The Bridgewater Treatises
on the Power, Wisdom, and Goodness of God,
As Manifested in the Creation.
ANIMAL AND VEGETABLE PHYSIOLOGY, CONSIDERED
WITH REFERENCE TO NATURAL THEOLOGY.
PETER MARK ROGET, M. D.
Secretary to the Royal
Society, Fullerian Professor of Physiology in the
Royal Institution of Great Britain, Vice President of the Society
of Arts, Fellow of the Royal College of Physicians,
Consulting Physician to the Queen Charlotte's
Lying-in Hospital, and to the Northern
In Two Volumes
Lea & Blanchard,
This electronic edition prepared by Dr. David C. Bossard
from original documents in his personal library.
Copyright © 2006 by David C. Bossard.
LIST OF ENGRAVINGS
NOTE: Text images have a resolution of 100 ppi. High resolution
images (400 ppi) are available here.
PART II. THE VITAL FUNCTIONS.
CHAPTER I. -- OBJECTS OF NUTRITION.
 THE mechanical structure and
properties of the organized fabric, which have occupied our attention
in the preceding volume, are necessary for the maintenance of life, and
the exercise of the vital powers. But, however artificially that fabric
may have been constructed, and however admirable the skill and the
foresight which have been displayed in ensuring the safety of its
elaborate mechanism, and in preserving the harmony of its complicated
movements, it yet of necessity contains within itself the elements of
its own dissolution. The nimal machine, in common with every other
mechanical contrivance, is subject to wear and deteriorate' by constant
use. Not only in the greater movements of the limbs, but also in the
more delicate actions of the internal organs, we may trace the
operation of many causes inevitably leading to their ultimate
destruction. ... Provision must accordingly be made for remedying these
constant causes of decay by the supply of those peculiar, materials
which the organs require for recruiting their declining energies.
... We may take as an example one of the simplest of organic
products, namely, Sugar; a substance which has been analyzed with the
greatest accuracy by modern chemists: yet to reproduce this sugar, by
the artificial combination of its simple elements, is a problem which
has hitherto baffled all the efforts of philosophy. [Note: The complex
sucrose cycle was first described in the 1960s, 130 years after this
writing -- dcb]
 The elements of organic substances are not very numerous: the
principal of them being oxygen, carbon, hydrogen, nitrogen, sulphur,
and phosphorus, together with a few of the-alkaline, earthy, and
metallic bases. These substances are variously united, so as to form
certain specific compounds, which, although they are susceptible, in
difibrent instances, of endless modifications, yet possess such a
general character of uniformity, as to allow of their being arranged in
certain classes; the most characteristic substance in each class
constituting what is called a proximate organic principle. Thus, in the
vegetable kingdom we have Lignin, Tannin, Mucilage, Oil, Sugar, Fecula,
&c. The animal kingdom, in like manner, furnishes Gelatin, Albumen,
Fibrin, Mucus, Entomoline, Elearin, Stearin, and many others.
 This peculiar mode of combination gives rise to a remarkable
condition, which attaches to the chemical properties of organic
compounds. The attractive forces, by which their several ingredients
are held together, being very numerous, require to be much more nicely
balanced, in order to retaim them in combination. Slight causes are
sufficient to disturb, or even overset, this equipoise of affinities,
and often produce rapid changes of form, or even complete
decomposition. The principles, thus retained in a kind of forced union,
have a constant tendency to react upon one another and to produce, from
slight variations of circumstances, a totally new order of
combinations. Thus, a degree of heat which would occasion no change in
most mineral substances. will at once effect the complete disunion of
the elements o an animal or vegetable body. Organic substances are, in
like manner, unable to resist the slower, but equally destructive
agency of water and atmospheric air; and they are also liable to
various spontaneous changes, such as those constituting fermentation
and putrefaction, which occur when their vitality is extinct, and when
they are consequently abandoned to the uncontrolled operation of their
natural chemical affinities. This
tendency to decomposition may, indeed, be regarded as inherent in all
organized substances, and as requiring for its counteraction, in the
living system, that perpetual renovation of materials which is supplied
by the powers of nutrition. [emphasis added -- dcb] ... 
Hence, the continued interchange and renewal of particles which take
place in the more active organs of the system, especially in the higher
classes of animals. In the fabric of those animals which possess an
extensive system of circulating and absorbing vessels, the changes
which are effected are so considerable and so rapid, that even in the
densest textures, such as the bones, scarcely any portion of the
substance which originally composed them is permanently retained in
their structure. To so great an extent is this renovation of materials
carried on in the human system, that doubts may very reasonably be
entertained as to the identity of any portion of the body after the
lapse of a certain time. The period assigned by the ancients for this
entire change of the substance of the body, was seven or eight years:
but modern inquiries, which show us the rapid reparation that takes
place in injured parts, and the quick renewal o1 the bones themselves,
tend to prove that even a shorter time than this is adequate to the
complete renovation of every portion of the living fabric.
 Imperfect as is our knowlