 
other route, therefore, is opened for the air-namely, 
through the nose-which lets the breath pass back- 
ward and forward, while the lips, in the act of suck- 
ing, are necessarily shut close upon the body from 
which the nutriment is drawn. This is a circum- 
stance which always appeared to me worthy of no- 
tice. The nose would have been necessary, although 
it had not been the organ of smelling. The making 
it the seat of a sense was superadding a new use to 
a part already wanted ; was taking a wise advantage 
of an antecedent and a constitutional necessity.42 
42 When our author describes the variety of functions perform- 
ed by the mouth and tongue, he is in admiration at the simplicity 
of the instrument. But this is only an apparent simplicity : the 
complexity of structure is concealed. Indeed, it has been this 
•very consideration which led to the new investigations into the 
nervous system. Without entering far into this subject, we take 
the tongue in illustration. It is a fine organ of touch : it is the 
seat of the sense of taste: it is necessary to deglutition : itsmod- 
ulations'are infinite in speech ; but the reason of a body so simple 
in its outward form being capable of performing offices apparently 
so discordant, is visible only to the anatomist, who traces the nerves 
into this organ. Then he discovers, besides the nerve proceeding 
from the papillae of the tongue to the sensorium, that there are 
nerves of volition governing the muscles of the tongue. In addi- 
tion to these, there is a nerve which regulates the action of swal- NATURAL THEOLOGY. 
147 
But to return to that which is the proper subject of 
the present section : the celerity and precision of mus- 
cular motion. These qualities may be particularly 
observed in the execution of many species of instru- 
mental music, in which the changes produced by the 
hand of the musician are exceedingly rapid ; are ex- 
actly measured, even when most minute ; and display, 
on the part of the muscles, an obedience of action 
alike wonderful for its quickness and its correctness. 
Or, let a person only observe his own hand while he 
is writing; the number of muscles which are brought 
to bear upon the pen; how the joint and adjusted 
operation of several tendons is concerned in every 
stroke, yet that five hundred such strokes are drawn 
in a minute. Not a letter can be turned without more 
than one, or two, or three tendinous contractions, def- 
inite both as to the choice of the tendon and as to 
the space through which the contraction moves; yet 
how currently does the work proceed ! and, when we 
look at it, how faithful have the muscles been to their 
duty; how true to the order which endeavour or habit 
hath inculcated! For, let it be remembered, that 
while a man's handwriting is the same, an exacti- 
tude of order is preserved whether he write well or 
ill. These two instances of music and writing show 
not only the quickness and precision of muscular ac 
tion, but the docility. 
II. Regarding the particular configuration of mus- 
cles, sphincter or circular muscles appear to be admi- 
rable pieces of mechanism. It is the muscular power 
lowing, and which combines the motions of the gullet with those 
of the tongue; and in the same manner another nerve, tending to 
the organ of voice in the larynx, branches off to the tongue, and 
associates it with the organ of the voice, so as to produce articu- 
late language : these nervous chords are the true organization by 
which one member, simple in its exterior form, has a complexity 
in its internal relations. And thus it is, that in many instances or- 
gans which are apparently simple, and through which we perform 
many offices so easily that we think not at all of what is necessa- 
ry to their execution, have yet internally, and to the eye of the 
anatomist, a thousand minute circumstances or relations on which 
the perfection of their action depends. 148 
NATURAL THEOLOGY. 
most happily applied; the same quality of the mus- 
cular substance, but under a new modification. The 
circular disposition of the fibres is strictly mechani- 
cal ; but, though the most mechanical, is not the only 
thing in sphincters which deserves our notice. The 
regulated degree of contractile force with which they 
are endowed, sufficient for retention, yet vincible when 
requisite, together with their ordinary state of actual 
contraction, by means of which their dependance upon 
the will is not constant but occasional, gives to them 
a constitution of which the convenience is inestima- 
ble. This their semi-voluntary character is exactly 
such as suits with the wants and functions of the an- 
imal. 
III. We may also, upon the subject of muscles, ob- 
serve, that many of our most important actions are 
achieved by the combined help of different muscles. 
Frequently, a diagonal motion is produced by the con- 
traction of tendons pulling in the direction of the sides 
of the parallelogram. This is the case, as hath been 
already noticed, with some of the oblique nutations 
of the head. Sometimes the number of co-operating 
muscles is very great. Dr. Nieuentyt, in the Leipsic 
Transactions, reckons up a hundred muscles that are 
employed every time we breathe; yet we take in or 
let out our breath, without reflecting what a work is 
thereby performed; what an apparatus is laid in of 
instruments for the service, and how many such con- 
tribute their assistance to the effect. Breathing with 
ease is a blessing of every moment; yet, of all others, 
it is that which we possess with the least conscious- 
ness. A man in an asthma is the only man who 
knows how to estimate it. 
IV. Mr. Home has observed,* that the most impor- 
tant and the most delicate actions are performed in 
the body by the smallest muscles; and he mentions, 
as his examples, the muscles which have been dis- 
covered in the iris of the eye and the drum of the ear. 
The tenuity of these muscles is astonishing: they 
• Phil Trans., part i., 1800, p. 8. NATURAL THEOLOGY. 
149 
are microscopic hairs ; must be magnified to be vis- 
ible ; yet are they real effective muscles : and not 
only such, but the grandest and most precious of our 
faculties, sight and hearing, depend upon their health 
and action. 
[The figure here represents the action of the biceps muscle 
which lies on the arm, and is inserted upon the radius of the fore 
arm in sustaining a weight in the hand.] 
V. The muscles act in the limbs with what is call- 
ed a mechanical disadvantage. The muscle at the 
shoulder, by which the arm is raised, is fixed nearly 
in the same manner as the load is fixed upon a steel- 
yard, w'ithin a few decimals, we will say, of an inch 
from the centre upon which the steelyard turns. In 
this situation we find that a very heavy draught is no 
more than sufficient to countervail the force of a small 
lead plummet, placed upon the long arm of the steel- 
yard, at the distance of, perhaps, fifteen or twenty 
inches from the centre, and on the other side of it. 
And this is the disadvantage which is meant; and an 
absolute disadvantage, no doubt, it would be, if the ob- 
ject were to spare the force of muscular contraction. 
But observe how conducive is this constitution to ani- 
mal convenience. Mechanism has always in view 
one or other of these two purposes, either to move a 
great weight slowly and through a small space, or to 
move a light weight rapidly through a considerable 
sweep. For the former of these purposes, a different 
species of lever and a different collocation of the mua« 150 
cles might be better than the present; but for the sec- 
ond, the present structure is the true one. Now so 
it happens that the second, and not the first, is that 
which the occasions of animal life principally call for. 
In what concerns the human body, it is of much more 
consequence to any man to be able to carry his hand 
to his head with due expedition, than it would be to 
have the power of raising from the ground a heavier 
load (of two or three more hundred weight, we will 
suppose) than he can lift at present. 
This last is a faculty which, on some extraordinary 
.occasions, he may desire to possess ; but the other is 
what he wants and uses every hour or minute. In 
like manner, a husbandman or a gardener will do 
more execution, by being able to carry his scythe, 
his rake, or his flail, with a sufficient despatch through 
a sufficient space, than if, with greater strength, his 
motions were proportionably more confined and slow. 
It is the same with a mechanic in the use of his tools. 
It is the same, also, with other animals in the use of 
their limbs. In general, the vivacity of their motions 
would be ill-exchanged for greater force under a clum- 
sier structure. 
We have offered our observations upon the struc- 
ture of muscles in general; we have also noticed cer- 
tain species of muscles; but there are also single mus- 
cles which bear marks of mechanical contrivance ap- 
propriate as well as particular. Out of many instan- 
ces of this kind we select the following : 
I. Of muscular actions, even of those which are 
■well understood, some of the most curious are inca- 
pable of popular explanation ; at least without the aid 
of plates and figures. This is in a great measure the 
case with a very familiar, but, at the same time, a 
very complicated motion, that of the lower jaw: and 
with the muscular structure by which it is produced. 
One of the muscles concerned may, however, be de- 
scribed in such a manner as to be, 1 think, sufficiently 
comprehended for our present purpose. The problem 
is to pull the lower jaw down. The obvious method 
should seem to be to place a straight muscle, viz., to 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
151 
fix a string from the chin to the breast, the contrac- 
tion of which would open the mouth, and produce the 
motion required at once. But it is evident that the 
form and liberty of the neck forbid a muscle being 
laid in such a position; and that, consistently with 
the preservation of this form, the motion which we 
want must be effectuated by some muscular ihechan- 
ism disposed farther back in the jaw. The mechan- 
ism adopted is as follows: A certain muscle, called 
the digastric, rises on the side of the face, consider- 
ably above the insertion of the lower jaw, and comes 
down, being converted in its progress into a round 
tendon. Now it is manifest that the tendon, while it 
pursues a direction descending towards the jaw, must, 
by its contraction, pull the jaw up instead of down. 
What, then, was to be done 1 This, we find, is done : 
The descending tendon, when it is got low enough, is 
passed through a loop, or ring, or pulley, in the os hy- 
oides, and then made to ascend; and, having thus 
changed its line of direction, is inserted into the inner 
part of the chin: by which device, viz., the turn at 
the loop, the action of the muscle (which in all mus- 
cles is contraction), what before would have pulled the 
jaw up, now as necessarily draws it down. " The 
mouth," says Heister, " is opened by means of this 
trochlea in a most wonderful and elegant manner." 
II. What contrivance can be more mechanical than 
the following, viz., a slit in one tendon to let another 
tendon pass through it? This structure is found in 
the tendons which move the toes and fingers. The 
long tendon, as it is called, in the foot, which bends 
the first joint of the toe, passes through the short 
tendon which bends the second joint, which-course 
allows to the sinew more liberty, and a more com- 
modious action than it would otherwise have been 
capable of exerting.* There is nothing, I believe, in 
a silk or cotton mill, in the belts, or straps, or ropes, 
by which motion is communicated from one part of 
the machine to another, that is more artificial, or 
more evidently so, than this perforation. 
* Ches. Anat., p. 119. III. The next circumstance which I shall mention 
under this head of muscular arrangement is so decis- 
ive a mark of intention, that it always appeared to 
me to supersede, in some measure, the necessity of 
seeking for any other observation upon the subject; 
and that circumstance is, the tendons which pass 
from the leg to the foot being bound down by a lig- 
ament to the ankle. The foot is placed at a consid- 
erable angle with the leg. It is manifest, therefore, 
that flexible strings, passing along the interior of the 
angle, if left to themselves, would, when stretched, 
start from it. The obvious preventive is to tie them 
down. And this is done, in fact. Across the instep, 
or, rather, just above it, the anatomist finds a strong 
ligament, under which the tendons pass to the foot. 
The effect of the ligament as a bandage can be made 
evident to the senses; for, if it be cut, the tendons 
start up. The simplicity, yet the clearness of this 
contrivance, its exact resemblance to established re- 
sources of art, place it among the most indubitable 
manifestations of design with which we are acquaint- 
ed. 
There is also a farther use to be made of the pres- 
ent example, and that is, as it precisely contradicts 
the opinion that the parts of animals may have been 
all formed by what is called appetency, i. e., endeav- 
our perpetuated and imperceptibly working its effect 
through an incalculable series of generations. We 
have here no endeavour, but the reverse of it; a con- 
stant renitency and reluctance. The endeavour is 
all the other way. The pressure of the ligament 
constrains the tendons ; the tendons react upon the 
pressure of the ligament. It is impossible that the 
ligament should ever have been generated by the ex- 
ercise of the tendon, or in the course of that exer- 
cise, forasmuch as the force of the tendon perpen- 
dicularly resists the fibre which confines it, and is 
constantly endeavouring not to form, but to rupture 
and displace, the threads of which the ligament is 
composed. 
152 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
153 
Keill has reckoned up in the human body four 
hundred and forty-six muscles, dissectible and de- 
scribable ; and hath assigned a use to every one of 
the number. This cannot be all imagination. 
Bishop Wilkins hath observed from Galen, that 
there are at least ten several qualifications to be at- 
tended to in each particular muscle; viz., its proper 
figure ; its just magnitude; its fulcrum ; its point of 
action, supposing the figure to be fixed; its colloca- 
tion with respect to its two ends, the upper and the 
lower ; the place ; the position of the whole muscle ; 
the introduction into it of nerves, arteries, veins. 
How are things including so many adjustments to be 
made I or, when made, how are they to be put to- 
gether, without intelligence 1 
I have sometimes wondered why we are not struck 
with mechanism in animal bodies as readily and as 
strongly as we are struck with it, at first sight, in a 
watch or a mill. One reason of the difference may 
be, that animal bodies are, in a great measure, made 
up of soft flabby substances, such as muscles and 
membranes; whereas we have been accustomed to 
trace mechanism in sharp lines, in the configuration 
of hard materials, in the moulding, chiselling, and 
filing into shapes of such articles as metals or wood. 
There is something, therefore, of habit in the case ; 
but it is sufficiently evident that there can be no 
proper reason for any distinction of the sort. Mech- 
anism may be displayed in the one kind of substance 
as well as in the other. 
Although the few instances we have selected, even 
as they stand in our description, are nothing short, 
perhaps, of logical proofs of design, yet it must not 
be forgotten that, in every part of anatomy, descrip- 
tion is a poor substitute for inspection. It is well 
said by an able anatomist,* and said in reference to 
the very part of the subject which we have been 
treating of: " Imperfecta haec musculorum descrip 
* Steno, in Blas. Anat. Animal, p. 2, c. 4. 154 
tio non minus arida est legentibus quam inspectanti- 
bus fuerit jucunda eorundem praparatio. Elegantis- 
sima enim mechanic's artificia, creber rime in illis 
obvia, verbis nonnisi obscure exprimuntur: carnium 
autem ductu, tendinum, colore, insertionum propor- 
tione, et trochlearium, distributione, oculis exposita, 
omnem superant admirationem." 
NATURAL THEOLOGY. 
CHAPTER X. 
OF THE VESSELS OF ANIMAL BODIES 
The circulation of the Hood through the bodies of 
men and quadrupeds, and the apparatus by which it 
is carried on, compose a system, and testify a con- 
trivance, perhaps the best understood of any part of 
the animal frame. The lymphatic system, or the 
nervous system, may be more subtle and intricate; 
nay, it is possible that in their structure they may 
be even more artificial than the sanguiferous, but we 
do not know so much about them. 
The utility of the circulation of the blood I assume 
as an acknowledged point. One grand purpose is 
plainly answered by it, the distributing to every part, 
every extremity, every nook and corner of the body, 
the nourishment which is received into it by one 
aperture. What enters at the mouth finds its way to 
the fingers' ends. A more difficult mechanical prob- 
lem could hardly, I think, be proposed, than to dis- 
cover a method of constantly repairing the waste, 
and of supplying an accession of substance to every 
part of a complicated machine at the same time. 
This system presents itself under two views : first, 
the disposition of the bloodvessels, i. e., the laying 
of the pipes ; and, secondly, the construction of the 
engine at the centre, viz., the heart, for driving the 
blood through them. NATURAL THEOLOGY. 
155 
[This figure represents the heart and great bloodvessels, and 
may convey some idea of the circulation of the blood. We un- 
derstand A to be the great vein returning the blood from the 
body; B the right sinus or auricle. From this cavity of the heart 
the blood is carried into C, the ventricle; and from this ventricle 
the pulmonary artery goes off. This great artery of the lungs is 
for the conveyance of the blood which is returned from the body 
into the lungs. Now the great vein A, the auricle B, the ventri- 
cle C, and the pulmonary artery D D, belong to the right side of 
the heart; or, to take a more important distinction, they convey 
dark-coloured blood, which is unfit for the uses of the system. 
But, when the blood reaches the lungs, and is exposed to the at- 
mosphere we breathe, it throws off the carbon, becomes bright 
in colour, and is called arterial blood. It returns to the heart, 
not to the cavities which we have enumerated, but by the veins 
of the lungs to the other side of the heart, the left; that is, to 156 
another auricle and another ventricle. From this left ventricle 
there ascends the aorta, the great artery of the body, E E. This 
great vessel conveys the blood to every part that has life. From 
all parts of the body the blood is gathered again by the extremi- 
ties of the veins, and so returns to the point of the auricle from 
which we began to trace it. This short nreface may make the 
observations of the author easily intelligible.] 
NATURAL THEOLOGY. 
I. The disposition of the bloodvessels, as far as 
regards the supply of the body, is like that of the 
water-pipes in a city, viz., large and main trunks 
branching off by smaller pipes (and these again by 
still narrower tubes) in every direction, and towards 
every part in which the fluid which they convey can 
be wanted.43 So far the water-pipes which serve a 
town may represent the vessels which carry the 
blood from the heart. But there is another thing 
necessary to the blood, which is not wanted for the 
water; and that is, the carrying of it back again to 
its source. For this office a reversed system of ves- 
sels is prepared, which, uniting at their extremities 
with the extremities of the first system, collects the 
divided and subdivided streamlets by, first, capillary 
ramifications into larger branches ; secondly, by these 
branches into trunks ; and thus returns the blood (al- 
most exactly inverting the order in which it went 
out) to the fountain whence its motion proceeded. 
All which is evident mechanism. 
The body, therefore, contains two systems of 
bloodvessels, arteries and veins. Between the con- 
stitution of the systems there are also two differen- 
ces, suited to the functions which the systems have 
to execute. The blood, in going out, passing always 
from wider into narrower tubes, and, in coming back, 
from narrower into wider, it is evident that the im- 
pulse and pressure upon the sides of the bloodvessel 
43 It should be observed, that when an artery divides into two 
or more branches, their united areas are greater than the area of 
the main artery. Thus it should be on hydrostatic principles. 
When a tube for conveying fluids is divided, the friction is in- 
creased ; and an engineer, to meet this difficulty, has to enlarge 
the branches, as we rind them enlarged in the circulating system. 
-Am. Ed. NATURAL THEOLOGY, 
157 
will be much greater in one case than the other. 
Accordingly, the arteries which carry out the blood 
are formed of much tougher and stronger coats than 
the veins which bring it back. That is one differ- 
ence : the other is still more artificial, or, if I may 
so speak, indicates still more clearly the care and 
anxiety of the artificer. Forasmuch as, in the ar- 
teries, by reason of the greater force with which the 
blood is urged along them, a wound or rupture would 
be more dangerous than in the veins, these vessels 
are defended from injury, not only by their texture, 
but by their situation, and by every advantage of sit- 
uation which can be given to them. They are buried 
sinuses, or they creep along grooves made for them 
in the bones; for instance, the under edge of the 
ribs is sloped and furrowed solely for the passage of 
these vessels. Sometimes they proceed in channels, 
protected by stout parapets on each side, which last 
description is remarkable in the bones of the fingers, 
these being hollowed out, on the under side, like a 
scoop, and with such a concavity that the finger may 
be cut across to the bone without hurting the artery 
which runs along it. At other times, the arteries 
pass in canals wrought in the substance, and in the 
very middle of the substance, of the bone. This 
takes place in the lower jaw, and is found where 
there would otherwise be danger of compression by 
sudden curvature. All this care is wonderful, yet 
not more than what the importance of the case re- 
quired. To those who venture their lives in a ship, 
it has been often said that there is only an inchboard 
between them and death; but in the body itself, es- 
pecially in the arterial system, there is, in many 
parts, only a membrane, a skin, a thread. For which 
reason, this system lies deep under the integuments ; 
whereas the veins, in which the mischief that ensues 
from injuring the coats is much less, lie in general 
above the arteries, come nearer to the surface, are 
more exposed. 
It may be farther observed, concerning the two 
systems taken together, that though the arterial, with 
Vol. L-O 158 
NATURAL THEOLOGY. 
its trunk, and branches, and small twigs, may be im- 
agined to issue or proceed, in other words, to grow 
from the heart like a plant from its root, or the fibres 
of a leaf from its footstalk (which, however, were 
it so, would be only to resolve one mechanism into 
another), yet the venal, the returning system, can 
never be formed in this manner. The arteriefe might 
go on shooting out from their extremities, i. e., length- 
ening and subdividing indefinitely; but an inverted 
system, continually uniting its streams, instead of 
dividing, and thus carrying back what the other sys- 
tem carried out, could not be referred to the same 
process.44 
11. The next thing to be considered is the engine 
which works this machinery, viz., the heart. For 
our purpose it is unnecessary to ascertain the prin- 
ciple upon which the heart acts. Whether it be irri- 
tation excited by the contact of the blood, by the in- 
flux of the nervous fluid, or whatever else be the 
cause of its motion, it is something which is capable 
of producing, in a living muscular fibre, reciprocal 
contraction and relaxation. This is the power we 
have to work with; and the inquiry is, how this pow- 
er is applied in the instance before us. There is 
provided, in the central part of the body, a hollow 
muscle, invested with spiral fibres, running in both 
directions, the layers intersecting one another; in 
some animals, however, appearing to be semicircu- 
lar rather than spiral. By the contraction of these 
fibres, the sides of the muscular cavities are necessa- 
44 It is also to be observed, that the veins are not only conduits 
for conveying, but also reservoirs for holding supplies of blood 
against the time it is needed. Being so placed that they are lia- 
ble to be pressed by the action of the muscles, the consequence 
is, that, while we are at rest, the blood moves on slowly ; " but, 
when we are roused into action, it is pressed onward, the dimen- 
sions of the reservoirs are diminished, and the blood is accumu- 
lated upon the more active heart, and is ready to answer the de- 
mands of the system which that very activity requires. The sen- 
sations at the heart exciting the respiration, the chest is expanded 
and the veins enlarged ; and by the alternate suction and compres- 
sion of the greater veins, the heart is liberally supplied."-Am. Ed. NATURAL THEOLOGY. 
159 
rily squeezed together, so as to force out from them 
any fluid which they may at that time contain: by 
the relaxation of the same fibres, the cavities are in 
their turn dilated, and, of course, prepared to admit 
every fluid which may be poured into them. Into 
these cavities are inserted the great trunks, both of 
the arteries which carry out the blood, and of the 
veins which bring it back. This is a general account 
of the apparatus ; and the simplest idea of its action 
is, that by each contraction a portion of blood is 
forced by a syringe into the arteries, and at each dil- 
atation an equal portion is received from the veins 
Tnis produces, at each pulse, a motion and change 
in the mass of blood to the amount of what the cav- 
ity contains, which, in a full-grown human heart, I 
understand is about an ounce, or two tablespoon- 
fuls. How quickly these changes succeed one an- 
other, and, by this succession, how sufficient they are 
to support a stream or circulation throughout the 
system, may be understood by the following compu- 
tation, abridged from Keill's Anatomy, p. 117, ed. 3 : 
" Each ventricle will, at least, contain one ounce of 
blood. The heart contracts four thousand times in 
one hour; from which it follows, that there pass 
through the heart every hour four thousand ounces, 
or three hundred and fifty pounds of blood. Now 
the whole mass of blood is said to be about twrenty- 
five pounds : so that a quantity of blood equal to the 
whole mass of blood passes through the heart four- 
teen times in one hour, which is about once in every 
four minutes."45 
45 The action of the heart is insufficient of itself to keep up a 
continual flow of blood through the body, and a vast deal of power 
would be lost between its pulsations by the fluids returning par- 
tially to a state of rest, and requiring a new force to impel it. But 
this is obviated by means of the elasticity of the coats of the ar- 
teries, through which an uninterrupted stream is kept up, and no 
power is lost. It is analogous to the use which is made of the 
elasticity of the air in fire-engines ; the air being confined above 
the water, and compressed as it rises, at length drives it out in a 
continuous stream, though the forcing pumps of the engine, act 
alternately.-rim. Ed. 160 
NATURAL THEOLOGY. 
Consider what an affair this is when we come to 
very large animals. The aorta of a whale is larger 
in the bore than the main pipe of the water-works at 
London Bridge ; and the water, roaring in its passage 
through that pipe, is inferior, in impetus and velocity, 
to the blood gushing from the whale's heart. Hear 
Dr. Hunter's account of the dissection of a whale : 
" The aorta measured a foot diameter. Ten or fif- 
teen gallons of blood are thrown out of the heart at 
a stroke, with an immense velocity, through a tube 
of a foot diameter. The whole idea fills the mind 
with wonder."* 
The account which we have here stated of the in- 
jection of blood into the arteries by the contraction, 
and of the corresponding reception of it from the 
veins by the dilatation, of the cavaties of the heart, 
and of -the" circulation being thereby maintained 
through the bloodvessels of the body, is true, but 
imperfect. The heart performs this office, but it is 
in conjunction with another of equal curiosity and 
importance. Tt was necessary that the blood should 
be successively brought into contact, or contiguity, or 
proximity with the air. I do not know that the chym- 
ical reason upon which this necessity is founded has 
been yet sufficiently explored. It seems to be made 
appear, that the atmosphere which we breathe is 
a mixture of two kinds of air, one pure and vital, the 
other, for the purposes of life, effete, foul, and nox- 
ious ;46 that, when we have drawn in our breath, the 
blood in the lungs imbibes from the air thus brought 
into contiguity with it a portion of its pure ingredi- 
ent, and, at the same time, gives out the effete or cor- 
rupt air which it contained, and w'hich is carried 
away, along with the halitus, every time we expire. 
At least, by comparing the air which is breathed 
from the lungs with the air which enters the lungs, 
* Dr. Hunter's account of the dissection of a whale.-(Phil. 
Trans.) 
46 The atmosphere contains, in every 100 parts, of oxygen 21 
parts, nitrogen or azote 79 parts, carbonic acid gas a fractional 
part. NATURAL THEOLOGY. 
161 
it is found to have lost some of its pure part, and to 
have brought away with it an addition of its impure 
part. Whether these experiments satisfy the ques- 
tion as to the need which the blood stands in of being 
visited by continual accesses of air, is not for us to 
inquire into, nor material to our argument: it is suf- 
ficient to know that, in the constitution of most ani- 
mals, such a necessity exists, and that the air, by 
some means or other, must be introduced into a near 
communication with the blood.47 The lungs of ani- 
mals are constructed for this purpose. They con- 
sist of bloodvessels and airvessels lying close to 
each other; and, whenever there is a branch of the 
trachea or windpipe, there is a branch accompanying 
it of the vein and artery, and the airvessel is always 
in the middle between the bloodvessels.* The in- 
ternal surface of these vessels, upon which the appli- 
cation of the air to the blood depends, would, if col- 
lected and expanded, be, in a man, equal to a super- 
ficies of fifteen feet square. Now, in order to give 
the blood in its course the benefit of this organiza- 
tion (and this is the part of the subject with which 
we are chiefly concerned), the following operation 
takes place. As soon as the blood is received by the 
heart from the veins of the body, and before that is 
sent out again into its arteries, it is carried, by the 
force of the contraction of the heart and by means 
47 The most simple view, and the best supported, is this: 
that the dark venous blood which is returning from the circula- 
tion through the body is loaded with carbon. When it is carried 
to the right side of the heart, and from that into the lungs, the 
branches of the pulmonary artery are distributed in great mi- 
nuteness on ceils infinite in number. These cells communicate 
with the extreme branches of the windpipe ; and, as the atmo- 
sphere is received into these cells, the circulating blood comes to be 
exposed to its influence, for neither the coats of the minute ves- 
sels which contain the blood, nor the fine membrane of the cells 
which contain the air, prevents the influence of the atmosphere 
upon the blood. The carbon of the blood, meeting the oxygen in 
the atmosphere, forms carbonic acid gas; and the air expelled in 
expiration, thus loaded, carries away, of course, a portion of 
jnoisture by exhalation. 
* Keill's Anatomy, p. 121. 162 
NATURAL THEOLOGY. 
of a separate and supplementary artery, to the lungs, 
and made to enter the vessels of the lungs; from 
[The figure represents the two sides of the heart separated; 
that to the left of the figure, but on the right side of the body, 
containing the venous blood, which must pass through the lungs 
to serve the purposes of the economy, ana that on the left side 
containing arterial blood, which is sent out into the body. Man, 
and all animals of warm blood, have the whole mass of blood 
passing through the lungs, and a double heart, as here represent- 
ed, each consisting of a vein, an auricle, a ventricle, and an artery. 
The arrows point out the course of the circulation. NATURAL THEOLOGY. 
163 
which, after it has undergone the action, whatever it 
may be, of that viscus, it is brought back by a large 
vein once more to the heart, in order, when thus 
concocted and prepared, to be thence distributed 
anew into the system. This assigns to the heart a 
double office. The pulmonary circulation is a sys- 
tem within a system, and one action of the heart is 
the origin of both. 
For this complicated function four cavities become 
necessary, and four are accordingly provided; two 
called ventricles, which send out the blood, viz., one 
into the lungs in the first instance, the other into the 
mass after it has returned from the lungs; two 
others, also, called auricles, which receive the blood 
from the veins, viz., one as it comes immediately 
from the body, the other as the same blood comes a 
second time after its circulation through the lungs. 
So that there are two receiving cavities and two 
forcing cavities. The structure of the heart has ref- 
erence to the lungs, for without the lungs one of 
each would have been sufficient. The translation of 
the blood in the heart itself is after this manner. The 
receiving cavities respectively communicate with 
the forcing cavities, and, by their contraction, unload 
the received blood into them. The forcing cavities, 
when it is their turn to contract, compel the same 
blood into the mouths of the arteries. 
The account here given will not convey to a reader 
ignorant of anatomy anything like an accurate notion 
of the form, action, or use of the parts (nor can any 
short and popular account do this), but it is abun- 
dantly sufficient to testify contrivance ; and, although 
imperfect, being true as far as it goes, may be relied 
upon for the only purpose for which we offer it, the 
purpose of this conclusion. . 
" The wisdom of the Creator," saith Hamburgher, 
"is in nothing seen more gloriously than in the 
heart." And how well doth it execute its office! 
An anatomist, who understood the structure of the 
heart, might say beforehand that it would play : but 
he would expect, I think, from the complexity of its 164 
mechanism, and the delicacy of many of its parts, 
that it should always be liable to derangement, or 
that it would soon work itself out. Yet shall this 
wonderful machine go night and day, for eighty years 
together, at the rate of a hundred thousand strokes 
every twenty-four hours, having at every stroke a 
great resistance to overcome, and shall continue this 
action for this length of time without disorder and 
without weariness! 
NATURAL THEOLOGY. 
[This'figure will assist the explanation of the following pages. 
It presents a section of the ventricle and the artery. Suppose 
that the blood enters in the direction of the arrow, it passes be- 
tween two valves of very particular construction. They are of a 
triangular shape, and held out by little cords, which are called the 
cordce tendinece. These cords are attached to muscles, which, 
from their appearance, are called columnar carnece; and these 
fibres are continuous with the fibrous substance of the heart itself. 
Now, when the ventricle is distended with blood, the valves are 
drawn by their tendons in such a manner as almost to close the 
orifice; and certainly so to dispose them, that, the instant the 
blood takes a direction backward into the vein by the contraction 
of the ventricle, they fall together, and, like a floodgate, stop the 
current in that direction. Were there no cordce tendinem or colum- 
ns carnece, these valves would be floated back into the auricle and 
lose their office. But the most admirable part of the contrivance NATURAL THEOLOGY. 
165 
is, that the columnce carnece, receiving the same impulse to contract 
as the walls of the heart itself, act at the same instant with it; 
and, by contracting in proportion as the walls approach each other, 
they hold the margins of the valves like the leeches of a sail when 
bagged by the wind. The blood, being prevented passing back- 
ward, is urged into the great artery still in the direction of the ar- 
row. And now it will be observed that the artery must be dilated 
when the heart contracts. And the artery itself being both elas- 
tic and muscular, reacting upon this impulse, it will contract 
while the ventricle is dilating. The blood would fall back from 
the great artery into the ventricle, were it not again prevented by 
the mechanical intervention of valves, a represents the semilunar 
valve of the aorta at the root of that great artery ; and it is a sur- 
prising thing to see how offices so nearly alike are performed by a 
mechanism entirely different. This valve consists of three little 
bags, which are driven up by the force of the blood in the natural 
course of the circulation ; but when, by the action of the aorta, 
the blood makes a motion backward, it fills these three little bags, 
and they fall together, and prevent the blood flowing back into the 
heart.] 
But farther: from the account which has been 
given of the mechanism of the heart, it is evident that 
it must require the interposition of valves; that the 
success indeed of its action must depend upon these ; 
for, when any one of its cavities contracts, the neces- 
sary tendency of the force will be to drive the en- 
closed blood, not only into the mouth of the artery 
where it ought to go, but also back again into the 
mouth of the vein from which it flowed. In like 
manner, when, by the relaxation of the fibres, the 
same cavity is dilated, the blood would not only run 
into it from the vein, which was the course intended, 
but back from the artery, through which it ought to 
be moving forward. The way of preventing a reflux 
of the fluid, in both these cases, is to fix valves, 
which, like floodgates, may open a way to the stream 
in one direction, and shut up the passage against 
it in another. The heart, constituted as it is, can 
no more work without valves than a pump can. 
When the piston descends in a pump, if it were not 
for the stoppage by the valve beneath, the motion 
would only thrust down the water which it had be- 
fore drawn up. A similar consequence would frus- 
trate the action of the heart. Valves, therefore, 166 
NATURAL THEOLOGY. 
properly disposed, t. e., properly with respect to the 
course of the blood which it is necessary to promote, 
are essential to the contrivance. And valves so dis- 
posed are accordingly provided. A valve is placed in 
the communication between each auricle and its ven- 
tricle, lest, when the ventricle contracts, part of the 
blood should get back again into the auricle, instead 
of the whole entering, as it ought to do, the mouth of 
the artery. A valve is also fixed at the mouth of 
each of the great arteries which take the blood from 
the heart, leaving the passage free so long as the 
blood holds its proper course forward; closing it 
whenever the blood, in consequence of the relaxation 
of the ventricle, would attempt to flow back. There 
is some variety in the construction of these valves, 
though all the valves of the body act nearly upon the 
same principle, and are destined to the same use. In 
general, they consist of a thin membrane, lying close 
to the side of the vessel, and consequently allowing 
an open passage while the stream runs one way, but 
thrust out from the side by the fluid getting behind it, 
and opposing the passage of the blood when it would 
flow the other way. Where more than one mem- 
brane is employed, the different membranes only 
compose one valve. Their joint action fulfils the of- 
fice of a valve: for instance, over the entrance of 
the right auricle of the heart into the right ventricle, 
three of these skins or membranes are fixed, of a tri- 
angular figure, the bases of the triangles fastened to 
the flesh, the sides and summits loose, but, though 
loose, connected by threads of a determinate length 
with certain small fleshy prominences adjoining. 
The effect of this construction is, that, when the ven- 
tricle contracts, the blood, endeavouring to escape in 
all directions, and, among other directions, pressing 
upward, gets between these membranes and the sides 
of the passage, and thereby forces them up into such 
a position as that, together, they constitute, when 
raised, a hollow cone (the strings before spoken of 
hindering them from proceeding or separating far- 
ther) ; which cone, entirely occupying the passage, NATURAL THEOLOGY. 
167 
prevents the return of the blood into the auricle. A 
shorter account of the matter may be this: so long 
as the blood proceeds in its proper course, the mem- 
branes which compose the valve are pressed close to 
the side of the vessel, and occasion no impediment to 
the circulation; when the blood would regurgitate, 
they are raised from the side of the vessel, and, meet- 
ing in the middle of its cavity, shut up the channel. 
Can any one doubt of contrivance here, or is it pos- 
sible to shut our eyes against the proof of it l48 
48 We cannot resist following up these observations with some 
minute notices of the appropriate structure. A sail distended 
with the wind would be torn up, were not the margins secured: 
accordingly, the canvass is folded over a strong cord, which is 
called the bolt-rope. So the margins of these semilunar valves 
are as finely finished as any sheet from the dockyard. There is a 
ligament which runs along the margin, and strengthens it to sus- 
tain the impulse of the back-stroke of the artery. And were 
those cordce tendinea, which we have described as like the leeches 
of a sail, attached to the corner of the mitral valve without farther 
security, they would be torn off on the first pulsation. But as the 
leeches are secured to the bolt-ropes of the sail, so are the cordce 
tendinece continued into firm ligamentous cords, which strengthen 
the valves. 
Our author says well, that the valve is thrown down on the side 
of the artery when the blood is in its course. But, were this really 
the case, the refluent blood would not easily catch the edge of the 
valve to throw it up. Now this difficulty is met very curiously, 
and in two different modes. The cordce tendinece prevent the 
margins of the mitral valve within the ventricle from flapping close 
against the side of the cavity ; and as to the semilunar valves at 
the root of the great artery, they are prevented falling against the 
walls in another mode: the section of the artery at its root is not 168 
NATURAL THEOLOGY. 
This valve, also, is not more curious in its struc- 
ture than it is important in its office. Upon the 
play of the valve, even upon the proportional length 
of the strings or fibres which check the ascent of the 
membranes, depends, as it should seem, nothing less 
than the life itself of the animal. We may here like- 
wise repeat, what we before observed concerning 
some of the ligaments of the body, that they could 
not be formed by any action of the parts themselves. 
There are cases in which, although good uses appear 
to arise from the shape or configuration of a part, yet 
that shape or configuration itself may seem to be pro- 
duced by the action of the part, or by the action or 
pressure of adjoining parts. Thus the bend and the 
internal smooth concavity of the ribs may be attrib- 
uted to the equal pressure of the soft bowels; the 
particular shape of some bones and joints to the trac- 
tion of the annexed muscles, or to the position of con- 
tiguous muscles. But valves could not be so formed. 
Action and pressure are all against them. The blood, 
in its proper course, has no tendency to produce such 
things; and in its improper or reflected current, has a 
tendency to prevent their production. While we see, 
a regular circle, but it is formed into three little bags or sinuses ; 
and as each of the three valves has a little sinus behind it, its mar- 
gin never reaches the wall of the artery. The consequence of 
which is, that in the instant that the column of blood takes a 
retrograde direction, the margins of the valve are caught, and 
they are thrown up to close the passage. Nothing can be more 
admirably mechanical. 
Since our author has so properly insisted upon the mechanism 
of the heart as the very strength of his argument, we shall men- 
tion one circumstance more as showing what may be called the 
perfection of the workmanship. It has been explained that the 
valves of the great artery consist of three semicircular mem- 
branes. Now if we consider the effect of these three semicircles 
meeting, there must be a triangular space in their centre, an im- 
perfection in the point of their union, as it were. To remedy this 
defect, on the centre of the margin of each valve there is a little 
body like a small excrescence or tongue: and, when these three 
bodies meet, they exactly fill up the triangular space which is left 
in the centre of the three semicircles. It is as if an ingenious 
workman had contrived a thing the most apposite to remedy a 
defect. 169 
therefore, the use and necessity of this machinery, 
we can look to no other account of its origin or for- 
mation than the intending mind of a Creator. Nor 
can we, without admiration, reflect that such thin 
membranes, such weak and tender instruments as 
these valves are, should be able to hold out for seventy 
or eighty years. 
Here, also, we cannot consider but with gratitude, 
how happy it is that our vital motions are involuntary. 
We should have enough to do if we had to keep our 
hearts beating and our stomachs at work. Did these 
things depend, we will not say upon our effort, but 
upon our bidding, our care, our attention, they would 
leave us leisure for nothing else. We must have 
been continually upon the watch and continually in 
fear; nor would this constitution have allowed of 
sleep. 
It might, perhaps, be expected, that an organ so 
precious, of such" central and primary importance as 
the heart is, should be defended by a case. The fact 
is, that a membranous purse or bag, made of strong, 
tough materials, is provided for it: holding the heart 
within its cavity : sitting loosely and easily about it; 
guarding its substance, without confining its motion; 
and containing, likewise, a spoonful or two of water, 
just sufficiennt to keep the surface of the heart in a 
state of suppleness and moisture. How should such 
a loose covering be generated by the action of the 
heart 1 Does not the enclosing of it in a sack, an- 
swering no other purpose but that enclosure, show the 
care that has been taken of its preservation ? 
One use of the circulation of the blood probably* 
(among other uses) is, to distribute nourishment to 
the different parts of the body. How minute and mul- 
tiplied the ramifications of the bloodvessels for that 
purpose are; and how thickly spread over at least the 
superfices of the body, is proved by the single obser- 
vation, that we cannot prick the point of a pin into the 
NATURAL THEOLOGY. 
* On page 154, the author, speaking of the circulation, says, 
"one grand purpose is plainly answered by it," &c.-Am. Ed. 
Vol. I.-P 170 
flesh without drawing blood, t. e., without finding a 
bloodvessel. Nor internally is their diffusion less 
universal. Bloodvessels run along the surface of 
membranes, pervade the substance of muscles, pene- 
trate the bones. Even into every tooth we trace, 
through a small hole in the root, an artery to feed the 
bone, as well as a vein to bring back the spare blood 
from it; both which, with the addition of an accom- 
panying nerve, form a thread only a little thicker than 
a horsehair. 
Wherefore, when the nourishment taken in at the 
mouth has once reached and mixed itself with the 
blood, every part of the body is in the way of being 
supplied with it. And this introduces another grand 
topic, namely, the manner in which the aliment gets 
into the blood; which is a subject distinct from the pre- 
ceding, and brings us to the consideration of another 
entire system of vessels. 
HI. For this necessary part of the animal economy 
an apparatus is provided, in a great measure capable 
of being what anatomists call demonstrated, that is, 
shown in the dead body; and a line or course of con- 
veyance, which we can pursue by our examination. 
First, the food descends by a wide passage into the 
intestines, undergoing two great preparations on its 
way : one in the mouth by mastication and moisture 
(can it be doubted with what design the teeth were 
placed in the road to the stomach, or that there was 
choice in fixing them in this situation 1), the other by 
digestion in the stomach itself. Of this last surpri- 
sing dissolution I say nothing, because it is chymistry, 
and I am endeavouring to display mechanism. The 
figure and position of the stomach (I speak all along 
with a reference to the human organ) are calculated 
for detaining the food long enough for the action of 
its digestive juice. It has the shape of the pouch of 
a bagpipe; lies across the body ; and the pylorus, or 
passage by which the food leaves it, is somewhat 
higher in the body than the cardia or orifice by which 
it enters; so that it is by the contraction of the mus- 
cular coat of the stomach that the contents, after hav- 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
171 
ing undergone the application of the gastric men- 
struum, are gradually pressed out. In dogs and cats, 
this action of the coats of the stomach has been dis- 
played to the eye.49 It is a slow and gentle undula- 
tion, propagated from one orifice of the stomach to 
the other. For the same reason that I omitted, for 
the present, offering any observation upon the diges- 
tive fluid, I shall say nothing concerning the bile or 
the pancreatic juice, farther than to observe upon the 
mechanism, viz., that, from the glands in which these 
secretions are elaborated, pipes are laid into the first 
of the intestines, through which pipes the product of 
each gland flows into the bowel, and is there mixed 
■with the aliment as soon almost as it passes the stom- 
ach ; adding also as a remark, how grievously this 
same bile offends the stomach itself, yet cherishes 
the vessel that lies next to it. 
Secondly. We have now the aliment in the intes- 
tines converted into pulp ; and though lately consist- 
ing of ten different viands, reduced to nearly a uni- 
form substance, and to a state fitted for yielding its 
essence, which is called chyle, but which is milk, or 
more nearly resembling milk than any other liquor 
with which it can be compared. For the straining off 
this fluid from the digested aliment, in the course of 
its long progress through the body, myriads of capil- 
lary tubes, i. e., pipes as small as hairs, open their ori- 
fices into the cavity of every part of the intestines. 
These tubes, which are so fine and slender as not to 
be visible unless when distended with chyle, soon 
unite into larger branches. The pipes formed by this 
union terminate in glands, from which other pipes, of 
49 We may now extend this remark to men. Dr. Beaumont; of 
the American army, has recently had an opportunity of inspecting 
the interior coats and cavity of the stomach, both when it was act- 
ing upon food and when it was empty. A Canadian, by the name 
of St. Martin, having been wounded by the accidental discharge 
of a musket, the stomach was found to be perforated, and the 
opening remained after the parts healed. Dr. Beaumont embraced 
this opportunity, and instituted a great number of very interesting 
experiments and observations, the result of which he has imbod 
led in his work.-Am. Ed. 172 
a still larger diameter, arising, carry the chyle from 
all parts into a common reservoir or receptacle. This 
receptacle is a bag of size enough to hold about two 
tablespoonfuls; and from this vessel a duct or main 
pipe prpceeds, climbing up the back part of the chest, 
and afterward creeping along the gullet till it reach the 
neck. Here it meets the river; here it discharges itself 
into a large vein, which soon conveys the chyle, now 
flowing along with the old blood, to the heart. This 
whole route can be exhibited to the eye ; nothing is left 
to be supplied by imagination or conjecture. Now, 
besides the subservience of this structure, collective- 
ly considered, to a manifest and necessary purpose, 
we may remark two or three separate particulars in 
it, which show, not only contrivance, but the perfec- 
tion of it. We may remark, first, the length of the 
intestines, which, in the human subject, is six times 
that of the body. Simply for a passage, these volu- 
minous bowels, this prolixity of gut, seems in nowise 
necessary; but, in order to allow time and space for 
the successive extraction of the chyle from the diges- 
tive aliment, namely, that the chyle which escapes 
the lacteals of one part of the guts may be taken up 
by those of some other part, the length of the canal 
is of evident use and conduciveness. Secondly, we 
must also remark their peristaltic motion, which is 
made up of contractions following one another like 
waves upon the surface of a fluid, and not unlike what 
we observe in the body of an earthworm crawling 
along the ground, and which is effected by the joint 
action of longitudinal and of spiral, or rather, per- 
haps, of a great number of separate semicircular 
fibres. This curious action pushes forward the gross- 
er part of the aliment, at the same time that the more 
subtle parts, which we call chyle, are, by a series of 
gentle compressions, squeezed into the narrow orifices 
of the lacteal veins. Thirdly, it was necessary that 
these tubes, which we denominate lacteals, or their 
mouths at least, should be made as narrow as pos- 
sible, in order to deny admission into the blood to any 
particle which is of size enough to make a lodgment 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
173 
afterward in the small arteries, and thereby to ob- 
struct the circulation; and it was also necessary that 
this extreme tenuity should be compensated by mul- 
titude ; for a large quantity of chyle (in ordinary con- 
stitutions not less, it has been computed, than two or 
three quarts in a day) is, by some means or other, to 
be passed through them. Accordingly, we find the 
number of lacteals exceeding all powers of computa- 
tion, and their pipes so fine and slender as not to be 
visible, unless filled, to the naked eye, and their ori- 
fices, which open into the intestines, so small as 
not to be discernible even by the best microscope. 
Fourthly, the main pipe, which carries the chyle from 
the reservoir to the blood, viz., the thoracic duct, be- 
ing fixed in an almost upright position, and wanting 
that advantage of propulsion which the arteries pos 
sess, is furnished with a succession of valves to check 
the ascending fluid, when once it has passed them, 
from falling back. These valves look upward, so as 
to leave the ascent free, but to prevent the return of 
the chyle, if, for want of sufficient force to push it 
on, its weight should at any time cause it to descend. 
Fifthly, the chyle enters the blood in an odd place, 
but perhaps the most commodious place possible, viz., 
at a large vein in the neck, so situated with respect 
to the circulation as speedily to bring the mixture 
to the heart. And this seems to be a circumstance 
of great moment; for, had the chyle entered the blood 
at an artery or at a distant vein, the fluid composed 
of the old and the new materials must have perform- 
ed a considerable part of the circulation before it re- 
ceived that churning in the lungs which is probably 
necessary for the intimate and perfect union of the 
blood with the recent chyle. Who could have dream- 
ed of a communication between the cavity of the in- 
testines and the left great vein of theneck? Who 
could have suspected that this communication should 
be the medium through which all nourishment is de- 
rived to the body, or this the place where, by a side 
inlet, the important junction is formed between the 
blood and the material which feeds it 1 174 
We postponed the consideration of digestion, lest 
it should interrupt us in tracing the course of the 
food to the blood; but, in treating of the alimentary- 
system, so principal a part of the process cannot be 
omitted. 
Of the gastric juice, the immediate agent by which 
that change which food undergoes in our stomachs is 
effected, we shall take our account from the numer- 
ous, careful, and varied experiments of the Abbe 
Spallanzani. 
1. It is not a simple diluent, but a real solvent. A 
quarter of an ounce of beef had scarcely touched the 
stomach of a cow when the solution began. 
2. It has not the nature of saliva j50 it has not the 
nature of bile ; but is distinct from both. By exper- 
iments out of the body, it appears that neither of 
these secretions acts upon alimentary substances in 
the same manner as the gastric juice acts. 
3. Digestion is not putrefaction; for the digesting 
fluid resists putrefaction most pertinaciously; nay, 
not only checks its farther progress, but restores pu- 
trid substances. 
4. It is not a fermentative process ; for the solution 
begins at the surface, and proceeds towards the cen- 
tre, contrary to the order in which fermentation acts 
and spreads.61 
5. It is not the digestion of heat; for the cold maw 
of a cod or sturgeon will dissolve the shells of crabs 
or lobsters, harder than the sides of the stomach 
which contains them. 
NATURAL THEOLOGY. 
60 Dr. Beaumont's experiments would seem to show, that saliva 
does not aid digestion, except as it moistens and tends to divide 
the food. Food properly comminuted was digested as quickly 
when introduced directly into the stomach through the opening of 
the wound, as when chewed and swallowed in the usual manner. 
-Am. Ed. 
61 It is now ascertained that the digestion does not begin, as was 
supposed, only at the parts contiguous to the coats of the stom- 
ach, there being a constant churning motion by which the food is 
at once mixed with the gastric juice. Almost immediately after 
it is swallowed, each separate piece is found to be more or less 
acted upon.-Am. Ed. Ill a word, animal digestion carries about it the 
marks of being a power and a process completely 
sui generis, distinct from every other, at least from 
every chymical process with which we are acquaint- 
ed. And the most wonderful thing about it is its ap- 
propriation, its subservience to the particular econo- 
my of each animal. The gastric juice of an owl, fal- 
con, or kite will not touch grain ; no, not even to finish 
the macerated and half-digested pulse which is left 
in the crops of the sparrows that the bird devours.52 
In poultry the trituration of the gizzard and the gas- 
tric juice conspire in the work of digestion. The 
gastric juice will not dissolve the grain while it is 
whole. Entire grains of barley, enclosed in tubes 
or spherules, are not affected by it. But if the same 
grain be by any means broken or ground, the gastric 
juice immediately lays hold of it. Here, then, is 
wanted, and here we find, a combination of mechan- 
ism and chymistry. For the preparatory grinding, 
the gizzard lends its mill; and, as all millwork 
should be strong, its structure is so beyond that of 
any other muscle belonging to the animal. The in- 
ternal coat also, or lining of the gizzard, is, for the 
same purpose, hard and cartilaginous. But, foras- 
much as this is not the sort of animal substance suit- 
ed for the reception of glands or for secretion, the 
gastric juice in this family is not supplied, as in 
membraneous stomachs, by the stomach itself, but by 
the gullet, in which the feeding glands are placed, 
and from which it trickles down into the stomach. 
In sheep, the gastric fluid has no effect in digest- 
ing plants unless they have been previously masticated. 
It only produces a slight maceration, nearly such as 
common water would produce, in a degree of heat 
somewhat exceeding the medium temperature of the 
atmosphere. But, provided that the plant has been 
reduced to pieces by chewing, the gastric juice then 
NATURAL THEOLOGY. 
175 
62 One of the many modes by which seeds are carried to a dis- 
tance, and Sir Joseph Banks gave us reason to believe that it 
served as a preparation for sowing, as seeds so carried geminate! 
sooner. 176 
proceeds with it, first, by softening its substance; 
next, by destroying its natural consistency; and, 
lastly, by dissolving it so completely as not even to 
spare the toughest and most stringy parts, such as 
the nerves of the leaves. 
So far our accurate and indefatigable abbe. Dr. 
Stevens, of Edinburgh, in 1777, found, by experiments 
tried with perforated balls, that the gastric juice of 
the sheep and the ox speedily dissolved vegetables, 
but made no impression upon beef, mutton, and other 
animal bodies. Mr. Hunter discovered a property 
of this fluid of a most curious kind, viz., that in the 
stomachs of animals which feed upon flesh, irre- 
sistibly as this fluid acts upon animal substances, it 
is only upon the dead substance it operates at all. 
The Ziinn# fibre suffers no injury from lying in con- 
tact with it. Worms and insects are found alive in 
the stomachs of such animals. The coats of the hu- 
man stomach, in a healthy state, are insensible to 
its presence ; yet, in cases of sudden death (wherein 
the gastric juice, not having been weakened by dis- 
ease, retains its activity), it has been known to eat a 
hole through the bowel which contains it.* How 
nice is this discrimination of action, yet how neces- 
sary ! 
But to return to our hydraulics. 
IV. The gall-bladder is a very remarkable contri- 
vance. It is the reservoir of a canal. It does not 
form the channel itself, i. e., the direct communica- 
tion between the liver and the intestine, which is by 
another passage, viz., the ductus hepaticus, continu- 
ed under the name of the ductus communis ; but it 
lies adjacent to this channel, joining it by a duct of 
its own, the ductus cysticus : by which structure it 
is enabled, as occasion may require, to add its con- 
tents to and increase the flow of bile into the duode- 
num. And the position of the gall-bladder is such as 
to apply this structure to the best advantage. In its 
natural position it touches the exterior surface of the 
Stomach, and, consequently, is compressed by the dis- 
NATURAL THEOLOGY. 
* Phil. Trans., vol. 447. NATURAL THEOLOGY. 
177 
tcntion of that vessel: the effect of which compres- 
sion is to force out from the bag, and send into the 
duodenum, an extraordinary quantity of bile, to meet 
the extraordinary demand which the repletion of the 
stomach by food is about to occasion. Cheselden 
describes the gall-bladder as seated against the duo- 
denum, and thereby liable to have its fluid pressed 
out by the passage of the aliment-through that cavi- 
ty, which likewise will have the effect of causing it 
to be received into the intestine at a right time and 
in a due proportion. 
There may be other purposes answered by this 
contrivance, and it is probable that there are. The 
contents of the gall-bladder are not exactly of the 
same kind as what passes from the liver through the 
direct passage. It is possible that the gall may be 
changed, and for some purposes meliorated, by keep- 
ing.53 
The entrance of the gall-duct into the duodenum 
furnishes another observation. Whenever either 
smaller tubes are inserted into larger tubes, or tubes 
into vessels and cavities, such receiving tubes, ves- 
sels, or cavities, being subject to muscular constric- 
tion, we always find a contrivance to prevent regur- 
gitation. In some cases valves are used; in other 
cases, among which is that now before us, a different 
expedient is resorted to, which may be thus descri- 
bed : the gall-duct enters the duodenum obliquely; 
after it has pierced the first coat, it runs near two 
fingers' breadth between the coats before it opens 
into the cavity of the intestine.* The same contri- 
vance is used in another part, where there is exactly 
the same occasion for it, viz., in the insertion of the 
ureters in the bladder. These enter the bladder near 
63 The horse has no gall-bladder, the reason of which is suppo- 
sed to be, that the animal, being framed for sudden and powerful 
as well as long-continued exertion, his stomach is very small, and 
the process of digestion almost continual, whereas the gall-bladder 
seems to be necessary only where the digestive process is perform- 
ed in a large stomach, and the food descends in large quantities 
and a longer intervals.-Am. Ed. 
* Keill's Anat, p. 62. 178 
NATURAL THEOLOGY. 
its neck, running obliquely for the space of an inch 
between its coats.* It is, in both cases, sufficiently 
evident that this structure has a necessary mechan- 
ical tendency to*resist regurgitation; for whatever 
force acts in such a direction as to urge the fluid back 
into the orifices of the tubes, must, at the same time, 
stretch the coats of the vessels, and thereby com- 
press that part of the tube which is included between 
them. 
V. Among the vessels of the human body, the pipe 
which conveys the saliva from the place where it is 
made to the place where it is wanted, deserves to be 
reckoned among the most intelligible pieces of mech- 
anism with which we are acquainted. The saliva, 
we all know, is used in the mouth; but much of it is 
produced on the outside of the cheek by the parotid 
gland, which lies between the ear and the angle of 
the lower jaw. In order to carry the secreted juice 
to its destination, there is laid from the gland on the 
outside a pipe about the thickness of a wheat-straw, 
and about three fingers' breadth in length, which, af- 
ter riding over the masseter muscle, bores for itself a 
hole through the very middle of the cheek, enters by 
that hole, which is a complete perforation of the buc- 
cinator muscle, into the mouth, and there discharges 
its fluid very copiously. 
VI. Another exquisite structure, differing, indeed, 
from the four preceding instances in that it does not 
relate to the conveyance of fluids, but still belonging, 
like these, to the class of pipes or conduits of the 
body, is seen in the larynx. We all know that there 
go down the throat two pipes, one leading to the stom- 
ach, the other to the lungs: the one being the pas- 
sage for the food, the other for the breath and voice ; 
we know also that both these passages open into the 
bottom of the mouth: the gullet necessarily, for the 
conveyance of food, and the windpipe, for speech and 
the modulation of sound, not much less so : therefore 
the difficulty was, the passages being so contiguous, 
* Ches. Anat., p. 260, to prevent the food, especially the liquids, which we 
swallow into the stomach, from entering the wind- 
pipe, i. e., the road to the lungs; the consequence of 
which error, when it does happen, is perceived by the 
convulsive throes that are instantly produced. This 
business, which is very nice, is managed in this man- 
ner- The gullet (the passage for food) opens into the 
mouth like the cone or upper part of a funnel, the ca- 
pacity of which forms indeed the bottom of the mouth. 
Into the side of this funnel, at the part which lies the 
lowest, enters the windpipe by a chink or slit, with a 
lid or flap, like a little tongue, accurately fitted to the 
orifice. The solids or liquids which we swallow pass 
over this lid or flap as they descend by the funnel into 
the gullet. Both the weight of the food and the ac- 
tion of the muscles concerned in swallowing contrib- 
ute to keep the lid close down upon the aperture 
while anything is passing; whereas, by means of its 
natural cartilaginous spring, it raises itself a little as 
soon as the food is passed, thereby allowing a free 
inlet and outlet for the respiration of air by the lungs. 
Such is its structure; and we may here remark the 
almost complete success of the expedient, viz., how 
seldom it fails of its purpose compared with the num- 
ber of instances in which it fulfils it. Reflect how 
frequently we swallow, how constantly we breathe. 
In a city feast, for example, what deglutition, what 
anhelation ! yet does this little cartilage, the epiglot- 
tis, so effectually interpose its office, so securely guard 
the entrance of the windpipe, that, while morsel after 
morsel, draught after draught, are coursing one an- 
other over it, an accident of a crumb or a drop slip- 
ping into this passage (which, nevertheless, must be 
opened for the breath every second of time) excites 
in the whole company, not only alarm by its danger, 
but surprise by its novelty. Not two guests are 
choked in a century. 
There is no room for pretending that the action of 
the parts may have gradually formed the epiglottis: 
I do not mean in the same individual, but in a succes- 
sion of generations. Not only the action of the parts 
NATURAL THEOLOGY. 
179 180 
has no such tendency, but the animal could not live, 
nor, consequently, the parts act, either without it or 
with it in a half-formed state. The species was not 
to wait for the gradual formation or expansion of a 
part which was from the first necessary to the life of 
the individual. 
Not only is the larynx curious, but the whole wind- 
pipe possesses a structure adapted to its peculiar of- 
fice. It is made up (as any one may perceive by put- 
ting his fingers to this throat) of stout cartilaginous 
ringlets, placed at small and equal distances from one 
another. Now this is not the case with any other of 
the numerous conduits of the body. The use of these 
cartilages is to keep the passage for the air constantly 
open, which they do mechanically. A pipe with soft 
membranous coats, liable to collapse and close when 
empty, would not have answered here; although this 
be the general vascular structure, and a structure 
which serves very well for those tubes which are 
kept in a state of perpetual distention by the fluid 
they enclose, or which afford a passage to solid and 
protruding substances. 
Nevertheless (which is another particularity well 
worthy of notice), these rings are not complete ; that 
is, are not cartilaginous and stiff all around, but their 
hinder part, which is contiguous to the gullet, is 
membranous and soft, easily yielding to the disten- 
tions of that organ occasioned by the descent of solid 
food. The same rings are also bevelled off at the 
upper and lower edges, the better to close upon one 
another when the trachea is compressed or short- 
ened. 
The constitution of the trachea may suggest like- 
wise another reflection. The membrane which lines 
its inside is perhaps the most sensible, irritable mem- 
brane of the body. It rejects the touch of a crumb 
of bread or a drop of water with a spasm which con- 
vulses the whole frame; yet, left to itself and its 
proper office, the intromission of air alone, nothing 
can be so quiet. It does not even make itself felt; 
a man does not know that he has a trachea. This 
natural theology. NATURAL THEOLOGY. 
181 
capacity of perceiving with such acuteness, this im- 
patience of offence, yet perfect rest and ease when 
let alone, are properties, one would have thought, not 
likely to reside in the same subject.54 It is to the 
junction, however, of these almost inconsistent qual- 
ities, in this as well as in some other delicate parts 
of the body, that we owe our safety and our comfort; 
our safety to their sensibility, our comfort to their 
repose.55 
The larynx, or, rather, the whole windpipe taken 
together (for the larynx is only the upper part of the 
windpipe), besides its other uses, is also a musical 
instrument; that is to say, it is mechanism expressly 
adapted to the modulation of sound; for it has been 
found, upon trial, that, by relaxing or tightening the 
54 When air is expired from the lungs, the trachea, by the con- 
traction of the muscular fibres placed next the gullet, is diminished, 
so that the air has to pass much more rapidly on leaving than on 
entering the lungs, and, of course, with more force. Hence, should 
any foreign substance get into the trachea, breathing will tend to 
drive it out, and thus prevent injury, perhaps death.-Am. Ed. 
33 Our author touches here upon the sensibilities which govern 
the motions of the chest; a subject which might be enlarged upon 
to fill a volume. But, considering the object of this work, we 
ought not to omit the occasion of observing the union of a property 
of life with the most complex mechanical structure imaginable. 
We have seen, in former notes, that for the grand and vital purpose 
of decarbonizing the blood, the atmospheric air must be drawn 
deep into the lungs ; and the problem is, to permit the vital air to 
pass, and yet prevent foreign matter from finding access. On this 
subject see the preceding note. But the more remarkable cir- 
cumstance in connexion with the statement in the text is, that the 
whole of this apparatus for respiration is taken from the gover- 
nance of the will, and placed under a power more constantly vig- 
ilant and more absolutely peremptory. The sensibility about the 
glottis holds in control a hundred muscles ; and, while it excites 
the action, directs the force of the stream of expired air with ex- 
traordinary exactness to the very point where the irritating mat- 
ter lodges, be it in the passages of the throat or in the cavities of 
the nose. There are many instances of the same kind in the 
economy of the frame, where actions are excited by sensibilities 
seated in certain spots, some of them attended with suffering, by 
which our voluntary efforts are brought in aid, and others where 
there is neither sensation nor volition, and yet the muscles are 
controlled and regulated, and the offices performed with undevi- 
ating precision. 
Vol. I.^-Q 182 
NATURAL THEOLOGY. 
tendinous bands at the extremity of the windpipe, 
and blowing in at the other end, all the cries and 
notes might be produced of which the living animal 
was capable. It can be sounded just as a pipe or 
flute is sounded. 
Birds, says Bonnet, have, at the lower end of the 
windpipe, a conformation like the reed of a hautboy, 
for the modulation of their notes. A tuneful bird is 
a ventriloquist. The seat of the song is in the 
breast. 
The use of the lungs in the system has been said 
to be obscure; one use, however, is plain, though, in 
some sense, external to the system, and that is, the 
formation, in conjunction with the larynx, of voice 
and speech. They are, to animal utterance, what 
the bellows are to the organ. 
For the sake of method, we have considered animal 
bodies under three divisions, their bones, their mus- 
cles, and their vessels ; and we have stated our ob- 
servations upon these parts separately. But this is 
to diminish the strength of the argument. The wis- 
dow of the Creator is seen, not in their separate, but 
their collective action; in their mutual subservience 
and dependance: in their contributing together to one 
effect and one use. It has been said that a man can- 
not lift his hand to his head without finding enough 
to convince him of the existence of a God. And it 
is well said; for he has only to reflect, familiar as 
this action is, and simple as it seems to be, how 
many things are requisite for the performing of it; 
how many things which we understand, to say no- 
thing of many more, probably, which we do not: viz., 
first, a long, hard, strong cylinder, in order to give to 
the arm its firmness and tension; but which, being 
rigid, and in its substance inflexible, can only turn 
upon joints ; secondly, therefore, joints for this pur- 
pose ; one at the shoulder to raise the arm, another 
at the elbow to bend it; these joints continually fed NATURAL THEOLOGY. 
183 
with a soft mucilage to make the parts slip easily 
upon one another, and holden together by strong 
braces to keep them in their position: then, thirdly, 
strings and wires, i. e., muscles and tendons, arti- 
ficially inserted, for the purpose of drawing the bones 
in the directions in which the joints allow them to 
move. Hitherto we seem to understand the mecha- 
nism pretty well; and, understanding this, we possess 
enough for our conclusion: nevertheless, we have 
hitherto only a machine standing still; a dead organ- 
ization ; an apparatus. To put the system in a state 
of activity, to set it at work, a farther provision is 
necessary, viz., a communication with the brain by 
means of nerves. We know the existence of this 
communication, because we can see the communica- 
ting threads, and can trace them to the brain : its ne- 
cessity we also know, because, if the thread be cut, 
if the communication be intercepted, the muscle be- 
comes paralytic ; but beyond this we know little, the 
organization being too minute and subtile for our in- 
spection. 
To what has been enumerated, as officiating in the 
single act of a man's raising his hand to his head, 
must be added likewise all that is necessary, and all 
that contributes to the growth, nourishment, and sus- 
tentation of the limb, the repair of its waste, the 
preservation of its health : such as the circulation of 
the blood through every part of its lymphatics, ex- 
halents, absorbents ; its excretions and integuments. 
All these share in the result, join in the effect; and 
how all these, or any of them, come together with- 
out a designing, disposing intelligence, it is impossi- 
ble to conceive. 184 
NATURAL THEOLOGY. 
CHAPTER XI. 
OF THE ANIMAL STRUCTURE REGARDED AS A MASS. 
Contemplating an animal body in its collective ca- 
pacity, we cannot forget to notice what a number of 
instruments are brought together, and often within 
how small a compass. It is a cluster of contrivan- 
ces. In a canary-bird, for instance, and in the sin- 
gle ounce of matter which composes his body (but 
which seems to be all employed), we have instru- 
ments for eating, for digesting, for nourishment, for 
breathing, for generation, for running, for flying, for 
seeing, for hearing, for smelling: each appropriate, 
each entirely different from all the rest. 
The human or, indeed, the animal frame, consid- 
ered as a mass or assemblage, exhibits in its compo- 
sition three properties, which have long struck my 
mind as indubitable evidences not only of design, but 
of a great deal of attention and accuracy in prose- 
cuting the design. 
I. The first is, the exact correspondence of the 
two sides of the same animal: the right hand an- 
swering to the left, leg to leg, eye to eye, one side 
of the countenance to the other; and with a precis- 
ion, to imitate which in any tolerable degree forms 
one of the difficulties of statuary, and requires, on 
the part of the artist, a constant attention to this 
property of his work, distinct from every other. 
It is the most difficult thing that can be to get a 
wig made even; yet how seldom is the face awry! 
And what care is taken that it should not be so, the 
anatomy of its bones demonstrates. The upper part 
of the face is composed of thirteen bones, six on 
each side, answering each to each, and the thirteenth, 
without a fellow, in the middle. The lower part of 
the face is in like manner composed of six bones, NATURAL THEOLOGY. 
185 
three on each side, respectively corresponding, and 
the lower jaw in the centre. In building an arch, 
could more be done in order to make the curve true, 
i. e., the parts equidistant from the middle, alike in 
figure and position 1 
The exact resemblance of the eyes, considering 
how compounded this organ is in its structure ; how 
various and how delicate are the shades of colour 
with which its iris is tinged; how differently, as to 
effect upon appearance, the eye may be mounted in 
its socket, and how differently, in different heads, eyes 
actually are set, is a property of animal bodies much 
to be admired. Of ten thousand eyes, 1 do not know 
that it would be possible to match one, except with 
its own fellow, or to distribute them into suitable 
pairs by any other selection than that which obtains. 
This regularity of the animal structure is rendered 
more remarkable by the three following considera- 
tions : 
1. The limbs, separately taken, have not this cor- 
relation of parts, but the contrary of it. A knife 
drawn down the chine cuts the human body into two 
parts, externally equal and alike; you cannot draw 
a straight line which will divide a hand, a foot, the 
leg, the thigh, the cheek, the eye, the ear, into two 
parts equal and alike. Those parts which are placed 
upon the middle or partition line of the body, or 
which traverse that line, as the nose, the tongue, and 
the lips, may be so divided, or, more properly speak- 
ing, are double organs ; but other parts cannot. This 
shows that the correspondence which we have been 
describing does not arise by any necessity in the na- 
ture of the subject; for, if necessary, it would be 
universal; whereas it is observed only in the system 
or assemblage. It is not true of the separate parts: 
that is to say, it is found where it conduces to beauty 
or utility; it is not found where it would subsist at 
the expense of both. The two wings of a bird al- 
ways correspond: the two sides of a feather fre- 
quently do not. In centipedes, millepedes, and the 
whole tribe of insects, no two legs on the same side 186 
NATURAL THEOLOGY. 
are alike; yet there is the most exact parity between 
the legs opposite to one another. 
2. The next circumstance to be remarked is, that, 
while the cavities of the body are so configurated as 
externally to exhibit the most exact correspondence 
of the opposite sides, the contents of these cavities 
have no such correspondence. A line drawn down 
the middle of the breast divides the thorax into two 
sides exactly similar; yet these two sides enclose 
very different contents. The heart lies omthe left 
side, a lobe of the lungs on the right, balandlig each 
other neither in size nor shape. The same thing 
holds of the abdomen. The liver lies on the right 
side, without any similar viscus opposed to it on the 
left. The spleen, indeed, is situated over against the 
liver, but agreeing with the liver neither in bulk nor 
form. There is no equipollency between these. 
The stomach is a vessel, both irregular in its shape 
and oblique in its position. The foldings and doub- 
lings of the intestines do not present a parity of sides. 
Yet that symmetry which depends upon the correla- 
tion of the sides is externally preserved throughout 
the whole trunk, and is the more remarkable in the 
lower parts of it, as the integuments are soft; and 
the shape, consequently, is not, as the thorax is by 
its ribs, reduced by natural stays. It is evident, 
therefore, that the external proportion does not arise 
from any equality in the shape or pressure of the in- 
ternal contents. What is it, indeed, but a correction 
of inequalities'? an adjustment, by mutual compensa- 
tion, of anomalous forms into a regular congeries? 
the effect, in a word, of artful, and, if we might be 
permitted to speak, of studied collocation ? 
3. Similar also to this is the third observation: 
that an internal inequality in the feeding vessels is 
so managed as to produce no inequality of parts 
which were intended to correspond. The right arm 
answers accurately to the left, both in size and 
shape; but the arterial branches which supply the 
two arms do not go off from their trunk in a pair, in 
the same manner, at the same place, or at the same NATURAL THEOLOGY. 
187 
angle. Under which want of similitude it is very dif- 
ficult to conceive how the same quantity of blood 
should be pushed through each artery; yet the re- 
sult is right; the two limbs which are nourished by 
them perceive no difference of supply, no effects of 
excess or deficiency. 
Concerning the difference of manner in which the 
subclavian and carotid arteries, upon the different 
sides of the body, separate themselves from the 
aorta, Cheselden seems to have thought that the ad- 
vantage which the left gain by going off at an angle 
much more acute than the right, is made up to the 
right by their going off together in one branch.* It 
is very possible that this may be the compensating 
contrivance; and, if it be so, how curious, how hy- 
drostatical! 
II. Another perfection of the animal mass is the 
package. I know nothing whiclWis so surprising. 
Examine the contents of the trunk of any large ani- 
mal. Take notice how soft, how|tender, how intri- 
cate they are; how constantly in action, how ne- 
cessary to life ! Reflect upon the danger of any in- 
jury to their substance, any derangement to their 
position, any obstruction to their office. Observe the 
heart pumping at the centre at the rate of eighty 
strokes in a minute; one set of pipes carrying the 
stream away from it, another set bringing in its 
course the fluid back to it again; the lungs perform- 
ing their elaborate office, viz., distending and con- 
tracting their many thousand vesicles by a reciproca- 
tion which cannot cease for a minute; the stomach 
exercising its powerful chymistry; the bowels silent- 
ly propelling the changed aliment, collecting from it 
as it proceeds, and transmitting to the blood an inces- 
sant supply of prepared and assimilated nourishment; 
that blood pursuing its course ; the liver, the kidneys, 
the pancreas, the parotid, with many other known 
and distinguished glands, drawing off from it, all the 
while, their proper secretions. These several oper- 
* Ches. Anat., p. 184, ed. 3, p. 7. 188 
NATURAL THEOLOGY. 
ations, together with others more subtile but less ca- 
pable of being investigated, are going on within us 
at one and the same time. Think of this; and then 
observe how the body itself, the case which holds 
this machinery, is rolled, and jolted, and tossed about, 
the mechanism remainingunhurt, and with very little 
molestation even of its nicest motions. Observe a 
rope-dancer, a tumbler, or a monkey; the sudden inver- 
sions and contortions which the internal parts sustain 
by the postures into which their bodies are thrown; 
or, rather, observe the shocks which these parts, even 
in ordinary subjects, sometimes receive from falls 
and bruises, or by abrupt jerks and twists, without 
sensible or with soon recovered damage. Observe 
this, and then reflect how firmly every part must be se- 
cured, how carefully surrounded, how well tied down 
and together. 
This irroperty of animal bodies has never, T think, 
been under a distinct head, or so fully as 
it I may be allowed, therefore, in order to 
verify my observations concerning it, to set forth a 
short anatomical detail, though it oblige me to use 
more technical language than I should wish to intro- 
duce into a work of this kind. 
1. The heart (such care is taken of the centre of 
life) is placed between two soft lobes of the lungs; 
is tied to the mediastinum and to the pericardium, 
which pericardium is not only itself an exceedingly 
strong membrane, but adheres firmly to the duplica- 
ture of the mediastinum, and, by its point, to the mid- 
dle tendon of the diaphragm. The heart is also sus- 
tained in its place by the great bloodvessels which 
issue from it.* 
2. The lungs are tied to the sternum by the medi- 
astinum before, to the vertebrae by the pleura behind. 
It seems, indeed, to be the very use of the mediastinum 
(which is a membrane that goes straight through the 
middle of the thorax, from the breast to the back) to 
keep the contents of the thorax in their places; in 
* Keill's Anat., p. 107, ed. 3. NATURAL THEOLOGY. 
189 
particular, to hinder one lobe of the lungs from incom- 
moding another, or the parts of the lungs from press- 
ing upon each other when we lie on one side.* 
3. The liver is fastened in the body by two liga- 
ments : the first, which is large and strong, comes 
from the covering of the diaphragm, and penetrates 
the substance of the liver ; the second is the umbili- 
cal vein, which, after birth, degenerates into a liga- 
ment. The first, which is the principal, fixes the 
liver in its situation while the body holds an erect 
posture; the second prevents it from passing upon 
the diaphragm when we lie down; and both together 
sling or suspend the liver when we lie upon our backs, 
so that it may not compress or obstruct the ascend- 
ing vena cavaj to which belongs the important office 
of returning the blood from the body to the heart. 
4. The bladder is tied to the navel by the urachus, 
transformed into a ligament: thus, what was a pas- 
sage for urine to the foetus, becomes, afterbirth, a 
support or stay to the bladder. The peritonaeum also 
keeps the viscera from confounding themselves with, 
or pressing irregularly upon, the bladder; for the kid- 
neys and bladder are contained in a distinct duplica- 
ture of that membrane, being thereby partitioned off 
from the other contents of the abdomen. 
5. The kidneys are lodged in a bed of fat. 
6. The pancreas, or sweetbread, is strongly tied to 
the peritonaeum, which is the great wrapping-sheet 
that encloses all the bowels contained in the lower 
belly.J 
7. The spleen also is confined to its place by an 
adhesion to the peritonaeum and diaphragm, and by a 
connexion with the omentum.§ It is possible, in my 
opinion, that the spleen may be merely a sluffing, a 
soft cushion to fill up a vacancy or hollow, which, 
unless occupied, would leave the package loose and 
unsteady: for, supposing that it answers no other 
purpose than this, it must be vascular, and admit of a 
* Keill's Anat., p. 119, ed. 3. t Ches. Anat., p. 162. 
t Ibid., p. 57. § Ibid., p. 167. 190 
NATURAL THEOLOGY. 
circulation through it, in order to be kept alive or be 
a part of a living body.56 
8. The omentum, epiploon, or cawl, is an apron 
tucked up, or doubling upon itself at its lowest part. 
The upper edge is tied to the bottom of the stomach, 
to the spleen, as hath already been observed, and to 
part of the duodenum. The reflected edge also, after 
forming the doubling, comes up behind the front flap, 
and is tied to the colon and adjoining viscera.* 
9. The septa of the brain probably prevent one 
part of the organ from pressing with too great a 
weight upon another part. The processes of the 
dura mater divide the cavity of the scull, like so 
many inner partition walls, and thereby confine each 
hemisphere and lobe of the brain to the chamber 
which is assigned to it, without its being liable to rest 
upon, or intermix with, the neighbouring parts. The 
great art and caution of packing is to prevent one 
thing Ifhrting another. This, in the head, the chest, 
and the abdomen of an animal body, is, among other 
methods, provided for by membranous partitions and 
wrappings, which keep the parts separate. 
The above may serve as a short account of the 
manner in which the principal viscera are sustained 
in their places. But of the provisions for this pur- 
pose, by far, in my opinion, the most curious, and 
tvhere also such a provision was most wanted, is in 
the guts. It is pretty evident, that a long narrow 
tube (in man about five times the length of the body), 
laid from side to side in folds upon one another, wind- 
ing in oblique and circuitous directions, composed also 
of"a soft and yielding substance, must, without some 
extraordinary precaution for its safety, be continually 
displaced by*the various sudden and abrupt motions 
56 Our author has not failed to fall into the snare which lies in 
the path of the adventurous theorist. We have here a new the- 
ory of the spleen. The spleen, in truth, has a double office : it is 
ever found attached to the digesting part of the intestinal canal; 
and is reasonably considered to afford occasional increase of cir- 
culation to the stomach, and to supply blood to the liver of that 
quality which appears necessary to a copious secretion of bile. 
* Ches. Anat., p. 167. NATURAL THEOLOGY. 
191 
of the body which contains it. I should expect that, 
if not bruised or wounded by every fall, or leap, or 
twist, it would be entangled, or be involved with it- 
self; or, at the least, slipped and shaken out of the 
order in which it is disposed, and which order is ne- 
cessary to be preserved for the carrying on of the 
important functions which it has to execute in the 
animal economy. Let us see, therefore, how a dan- 
ger so serious, and yet so natural to the length, nar- 
rowness, and tubular form of the part, is provided 
against. The expedient is admirable, and it is this : 
The intestinal canal, throughout its whole process, is 
knit to the edge of a broad, fat membrane, called the 
mesentery. It forms the margin of this mesentery, 
being stitched and fastened to it like the edging of a 
ruffle , being four times as long as the mesentery it- 
self, it is what a seamstress would call "puckered or 
gathered on" to it. This is the nature of the con- 
nexion of the gut with the mesentery; and being thus 
joined to, or, rather, made a part of, the mesentery, it 
is folded and wrapped up together with it. Now 
the mesentery, having a considerable dimension in 
breadth, being in its substance withal both thick and 
suety, is capable of a close and safe folding, in com- 
parison of what the intestinal tube would admit of 
if it had remained loose. The mesentery, likewise, 
not only keeps the intestinal canal in its proper place 
and position, under all the turns and windings of its 
course, but sustains the numberless small vessels, 
the arteries, the veins, the lympheducts, and, above 
all, the lacteals, which lead from or to almost every 
point of its coats and cavity. This membrane, which 
appears to be the great support and security of the 
alimentary apparatus, is itself strongly tied to the 
first three vertebrae of the loins.* 
III. A third general property of animal forms is 
ieauiy. I do not mean relative beauty, or that of one 
individual above another of the same species ; but I 
mean, generally, the provision which is made in the 
* Keill's Anat., p. 45. 192 
body of almost every animal to adapt its appearance 
to the perception of the animals with which it con- 
verses. In our own species, for example, only con- 
sider what the parts and materials are of which the 
fairest body is composed; and no farther observation 
will be necessary to show how well these things are 
wrapped up, so as to form a mass which shall be ca- 
pable of symmetry in its proportion and of beauty in 
its aspect; how the bones are covered, the bowels 
concealed, the roughness of the muscle smoothed and 
softened; and how over the whole is drawn an in- 
tegument, which converts the disgusting materials of 
a dissecting-room into an object, of attraction to the 
sight, or one upon which it rests at least with ease 
and satisfaction. Much of this effect is to be attrib- 
uted to the intervention of the cellular or adipose 
membrane, which lies immediately under the skin; 
is a kind of lining to it; is moist, soft, slippery, and 
compressible; everywhere filling up the insterstices 
of the muscles, and forming thereby their roundness 
and flowing line, as well as the evenness and polish 
of the whole surface. 
All which seems to be a strong indication of de- 
sign, and of a design studiously directed to this pur- 
pose. And it being once allowed that such a purpose 
existed with respect to any of the productions of na- 
ture, we may refer, with a considerable degree of 
probability, other particulars to the same intention; 
such as the tints of flowers, the plumage of birds, the 
bright scales of fishes, the painted wings of butter- 
flies and beetles, the rich colours and spotted lustre 
of many tribes of insects. 
There are parts also of animals ornamental, and 
the properties by which they are so not subservient, 
that we know of, to any other purpose. The irides 
of most animals are very beautiful, without condu- 
cing at all, by their beauty, to the perfection of vision; 
and nature could in no part have employed her pen- 
cil to so much advantage, because no part presents 
itself so conspicuously to the observer, or communi- 
cates so great an effect to the whole aspect. 
NATURAL THEOLOGY. In plants, especially in the flowers of plants, the 
principle of beauty holds a still more considerable 
place in their composition; is still more confessed 
than in animals. Why, for one instance out of a 
thousand, does the corolla of the tulip, when advanced 
to its size and maturity, change its colour] The 
purposes, so far as we can see, of vegetable nutrition, 
might have been carried on as well by its continuing 
green. Or, if this could not be, consistently with the 
progress of vegetable life, why break into such a va- 
riety of colours ] This is no proper effect of age, or 
of declension in the ascent of the sap; for that, like 
the autumnal tints, would have produced one colour 
on one leaf, with marks of fading and withering. It 
seems a lame account to call it, as it has been called, 
a disease of the plant. Is it not more probable that 
this property, which is independent, as it should 
seem, of the wants and utilities of the plant, was cal- 
culated for beauty, intended for display I 
A ground, I know, of objection has been taken 
against the whole topic of argument, namely, that 
there is no such thing as beauty at all; in other 
words, that whatever is useful and familiar comes of 
course to be thought beautiful; and that things ap- 
pear to be so only by their alliance with these qual- 
ities. Our idea of beauty is capable of being in so 
great a degree modified by habit, by fashion, by the 
experience of advantage or pleasure, and by associ- 
ations arising out of that experience, that a question 
has been made whether it be not altogether gener- 
ated by these causes, or would have any proper ex- 
istence without them. It seems, however, a carry- 
ing of the conclusion too far, to deny the existence 
of the principle, viz., a native capacity of perceiving 
beauty, on account of an influence, or of varieties 
proceeding from that influence, to which it is subject, 
seeing that principles the most acknowledged are lia- 
ble to be affected in the same manner. I should ra- 
ther argue thus: The question respects objects of 
sight. Now every other sense hath its distinction 
of agreeable and disagreeable. Some tastes offend 
NATURAL THEOLOGY. 
193 
Vol. I.-R 194 
the palate, others gratify it. In brutes and insects, 
this distinction is stronger and more regular than in 
man. Every horse, ox, sheep, swine, when at liberty 
to choose, and when in a natural state, that is, when 
not vitiated by habits forced upon it, eats and rejects 
the same plants. Many insects, which feed upon par- 
ticular plants, will rather die than change their ap- 
propriate leaf. All this looks like a determination in 
the sense itself to particular tastes. In like manner, 
smells affect the nose with sensations pleasurable or 
disgusting. Some sounds, or compositions of sound, 
delight the ear: others torture it. Habit can do much 
in all these cases (and it is well for us that it can; 
for it is this power which reconciles us to many ne- 
cessities) : but has the distinction, in the mean time, 
of agreeable and disagreeable, no foundation in the 
sense itself 1 • What is true of the other senses is 
most probably true of the eye (the analogy is irre- 
sistible), viz., that there belongs to it an original con- 
stitution, fitted to receive pleasure from some im- 
pressions, and pain from others. 
I do not, however, know that the argument which 
alleges beauty as a final cause rests upon this con- 
cession. We possess a sense of beauty, however we 
come by it. It in fact exists. Things are not indif- 
ferent to this sense ; all objects do not suit it; many 
which we see are agreeable to it: many others dis- 
agreeable. It is certainly not the effect of habit upon 
the particular object, because the most agreeable 
objects are often the most rare; many, which are 
very common, continue to be offensive. If they 
be made supportable by habit, it is all which habit 
can do ; they never become agreeable. If this sense, 
therefore, be acquired, it is a result; the produce 
of numerous and complicated actions of external 
objects upon the senses, and of the mind upon its 
sensations. With this result, there must be a certain 
congruity to enable any particular object to please; 
and that congruity, we contend, is consulted in the 
aspect which is given to animal and vegetable bodies. 
IV. The skin and covering of animals is that upon 
NATURAL THEOLOGY. W-I---twt jj 
diud. , 
,'r'rin tliis village, on the 4th inst., Josephine, wife 
of Gustavus Shepard, Esq., and daughter of William 
and Sarah Lyon, of New York, aged 20 years. 
[Editors in Vermont and Michigan are requested 
to copy the above.] I Wright, and the President Directors and Company ( 
of the Bank of Safina, defendants. t 
In pursuance of a decree of this court, made in the ' 
above entitled cause, and bearing date on the sixth ' 
day of March, 1841,1 shall sell at public auction, on t 
the ninth day of May next., at 12 o'clcak at noon, at j 
the Eagle Tavern in the village of Lockport, Niaga- 1 
ra county, the .following premises, .viz: 195 
which their appearance chiefly depends; and it is 
that part which, perhaps, in all animals, is most dec- 
orated and most free from impurities. But, were 
beauty or agreeableness of aspect entirely out of 
the question, there is another purpose answered by 
this integument, and by the collocation of the parts 
of the body beneath it, which is of still greater im- 
portance; and that purpose is concealment. Were it 
possible to view through the skin the mechanism of 
our bodies, the sight would frighten us out of our 
wits. " Durst we make a single movement," asks a 
lively French writer, " or step from the place we 
were in, if we saw our blood circulating, the tendons 
pulling, the lungs blowing, the humours filtrating, and 
all the incomprehensible assemblage of fibres, tubes, 
pumps, valves, currents, pivots, which sustain an ex- 
istence at once so frail and so presumptuous V' 
V. Of animal bodies, considered as masses, there 
is another property more curious than it is generally 
thought to be, which is the faculty of standing : and 
it is more remarkable in two-legged animals than in 
quadrupeds, and, most of all, as being the tallest, and 
resting upon the smallest base, in man. There is 
more, I think, in the matter than we are aware of. 
The statue of a man, placed loosely upon a pedes- 
tal, would not be secure of standing half an hour. 
You are obliged to fix its feet to the block by bolts 
and solder, or the first shake, the first gust of wind, 
is sure to throw it down. Yet this statue shall ex- 
press all the mechanical proportions of a living model. 
It is not, therefore, the mere figure, or merely pla- 
cing the centre of gravity within the base, that is suf- 
ficient. Either the law of gravitation is suspended 
in favour of living substances, or something more is 
done for them in order to enable them to uphold their 
posture. There is no reason whatever to doubt that 
their parts descend by gravitation in the same man- 
ner as those of dead matter. The gift, therefore, 
appears to me to consist in a faculty of perpetually 
shifting the centre of gravity, by a set of obscure, 
indeed, but of quick-balancing actions, so as to keep 
NATURAL THEOLOGY. 196 
NATURAL THEOLOGY. 
the line of direction, which is a line drawn from that 
centre to the ground, within its prescribed limits. 
Of these actions it may be observed, first, that they 
in part constitute what we call strength. The dead 
body drops down. The mere adjustment, therefore, 
of weight and pressure, which may be the same the 
moment after death as the moment before, does not 
support the column. In cases also of extreme weak- 
ness, the patient cannot stand upright. Secondly, 
that these actions are only in a small degree volun- 
tary. A man is seldom conscious of his voluntary 
powers in keeping himself upon his legs. A child 
learning to walk is the greatest posture-master in the 
world ; but art, if it may be so called, sinks into habit, 
and he is soon able to poise himself in a great vari- 
ety of attitudes, without being sensible either of cau- 
tion or effort. But still there must be an aptitude of 
parts, upon which habit can thus attach; a previous 
capacity of motions which the animal is thus taught 
to exercise, and the facility with which this exercise 
is acquired, forms one object of our admiration. 
What parts are principally employed, or in what 
manner each contributes to its office, is, as has al- 
ready been confessed, difficult to explain. Perhaps 
the obscure motion of the bones of the feet may have 
their share in this effect. They are put in action by 
every slip or vacillation of the body, and seem to assist 
in restoring its balance. Certain it is, that this cir- 
cumstance in the structure of the foot, viz., its being 
composed of many small bones, applied to and artic- 
ulating with one another by diversely shaped sur- 
faces, instead of being made of one piece, like the 
last of a shoe, is very remarkable. NATURAL THEOLOGY. 
197 
I suppose, also, that it would be difficult to stand firm- 
ly upon stilts or wooden legs, though their base exact- 
ly imitated the figure and dimensions of the sole of 
the foot. The alternation of the joints, the knee joint 
bending backward, the hip joint forward; the flexi- 
bility, in every direction, of the spine, especially in 
the loins and neck, appear to be of great moment in 
preserving the equilibrium of the body. With respect 
to this last circumstance, it is observable, that the 
vertebrae are so confined by ligaments as to allow no 
more slipping upon their bases than what is just suf- 
ficient to break the shock which any violent motion 
may occasion to the body. A certain degree, also, 
of tension of the sinews appears to be essential to an 
erect posture; for it is by the loss of this that the 
dead or paralytic body drops down. 
The whole is a wonderful result of combined pow- 
ers and of very complicated operations. Indeed, 
that standing is not so simple a business as we ima- 
gine it to be, is evident from the strange gesticulations 
of a drunken man, who has lost the government of 
his centre of gravity.57 
We have said that this property is the most worthy 
of observation in the human body; but a bird, rest- 
ing upon its perch or hopping upon a spray, affords 
57 All this is admirably well put by our author. Yet when he 
says, " the gift consists in the faculty of perpetually shifting the 
centre of gravity by a set of obscure, indeed, but of auick-balan- 
cing actions," he states a fact, but omits the most surprising cir- 
cumstance of all. No doubt such efforts are made; but what 
directs them ? If a man should balance a staff, resting it on the 
point of the finger, he shifts the finger continually , in doing which 
he is directed by the eye; he sees the staff inclining. How does 
a man judge of the inclination of his body in the very first degree 
of deviation from the perpendicular? He does not see himself, 
nor is he directed by the objects around him, since a blind man 
will stand as securely as one who sees. The fact is, that he has 
a knowledge of muscular action, a sensibility to the finest adjust- 
ment of the muscles, by which he directs their efforts. This 
sense is, of all, the most marvellous : a sensibility to an internal 
motion, more minute and curious than are the sensibilities to ex- 
ternal impression; and which, as may be easily proved, ministers 
to a variety of properties in the living body, and especially to the 
organs of sense themselves. 198 
NATURAL THEOLOGY. 
no mean specimen of the same faculty. A chicken 
runs off as soon as it is hatched from the egg; yet a 
chicken, considered geometrically, and with relation 
to its centre of gravity, its line of direction, and its 
equilibrium, is a very irregular solid. Is this gift, 
therefore, or instruction 1 May it not be said to be 
with great attention that nature hath balanced the 
body upon its pivots 1 
I observe also, in the same bird, a piece of useful 
mechanism of this kind. In the trussing of a fowl, 
upon bending the legs and thighs up towards the body, 
the cook finds that the claws close of their own ac- 
cord. Now let it be remembered that this is the 
position of the limbs in which the bird rests upon its 
perch. And in this position it sleeps in safety ; for the 
claws do their office in keeping hold of the support, 
not by any exertion of voluntary power, which sleep 
might suspend, but by the traction of the tendons, in 
consequence of the attitude which the legs and thighs 
take by the bird sitting down, and to which the mere 
weight of the body gives the force that is necessary. 
VI. Regarding the human body as a mass ; regard- 
ing the general conformations which obtain in it; re- 
garding, also, particular parts in respect to those con- 
formations, we shall be led to observe what I call 
" interrupted analogies." The following are examples 
of what I mean by these terms; and I do not know- 
how such critical deviations can, by any possible hy- 
pothesis, be accounted for without design. 
I. All the bones of the body are covered with a 
periosteum except the teeth, where it ceases ; and an 
enamel of ivory, which saws and files will hardly 
touch, comes into its place. No one can doubt of the 
use and propriety of this difference; of the " anal- 
ogy" being thus " interrupted;" of the rule, which 
belongs to the confirmation of the bones stopping 
where it does stop ; for, had so exquisitely sensible a 
membrane as the periosteum invested the teeth, as 
it invests every other bone of the body, their action, 
necessary exposure, and irritation would have subject- 
ed the animal to continual pain. General as it is, it NATURAL THEOLOGY. 
199 
was not the sort of integument which suited the 
teeth ; what they stood in need of was a strong, hard, 
insensible, defensive coat; and exactly such a cover- 
ing is given to them, in the ivory enamel which ad- 
heres to their surface.58 
II. The scarf-skin, which clothes all the rest of the 
body, gives way, at the extremities of the toes and 
fingers, to nails. A man has only to look at his hand, 
to observe with what nicety and precision that cover- 
ing, which extends over every other part, is here 
superseded by a different substance and a different 
texture. Now, if either the rule had been necessary, 
or the deviation from it accidental, this effect would 
58 Sir C. Bell notices the admirable provision made by the Cre- 
ator for the preservation of the teeth. Being subjected to constant 
pressure and attrition, we might expect that they would be driven 
into their sockets or worn away. But there is a vital principle in 
the teeth, in virtue of which they not only resist pressure, but are 
protruded by means of it, as we see in children. After reaching 
their full size, they will remain stationary if used ; but if by any 
accident, such as the loss of the opposite tooth, they are not em- 
ployed, they rise too high, project, and fall out. In the case of 
ruminating animals, however, where there are no teeth in the 
forepart of the upper jaw, and where, of course, there is no occa- 
sion to provide against pressure, the lower teeth do not rise and 
fall out as they would in a man. 
In regard to attrition, it is curious to observe how its effects are 
guarded against. In animals that gnaw, such as the beaver, squir- 
rel, &c., the front teeth must always be kept sharp; and, to effect 
this, they have the enamel only in front, which, wearing away less 
rapidly than the bone which is behind, preserves the sharp edge of 
the tooth. At the same time, by constant additions at the root, 
they are thrust forward and kept of the proper size. In animals 
that live on grass, grain, &c., the teeth need to be kept rough for 
grinding ; and a provision is made for this similar to what we meet 
with in millstones. For as the burrstone is composed of a hard 
substance (feldspar) imbedded in one much softer, its roughness is 
continually preserved by the unequal wearing away of the mate- 
rials. In like manner the tooth of a gramnivorous animal is com- 
posed of alternate layers of the hardest bone and still harder en- 
amel. 
In the case of the elephant, the provision for protecting the teeth 
against the great force which acts upon them is very peculiar. 
Beside being of the strongest material, they have a power of re- 
volving, by which, as soon as one corner is worn away, a new and 
perfect one is presented.-Am. Ed. 200 
NATURAL THEOLOGY. 
not be seen. When I speak of the rule being neces- 
sary, I mean the formation of the skin upon the sur- 
face being produced by a set of causes constituted 
without design, and acting, as all ignorant causes 
must act, by a general operation. Were this the 
case, no account could be given of the operation be- 
ing suspended at the fingers' ends, or on the back 
part of the fingers, and not on the fore part. On the 
other hand, if the deviation were accidental, an er- 
ror, an anamelism; were it anything else than settled 
by intention, we should meet with nails upon other 
parts of the body; they would be scattered over the 
surface like warts or pimples.59 
III. All the great cavities of the body are enclosed 
by membranes except the scull. Why should not 
the. brain be content with the same covering as that 
which serves for the other principal organs of the 
body? The heart, the lungs, the liver, the stomach, 
the bowels, have all soft integuments, and nothing 
else. The muscular coats are all soft and membra- 
neous. I can see a reason for this distinction in the 
final cause, but in no other. The importance of the 
brain to life (which experience proves to be imme- 
diate), and the extreme tenderness of its substance, 
make a solid case more necessary for it than for any 
other part; and such a case the hardness of the scull 
supplies. When the smallest portion of this natural 
casket is lost, how carefully, yet how imperfectly, is it 
replaced by a plate of metal! If an anatomist should 
59 The human nail is calculated to support the cushion of the 
extremity of the finger, and is important to us in grasping or hold 
ing anything ; but more so still in sustaining that cushion as the 
chief organ of touch. There are other parts of the body which 
have exquisite sensibility, yet they are not provided so as to give 
us that information of the conditon of matter which we have 
through the finger, and in a less degree through the whole inner 
surface of the hand. We easily feel, for example, the pulsation 
of the artery at the wrist, through the combination of the sensibil- 
ity of the nerve of touch with the elastic cushion of the finger. 
The best proof of the use of the elastic cushion is this: although the 
tip of the tongue feels so exquisitely that the presence of a hair of 
wool troubles us, yet, if we apply it to the pulse, we shall not be 
sensible of the beat. NATURAL THEOLOGY. 
201 
say that this bony protection is not confined to the 
brain, but is extended along the course of the spine, 
I answer, that he adds strength to the argument. If 
he remark that the chest is also fortified by bones, I 
reply, that I should have alleged this instance my- 
self, if the ribs had not appeared subservient to the 
purpose of motion as well as of defence. What dis- 
tinguishes the scull from every other cavity is, that 
the bony covering completely surrounds its contents, 
and is calculated, not for motion, but solely for de- 
fence. Those hollows, likewise, and inequalities 
which we observe in the inside of the scull, and 
which exactly fit the folds of the brain, answer the 
important design of keeping the substance of the 
brain steady, and of guarding it against concussions. 
CHAPTER XII. 
COMPARATIVE ANATOMY. 
Whenever we find a general plan pursued, yet with 
such variations in it as are, in each case, required by 
the particular exigency of the subject to which it is 
applied, we possess, in such a plan and such adapta- 
tion, the strongest evidence that can be afforded of 
•intelligence and design: an evidence which the most 
completely excludes every other hypothesis. If the 
general plan proceeded from any fixed necessity in 
the nature of things, how could it accommodate itself 
to the various wants and uses which it had to serve 
under different circumstances and on different occa- 
sions 1 Arkwright's mill was invented for the spin- 
ning of cotton. We see it employed for the spinning 
of wool, flax, and hemp, with such modifications of 
the original principle, such variety in the same plan, 
as the texture of those different materials rendered 
necessary. Of the machine's being put together with 202 
NATURAL THEOLOGY 
design, if it were possible to doubt while we saw it 
only under one mode and in one form ; when we 
came to observe it in its different applications, with 
such changes of structure, such additions and supple- 
ments, as the special and particular use in each case 
demanded, we could not refuse any longer our assent 
to the proposition, " that intelligence, properly and 
strictly so called (including under that name fore- 
sight, consideration, reference to utility), had been 
employed, as well in the primitive plan as in the sev- 
eral changes and accommodations which it is made 
to undergo." 
Very much of this reasoning is applicable to what 
has been called Comparative Anatomy. In their gen- 
eral economy, in the outlines of the plan, in the con- 
struction as well as offices of their principal parts, 
there exists between all large terrestrial animals a 
close resemblance. In all, life is sustained and the 
body nourished by nearly the same apparatus. The 
heart, the lungs, the stomach, the liver, the kidneys, 
are much alike in all. The same fluid (for no distinc- 
tion of blood has been observed) circulates through 
their vessels, and nearly in the same order. The 
same cause, therefore, whatever that cause was, has 
heen concerned in the origin, has governed the pro- 
duction, of these different animal forms. 
When we pass on to smaller animals or to the in- 
habitants of a different element, the resemblance be- 
comes more distant and more obscure, but still the 
plan accompanies us. 
And, what we can never enough commend, and 
which it is our business at present to exemplify, the 
plan is attended, through all its varieties and deflec- 
tions, by subserviences to special occasions and util- 
ities. 
I. The covering of different animals (though wheth- 
er I am correct in classing this under their anatomy 
I do not know) is the first thing which presents itself 
to our observation; and is, in truth, both for its vari- 
ety and its suitableness to their several natures, as 
much to be admired as any part of their structure NATURAL THEOLOGY. 
203 
We have bristles, hair, wool, furs, feathers, quills, 
prickles, scales; yet in this diversity, both of mate- 
rial and form, we cannot change one animal's coat 
for another without evidently changing it for the 
worse; taking care, however, to remark, that these 
coverings are, in many cases, armour as well as cloth- 
ing, intended for protection as well as warmth. 
The human animal is the only one which is naked, 
and the only one which can clothe itself. This is one 
of the properties which renders him an animal of 
all climates and of all seasons. He can adapt the 
warmth or lightness of his covering to the tempera- 
ture of his habitation. Had he been born with a 
fleece upon his back, although he might have been 
comforted by its warmth in high latitudes, it would 
have oppressed him by its weight and heat as the 
species spread towards the equator. 
What art, however, does for men, nature has, in 
many instances, done for those animal's which are in- 
capable of art. Their clothing, of its own accord, 
changes with their necessities. This is particularly 
the case with that large tribe of quadrupeds which 
are covered with furs. Every dealer in hareskins 
and rabbit-skins knows how much the fur is thicken- 
ed by the approach of winter. It seems to be a part 
of the same constitution and the same design, that 
wool in hot countries degenerates, as it is called, but, 
in truth (most happily for the animal's ease), passes 
into hair: while, on the contrary, that hair, in the 
dogs of the polar regions, is turned into wool, or 
something very like it. To which may be referred 
what naturalists have remarked, that bears, wolves, 
foxes, hares, which do not take the water, have the 
fur much thicker on the back than the belly ; whereas, 
in the beaver, it is the thickest upon the belly, as are 
the feathers in water-fowl. We know the final cause 
of all this, and we know no other. 
The covering of birds cannot escape the most vul- 
gar observation: its lightness, its smoothness, its 
warmth; the disposition of the feathers all inclined 
backward, the down about their stem, the overlap- 204 
NATURAL THEOLOGY. 
ping of their tips, their different configuration in dif- 
ferent parts, not to mention the variety of their col- 
ours, constitute a vestment for the body so beautiful, 
and so appropriate to the life which the animal is to 
lead, as that, I think, we should have had no concep- 
tion of anything equally perfect if we had never 
seen it, or can now imagine anything more so. Let 
us suppose (what is possible only in supposition) a 
person who had never seen a bird to be presented 
with a plucked pheasant, and bid to set his wits to 
work how to contrive for it a covering which shall 
unite the qualities of warmth, levity, and least resist- 
ance to the air, and the highest degree of each; giv- 
ing it also as much of beauty and ornament as he 
could afford. He is the person to behold the work 
of the Deity, in this part of his creation, with the 
sentiments which are due to it. 
The commendation which the general aspect of 
the feathered world seldom fails of exciting, will be 
increased by farther examination. It is one of those 
cases in which the philosopher has more to admire 
than the common observer. Every feather is a me- 
chanical wonder. If we look at the quill, we find 
properties not easily brought together, strength and 
lightness. I know few things more remarkable than 
the strength and lightness of the very pen with which 
I am writing. If wre cast our eye to the upper part 
of the stem, we see a material, made for the purpose, 
used in no other class of animals, and in no other 
class of birds, tough, light, pliant, elastic. The pith 
also, which feeds the feathers, is, among animal sub- 
stances, sui generis, neither bone, flesh, membrane, 
nor tendon.* 
But the artificial part of a feather is the heard, or, 
as it is sometimes, I believe, called, the vane. By 
the beards are meant what are fastened on each side 
of the stem, and what constitute the breadth of the 
* The quill part of a feather is composed of circular and lon- 
gitudinal fibres. In making a pen, you must scrape off the coat 
of circular fibres, or the quill will split in a ragged, jagged man 
ner, making what boys call cat's teeth. NATURAL THEOLOGY. 
205 
feather; what we usually strip off from one side or 
both when we make a pen. The separate pieces, or 
laminae, of which the beard is composed, are called 
threads, sometimes filaments or rays. Now the first 
thing which an attentive observer will remark is, 
how much stronger the beard of the feather shows 
itself to be when pressed in a direction perpendicular 
to its plane, that when rubbed, either up or down, in 
the line of the stem; and he will soon discover the 
structure which occasions this difference, viz., that 
the laminae whereof these beards are composed are 
flat, and placed with their flat sides towards each 
other, by which means, while they easily bend for 
the approaching of each other, as any one may per- 
ceive by drawing his finger ever so lightly upward, 
they are much harder to bend out of their plane, 
which is the direction in which they have to encoun- 
ter the impulse and pressure of the air, and in which 
their strength is wanted and put to the trial. 
This is one particularity in the structure of a feath- 
er : a second is still more extraordinary. Whoever 
examines a feather cannot help taking notice that 
the threads or laminae of which we have been speak- 
ing, in their natural state, unite; that their union is 
something more than the mere apposition of loose 
surfaces; that they are not parted asunder without 
some degree of force ; that, nevertheless, there is no 
glutinous cohesion between them ; that, therefore, by 
some mechanical means or other, they catch or clasp 
among themselves, thereby giving to the beard or 
vane its closeness and compactness of texture. Nor 
is this all: when two laminae which have been separ- 
ated by accident or force are brought together again, 
they immediately reclasp; the connexion, whatever 
it was, is perfectly recovered, and the beard of the 
feather becomes as smooth and firm as if nothing had 
happened to it. Draw your finger down the feather, 
which is against the grain, and you break, probably, 
the junction of some of the contiguous threads ; draw 
your finger up the feather, and you restore all things 
to their former state. This is no common contri- 
Vol. I.- 206 
NATURAL THEOLOGY. 
vance: and now for the mechanism by which it is 
effected. The threads or laminae above mentioned 
are interlaced with one another; and the interlacing 
is performed by means of a vast number of fibres or 
teeth, which the laminae shoot forth on each side, and 
which hook and grapple together. A friend of mine 
counted fifty of these fibres in one twentieth of an 
inch. These fibres are crooked, but curved after a 
different manner ; for those which proceed from the 
thread on the side towards the extremity of the feath- 
er are longer, more flexible, and bent downward; 
whereas those which proceed from the side towards 
the beginning or quill end of the feather are shorter, 
firmer, and turn upward. The process, then, which 
takes place, is as follows: when two laminae are 
pressed together, so that these long fibres are forced 
far enough over the short ones, their crooked parts 
fall into the cavity made by the crooked parts of the 
others, just as the latch that is fastened to a door en- 
ters into the cavity of the catch fixed to the door- 
post, and there hooking itself, fastens the door; for 
it is properly in this manner that one thread of a feath- 
er is fastened to the other. 
This admirable structure of the feather, which it 
is easy to see with the microscope, succeeds per- 
fectly for the use to which nature has designed it; 
which use was, not only that the laminae might be 
united, but that, when one thread or lamina has been 
separated from another by some external violence, it 
might be reclasped with sufficient facility and expe- 
dition.* 
In the ostrich, this apparatus of crotchets and fibres, 
of hooks and teeth, is wanting; and we see the 
consequence of the want. The filaments hang loose 
and separate from one another, forming only a kind 
of down, which constitution of the feathers, however 
it may fit them for the flowing honours of a lady's 
headdress, may be reckoned an imperfection in the 
* The above account is taken from Memoirs for a Natural His- 
tory of Animals, by the Royal Academy of Paris, published in 
1701, p. 219. NATURAL THEOLOGY. 
207 
birds, inasmuch as wings composed of these feathers, 
although they may greatly assist it in running, do 
not serve for flight. 
But, under the present division of our subject, our 
business with feathers is as they are the covering of 
the bird. And herein a singular circumstance oc- 
curs. In the small order of birds which winter with 
us, from a snipe downward, let the external colour 
of the feathers be what it will, their Creator has uni- 
versally given them a bed of black down next their 
bodies. Black, we know, is the warmest colour; 
and the purpose here is, to keep in the heat arising 
from the heart and circulation of the blood.60 It is 
farther likewise remarkable, that this is not found in 
larger birds ; for which there is also a reason. Small 
birds are much more exposed to the cold than large 
ones, forasmuch as they present, in proportion to 
their bulk, a much larger surface to the air. If a 
turkey were divided into a number of wrens (sup- 
posing the shape of the turkey and the wren to be 
similar), the surface of all the wrens would exceed 
the surface of the turkey in the proportion of the 
length, breadth (or of any homologous line) of a tur- 
60 When we attempt to apply the lights of experimental philos- 
ophy to this subject, the inquiry is not a little embarrassing. A 
loose woolly texture or down, as it implies the presence of air in 
its interstices, air being a bad conductor of heat, is therefore a 
warm covering; it prevents the expenditure of animal heat. 
When we consider the colour of the coverings of birds, we must 
take new elements into our process of reasoning ; we must reflect 
on the effects of the conduction and radiation of heat. The con- 
duction is the conveyance of heat, and the radiation is the parting 
with it into the atmosphere or into space. We have already ex- 
plained why the interior covering of the arctic bird should be 
loose; as to the colour, its effect must result from radiation. It 
appears (to use the vulgar language) that the influence of cold, 
both on quadrupeds and birds, is to increase their woolly or downy 
covering, and, in many instances, to change the exterior colour to 
white : in other and more correct words, a provision is made for 
changing their clothinjfiso as to suit their altered circumstances. 
This change of colour corresponds with philosophical experi- 
ments: a white surface absorbing the least, and radiating the 
least, it should therefore tend to confine the vital heat within the 
animal, and carry it off slowlv to the atmosphere. 208 
NATURAL THEOLOGY. 
key to that of a wren, which would be, perhaps, a 
proportion of ten to one. It was necessary, there- 
fore, that small birds should be more warmly clad 
than large ones; and this seems to be the expedient 
by which that exigency is provided for. 
II. In comparing different animals, I know no part 
of their structure which exhibits greater variety, or, 
in that variety, a nicer accommodation to their re- 
spective convenience than that which is seen in the 
different formations of their mouths. Whether the 
purpose be the reception of aliment merely, or the 
catching of prey, the picking up of seeds, the crop- 
ping of herbage, the extraction of juices, the suction 
of liquids, the breaking and grinding of food, the taste 
of that food, together with the respiration of air, and, 
in conjunction with it, the utterance of sound ; these 
various offices are assigned to this one part, and, in 
different species, provided for as they are wanted by 
its different constitution. In the human species, for- 
asmuch as there are hands to convey the food to the 
mouth, the mouth is flat, and, by reason of its flat- 
ness, fitted only for reception; whereas the projecting 
jaws, the wide rictus, the pointed teeth of the dog 
and his affinities, enable them to apply their mouths 
to snatch and seize the object of their pursuit. The 
full lips, the rough tongue, the corrugated cartilagi- 
nous palate, the broad, cutting teeth of the ox, the 
deer, the horse, and the sheep, qualify this tribe for 
browsing upon their pasture; either gathering large 
mouthfuls at once where the grass is long, which is 
the case with the ox in particular, or biting close 
where it is short, which the horse and the sheep are 
able to do in a degree that one could hardly expect. 
The retired under jaw of a swine works in the ground, 
after the protruding snout, like a prong or plough- 
share, has made its way to the roots upon which it 
feeds. A conformation so happy was not the gift of 
chance. 
In birds, this organ assumes a new character; new 
both in substance 'and in form, but in both wonder- 
fully adapted to the wants and uses of a distinct mode NATURAL THEOLOGY. 
209 
of existence. We have no longer the fleshy lips, the 
teeth of enamelled bone ; but we have, in the place of 
these two parts, and to perform the office of both, a 
hard substance (of the same nature with that which 
composes the nails, claws, and hoofs of quadrupeds), 
cut out into proper shapes, and mechanically suited 
to the actions which are wanted. The sharp edge 
and tempered point of the sparrouPs bill picks almost 
every kind of seed from its concealment in the plant, 
and not only so, but hulls the grain, breaks and shat- 
ters the coats of the seed, in order to get at the ker- 
nel. The hooked beak of the hawk tribe separates the 
flesh from the bones of the animals which it feeds 
upon almost with the cleanness and precision of a 
dissector's knife. The butcher-bird transfixes its 
prey upon the spike of a thorn while it picks its 
bones. In some birds of this class we have the cross- 
bill, i. e., both the upper and lower bill hooked, and 
their tips crossing. The spoon-bill enables the goose 
to graze, to collect its food from the bottom of pools, 
or to seek it amid the soft or liquid substances with 
which it is mixed. The long, tapering bill of the 
snipe and woodcock penetrate still deeper into moist 210 
earth, which is the bed in which the food of that spe- 
cies is lodged. This is exactly the instrument which 
the animal wanted. It did not want strength in its 
bill, which was inconsistent with the slender form of 
the animal's neck, as well as unnecessary for the 
kind of aliment upon which it subsists; but it wanted 
length to reach its object.61 
NATURAL THEOLOGY. 
C1 With the instrument, as we have before hinted, we should 
expect a particular instinctive action, and a corresponding muscu- 
lar power. As an animal with horns has a powerful neck, so has 
the neck of the heron, which is introduced here, an extraordinary 
muscular power, without which, indeed, the long and sharp bill 
would be of little use. When the dog approaches the wounded 
heron, the bird throws itself upon its back, and, retracting its long 
neck, suddenly darts it out with a force which strikes the bill deep 
into the dog. If you hold your hat towards the bird, the bill will 
be struck quite through it. In contending with the hawk, when 
the latter is spitted, it is not by the rapid descent of the hawk, but 
by the force with which the heron drives its bill. 
The strength of the bill of the parrot, and that of all birds which 
break the stones of fruit, or nuts, or hard seeds, is in another di- 
rection : the bill is hooked, yet is differently formed from that of 
the carnivorous bird. The intention is, in the first place, that 
the point shall play vertically, which, with the strengthening of 
successive layers near the point, enables it to break hard mate- 
rials; and, secondly, that by this form the nut or seed may be 
brought nearer the joining or articulation of the jaw, which gives 
the same advantage that we have when we put a nut nearer the 
joint of the nut-cracker, that is, nearer the fulcrum. 
One disadvantage of this form and shortness of the bill would 
be, that the mandibles could not open wide enough to take in a 
large seed; but it is provided that the upper mandible shall move NATURAL THEOLOGY. 
211 
But the species of bill which belongs to the birds 
that live by suction deserves to be described in its re- 
lation to that office. They are what naturalists call 
serrated or dentated bills; the inside of them, towards 
the edge, being thickly set with parallel or concen- 
tric rows of short, strong, sharp-pointed prickles. 
These, though they should be called teeth, are not for 
the purpose of mastication, like the teeth of quadru- 
peds, nor yet, as in fish, for the seizing and retaining 
of their prey, but for quite a different use. They 
form a filter. The duck, by means of them, discusses 
the mud; examining with great accuracy the puddle, 
the brake, every mixture which is likely to contain 
her food. The operation is thus carried on: The 
liquid or semi-liquid substances in which the animal 
has plunged her bill, she draws, by the action of 
upon the scull as well as the lower one, a subject which has not 
escaped our author's attention. 
The form of the bill of the crossbill, which he mentions, looks 
like an imperfection, but is attended with real advantages. It is 
not for cutting, but rather for splitting up a seed into halves, and 
tearing the cones of the fir-tree. 
One of the most curious provisions is in the bill of the sea crow. 
The mandibles are compressed into the form of simple laminse, 
and the lower mandible projects beyond the upper one ; so that, 
as he skims along the water, he dips his bill and lifts his food by 
the most appropriate instrument. 212 
NATURAL THEOLOGY. 
her lungs, through the narrow interstices which lie 
between these teeth, catching, as the stream passes 
across her beak, whatever it may happen to bring 
with it that proves agreeable to her choice, and easily 
dismissing all the rest. Now suppose the purpose 
to have been, out of a mass of confused and hetero- 
geneous substances, to separate for the use of the 
animal, or, rather, to enable the animal to separate 
for its own, those few particles which suited its taste 
and digestion, what more artificial or commodious in- 
strument of selection could have been given to it than 
this natural filter? It has been observed, also (what 
must enable the bird to choose and distinguish with 
greater acuteness, as well, probably, as what greatly 
increases its luxury), that the bills of this species are 
furnished with large nerves; that they are covered 
with a skin ; and that the nerves run down to the very 
extremity. In the curlew, woodcock, and snipe, there 
are three pairs of nerves, equal almost to the optic 
nerve in thickness, which pass first along the roof of 
the mouth, and then along the upper chap down to the 
point of the bill, long as the bill is.62 
But to return to the train of our observations. The 
similitude between the bills of birds and the mouths 
of quadrupeds is exactly such as, for the sake of the 
argument, might be wished for. It is near enough to 
show the continuation of the same plan: it is remote 
enough to exclude the supposition of the difference 
being produced by action or use. A more prominent 
contour or a wider gap might be resolved into the 
effects of continued efforts, on the part of the spe- 
cies, to thrust out the mouth or open it to the stretch. 
But by what course of action, or exercise, or en- 
deavour, shall we get rid of the lips, the gums, the 
teeth, and acquire in the place of them pincers of 
horn ? By what habit shall we so completely change, 
not only the shape of the part, but the substance of 
which it is composed ? The truth is, if we had seen 
02 These are branches of the fifth nerve of the head, which 
alone, of all the nine nerves of the brain, bestows sensibility on 
the organ of touch. NATURAL THEOLOGY. 
213 
no other than the mouths of quadrupeds, we should 
have thought no other could have been formed : little 
could we have supposed that all the purposes of a 
mouth furnished with lips and armed with teeth could 
be answered by an instrument which had none of 
these; could be supplied, and that with many addi- 
tional advantages, by the hardness, and sharpness, 
and figure of the bills of birds. Everything about 
the animal mouth is mechanical. The teeth of fish 
have their points turned backward, like the teeth of 
a wool or cotton card.63 The teeth of lobsters work 
one against another, like the sides of a pair of shears. 
In many insects, the mouth is convened into a pump 
or sucker, fitted at the end sometimes with a wimble, 
sometimes with a forceps; by which double provis- 
ion, viz., of the tube and the penetrating form of the 
point, the insect first bores through the integuments 
of its prey, and then extracts the juices. And what 
is most extraordinary of all, one sort of mouth, as 
the occasion requires, shall be changed into another 
sort. The caterpillar could not live without teeth; 
in several species, the butterfly formed from it could 
not use them. The old teeth, therefore, are cast off 
with the exuviae of the grub; a new and totally dif- 
ferent apparatus assumes their place in the fly. 
Amid these novelties of form, we sometimes forget 
that it is all the while the animal's mouth; that, 
whether it be lips, or teeth, or bill, or beak, or shears, 
or pump, it is the same part diversified; and it is also 
remarkable that, under all the varieties of configura- 
tion with which we are acquainted, and which are 
very great, the organs of taste and smelling are situ- 
ated near each other. 
III. To the mouth adjoins the gullet: in this part, 
also, comparative anatomy discovers a difference of 
structure adapted to the different necessities of the 
animal. In brutes, because the posture of their neck 
conduces little to the passage of the aliment, the 
63 To enable them the better to retain their prey, struggling to 
escape.-Am. Ed. 214 
fibres of the gullet which act in this business run in 
two close spiral lines, crossing each other: in men 
these fibres run only a little obliquely from the upper 
end of the oesophagus to the stomach, into which, by a 
gentle contraction, they easily transmit the descend- 
ing morsels ; that is to say, for the more laborious deg- 
lutition of animals which thrust their food up instead 
of down, and also through a longer passage, a pro- 
portionably more powerful apparatus of muscles is 
provided ; more powerful, not merely by the strength 
of the fibres, which might be attributed to the great- 
er exercise of their force, but in their collocation, 
which is a determinate circumstance, and must have 
been original. 
IV. The gullet leads to the intestines: here, like- 
wise, as before, comparing quadrupeds with man, 
under a general similitude we meet with appropriate 
differences. The valvula, conniventes, or, as they are 
by some called, the semilunar valves, found in the 
human intestine, are wanting in that of brutes. 
These are wrinkles or plates in the innermost coat 
of the guts, the effect of which is to retard the prog- 
ress of the food through the alimentary canal. It 
is easy to understand how much more necessary such 
a provision may be to the body of an animal of an 
erect posture, and in which, consequently, the weight 
of the food is added to the action of the intestine, 
than of a quadruped, in which the course of the food, 
from its entrance to its exit, is nearly horizontal; 
but it is impossible to assign any cause, except the 
final cause, for this distinction actually taking place. 
So far as depends upon the action of the part, this 
structure was more to be expected in a quadruped 
than in a man. In truth, it must in both have been 
formed, not by action, but in direct opposition to ac- 
tion and to pressure ; but the opposition which would 
arise from pressure is greater in the upright trunk 
than in any other. That theory, therefore, is point- 
edly contradicted by the example before us. The 
structure is found where its generation, according 
to the method by which the theorist would have it 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
215 
generated, is the most difficult; but, observe, it is 
found where its effect is the most useful.* 
The different length of the intestines in carnivo- 
rous and herbivorous animals has been noticed on a 
former occasion. The shortest, I believe, is that of 
some birds of prey, in which the intestinal canal is 
little more than a straight passage from the mouth to 
the vent. The longest is in the deer kind. The in- 
testines of a Canadian stag, four feet high, measured 
ninety-six feet.j- The intestine of a sheep, unravel- 
led, measured thirty times the length of the body. 
The intestine of a wildcat is only three times the 
length of the body. Universally, where the sub- 
stance upon which the animal feeds is of slow con- 
coction, or yields its chyle with more difficulty, there 
the passage is circuitous and dilatory, that time and 
space may be allowed for the change and the absorp- 
tion which are necessary. Where the food is soon 
dissolved or already half assimilated, an unnecessa- 
ry or perhaps hurtful detention in avoided, by giving 
to it a shorter and a readier route. 
V. In comparing the bones of different animals, we 
are struck, in the bones of birds, with a propriety 
which could only proceed from the wisdom of an in- 
telligent and designing Creator.64 In the bones of an 
* It may be questioned whether those extremely soft rugae or 
folds of the villous coat of the intestine can, in the least, retard 
the passage of the food through its canal; nor does the erect at- 
titude of man require them ; for, since there are as many of the 
convolutions ascending as there are descending, the weight of the 
food can have no influence in the action of the intestine: it is 
certain, however, that this arrangement of the internal coat af- 
fords a more extensive surface for the lacteals and secreting vessels: 
and this appears to be the real use of the valvulas conniventes-.- 
Paxton. 
+ Mem. Acad. Paris, 1701, p. 170. 
64 In comparing the bones of different animals, the author con- 
fines himself to birds and quadrupeds. The comparison might be 
extended to all animals, and should embrace not only the form, 
but also the composition of the bones. If we begin with the lower 
animals, such as the sponge, snail, &c., and ascend through rep- 
tiles, fishes, mammalia, up to man, we shall find that the material 
varies in its quality and proportions, so as to secure the nicest adap- 
tation of the shell or bone to- the wants and condition of the an- 216 
NATURAL THEOLOGY. 
animal which is to fly, the two qualities required are 
strength and lightness. Wherein, therefore, do the 
bones of birds (I speak of the cylindrical bones) dif- 
fer in these respects from the bones of quadrupeds I 
In three properties : first, their cavities are much 
larger in proportion to the weight of the bone than 
in those of quadrupeds; secondly, these cavities are 
empty; thirdly, the shell is of a firmer texture than 
is the substance of other bones. It is easy to ob- 
serve these particulars even in picking the wing or 
leg of a-chicken. Now the weight being the same, 
the diameter, it is evident, will be greater in a hol- 
low bone than in a solid one, and with the diameter, 
as every mathematician can prove, is increased, cet- 
eris paribus, the strength of the cylinder or its re- 
sistance to breaking. In a word, a bone of the same 
weight would not have been so strong in any other 
form ; and to have made it heavier would have in- 
commoded the animal's flight.65 Yet this form could 
imal. Thus, in the sponge, silicious and calcareous particles are 
employed to harden the membraneous and horny substance. In 
the snail and other testaceous animals, carbonate of lime is used 
for the same purpose. In the Crustacea, phosphate of lime is 
added to the carbonate; while in animal bone there are, besides 
these materials, certain membranes and vessels by which it main- 
tains life. In fishes, where less resistance and more elasticity is 
required, the bones hdVe less of the earthy parts and more carti- 
lage. In the higher classes of animals, not only is the bone of 
each class peculiar in the proportion of the ingredients, but each 
bone of the same skeleton, as of man, has a due proportion of 
earth, and cartilage, and fibre, to suit its office. " The temporal 
bone in which the ear is situated is as dense as marble, and, of 
course, is suited to the propagation of sound : the heel-bone, or the 
projection of the elbow, on which the powerful muscles pull, is, 
on the other hand, fibrous, as if partaking of the nature of tendon 
or rope; while the columnar bones which support the weight have 
an intermediate degree of density," as well as an admirable form. 
-Am. Ed. 
65 When a cylinder of wood or of any other substance breaks, 
two opposite effects are produced. On the upper or outer side, the 
fibres of the substance are torn asunder; on the under or inner 
side, they are driven into one another. Therefore, between these 
portions acting so differently there will be an intermediate and 
neutral part, which might be removed without materially impair- 
ing the strength of the cylinder. On the other hand, should this NATURAL THEOLOGY. 
217 
not be acquired by use, or the bone become hollow 
or tubular by exercise. What appetency could ex- 
cavate a bone 1 
VI. The lungs also of birds, as compared with the 
lungs of quadrupeds, contain in them a provision dis- 
tinguishingly calculated for this same purpose of lev- 
itation, namely, a communication (not found in other 
kinds of animals) between the air-vessels of the lungs 
and the cavities of the body; so that, by the intromis- 
sion of air from one to the other (at the will, as it 
should seem, of the animal), its body can be occa- 
sionally puffed out, and its tendency to descend in 
the air, or its specific gravity, made less. The bod- 
ies of birds are blown up from their lungs (which no 
other animal bodies are), and thus rendered buoyant.66 
VII. All birds are oviparous. This likewise car- 
ries on the work of gestation with as little increase 
as possible of the weight of the body. A gravid ute- 
rus would have been a troublesome burden to a bird 
in its flight. The advantage in this respect of an 
oviparous procreation is, that while the whole brood 
are hatched together, the eggs are excluded singly, 
and at considerable intervals. Ten, fifteen, or twen- 
ty young birds may be produced in one cletch or co- 
vey, yet the parent bird have never been encumbered 
by the load of more than one full-grown egg at one 
time.67 
neutral or superfluous part be arranged round the circumference 
so as to enlarge it, this would strengthen the cylinder, since the 
greater the circumference the greater the number of fibres, whose 
adhesion must be overcome before the cylinder breaks. Hence 
the hollow form is the form of strength, the quantity of matter 
being given.-Am. Ed. 
66 As a counterpart to birds, we may take the case of an animal 
which has to dive into water and crawl at the bottom, not at great 
depths. Here, instead of the power of expanding the body, the 
animal needs the power of compressing it; and this is effected, in 
the case of the crocodile, &c., by substituting for the arched form 
of the ribs, which admits but a slight change of figure, ribs com- 
posed of distinct pieces, and so jointed as to enable them to di- 
minish the volume of the chest to the requisite degree. The frog 
has no ribs.-Am. Ed. 
61 It has been elsewhere observed, that when predatory birds 
Vol. I.-T 218 
VIII. A principal topic of comparison between an- 
imals is in their instruments of motion. These come 
before us under three divisions: feet, wings, and fins. 
1 desire any man to say which of the three is best 
fitted for its use, or whether the same consummate 
art be not conspicuous in them all. The constitu- 
tion of the elements in which the motion is to be 
performed is very different. The animal action must 
necessarily follow that, constitution. The Creator, 
therefore, if we might so speak, had to prepare for 
different situations, for different difficulties ; yet the 
purpose is accomplished not less successfully in one 
case than in the other. And as between wings and 
the corresponding limbs of quadrupeds, it is accom- 
plished without deserting the general idea. The idea 
is modified, not deserted. Strip a wing of its feath- 
ers, and it bears no obscure resemblance to the fore 
leg of a quadruped. The articulations at the shoul- 
der and the cubitus are much alike; and, what is a 
closer circumstance, in both cases the upper part of 
the limb consists of a single bone, the lower part of 
two. 
But, fitted up with its furniture of feathers and 
quills, it becomes a wonderful instrument, more arti- 
ficial than its first appearance indicates, though that 
be very striking; at least, the use which the bird 
makes of its wings in flying is more complicated and 
more curious than is generally known. One thing is 
certain, that if the flapping of the wings in flight were 
no more than the reciprocal motion of the same sur- 
NATURAL THEOLOGY. 
gorge themselves, they are sometimes unable to rise on the wing; 
a sufficient demonstration that the burden of an offspring would 
have unsuited them for flight.*' 
* Another provision for giving lightness to birds that are in- 
tended for flight is to extend the trachea or windpipe. On com- 
paring the tame with the wild swan, we shall find that in the lat- 
ter the windpipe is curiously convoluted within the sternum or 
breastbone. In birds intended for long journeys, such as birds of 
passage, there is also a noticeable provision for adding strength to 
the wings, and that is, by giving to the breastbone or keel, to which 
the muscles of these wings are attached, greater size and prom 
inence.-Am. Ed. NATURAL THEOLOGY. 
219 
face in opposite directions, either upward and down- 
ward, or estimated in any oblique line, the bird would 
lose as much by one motion as she gained by an- 
other. The skylark could never ascend by such an 
action as this; for, though the stroke upon the air by 
the under side of her wing would carry her up, the 
stroke from the upper side would bring her down. 
In order, therefore, to account for the advantage 
which the bird derives from her wing, it is necessary 
to suppose that the surface of the wing, measured 
upon the same plane, is contracted while the wing 
is drawn up, and drawn out to its full expansion 
when it descends upon the air for the purpose of 
moving the body by the reaction of that element. 
Now the form and structure of the wing, its external 
convexity, the disposition, and particularly the over- 
lapping of its larger feathers, the action of the mus- 
cles and joints of the pinions, are all adapted to this 
alternate adjustment of its shape and dimensions. 
Such a twist, for instance, or semi-rotatory motion, 
is given to the great feathers of the wing,68 that they 
strike the air with their flat side, but rise from the 
stroke slantwise. The turning of the oar in rowing, 
while the rower advances his hand for a new stroke, 
is a similar operation to that of the feather, and takes 
its name from the resemblance. I believe that this 
faculty is not found in the great feathers of the tail. 
This is the place also for observing that the pinions 
are so set upon the body as to bring down the wings, 
not vertically, but in a direction obliquely tending to- 
wards the tail; which motion, by virtue of the com- 
mon resolution of forces, does two things at the same 
time, supports the body in the air, and carries it for- 
ward. The steerage of a bird in its flight is effected 
partly by the wings, but. in a principal degree by the 
tail. And herein we meet with a circumstance not 
a little remarkable. Birds with long legs have short 
tails, and in their flight place their legs close to their 
bodies, at the same time stretching them out back- 
68 Mechanics have adopted the same principle in constructing 
and giving form to the sails of a windmill.-Am. Ed. 220 
ward as far as they can. In this position the legs 
extend beyond the rump, and become the rudder; 
supplying that steerage which the tail could not. 
From the wings of birds, the transition is easy to 
the fins of fish.69 They are both, to their respective 
tribes, the instruments of their motion; but, in the 
work which they have to do, there is a considerable 
difference, founded in this circumstance. Fish, unlike 
birds, have very nearly the same specific gravity with 
the element in which they move. In the case of 
fish, therefore, there is little or no weight to bear up; 
what is wanted is only an impulse sufficient to carry 
the body through a resisting medium, or to maintain 
the posture, or to support or restore the balance of 
the body, which is always the most unsteady where 
there is no weight to sink it. For these offices, the 
fins are as large as necessary, though much smaller 
than wings; their action mechanical; their position, 
and the muscles by which they are moved, in the 
highest degree convenient. The following short ac- 
count of some experiments upon fish, made for the 
purpose of ascertaining the use of their fins, will be 
the best confirmation of w'hat we assert. In most 
fish, besides the great fin, the tail, we find two pairs 
of fins upon the sides, two single fins upon the back, 
and one upon the belly, or, rather, between the belly 
and the tail. The balancing use of these organs is 
proved in this manner. Of the large-headed fish, if 
you cut off the pectoral fins, i. e., the pair which lies 
close behind the gills, the head falls prone to the bot- 
tom : if the right pectoral fin only be cut off, the fish 
NATURAL THEOLOGY. 
69 This subject is necessarily treated at length in the Bridge- 
water Treatise of the Hand. We have had occasion to state, that 
in the higher division of animated nature, the vertebrata, one plan 
or system of bones, can be traced through every variety from man 
to fishes ; and this is more especially shown by the comparison of 
the arm with the anterior extremity of quadrupeds and the wing of 
birds, and even with the pectoral tin of the fish. The number of 
the bones, and the form and the application of the muscles to them 
vary, but yet they are accommodated in a manner so perfect, that, 
on examining any individual among the varieties of the species, 
we should say that nothing could be better suited to its purpose. NATURAL THEOLOGY. 
221 
leans to that side; if the ventral fin on the same side 
be cut away, then it loses its equilibrium entirely; 
if the dorsal and ventral fins be cut off, the fish reels 
to the right and left. When the fish dies, that is, 
when the fins cease to play, the belly turns upward. 
The use of the same parts for motion is seen in the 
following observation upon them when put in action. 
The pectoral, and, more particularly, the ventral fins, 
serve to raise and depress the fish; when the fish de- 
sires to have a retrograde motion, a stroke forward 
with the pectoral fin effectually produces it; if the 
fish desire to turn either way, a single blow with the 
tail the opposite way sends it round at once ; if the 
tail strike both ways, the motion produced by the 
double lash is progressive, and enables the fish to dart 
forth with an astonishing velocity.* The result is, 
not only in some cases the most rapid, but in all cases 
the most gentle, pliant, easy animal motion with 
which we are acquainted. However, when the tail is 
cut off, the fish loses all motion, and gives itself up to 
where the water impels it. The rest of the fins, 
therefore, so far as respects motion, seem to be 
merely subsidiary to this. In their mechanical use, 
the anal fin may be reckoned the keel; the ventral 
fins, out-riggers; the pectoral muscles, the oars; 
and if there be any similitude between these parts of 
a boat and a fish, observe that it is not the resem- 
blance of imitation, but the likeness which arises from 
applying similar mechanical means to the same pur- 
pose. 
We have seen that the tail in the fish is the great 
instrument of motion. Now, in cetaceous or warm- 
blooded fish, which are obliged to rise every two or 
three minutes to the surface to take breath, the tail, 
unlike what is in other fish, is horizontal; its stroke, 
consequently, perpendicular to to the horizon, which 
is the right direction for sending the fish to the top, 
or carrying it down to the bottom.70 
* Goldsmith, Hist of An. Nat., vol. vi., p. 154. 
7° The poising and motion of fishes in the water has interested Regarding animals in their instruments of motion, 
we have only followed the comparison through the 
first great division of animals into beasts, birds, and 
222 
NATURAL THEOLOGY. 
some of our greatest philosophers, as Galileo and Borelli. It is es- 
timated that fishes make their way through a medium which re- 
sists nine hundred times more than the atmosphere. But then, as 
it offers a certain resistance to their progress, it resists also the 
motion of their tail and fins by which they have their power of pro- 
gression. The breadth of the tail of fishes, compared with that of 
their fins, and its muscularity and power, declare what is affirmed 
to us upon authority, that the tail is the great instrument of their 
progression; and we can see that when the trout darts away, the 
force of his motion lays down the fins close upon his body. But 
the fins direct hirjn as outriggers, and the pectoral fins especially, 
by raising or depressing the head, give direction to the whole body 
under the force of the tail. The lateral fins, and particularly the 
pectoral fins, also sustain him in the right position in the water: 
without the co-operation of these with the tail, the fish would 
move like a boat sculled by one oar at the stern. As the digestion 
of fishes, as well as that of other animals, is attended with the 
extrication of air, and as the intestines are below the centre, the 
belly would be turned up but for the option of these lateral fins, 
as we see takes place in a dead fish. The tail and fins are the in- 
struments of motion; but the incessant action of the muscles 
which moves these is a just matter of admiration. If a fish move 
with his head down the stream, he must move more rapidly than 
the water, or the water gets under the operculum of the gills, and 
chokes him. He lies, therefore, continually with his head to the 
stream. We may see a trout lying for hours stationary, while the 
stream is running past him ; and they seem to remain so for days 
and nights. In salmon-fishing, the fly is played upon the broken 
water, in the midst of the torrent, and there the fish shows him- 
self rising from a part of the river where men could not preserve 
their footing, though assisted by poles, or locking their arms to- 
gether. When the salmon leaps, he makes extraordinary exer- 
tions. Just under the cataract and against the stream, he will 
rush for some yards, and rise out of the spray six or eight feet; 
and, amid the noise of the water, they may be heard striking 
against the rock with a sound like the clapping of the hands. 
If they find a temporary lodgment on the shelving rock, they lie 
quivering and preparing for another somerset, until they reach the 
top of the cataract. This exhibits not only the power of their 
muscles, assisted by the elasticity of their bones, but the force of 
instinct by which they are led to seek the shallow streams for de- 
positing their eggs. 
The porpoise will swim round and round a ship which is sailing 
at fourteen miles an hour : a thing almost as surprising as the fly 
circling round the horse's ears for a whole stage. NATURAL THEOLOGY. 
223 
fish. If it were our intention to pursue the consider- 
ation farther, I should take in that generic distinction 
among birds, the web-foot of water fowl. It is an in- 
stance which may be pointed out to a child. The 
utility of the web to water-fowl, the inutility to land- 
fowl, are so obvious that it seems impossible to no- 
tice the difference without acknowledging the design. 
I am at a loss to know how those who deny the 
agency of an intelligent Creator dispose of this exam- 
pie. There is nothing in the action of swimming, as 
carried on by a bird upon the surface of the water, 
that should generate a membrane between the toes. 
As to that membrane, it is an exercise of constant re- 
sistance. The only supposition I can think of is, that 
all birds have been originally water-fowl, and web- 
footed; that sparrows, hawks, linnets, &c., which fre- 
quent the land, have, in process of time, and in the 
course of many generations, had this part worn away 
by treading upon hard ground. To such evasive as- 
sumptions must atheism always have recourse ! And, 
after all, it confesses that the structure of the feet of 
birds, in their original form, was critically adapted to 
their original destination! The web-feet of amphib- 
To all this maybe added, that the solid which mathematicians 
have discovered, by refined application of the calculus, and have 
termed " the solid of least resistance," because it is the conforma- 
tion which is, less than any other, affected by the resistance of any 
medium, resembles a fish in its form. 224 
NATURAL THEOLOGY. 
ious quadrupeds, seals, otters, &c., fell under the 
same observation. 
IX. The five senses are common to most large an- 
imals; nor have we much difference to remark in 
their constitution, or much, however, which is refer- 
able to mechanism. 
The superior sagacity of animals which hunt their 
prey, and which, consequently, depend for their liveli- 
hood upon their nose, is well known in its use, but not 
at all known in the organization which produces it. 
The external ears of beasts of prey, of lions, ti- 
gers, wolves, have their trumpet-part, or concavity, 
standing forward, to seize the sounds which are be- 
fore them, viz., the sounds of the animals which they 
pursue or watch. The ears of animals of flight are 
turned backward, to give notice of the approach of 
their enemy from behind, whence he may steal upon 
them unseen. This is a critical distinction, and is mechanical; but it may be suggested, and, I think, 
not without probability, that it is the effect of contin- 
ual habit. 
The eyes of animals which follow their prey by 
night, as cats, owls, &c., possess a faculty not given 
to those of other species, namely, of closing the pu- 
pil entirely. The final cause of which seems to be 
this : It was necessary for such animals to be able to 
descry objects with very small degrees of light. 
This capacity depended upon the superior sensibility 
of the retina; that is, upon its being affected by the 
most feeble impulses. But that tenderness of struc- 
ture, which rendered the membrane thus exquisitely 
sensible, rendered it also liable to be offended by the 
access of stronger degrees of light. The contractile 
range, therefore, is increased in these animals, so as 
to enable them to close the aperture entirely, which 
includes the power of diminishing it in every degree; 
whereby at all times such portions, and only such 
portions of light are admitted, as may be received 
without injury to the sense. 
NATURAL THEOLOGY. 
225 
[The figure represents the iris of a lion. B B, the straight con- 
verging fibres ; C, the fibres which circle the inner margin of the 
iris.] 
There appears to be also in the figure, and in some 
properties of the pupil of the eye, an appropriate re- 
lation to the wants of different animals. In horses, 226 
oxen, goats, sheep, the pupil of the eye is elliptical, 
the transverse axis being horizontal; by which struc- 
ture, although the eye be placed on the side of the 
head, the anterior elongation of the pupil catches the 
forward rays, or those which come from objects im- 
mediately in front of the animal's face. 
NATUARL THEOLOGY. 
CHAPTER XIII. 
I believe that all the instances which I shall col- 
lect under this title might, consistently enough with 
technical language, have been placed under the head 
of Comparative Anatomy. But there appears to me 
an impropriety in the use which that term hath ob- 
tained ; it being, in some sort, absurd to call that a 
case of comparative anatomy in which there is no- 
thing to " comparein which a conformation is 
found in one animal, which hath nothing properly an- 
swering to it in another. Of this kind are the ex- 
amples which I have to propose in the present chap- 
ter; and the reader will see that, though some of 
them be the strongest, perhaps, he will meet with 
under any division of our subject, they must neces- 
sarily be of an unconnected and miscellaneous nature. 
To dispose them, however, into some sort of order, 
we will notice, first, particularities of structure which 
belong to quadrupeds, birds, and fish, as such, or to 
many of the kinds included in these classes of ani- 
mals ; and then, such particularities as are confined 
to one or two species. 
I. Along each side of the neck of large quadru- 
peds runs a stiff, robust cartilage, which butchers call 
the pax-wax. No person can carve the upper end 
of a crop of beef without driving his knife against it. 
It is a tough, strong, tendinous substance, braced from 
PECULIAR ORGANIZATIONS. NATURAL THEOLOGY. 
227 
the head to the middle of the back; its office is to 
assist in supporting the weight of the head. It is a 
mechanical provision, of which this is the undispu- 
ted use; and it is sufficient, and not more than suffi- 
cient, for the purpose which it has to execute. The 
head of an ox or a horse is a heavy weight, acting at 
the end of a long lever (consequently with a great 
purchase), and in a direction nearly perpendicular to 
the joints of the supporting neck. From such a 
force, so advantageously applied, the bones of the 
neck would be in constant danger of dislocation, if 
they were not fortified by this strong tape. No such 
organ is found in the human subject, because, from 
the erect position of the head (the pressure of it act- 
ing nearly in the direction of the spine), the junction 
of the vertebrae appears to be sufficiently secure with- 
out it. This cautionary expedient, therefore, is limit- 
ed to quadrupeds : the cautionary care of the Creator 
is seen where it is wanted.71 
II. The oil with which birds preen their feathers, 
and the organ which supplies it, is a specific provis- 
ion for the winged creation. On each side of the 
rump of birds is observed a small nipple, yielding 
upon pressure a butter-like substance, which the bird 
extracts by pinching the pap with its bill. With this 
oil or ointment, thus procured, the bird dresses his 
71 The author is not quite correct here, inasmuch as elastic liga 
ments are liberally supplied in the human spine : a range of pecu 
liar ligaments, the " ligamenta subflava," run along the course of 
the spine, and are highly elastic. The ligamentum nuchce is that 
ligament which runs from the prominence of the spine between 
the shoulders to the back of the head ; and the student who hangs 
his head over his book enjoys the advantage of this elastic sup- 
port so that it is strictly a matter comparative; we may trace it 
with increasing strength from the ligament that sustains a man's 
head, to that which, like the spring of a steelyard, weighs against 
the immense head of the elephant. 
These elastic ligaments vary with the length and motion of the 
neck, it would be tedious to describe their varieties in the cam- 
el, cameleopard, ostrich, &c. We may be satisfied with the fact,, 
that the elastic ligament is a structure extensively used in the an- 
imal textures, generally coming in aid of the muscles, or as a sub- 
stitute for them. 228 
NATURAL THEOLOGY, 
coat; and repeats the action as often as its own sen- 
sations teach it that it is in any part wanted, or as 
the excretion may be sufficient for the expense. The 
gland, the pap, the nature and quality of the excreted 
substance, the manner of obtaining it from its lodg- 
ment in the body, the application of it when obtain- 
ed, form, collectively, an evidence of intention which 
it is not easy to withstand. Nothing similar to it is 
found in unfeathered animals. What blind conalus 
of nature should produce it in birds, should not pro- 
duce it in beasts 1 
III. The air-bladder also of &fish affords a plain and 
direct instance, not only of contrivance, but strictly 
of that species of contrivance which we denominate 
mechanical. It is a philosophical apparatus in the 
body of an animal. The principle of the contrivance 
is clear: the application of the contrivance is also 
clear. The use of the organ to sustain, and at will, 
also, to elevate, the body of the fish in the water, is 
proved by observing, what has been tried, that, when 
the bladder is burst, the fish grovels at the bottom; 
and also that flounders, soles, skates, which are 
without the air-bladder, seldom rise in the water, and 
that with effort. The manner in which the purpose 
is attained, and the suitableness of the means to the 
end, are not difficult to be apprehended. The rising 
and sinking of a fish in water, so far as it is independ- 
ent of the stroke of the fins and tail, can only be 
regulated by the specific gravity of the body. When 
the bladder, contained in the body of the fish, is con- 
tracted, which the fish probably possesses a muscular 
power of doing, the bulk of the fish is contracted 
along with it; whereby, since the absolute weight re- 
mains the same, the specific gravity, which is the 
sinking force, is increased, and the fish descends; 
on the contrary, when, in consequence of the relaxa- 
tion of the muscles, the elasticity of the enclosed 
and now compressed air restores the dimensions of 
the bladder, the tendency downward becomes propor- 
tionably less than it was before, or is turned into a 
contrary tendency. These are known properties of NATURAL THEOLOGY. 
229 
bodies immersed in a fluid. The enamelled figures, 
or little glass bubbles, in a jar of water, are made to 
rise and fall by the same artifice. A diving-machine 
might be made to ascend and descend upon the like 
principle; namely, by introducing into the inside of 
it an air-vessel, which by its contraction would di- 
minish, and by its distension enlarge, the bulk of the 
machine itself, and thus render it specifically heavier 
or specifically lighter than the water which surrounds 
it. Suppose this to be done, and the artist to solicit 
a patent for his invention : the inspectors of the mod- 
el, whatever they might think of the use or value of 
the contrivance, could by no possibility entertain a 
question in their minds whether it were a contri- 
vance or not. No reason has been assigned, no rea- 
son can be assigned, why the conclusion is not as 
certain in the fish as it is in the machine; why the 
argument is not as firm in one case as the other. 
It would be very worthy of inquiry if it were pos- 
sible to discover by what method an animal which 
lives constantly in water is able to supply a reposi- 
tory of air. The expedient, whatever it be, forms 
part, and, perhaps, the most curious part of the provis- 
ion. Nothing similar to the air-bladder is found in 
land-animals; and a life in the water has no natural 
tendency to produce a bag of air. Nothing can be 
farther from an acquired organization than this is.72 
72 The sea varies in temperature and pressure at different depths, 
and no doubt the texture of the fish, and especially of its integu- 
ment, must conform to this variety. The swimming-bladder is the 
means of adjustment by which the fish lives at its native depths 
without waste of animal exertion : such is the power of expansion 
of the air-bladder when relieved from the pressure, that, when a 
fish is brought up from the greatest depth, it inverts and thrusts 
out the viscera from the mouth. We do not see, however, that 
naturalists have adverted to the place of this swimming-bladder. 
It lies close to the spine, and appears to counterbalance, in some 
measure at least, the air in the intestines by being thus placed above 
them. In the cetacea, as the whale, their buoyancy proceeds from 
the quantity of oil under their skin, especially of their head, and 
which it has been observed is bestowed in order to ensure their 
readily coming to the surface to breathe when their natural pow- 
ers are weakened. For the same reason, that they may raise their 
Vol. I.-U 230 
NATURAL THEOLOGY. 
These examples mark the attention of the Creator 
to the three great kingdoms of this animal creation, 
and to their constitution as such. The example which 
stands next in point of generality, belonging to a large 
tribe of animals, or, rather, to various species of that 
tribe, is the poisonous tooth of serpents. 
I. The fang of a viper is a clear and curious exam- 
ple of mechanical contrivance. It is a perforated 
tooth, loose at the root: in its quiet state, lying down 
flat upon the jaw, but furnished with a muscle, which, 
with a jerk, and by the pluck, as it were, of a string, 
suddenly erects it. Under the tooth, close to its root, 
and communicating with the perforation, lies a small 
bag containing the venom. When the fang is raised, 
the closing of the jaw presses its root against the bag 
underneath, and the force of this compression sends 
out the fluid with a considerable impetus through the 
tube in the middle of the tooth. What more unequiv- 
ocal or effectual apparatus could be devised for the 
double purpose of inflicting the wound and injecting 
the poison! Yet, though lodged in the mouth, it is 
so constituted as, in its inoffensive and quiescent 
state, not to interfere with the animal's ordinary office 
of receiving its food. It has been observed, also, that 
none of the harmless serpents, the black snake, the 
blind worm, &c., have these fangs, but teeth of an 
equal size ; not moveable as this is, but fixed into the 
jaw. 
II. In being the property of several different spe- 
cies, the preceding example is resembled by that 
which I shall next mention, which is the bag of the 
opossum. This is a mechanical contrivance, most 
properly so called. The simplicity of the expedient 
renders the contrivance more obvious than many 
others, and by no means less certain. A false skin 
heads to the surface, their tails are horizontal. In the jelly-fish, 
those soft animals which float in sheltered estuaries (the 
phora), there is an air-vessel which they can fill and empty, by 
which means they rise or sink at pleasures. Others (the villea), 
raise a sail. Some of this class propel themselves by taking m 
water and suddenly rejecting it. NATURAL THEOLOGY. 
231 
under the belly of the animal forms a pouch, into 
which the young litter are received at their birth; 
where they have an easy and constant access to the 
teats ; in which they are transported by the dam from 
place to place ; where they are at liberty to run in and 
out; and where they find a refuge from surprise and 
danger. It is their cradle, their asylum, and the ma- 
chine for their conveyance. Can the use of this 
structure be doubted of? Nor is it a mere doubling 
of the skin; but is a new organ, furnished with bones 
and muscles of its own. Two bones are placed before 
the os pubis, and joined to that bone as their base. 
These support and give a fixture to the muscles 
which serve to open the bag. To these muscles there 
are antagonists, which serve in the same manner to 
shut it; and this office they perform so exactly, that, 
in the living animal, the opening can scarcely be dis- 
covered, except when the sides are forcibly drawn 
asunder.* Is there any action in this part of the ani- 
mal, any process arising from that action, by which 
these members could be formed ? any account to be 
given of the formation, except design?73 
III. As a particularity, yet appertaining to more 
species than one, and also as strictly mechanical, we 
may notice a circumstance in the structure of the 
claws of certain birds. The middle claw of the her- 
* Goldsmith, Nat. Hist., voi. iv., p. 244. 
73 The kangaroo is another animal of this class; and the great 
disparity between its size when full grown and when first born 
has suggested an additional use for this pouch. Though at its 
full size it is about six feet long, and weighs a hundred and fifty 
pounds, it is at birth but one inch in length, and weighs but about 
six grains, and is as imperfectly developed in other respects as 
though but one quarter of the period allotted to its fcetal state 
had expired. Hence it may be inferred that this pouch is intend- 
ed as a kind of intermediate residence, in which the process of de- 
velopment may be completed. When first found, the young are 
glued, as it were, to the nipples of the parent by an opening which 
afterward becomes a mouth ; and they never quit their hold till, 
having reached the proper stage, they undergo a second birth. 
They then emerge from the pouch, act like the young of other 
animals, and only return occasionally for nourishment or protec 
tion.-Am. Ed.' 232 
on and cormorant is toothed and notched like a saw. 
These birds are great fishers, and these notches as- 
sist them in holding their slippery prey. The use is 
evident, but the structure such as cannot at all be 
accounted for by the effort of the animal or the ex- 
ercise of the part. Some other fishing birds have 
these notches in their bills, and for the same purpose. 
The gannet, or Soland goose, has the side of its bill 
irregularly jagged, that it may hold its prey the fast- 
er. Nor can the structure in this, more than in the 
former case, arise from the manner of employing the 
part. The smooth surfaces and soft flesh of fish were 
less likely to notch the bills of birds than the hard 
bodies upon which many other species feed. 
We now come to particularities, strictly so called, 
as being limited to a single species of animal. Of 
these, 1 shall take one from a quadruped and one 
from a bird. 
I. The stomach of the camel is well known to retain 
large quantities of water, and to retain it unchanged 
for a considerable length of time. This property 
qualifies it for living in the desert. Let us see, there- 
fore, what is the internal organization upon which a 
faculty so rare and so beneficial depends. A num- 
ber of distinct sacs or bags (in a dromedary thirty of 
these have been counted) are observed to lie between 
the membranes of the second stomach, and to open 
into the stomach near the top by small square aper- 
tures. Through these orifices, after the stomach is 
full, the annexed bags are filled from it: and the wa- 
ter so deposited is, in the first place, not liable to 
pass into the intestines ; in the second place, is kept 
separate from solid aliment; and, in the third place, 
is out of the reach of the digestive action of the 
stomach, or of mixture with the gastric juice. It ap- 
pears probable, or, rather, certain, that the animal, by 
the conformation of its muscles, possesses the pow- 
er of squeezing back this water from the adjacent 
bags into the stomach, whenever thirst excites it to 
put this power in action. 
II. The tongue of the woodpecker is one of those 
NATURAL THEOLOGY. singularities which nature presents us with when a 
singular purpose is to be answered. It is a particu- 
lar instrument for a particular use ; and what, except 
design, ever produces such ! The woodpecker lives 
chiefly upon insects lodged in the bodies of decayed 
or decaying trees. For the purpose of boring into 
the wood, it is furnished with a bill straight, hard, 
angular, and sharp. When, by means of this piercer, 
it has reached the cells of the insects, then comes 
the office of its tongue; which tongue is, first, of 
such a length that the bird can dart it out three or 
four inches from the bill, in this respect differing 
greatly from every other species of bird ; in the sec- 
ond place, it is tipped with a stiff, sharp, bony thorn; 
and, in the third place (which appears to me the 
most remarkable property of all), this tip is dentated 
on both sides like-the beard of an arrow or the barb 
of a hook. The description of the part declares its 
uses. The bird, having exposed the retreats of the 
insects by the assistance of its bill, with a motion 
inconceivably quick, launches out at them this long 
tongue, transfixes them upon the barbed needle at 
the end of it, and thus draws its prey within its 
mouth. If this be not mechanism, what is1? Should 
it be said that, by continual endeavours to shoot out 
the tongue to the stretch, the woodpecker species 
may by degrees have lengthened the organ itself be- 
yond that of other birds, what account can be given 
of its form, of its tip 1 how, in particular, did it get 
its barb, its dentation! These barbs, in my opinion, 
wherever they occur, are decisive proofs of mechan- 
ical contrivance.74 
NATURAL THEOLOGY. 
233 
■M What could have tempted Buffon to express his pity for this 
bird as abject and degraded, it is not easy to conceive; nor why 
it should be described as leading an insipid life, because continu- 
ally employed in boring and hammering the old stump of a tree. 
A late naturalist describes the woodpecker as enjoying the sweet 
hours of the morning, on the highest branch of the tallest tree, 
fluttering and playing with his mate and companions. No doubt 
his diligence, perseverance, and energy in plying his beak is very 
extraordinary. But, besides the wedgelike strength of the beak, 
and the power of the neck to strike with it, there is something 234 
III. I shall add one more example, for the sake of 
its novelty. It is always an agreeable discovery 
NATURAL THEOLOGY. 
remarkable in its sensibility. That nerve, the fifth pair, on which 
we have shown that all the sensibility of the head depends, trans- 
mits a large branch along the inside of the mandibles: and, as 
this nerve approaches the extremity, it perforates the bone by in- 
numerable small canals, so as to be given to the horny covering 
of the beak, which is thus possessed of a sensibility to feel in the 
crevices of the wood and under the bark; and the woodpecker is 
enabled by this means to direct the tongue, which our author cor- 
rectly describes as moving with extraordinary celerity, and with a 
point like a barbed arrow. 
We have represented the dissection of the head of this bird 
more accurately in its anatomy than is to be found in books. We 
offer it because it exhibits a very curious piece of mechanism, ad- 
justed to the tongue, to enable the animal to thrust it out far, and 
with unusual rapidity. A is the barbed tongue; B, two slender 
elastic ligamentous cartilages, of very peculiar structure and use. 
On one extremity they are attached to the bone which supports 
the upper mandible; from this we trace them over the scull down 
upon the sides of the neck; and, with a large sweep, turning un- 
der the lower mandible, and so continued into the tongue, and no$ 
terminating until they reach the horny point. C C C, a long mus,- 
cle which follows these ligamentous cartilages upon their concave 
side, arising from the bone of the lower mandible, and so sweep- 
ing round with the cartilages and over the scull, to have another 
fixed point at the upper mandible: these protrude the tongue. 
Two muscles are seen to arise from the sides of the larynx, which 
are the opponents of the last, and retract the tongue. Leaving 
the other parts of the anatomy, we beg the reader's attention to 
the action of the muscle CCC, which presents one of those cu- 
rious instances observed in comparative anatomy of a mechanism 
adapted to a particular purpose. The tongue is not only thrust 
out far by this apparatus, but is shot with great rapidity, in cor- 
respondence with its barbed point. This effect is produced by 
the two extremities of the muscle being fixed points, and the 
fibres of the muscle itself running on the concave side of the car- 
tilaginous bow, so as to form a smaller circle. We require no 
mathematical demonstration to prove that the tongue must be 
thrust out to a greater distance than the measure of contraction 
of the muscle. Let us tie the line of the fishing-rod to its slender 
top, and pull upon it at the butt: the motion of the top will be 
very extensive, even when only an inch of the line is drawn 
through the rings. This is a pretty accurate representation of 
what takes place by thb contraction of this protruding muscle. 
We have noticed that the upper end of this arch is fixed; the 
whole motion must therefore be given to the loose extremity in 
the tongue; and we cannot but observe that this peculiar arch 
and muscular ring are adapted for the rapid protrusion of the NATURAL THEOLOGY 
235 236 
when, having remarked in an animal an extraordina- 
ry structure, we come at length to find out an unex- 
pected use for it. The following narrative furnishes 
an instance of this kind. The babyroussa, or Indian 
hog, a species of wild boar, found in the East Indies, 
has two bent teeth, more than half a yard long, grow- 
ing upward, and (which is the singularity) from the 
upper jaw. These instruments are not wanted for 
offence, that service being provided for by two tusks 
issuing from the under jaw, and resembling those of 
the common boar; nor does the animal use them for 
defence. They might seem, therefore, to be both a 
superfluity and an encumbrance. But observe the 
event: the animal sleeps standing; and, in order to 
support its head, hooks its upper tusks upon the 
branches of trees.75 
NATURAL THEOLOGY. 
tongue, while its retraction is produced by a common muscle, 
that is, a muscle running in a straight course. 
Another curious part of this apparatus is, that a very large 
gland, which pours out a glutinous matter, is embraced and com- 
pressed by the action of the circular muscle. This viscid secre- 
tion, bedewing the tongue, furnishes an additional means for the 
bird to pick up insects, such as ants, without the necessity of 
sticking each with its arrow. Nothing can be more mechanical 
or more happily adapted to its purpose, than the whole of this 
structure, and, consequently, nothing better suited to strengthen 
the argument in the text. Indeed, it is not inferior to the means 
employed for giving rapidity of motion to the membrana nictitans 
of the eye of the bird. 
75 This notion of the babyroussa sleeping on its feet and hang- NATURAL THEOLOGY. 
237 
CHAPTER XIV. 
I can hardly imagine to myself a more distinguish- 
ing mark, and, consequently, a more certain proof of 
design, than preparation, i. e., the providing of things 
beforehand, which are not to be used for a consider- 
able time afterward : for this implies a contemplation 
of the future, which belongs only to intelligence. 
Of these prospective contrivances, the bodies of an- 
imals furnish various examples. 
I. The human teeth afford an instance, not only of 
prospective contrivance, but of the completion of the 
contrivance being designedly suspended. They are 
formed within the gums, and there they stop; the 
fact being, that their farther advance to maturity 
would not only be useless to the newborn animal, 
but extremely in its way; as it is evident that the 
act of sucking, by which it is for some time to be 
nourished, will be performed with more ease, both 
to the nurse and to the infant, while the inside of 
the mouth and edges of the gums are smooth and 
soft, than if set with hard-pointed bones. By the 
time they are wanted the teeth are ready. They 
have been lodged within the gums for some months 
past, but detained, as it were, in their sockets, so 
long as their farther protrusion would interfere with 
the office to which the mouth is destined. Nature, 
namely, that intelligence which was employed in cre- 
ation, looked beyond the first year of the infant's life : 
yet, while she was providing for functions which 
were after that term to become necessary, was care- 
PROSPECT1VE CONTRIVANCES. 
ing by its teeth the while, is a mere fancy. It has arisen from 
the difficulty of accounting for the teeth which rise out from the 
mouth, and turn up before the eyes. The better opinion is, that 
they guard the eyes in rushing through the thick underwood. 238 
ful not to incommode those which preceded them. 
What renders it more probable that this is the effect 
of design, is, that the teeth are imperfect, while all 
other parts of the mouth are perfect. The lips are 
perfect, the tongue is perfect; the cheeks, the jaws, 
the palate, the pharynx, the larynx, are all perfect: 
the teeth alone are not so. This is the fact with re- 
spect to the human mouth: the fact also is, that the 
parts above enumerated are called into use from the 
beginning; whereas the teeth would be only so many 
obstacles and annoyances if they were there. When 
a contrary order is necessary, a contrary order pre- 
vails. In the worm of the beetle, as hatched from 
the egg, the teeth are the first things which arrive at 
perfection. The insect begins to gnaw as soon as it 
escapes from the shell, though its other parts be only 
gradually advancing to their maturity. 
What has been observed of the teeth is true of the 
horns of animals; and for the same reason. The 
horn of a calf or a lamb does not bud, or, at least, 
does not sprqut to any considerable length, until the 
animal be capable of browsing upon its pasture; be- 
cause such a substance upon the forehead of the 
young animal would very much incommode the teat 
of the dam in the office of giving suck. 
But in the case of the teeth-of the human teeth, 
at least-the prospective contrivance looks still far- 
ther. A succession of crops is provided, and provi- 
ded from the beginning; a second tier being original- 
ly formed beneath the first, which do not come into 
use until several years afterward. And this double 
or suppletory provision meets a difficulty in the mech- 
anism of the mouth, which would have appeared al- 
most insurmountable. The expansion of the jaw 
(the consequence of the proportionable growth of 
the animal, and of its scull) necessarily separates 
the teeth of the first set, however compactly disposed, 
to a distance from one another, which would be very 
inconvenient. In due time, therefore, i. e., when the 
jaw has attained a great part of its dimensions, a 
new set of teeth springs up (loosening and pushing 
NATURAL THEOLOGY. out the old ones before them), more exactly fitted to 
the space which they are to occupy, and rising also 
in such close ranks as to allow for any extension of 
line which the subsequent enlargement of the head 
may occasion.76 
II. It is not very easy to' conceive a more evident- 
ly prospective contrivance than that which, in all vi- 
viparous animals, is found in the milk of the female 
parent. At the moment the young animal enters the 
world, there is its maintenance ready for it. The 
particulars to be remarked in this economy are nei- 
ther few nor slight. We have, first, the nutritious 
quality of the fluid, unlike, in this respect, every other 
excretion of the body : and in which nature hitherto 
remains unimitated, neither cookery nor chymistry 
having been able to make milk out of grass : we have, 
secondly, the organ for its reception and retention : 
we have, thirdly, the excretory duct annexed to that 
organ: and we have, lastly, the determination of the 
milk to the breast at the particular juncture when it 
is about to be wanted. We have all these properties 
in the subject before us; and they are all indications 
of design. The last circumstance is the strongest of 
any. If I had been to guess beforehand, I should 
have conjectured that, at the time when there was 
an extraordinary demand for nourishment in one part 
of the system, there would be the least likelihood of 
a redundancy to supply another part. The advanced 
pregnancy of the female has no intelligible tendency 
to fill the breasts with milk. The lacteal system is 
a constant wonder; and it adds to other causes of 
our admiration, that the number of the teats or paps 
in each species is found to bear a proportion to the 
NATURAL THEOLOGY. 
239 
76 The second or permanent set of teeth does not push out the 
deciduous or milk-teeth. The process is not mechanical. While 
yet a tender membrane is around the second tooth, those of the 
first set are suffering absorption at their fangs. Another circum- 
stance, which shows the provision not to be mechanical, is the 
wasting of the old alveolar process, and the growth of the new ; 
the new alveolar process or socket of the permanent tooth is form- 
ing at the time that the portion of the jaw which held the first 
tooth firm is yielding by absorption. 240 
NATURAL THEOLOGY. 
number of the young. In the sow, the bitch, the rab- 
bit, the cat, the rat, which have numerous litters, the 
paps are numerous, and are disposed along the whole 
length of the belly: in the cow and mare they are 
few. The most simple account of this is to refer it 
to a designing Creator.77 
But, in the argument before us, we are entitled to 
consider not only animal bodies when framed, but 
the circumstance under which they are framed : and 
in this view of the subject, the constitution of many 
of their parts is most strictly prospective. 
III. The eye is of no use at the time when it is 
formed. It is an optical instrument made in a dun- 
geon ; constructed for the refraction of light to a fo- 
cus, and perfect for its purpose, before a ray of light 
has had access to it; geometrically adapted to the 
properties and action of an element with which it 
has no communication. It is about indeed to enter 
into that communication: and this is precisely the 
thing which evidences intention. It is providing for 
the future in the closest sense which can be given to 
these terms; for it is providing for a future change; 
not for the then subsisting condition of the animal; 
not for any gradual progress or advance in that same 
condition, but for a new state, the consequence of a 
77 The only parallel to this is the care with which nature se- 
cures the nourishment of the embryon plant or the chick in the 
egg. The lobes of a bean or a pea, and of most seeds, consist of 
deposite of nutritious matter, and, when heat and moisture favour 
the development of the living property, vessels which are scat- 
tered in these lobes or cotyledons commence absorption of the 
matter, and carry it to the centre of the plant. It is remarkable 
that these lobes, having thus, in the first instance, supplied the 
young plant with nutritious matter, change their office, and, rising 
above the surface, become the first leaves. Thus we see how 
the nourishment is supplied, until the radicle is pushed down into 
the earth, and the leaves receive the influence of the atmosphere. 
So in the chick, the white or albumen of the egg goes to its nour- 
ishment while it is in the shell, and a duct leads from the mem- 
brane enclosing this mass of nutriment into the first intestine. 
And thus is the chick nourished, not only while included in the 
shell, but also during its first feeble existence, a period which cor- 
responds with that of lactation in mammalia. NATURAL THEOLOGY. 
241 
great and sudden alteration, which the animal is to 
undergo at its birth. Is it to be believed that the eye 
was formed, or, which is the same thing, that the 
series of causes was fixed by which the eye is form- 
ed, without a view to this change ; without a pros- 
pect of that condition, in which its fabric, of no use 
at present, is about to be of the greatest; without a 
consideration of the qualities of that element, hith- 
erto entirely excluded, but with which it was here- 
after to hold so intimate a relation! A young man 
makes a pair of spectacles for himself against he 
grows old, for which spectacles he has no want or 
use whatever at the time he makes them. Could 
this be done without knowing and considering the 
defect of vision to which advanced age is subject ? 
Would not the precise suitableness of the instrument 
to its purpose, of the remedy to the defect, of the 
convex lens to the flattened eye, establish the cer- 
tainty of the conclusion, that the case, afterward to 
arise, had been considered beforehand, speculated 
upon, provided for! all which are exclusively the 
acts of a reasoning mind. The eye formed in one 
state, for use only in another state, and in a different 
state, affords a proof no less clear of destination to 
a future purpose ; and a proof proportionably strong- 
er, as the machinery is more complicated and the 
adaptation more exact. 
IV. What has been said of the eye holds equally 
true of the lungs. Composed of air-vessels where 
there is no air; elaborately constructed for the alter- 
nate admission and expulsion of an elastic fluid 
where no such fluid exists, this great organ, with the 
whole apparatus belonging to it, lies collapsed in the 
foetal thorax, yet in order and in readiness for ac- 
tion the first moment that the occasion requires its 
service. This is having a machine locked up in store 
for future use, which incontestably proves that the 
case was expected to occur in which this use might 
be experienced ; but expectation is the proper act of 
intelligence. Considering the state in which an ani- 
mal exists before its birth, I should look for nothing 
Vol. I.-X 242 
less in its body than a system of lungs. It is like 
finding a pair of bellows in the bottom of the sea; 
of no sort of use in the situation in which they are 
found: formed for an action which was impossible to 
be exerted; holding no relation or fitness to the ele- 
ment which surrounds them, but both to another ele- 
ment in another place. 
As part and parcel of the same plan ought to be 
mentioned, in speaking of the lungs, the provisionary 
contrivances of the foramen ovale and ductus arterio ■ 
sus. In the foetus pipes are laid for the passage of 
the blood through the lungs ; but, until the lungs be in- 
flated by the inspiration of air, that passage is imper- 
vious, or in a great degree obstructed. What, then, 
is to be done 1 What would an artist, what would 
a master do upon the occasion 1 He would endeav- 
our, most probably, to provide a temporary passage, 
which might carry on the communication required 
until the other was open. Now this is the thing 
which is actually done in the heart. Instead of the 
circuitous route through the lungs which the blood 
afterward takes before it gets from one auricle of the 
heart to the other, a portion of the blood passes im- 
mediately from the right auricle to the left, through 
a hole placed in the partition which separates these 
cavities. This hole anatomists call the foramen ovale. 
This is likewise another cross cut, answering the 
same purpose, by what is called the ductus arteriosus, 
lying between the pulmonary artery and the aorta. 
But both expedients are so strictly temporary, that 
after birth the one passage is closed, and the tube 
which forms the other shrivelled up into a ligament. 
If this be not contrivance, what is 1 
But, forasmuch as the action of the air upon the 
blood in the lungs appears to be necessary to the per- 
fect concoction of the fluid, i. e., to the life and health 
of the animal (otherwise the shortest route might be 
the best), how comes it to pass that the foetus lives, 
and grows, and thrives without it! The answer is, 
that the blood of the foetus is the mother's; that it 
has undergone that action in her habit; that one pair 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
243 
of lungs serves for both. When the animals are sep- 
arated a new necessity arises; and, to meet this ne- 
cessity as soon as it occurs, an organization is pre- 
pared. It is ready for its purpose; it only waits for 
the atmosphere; it begins to play the moment the air 
is admitted to it.7® 
CHAPTER XV.' 
RELATIONS. 
When several different parts contribute to one ef- 
fect, or, which is the same thing, when an effect is 
produced by the joint action of different instruments, 
the fitness of such parts or instruments to one an- 
other for the purpose of producing, by their united 
action, the effect, is what I call relation; and, wher- 
ever this is observed in the works of nature or of man, 
it appears to me to carry along with it decisive evi- 
dence of understanding, intention, art. In examin- 
ing, for instance, the several parts of a watch, the 
spring, the barrel, the chain, the fusee, the balance, 
the wheels of various sizes, forms, and positions, what 
is it which would take an observer's attention as most 
plainly evincing a construction, directed by thought, 
Does not the whole condition of the embryon go to this argu- 
ment! At first there is a mere jelly, or what appears as such; a 
little farther advanced, and there are bones, and muscles, and 
nerves. But these lie quite inactive for a long term ; the nerve 
excites to no action; the muscles do not move; the joints are not 
exercised, they are perfected slowly. The period of full develop- 
ment is not arrived; they have not yet their stimulus to activity. 
The whole, then, is in a state of preparation. Conduit pipes with- 
out their fluids, glands and ducts without their secretions, sensi- 
bilities dormant, and a mechanism quite inoperative; a whole ani- 
mal system beautifully contrived, but only in "prospective contri 
vance." 244 
deliberation, and contrivance 1 It is the suitableness 
of these parts to one another; first, in the succession 
and order in which they act; and, secondly, with a 
view to the effect finally produced. Thus, referring 
the spring to the wheels, our observer sees in it* that 
which originates and upholds their motion; in the 
chain, that which transmits the motion to the fusee ; 
in the fusee, that which communicates it to the 
wheels ; in the conical figure of the fusee, if he refer 
to the spring, he sees that which corrects the inequal- 
ity of its force.79 Referring the wheels to one an- 
other, he notices, first, their teeth, which would have 
been without use or meaning if there had been only 
one wheel, or if the wheels had had no connexion be- 
tween themselves, or common bearing upon some 
joint effect; secondly, the correspondence of their 
position, so that the teeth of one wheel catch into the 
teeth of another; thirdly, the proportion observed in 
the number of teeth in each wheel, which determines 
the rate of going. Referring the balance to the rest 
of the works, he saw, when he came to understand 
its action, that which rendered their motions equable. 
Lastly, in looking upon the index and face of the 
watch, he saw the use and conclusion of the mecha- 
nism, viz., marking the succession of minutes and 
hours ; but all depending upon the motions within, all 
upon the system of intermediate actions between the 
spring and the pointer. What thus struck his atten- 
tion in the several parts of the watch, he might desig- 
nate by one general name of " relationand observ- 
ing with respect to all cases whatever, in which the 
origin and formation of a thing could be ascertained 
by evidence, that these relations were found in things 
produced by art and design, and in no other things, he 
would rightly deem of them as characteristic of such 
NATURAL THEOLOGY. 
79 The tension or moving force of the spring diminishes as the 
spring uncoils. To counteract this, and enable the spring to ex- 
ert a uniform force, the chain through which it acts on the wheels 
is wound round a fusee which continually increases in circumfer- 
ence, so that, as the force decreases, it acts on a wheel of greater 
diameter, or at the extremity of alonger lever, and, by this mechan- 
ical advantage, is still enabled to exert the same tension.-Am. Ed. productions. To apply the reasoning here described 
to the works of nature. 
The animal economy is full, is made up of these 
relations. 
I. There are, first, what in one form or other be- 
long to all animals, the parts and powers which suc- 
cessively act upon their food. Compare this action 
with the process of a manufactory. In men and 
quadrupeds the aliment is first broken and bruised by 
mechanical instruments of mastication, viz., sharp 
spikes or hard knobs pressing against or rubbing upon 
one another; thus ground and comminuted, it is car- 
ried by a pipe into the stomach, where it waits to 
undergo a great chymical action, which we call di- 
gestion : when digested, it is delivered through an 
orifice, which opens and shuts, as there is occasion, 
into the first intestine; there, after being mixed with 
certain proper ingredients, poured through a hole in 
the side of the vessel, it is farther dissolved: in this 
state the milk, chyle, or part which is wanted, and 
which is suited for animal nourishment, is strained off 
by the mouths of very small tubes opening into the 
cavity of the intestines*; thus freed from its grosser 
parts, the percolated fluid is carried by a long, wind- 
ing, but traceable course, into the main stream of the 
old circulation, which conveys it, in its progress, to 
every part of the body. Now I say again, compare 
this with the process of a manufactory, with the ma- 
king of cider, for example ; with the bruising the ap- 
ples in the mill, the squeezing of them when so bruis- 
ed in the press, the fermentation in the vat, the be- 
stowing of the liquor thus fermented in the hogsheads, 
the drawing off into bottles, the pouring out for use 
into the glass. Let any one show me any difference 
between these two cases as to the point of contri- 
vance. That which is at present under our considera- 
tion, the "relation" of the parts successively employ- 
ed, is-not more clear in the last case than in the first. 
The aptness of the jaws and teeth to prepare the 
food for the stomach is, at least, as manifest as that 
of the cider-mill to crush the apples for the press. 
NATURAL THEOLOGY. 
245 246 
The concoction of the food in the stomach is as ne- 
cessary for its future use as the fermentation of the 
stum in the vat is to the perfection of the liquor. The 
disposal of the aliment afterward, the action and 
change which it undergoes, the route which it is made 
to take, in order that, and until that, it arrive at its 
destination, is more complex, indeed, and intricate, 
but, in the midst of complication and intricacy, as 
evident and certain as is the apparatus of cocks, pipes, 
tunnels, for transferring the cider from one vessel to 
another; of barrels and bottles for preserving it till 
fit for use, or of cups and glasses for bringing it when 
wanted to the lip of the consumer. The character of 
the machinery is in both cases this: that one part 
answers to another part, and every part to the final 
result. 
This parallel between the alimentary operation and 
some of the processes of art might be carried farther 
into detail. Spallanzani has remarked* a circum- 
stantial resemblance between the stomachs of galli- 
naceous fowls and the structure of corn-mills. While 
the two sides of the gizzard perform the office of the 
millstones, the craw or crop supplies the place of the 
hopper. 
When our fowls are abundantly supplied with 
meat, they soon fill their craw; but it does not im- 
mediately pass thence into the gizzard; it always en- 
ters in very small quantities, in proportion to the 
progress of trituration, in like manner as, in a mill, a 
receiver is fixed above the two large stones which 
NATURAL THEOLOGY. 
* Disc, i., sec. liv. 
80 So great is the power with which the muscular stomach call- 
ed the gizzard acts, that Spallanzani found it breaking off without 
any injury to itself the sharp points of needles and lancets, fixed 
in lead balls, which he had forced down the throats of turkeys, 
&c. It is usually found to contain a number of small pebbles, 
which the animal is accustomed to pick up to assist the operations 
of the gizzard. " In fact," says Sir C. Bell, " this digastric mus- 
cle or gizzard is equivalent to the muscles of the jaws, and the peb- 
bles are a fair equivalent to the teeth, with this advantage, that, 
when they are ground down, the instinct of the bird supplies it 
with more."-Am. Ed. NATURAL THEOLOGY. 
247 
serve for grinding the corn, which receiver, although 
the corn be put into it in bushels, allows the grain to 
dribble only in small quantities into the central hole 
in the upper millstone. 
But we have not done with the alimentary history. 
There subsists a general relation between the exter- 
nal organs of an animal by which it procures its food, 
and the internal powers by which it digests it. Birds 
of prey, by their talons and beaks, are qualified to seize 
and devour many species, both of other birds and of 
quadrupeds. The constitution of the stomach agrees 
exactly with the form of the members. The gastric 
juice of a bird of prey, of an owl, falcon, or a kite, 
acts upon the animal fibre alone ; it will not act upon 
seeds or grasses at all.81 On the other hand, the 
conformation of the mouth of the sheep or the ox is 
suited for browsing upon herbage. Nothing about 
these animals is fitted for the pursuit of living prey. 
Accordingly, it has been found by experiments, tried 
not many years ago, with perforated balls, that the 
gastric juice of ruminating animals, such as the sheep 
and the ox, speedily dissolves vegetables, but makes 
no impression upon animal bodies. This accordance 
is still more particular. The gastric juice, even of 
granivorous birds, will not act upon the grain while 
whole and entire. In performing the experiment of 
digesting with the gastric juice in vessels, the grain 
must be crushed and bruised before it be submitted 
to the menstruum, that is to say, must undergo by art, 
without the body, the preparatory action which the 
gizzard exerts upon it within the body, or no diges- 
tion will take place. So strict, in this case, is the 
relation between the offices assigned to the digestive 
organ, between the mechanical operation and the 
chymical process. 
II. The relation of the kidneys to the bladder, and 
81 This statement, taken literally, is incorrect. " Hunter brought 
carnivorous birds to live on grains, and granivorous birds to live 
on meat. The necessity of accomplishing this, however, by 
very slow degrees, leaves the substance of the author's argument 
sustained."-Am. Ed. of the ureters to both, i. e., of the secreting organ to 
the vessel receiving the secreting liquor, and the pipe 
laid from one to the other for the purpose of conveying 
it from one to the other, is as manifest as it is among 
the different vessels employed in a distillery, or in 
the communications between them. The animal 
structure, in this case, being simple, and the parts 
easily separated, it forms an instance of correlation 
which may be presented by dissection to every eye, 
Dr which, indeed, without dissection, is capable of 
being apprehended by every understanding. This 
correlation of instruments to one another fixes in- 
tention somewhere : especially when every other so- 
lution is negatived by the conformation. If the blad- 
der had been merely an expansion of the ureter, pro- 
duced by retention of the fluid, there ought to have 
been a bladder for each ureter. One receptacle fed 
by two pipes issuing from different sides of the body, 
yet from both conveying the same fluid, is not. to be 
accounted for by any such supposition as this. 
III. Relation of parts to one another accompanies 
us throughout the whole animal economy. Can any 
relation be more simple, yet more convincing, than 
this, that the eyes are so placed as to look in the di- 
rection in which the legs move and the hands work ? 
It might have happened very differently if it had been 
left to chance. There were at least three quarters 
of the compass out of four to have erred in. Any 
considerable alteration in the position of the eye or 
the figure of the joints would, have disturbed the line, 
and destroyed the alliance between the sense and the 
limbs. 
IV. But relation, perhaps, is never so striking as 
when it subsists, not between different parts of the 
same thing, but between different things. The rela- 
tion between a lock and a key is more obvious than 
between different parts of the lock. A bow was de- 
signed for an arrow, and an arrow for a bow; and 
the design is more evident for their being separate 
implements. 
Nor do the works of the Deity want this clearest 
248 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
249 
species of relation. The sexes are manifestly made 
for each other. They form the grand relation of an- 
imated nature, universal, organic, mechanical, sub- 
sisting, like the clearest relations of art, in different 
individuals, unequivocal, inexplicable without design. 
So much so, that, were every other proof of con- 
trivance in nature dubious or obscure, this alone 
would be sufficient. The example is complete. No- 
thing is wanting to the argument. I see no way 
whatever of getting over it. 
V. The teats of animals which give suck bear a 
relation to the mouth of the suckling progeny, par- 
ticularly to the lips and tongue. Here also, as be- 
fore, is a correspondence of parts, which parts sub- 
sist in different individuals. 
These are general relations, or the relations of 
parts which are found either in all animals, or in large 
classes and descriptions of animals. Particular re- 
lations, or the relations which subsist between the 
particular configuration of one or more parts of cer- 
tain species of animals, and the particular configura- 
tion of one or more other parts of the same animal 
(which is the sort of relation that is, perhaps, most 
striking) are such as the following : 
I. In the swan, the web-foot, the spoon-bill, the 
long neck, the thick down, the graminivorous stom- 
ach, bear all a relation to one another, inasmuch as 
they all concur in one design, that of supplying the 
occasions of an aquatic fowl floating upon the sur- 
face of shallow pools of water, and seeking its food 
at the bottom. Begin with any one of these particu- 
larities of structure, and observe how the rest follow 
it. The web-foot qualifies the bird for swimming; 
the spoon-bill enables it to graze. But how is an an- 
imal floating upon the surface of pools of water to 
graze at the bottom, except by the mediation of a 
long neck I A long neck accordingly is given to it. 
Again, a warm-blooded animal, which was to pass its 
life upon water, required a defence against the cold- 
ness of that element. Such a defence is furnished 250 
to the swan in the muff in which its body is wrapped. 
But all this outward apparatus would have been in 
vain, if the intestinal system had not been suited to 
the digestion of vegetable substances: 1 say suited 
to the digestion of vegetable substances; for it is 
well known that there are two intestinal systems 
found in birds : one with a membraneous stomach and 
a gastric juice, capable of dissolving animal substan- 
ces alone, the other with a crop and gizzard calcula- 
ted for the moistening, bruising, and afterward di- 
gesting, of vegetable aliment. 
Or set off with any other distinctive part in the 
body of the swan; for instance, with the long neck. 
The long neck, without the web-foot, would have been 
an encumbrance to the bird; yet there is no neces- 
sary connexion between a long neck and a web-foot. 
In fact, they do not usually go together. How hap- 
pens it, therefore, that they meet only when a par- 
ticular design demands the aid of both! 
II. This mutual relation, arising from a subservi- 
ence to a common purpose, is very observable also 
in the parts of a mole. The strong short legs of that 
animal, the palmated feet, armed with sharp nails, 
the pig-like nose, the teeth, the velvet coat, the small 
external ear, the sagacious smell, the sunk, protected 
eye, all conduce to the utilities or to the safety of 
its under ground life. It is a special purpose, espe- 
cially consulted throughout. The form of the feet 
fixes the character of the animal. They are so 
many shovels ; they determine its action to that of 
rooting in the ground; and everything about its body 
agrees with its destination. The cylindrical figure 
of the mole, as well as the compactness of its form, 
arising from the terseness of its limbs, proportiona- 
bly lessens its labour; because, according to its bulk, 
it thereby requires the least possible quantity of earth 
to be removed for its progress. It has nearly the 
same structure of the face and jaws as a swine, and 
the same office for them. The nose is sharp, slen- 
der, tendinous, strong, with a pair of nerves going 
down to the end of it. The plush covering which, 
NATURAL THEOLOGY. NATURAL THEOLOGY. 
251 
by the smoothness, closeness, and polish of the short 
piles that compose it, rejects the adhesion of almost 
every species of earth, defends the animal from cold 
and wet, and from the impediment which it would 
experience by the mould sticking to its body. From 
soils of all kinds the little pioneer comes forth bright 
and clean. Inhabiting dirt, it is of all animals the 
neatest. 
But what I have always most admired in the mole 
is its eyes. This animal, occasionally visiting the sur- 
face, and wanting, for its safety and direction, to be 
informed when it does so, or when it approaches it, 
a perception of light was necessary. I do not know 
that the clearness of sight depends at all upon the 
size of the organ. What is gained by the largeness 
or prominence of the globe of the eye, is width in 
the field of vision. Such a capacity would be of no 
use to an animal which was to seek its food in the 
dark. The mole did not want to look about it; nor 
would a large advanced eye have been easily defend- 
ed from the annoyance to which the life of the ani- 
mal must constantly expose it. How indeed was the 
mole, working its way under ground, to guard its 
eyes at all? In order to meet this difficulty, the 
eyes are made scarcely larger than the head of a 
corking-pin; and these minute globules are sunk so 
deeply in the scull, and lie so sheltered within the 
velvet of its covering, as that any contraction of 
what may be called the eyebrows not only closes up 
the apertures which lead to the eyes, but presents a 
cushion, as it were, to any sharp or protruding sub- 
stance which might push against them. This aper- 
ture, even in its ordinary state, is like a pinhole in a 
piece of velvet, scarcely pervious to loose particles 
of earth. 
Observe, then, in this structure, that which we call 
relation. There is no natural connexion between a 
small, sunk eye, and a shovel, palmated foot. Palma- 
ted feet might have been joined with goggle eyes; or 
small eyes might have been joined with feet of any 
other form. What was it, therefore, which brought 252 
NATURAL THEOLOGY. 
them together in the mole ? That which brought to- 
gether the barrel, the chain, and the fusee in a watch 
-design; and design in both cases inferred, from the 
relation which the parts bear to one another in the 
prosecution of a common purpose. As hath already 
been observed, there are different ways of stating the 
relation, according as we sat out from a different 
part. In the instance before us, we may either con- 
sider the shape of the feet, as qualifying the animal 
for that mode of life and inhabitation to which the 
structure of the eye confines it; or we may consider 
the structure of the eye as the only one which would 
have suited with the action to which the feet are 
adapted. The relation is manifest, whichever of the 
parts related we place first in the order of our con- 
sideration. In a word, the feet of the mole are made 
for digging : the neck, nose, eyes, ears, and skin, are 
peculiarly adapted to an underground life; and this 
is what I call relation. 
CHAPTER XVI. 
Compensation is a species of relation. It is rela- 
tion when the defects of one part, or of one organ, 
are supplied by the structure of another part, or of 
another organ. Thus : 
I. The short, unbending neck of the elephant is com- 
pensated by the length and flexibility of his proboscis. 
He could not have reached the ground without it; 
or, if it be supposed that he might have fed upon fruit, 
leaves, or branches of trees, how was he to drink ? 
Should it be asked, why is the elephant's neck so 
short l it may be answered, that the weight of a head 
so heavy could not have been supported at the end of 
a longer lever. To a form, therefore, in some re- 
COMPENSATION. epects necessary, but in some respects also inadequate 
to the occasion of the animal, a supplement is added, 
which exactly makes up the deficiency under which 
he laboured. 
If it be suggested that this proboscis may have been 
produced, in a long course of generations, by the con- 
stant endeavour of the elephant to thrust out his nose 
(which is the general hypothesis by which it has late- 
ly been attempted to account for the forms of anima- 
ted nature), I would ask, How was the animal to 
subsist in the mean time, during the process, until 
this prolongation of snout were completed! What 
was to become of the individual while the species 
was perfecting I82 
Our business at present is simply to point out the 
relation which this organ bears to the peculiar figure 
of the animal to which it belongs. And herein all 
things correspond. The necessity of the elephant's 
proboscis arises from the shortness of his neck: the 
shortness of the neck is rendered necessary by the 
weight of the head. Were we to enter into an ex- 
amination of the structure and anatomy of the pro- 
boscis itself, we should see in it one of the most cu- 
rious of all examples of animal mechanism. The 
disposition of the ringlets and fibres, for the purpose, 
NATURAL THEOLOGY. 
253 
52 Geological researches, so happily combined with comparative 
anatomy, give us no room to conjecture that there has been any- 
thing like a progressive improvement in the species of animals. 
They have been created with all the characters in which they 
are now propagated; and, had it been otherwise, the species would 
have become extinct, or they would have lost their place in that 
balance of offence and defence by which it has pleased the Crea- 
tor to provide for their continuance. 
One would imagine that an idea so wild, as that an animal 
should produce the variety of organs or external instruments 
which we see, by an effort; an energy proceeding from itself, 
could never have been maintained in an age like the present, 
when it is so fully proved that there is no change upon the ex- 
tremity of an animal, no additional organ like this of the trunk of 
the elephant, no variety in its paw or its hoof, but what is at- 
tended with a corresponding alteration in the whole system of 
the creature ; of its bones, its teeth, its stomach, as well as in its 
appetites and desires. 
Vol I.-Y 254 
NATURAL THEOLOGY. 
first, of forming a long cartilaginous pipe; secondly, 
of contracting and lengthening that pipe ; thirdly, of 
turning it in every direction at the will of the animal; 
with the superaddition, at the end, of a fleshy produc- 
tion, of about the length and thickness of a finger, and 
performing the office of a finger, so as to pick up a 
straw from the ground. These properties of the 
same organ, taken together, exhibit a specimen, not 
only of design (which is attested by the advantage), 
but of consummate art, and, as I may say, of elab- 
orate preparation, in accomplishing that design. 
II. The hook in the wing of a bat is strictly a me- 
chanical, and, also, a compensating contrivance. At 
the angle of its wing there is a bent claw, exactly in 
the form of a hook, by which the bat attaches itself 
to the sides of rocks, caves, and buildings, laying 
hold of crevices, joinings, chinks, and roughnesses. It 
hooks itself by this claw; remains suspended by this 
hold; takes its flight from this position; which oper- 
ations compensate for the decrepitude of its legs and 
feet. Without her hook, the bat/would be the most 
helpless of all animals. She can neither run upon 
her feet, nor raise herself from the ground. These 
inabilities are made up to her by the contrivance in 
her wing; and, in placing a claw upon that part, the 
Creator has deviated from the analogy observed in 
winged animals. A singular defect required a singu- 
lar substitute. 
III. The crane kind are to live and seek their food 
among the waters; yet, having no web-foot, are in- 
capable of swimming. To make up for this deficien- 
cy, they are furnished with long legs for wading, or 
long bills for groping, or usually with both. This is 
compensation. But I think the true reflection upon the 
present instance is, how every part of nature is ten- 
anted by appropriate inhabitants. Not only is the 
surface of deep waters peopled by numerous tribes 
of birds that swim, but marshes and shallow pools 
are furnished with hardly less numerous tribes of 
birds that wade. 
IV. The common parrot has, in the structure of its NATURAL THEOLOGY. 
255 
beak, both an inconvenience and a compensation for 
it. When I speak of an inconvenience 1 have a view 
to a dilemma which frequently occurs in the works of 
nature, viz., that the peculiarity of structure by which 
an organ is made to answer one purpose necessarily 
unfits it for some other purpose. This is the case 
before us. The upper bill of the parrot is so much 
hooked, and so much overlaps the lower, that if, as 
in other birds, the lower chap alone had motion, the 
bird could scarcely gape wide enough to receive its 
food : yet this hook and overlapping of the bill could 
not be spared, for it forms the very instrument by 
which the bird climbs, to say nothing of the use which 
it makes of it in breaking nuts and the hard substan- 
ces upon which it feeds. How, therefore, has nature 
provided for the opening of this occluded mouth 1 By 
making the upper chap moveable as well as the lower. 
In most birds, the upper chap is connected, and makes 
but one piece, with the scull; but in the parrot the 
upper chap is joined to the bone of the head by a 
strong membrane placed on each side of it, which lifts 
and depresses it at pleasure.* 
V. The spider's web is a compensating contrivance. 
The spider lives upon flies, without wings to pursue 
them; a case, one would have thought, of great diffi- 
culty, yet provided for, and provided for by a resource 
which no stratagem, no effort of the animal, could 
have produced, had not both its external and internal 
structure been specifically adapted to the operation.83 
* Goldsmith's Nat. Hist., vol. v., p. 274. 
83 There are few things better suited to remove the disgust into 
which young people are betrayed on the view of some natural ob- 
jects, than this of the spider. They will find that the most de- 
spised creature may become a subject of admiration, and be select- 
ed by the naturalist to exhibit the marvellous works of the crea- 
tion. The terms given to these insects lead us to expect interest- 
ing particulars concerning them, since they have been divided into 
vagrants, hunters, swimmers, and water-spiders, sedentary, and 
mason-spiders; thus evincing a variety in their condition, activ- 
ity, and mode of life; and we cannot be surprised to find them 
varying in the performance or their rightful functions (as, for ex- 
ample, in their mode of breathing), as well as in their extremities 
and instruments. Of these instruments, the most striking is the 256 
NATURAL THEOLOGY. 
VI. In many species of insects the eye is fixed, and, 
consequently, without the power of turning the pupil 
apparatus for spinning and weaving, by which they not only fab- 
ricate webs to entangle their prey, but form cells for their resi- 
dence and concealment; sometimes living in the ground, some- 
times under water, yet breathing the atmosphere. Corresponding 
with their very singular organization are their instincts. We are 
familiar with the watchfulness and voracity of some spiders, when 
their prey is indicated by the vibration of the cords of their net- 
work. Others have the eye and disposition of the lynx or tiger, 
and, after crouching in concealment, leap upon their victims. 
Some conceal themselves under a silken hood or tube, six eyes 
only projecting. Some bore a hole in the earth, and line it as 
finely as if it were done with the trowel and mortar, and then 
hang it with delicate curtains. A very extraordinary degree of 
contrivance is exhibited in the trapdoor spider. This door, from 
which it derives its name, has a frame and hinge on the mouth of 
the cell, and is so provided that the claw of the spider can lay hold 
of it, and, whether she enters or goes out, says Mr. Kerby, the 
door shuts of itself. But the water-spider has a domicil more cu- 
rious still: it is under water, with an opening at the lower part for to the object. This great defect is, however, per- 
fectly compensated, and by a mechanism which we 
should not suspect. The eye is a multiplying-glass, 
with a lens looking in every direction and catching 
every object. By which means, although the orb of 
the eye is stationary, the field of vision is as ample as 
that of other animals, and is commanded on every 
side. When this lattice-work was first observed, the 
multiplicity and minuteness of the surfaces must have 
added to the surprise of the discovery. Adams tells 
us that fourteen hundred of these reticulations have 
been counted in the two eyes of a drone-bee. 
In other cases, the compensation is effected by the 
number and position of the eyes themselves. The 
spider has eight eyes, mounted upon different parts 
of the head ; two in front, two in the top of the head, 
two on each side. These eyes are without motion, 
but, by their situation, suited to comprehend every 
view which the wants or safety of the animal rendered 
it necessary for it to take. 
VII. The Memoirs for the Natural History of ani- 
NATURAL THEOLOGY. 
257 
her exit and entrance; and, although this cell be under water, it 
contains air like a diving-bell, so that the spider breathes the atmo- 
sphere. The air is renewed in the cell in a manner not easily- 
explained. The spider comes to the surface; a bubble of air is 
attracted to its body; with this air she descends, and gets under 
her cell, where the air is disengaged and rises into the cell; and 
thus, though under water, she lives in the air. There must be 
some peculiar property of the surface of this creature by which 
she can move in the water surrounded with an atmosphere, and 
live under the water breathing the air. 
The chief instrument by which the spider performs these won- 
ders is the spinning apparatus. The matter from which the threads 
are spun is a liquid contained in cells; the ducts from these cells 
open upon little projecting teats, and the atmosphere has so imme- 
diate an effect upon this liquid, that, upon exposure to it, the se- 
cretion becomes a tough and strong thread. Twenty-four of these 
fine strands form together a thread of the thickness of that of the 
silkworm. We are assured that there are three different sorts of 
material thus produced, which are indeed required for the various 
purposes to which they are applied; as, for example, to mix up 
the earth to form the cells; to line these cells as with fine cotton; 
to make light and floating threads by which they may be convey- 
ed through the air, as well as those meshes which are so geomet 
rically and correctly formed to entrap their prey. 258 
NATURAL THEOLOGY. 
mals, published by the French Academy, A.D. 1687, 
furnish us with some curious particulars in the eye 
of a chameleon. Instead of two eyelids, it is cover- 
ed by an eyelid with a hole in it. This singular 
structure appears to be compensatory, and to answer 
to some other singularities in the shape of the ani- 
mal. The neck of the chameleon is inflexible. To 
make up for this, the eye is so prominent as that 
more than half of the ball stands out of the head, by 
means of which extraordinary projection the pupil of 
the eye can be carried by the muscles in every di- 
rection, and is capable of being pointed towards every 
object. But, then, so unusual an exposure of the 
globe of the eye requires for its lubricity and defence 
a more than ordinary protection of eyelid, as well as 
a more than ordinary supply of moisture; yet the 
motion of an eyelid, formed according to the common 
construction, would be impeded, as it should seem, 
by the convexity of the organ. The aperture in the 
lid meets this difficulty. It enables the animal to 
keep the principal part of the surface of the eye un- 
der cover, and to preserve it in a due state of humid- 
ity, without shutting out the light, or without perform- 
ing every moment a nictitation which it is probable 
would be more laborious to this animal than to others. 
VIII. In another animal and in another part of the 
animal economy, the same Memoirs describe a most 
remarkable substitution. The reader will remember 
what we have already observed concerning the intes- 
tinal canal, that its length, so many times exceeding 
that of the body, promotes the extraction of the chyle 
from the aliment by giving room for the lacteal ves- 
sels to act upon it through a greater space. This 
long intestine, wherever it occurs, is in other animals 
disposed in the abdomen from side to side in return- 
ing folds. But in the animal now under our notice 
the matter is managed otherwise. The same inten- 
tion is mechanically effectuated, but by a mechanism 
of a different kind. The animal of which I speak is 
an amphibious quadruped, which our authors call the 
alopecias or sea-fox. The intestine is straight from NATURAL THEOLOGY. 
259 
one end to the other; but in this straight and, conse- 
quently, short intestine, is a winding, corkscrew, spi- 
ral passage, through which the food, not without 
several circumvolutions, and, in fact, by a long route, 
is conducted to its exit. Here the shortness of the 
gut is compensated by the obliquity of the perforation. 
IX. But the works of the Deity are known by ex- 
pedients. Where we should look for absolute desti- 
tution ; where we can reckon up nothing but wants, 
some contrivance always comes in to supply the pri- 
vation. A snail, without wings, feet, or thread, climbs 
up the stalks of plants by the sole aid of a viscid hu- 
mour discharged from her skin. She adheres to the 
stems, leaves, and fruits of plants by means of a 
sticking-plaster. A muscle, which might seem by its 
helplessness to lie at the mercy of every wave that 
went over it, has the singular power of spinning 
strong tendinous threads, by which she moors her 
shell to rocks and timbers. A cockle, on the contra- 
ry, by means of its stiff tongue, works for itself a 
shelter in the sand. The provisions of nature ex- 
tend to cases the most desperate. A lobster has in 
its constitution a difficulty so great, that one could 
hardly conjecture beforehand how nature would dis- 
pose of it. In most animals, the skin grows with 
their growth. If, instead of a soft skin, there be a 
shell, still it admits of a gradual enlargement. If the 
shell, as in the tortoise, consist of several pieces, the 
accession of substance is made at the sutures. Bi- 
valve shells grow bigger by receiving an accretion at 
their edge : it is the same with spiral shells at their 
mouth. The simplicity of their form admits of this. 
But the lobster's shell, being applied to the limbs of 
the body as well as to the body itself, allows not of 
either of the modes of growth which is observed to 
take place in other shells. Its hardness resists ex- 
pansion ; and its complexity renders it incapable of 
increasing its size by addition of substance to its 
edge. How, then, was the growth of the lobster to 
be provided for ? Was room to be made for it in the 
old shell, or was it to be successively fitted with new 260 
NATURAL THEOLOGY. 
ones 1 If a change of shell became necessary, how 
was the lobster to extricate himself from his present 
confinement 1 how was he to uncase his buckler, or 
draw his legs out of his boots 1 The process which 
fishermen have observed to take place is as follows : 
At certain seasons the shell of the lobster grows soft; 
the animal swells its body; the seams open, and the 
claws burst at the joints. When the shell has thus be- 
come loose upon the body, the animal makes a second 
effort, and, by a tremulous spasmodic motion, casts 
it off. In this state the liberated but defenceless fish 
retires into holes in the rock. The released body 
now suddenly pushes its growth. In about eight-and- 
forty hours a fresh concretion of humour upon the 
surface, i. e., a new shell, is formed, adapted in every 
part to the increased dimensions of the animal. This 
wonderful mutation is repeated every year. 
If there be imputed defects without compensation, 
I should suspect that they were defects only in ap- 
pearance. Thus the body of the sloth has often been 
reproached for the slowness of its motions, which has 
been attributed to an imperfection in the formation 
of its limbs. But it ought to be observed that it is 
this slowness which alone suspends the voracity of 
the animal. He fasts during his migration from one 
tree to another; and this fast may be necessary for 
the relief of his overcharged vessels, as well as to 
allow time for concoction of the mass of coarse and 
hard food which he has taken into his stomach. The 
tardiness of his pace seems to have reference to the 
capacity of his organs, and to his propensities with 
respect to food; i. e., is calculated to counteract the 
effects of repletion.84 
84 The criticisms in which Buffon has indulged with regard to 
fie defective wisdom and goodness evinced in the constitution 
of this animal, seem as impertinent as those noticed in a previous 
note in regard to the woodpecker. The animal has very little occa- 
sion to move. It does not drink. The leaves of a single tree fur- 
nish it with food for a quarter of a year. To defend itself .against 
enemies, it is supplied with powerful claws, a fearful cry, and an 
instinct which teaches it, when " a tiger cat is seen climbing up 
a branch, to go softly to the end of the branch and rock it till the 
tiger falls off."-Am. Ed. NATURAL THEOLOGY. 
261 
Or there may be cases in which a defect is artifi- 
cial, and compensated by the very cause which pro- 
duces it. Thus the sheep, in the domesticated state 
in which we see it, is destitute of the ordinary means 
of defence or escape ; is incapable either of resistance 
or flight. But this is not so with the wild animal. The 
natural sheep is swift and active; and, if it lose these 
qualities when it comes under the subjection of man, 
the loss is compensated by his protection. Perhaps 
there is no species of quadruped whatever which suf- 
fers so little as this does from the depredation of ani- 
mals of prey. 
For the sake of making our meaning better under- 
stood, we have considered this business of compen- 
sation under certain particularities of constitution, in 
which it appears to be most conspicuous. This view 
of the subject necessarily limits the instances to sin- 
gle species of animals. But there are compensa- 
tions, perhaps not less certain, which extend over 
large classes and to large portions of living nature. 
I. In quadrupeds, the deficiency of teeth is usually 
compensated by the faculty of rumination. The sheep, 
deer, and ox tribe are without fore-teeth in the upper 
jaw. These ruminate. The horse and ass are fur- 
nished with teeth in the upper jaw, and do not rumi- 
nate. In the former class, the grass and hay descend 
into the stomach nearly in the state in which they are 
cropped from the pasture or gathered from the bun- 
dle. In the stomach they are softened by the gastric 
juice, which in these animals is unusually copious: 
thus softened and rendered tender, they are returned 
a second time to the action of the mouth, where the 
grinding-teeth complete at their leisure the tritura- 
tion which is necessary, but which was before left 
imperfect; I say the trituration which is necessary ; 
for it appears from experiments that the gastric fluid 
of sheep, for example, has no effect in digesting 
plants unless' they have been previously masticated : 
that it only produces a slight maceration, nearly as 
common water would do in a like degree of heat; 
but that, when once vegetables are reduced to pieces 262 
NATURAL THEOLOGY. 
by mastication, the fluid then exerts upon them its 
specific operation. Its first effect is to soften them, 
and to destroy their natural consistency : it then goes 
on to dissolve them, not sparing even the toughest 
parts, such as the nerves of the leaves.* 
I think it very probable that the gratification also 
of the animal is renewed and prolonged by this fac- 
ulty. Sheep, deer, and oxen appear to be in a state of 
enjoyment while they are chewing the cud : it is then, 
perhaps, that they best relish their food.85 
II. In birds, the compensation is still more striking. 
They have no teeth at all. What have they, then, to 
make up for this severe want 1 I speak of granivor- 
ous and herbivorous birds: such as common fowls, 
turkeys, ducks, geese, pigeons, &c.; for it is concern- 
* Spall., Dis. iii., sect. cxl. 
86 Wherever a seed can lodge we find vegetables growing; and 
wherever we find digestible matter there are animals to live upon 
it; and the kind of food determines the organization of the crea- 
ture, not resulting from it, but provided for it. The class of rumi- 
nants feed on the coarser herbage where the vegetable is in abun- 
dance, but the actual nutritious matter is small in quantity com- 
pared with the mass. There is, therefore, an obvious necessity 
for a more complex apparatus to extract the smaller proportion of 
matter capable of being animalized : hence the maceration in the 
first stomach, hence the regurgitation and rumination, and the re- 
ception into the second and third stomach, in preparation for the 
proper digestion in the last. When the mass is digested, the nu- 
tritious part is still small in proportion to the whole: and, to per- 
mit that smaller portion of aliment to be absorbed and carried into 
the system, the intestinal canal must be long and complex, offer- 
ing resistance to the rapid descent of the food, and giving it lodg- 
ment : and thus there is always a correspondence between the 
complication of the stomach and the length of the intestines, and 
between both and the nature of the food. It is farther very re- 
markable, that, when animals of the same species live in different 
climates, where there is more or less abundance of vegetable food, 
there is an adaptation of their digestive organs. 
Where it is abundant, the configuration of the intestines, which 
is intended to delay its descent, is less complex. Where the food 
is more scarce, the intestine is longer, and the valvular obstruc- 
tion greater. This has been observed by Sir E. Home, in com- 
paring the cassowary of Java with the cassowary of New South 
Wales, and the American ostrich with the same bird inhabiting 
the deserts of Africa. The same comparison has been made be- 
tween the Leicestershire sheep and the mountain sheep of Scot 
land. NATURAL THEOLOGY. 
263 
ing these alone that the question need be asked. All 
these are furnished with a peculiar and most power- 
ful muscle, called the gizzard; the inner coat of 
which is fitted up with rough plaits, which, by a 
strong friction against one another, break and grind 
the hard substance as effectually, and by the same 
mechanical action, as a coffee-mill would do. It has 
been proved, by the most correct experiments, that the 
gastric juice of these birds will not operate upon the 
entire grain: not even when softened by water or 
macerated in the crop. Therefore, without a grind- 
ing-machine in its body, without the trituration of the 
gizzard, a chicken would have starved upon a heap 
of corn. Yet why should a bill and a gizzard go to- 
gether 1 why should a gizzard never be found where 
there are teeth 1 
Nor does the gizzard belong to birds as such. A giz- 
zard is not found in birds of prey: their food requires 
not to be ground down in a mill. The compensatory 
contrivance goes no farther than the necessity. In 
both classes of birds, however, the digestive organ 
within the body bears a strict and mechanical rela- 
tion to the external instruments for procuring food. 
The soft membraneous stomach accompanies a hook- 
ed, notched beak; short muscular legs ; strong, sharp, 
crooked talons; the cartilaginous stomach attends 
that conformation of bill and toes which restrains the 
bird to the picking of seeds or the cropping of plants.8*5 
86 We have said that it is the object to support animal life, and 
to give the enjoyment of existence ; and that, wherever the mean3 
are afforded of converting a material under the processes of diges- 
tion and assimilation, there animals will be found with an appa- 
ratus of digestion adapted to the food. Nothing certainly can be 
more curious than the vicarious action of the stomach and mouth. 
We see, for example, that where the bill precludes mastication in 
the mouth, it is performed in the stomach; and then muscles are 
found in the stomach as powerful as those of the jaws and teeth; 
and as to the teeth, or what is equivalent to them, we may say 
that they are continually renewed. In fact, no mechanical struc- 
ture of jaws and teeth could answer the purposes of nature here; 
no union of bone and enamel in the tooth could have withstood 
the attrition of the gizzard; and one of the most beautiful and 
interesting appliances of nature is the substitution, through the 264 
NATURAL THEOLOGY. 
III. But to proceed with our compensations. A 
very numerous and comprehensive tribe of terrestrial 
animals are entirely without feet; yet locomotive, 
and in a very considerable degree swift in their mo- 
tion. How is the want of feet compensated 1 It is 
done by the disposition of the muscles and fibres of 
the trunk. In consequence of the just collocation, 
and by means of the joint action of the longitudinal 
and annular fibres, that is to say, of strings and rings, 
the body and train of reptiles are capable of being 
reciprocally shortened and lengthened, drawn up and 
stretched out. The result of this action is a pro- 
gressive and, in some cases, a rapid movement of the 
whole body, in any direction to which the will of the 
animal determines it. The meanest creature is a 
collection of wonders. The play of the rings in an 
earthworm',\ps it crawls, the undulatory motion propa- 
gated along the body, the beards or prickles with which 
the annuli are armed, and which the animal can either 
shut up close to its body or let out to lay hold of the 
roughness of the surface upon which it creeps, and 
the power arising from all these of changing its place 
and position, afford, when compared with the provis- 
ions for motion in other animals, proofs of new and' 
appropriate mechanism. Suppose that we had never 
seen an animal move upon the ground without feet, 
and that the problem was: Muscular action, i. e., re- 
ciprocal contraction and relaxation being given, to 
describe how such an animal might be constructed 
instinct of the animal, of small stones of hard texture, generally 
consisting of silex, introduced within the grasp and action of this 
organ. It is a farther proof that the mastication, if we may use 
the term, is more perfect in the gizzard than where there is the 
most complex structure of teeth, and, therefore, that is the means 
of extracting the greater quantity of nutritious matter. Accord- 
ingly, there are gizzards in most classes of animals. They are 
not only found in birds, but in reptiles. The sea-turtle has what 
is termed a muscular stomach. Among fishes, the mullet and the 
gillaroo trout have muscular stomachs. The cuttle-fish, the nau- 
tilus, and even the earthworm, have a crop and gizzard; and in- 
sects. according as they live on a leaf or suck the blood, have the 
same difference in the internal arrangement of the structure fox 
assimilation as that which distinguishes the ox from the lion. capable of voluntarily changing place. Something, 
perhaps, like the organization of reptiles might have 
been hit upon by the ingenuity of an artist; or might 
have been exhibited in an automaton, by the combi- 
nation of springs, spiral wires, and ringlets: but to 
the solution of the problem would not be denied, sure- 
ly, the praise of invention and of successful thought: 
least of all could it ever be questioned whether intel- 
ligence had been employed about it or not.87 
NATURAL THEOLOGY. 
265 
87 Not unconnected with the subject of the last note is the pro- 
gression of animals : and we have none better suited for the object 
of this volume than the consideration of the infinite variety of the 
instruments of motion, from the blubber that floats like froth upon 
the water, to the eagle or the antelope. The genus medusa of 
Linnaeus embraces those animals like jelly which float in the sea. 
Some of these, when taken out of the water, will weigh fifty oun- 
ces, and, on being dried, not more than five or six grains. From 
this it would appear that they must be of the specific gravity of 
water, and hence their peculiar organization and mode of exist- 
ence : especially it accounts for their mode of progression, if it can 
be called so: since they are in a great measure passive, and float 
and are carried by the wind. For this purpose there is a vesicle 
or bladder filled with air, which in some rises above the water, 
and the animal is dragged as we might imagine a balloon would 
be after lighting on the water. The walls of this sac are muscu- 
lar, and the animal, by retaining or forcing out the air, can either 
take advantage of the wind, and is sometimes moved with great 
velocity, or sink under the surface, and movevenly with the cur- 
rent. There is every reason to believe that the air, which is the 
principal means of change of place, is secreted by the animal. 
From some of these animals tentacula hang down into the wa- 
ter for seizing their food, and perhaps for directing their progress. 
They have a power of distending them, or erecting them by for- 
cing water into their texture, by the contraction of vesicles near 
their base. Varieties of these animals hoist a plate or crest out 
of the water, which has a still greater resemblance to a sail. 
We have already noticed the fins of fishes, the wing of the bird, 
and the web-foot of the duck. " The meanest creature is, indeed, 
a collection of wonders." In the earthworm or the caterpillar, 
the head, or the anterior part of the body, is projected (and it is 
a difficult problem to produce extension by contraction) till it 
touches the ground, and slightly adheres to it, when the posterior 
part of the body is drawn forward. In many worms or caterpil- 
lars there are holders discoverable upon minute inspection, and 
their anatomy exhibits a perfect set of muscles attached to those 
exterior rough points, by which it is made evident that each of 
them is a foot. But nothing is more interesting than to see the 
Vol. L-Z 266 
change of the larva to the winged insect, where these muscles and 
their appropriate nerves disappear ; and new muscles, and new 
nerves, and new energies direct the creature that crept an inch in 
an hour, to outstrip, as we have said, the fleetest horse, or to rise 
upon the wind; for those who travel by the new railroads ob- 
serve bees to fly round them, and therefore to move above sixty 
miles an hour. The contrasts are the most curious between the 
fight of the bat and the motion of the mole; the same organiza- 
tion being calculated, with slight adaptation, for the atmosphere, 
and for moving under the earth. We might almost give the instance 
of the perforation of solid calcareous rock by the boring mollusca, 
which, by late observations, seems to be accomplished by means 
of the foot. 
NATURAL THEOLOGY. 
END OF VOL. I.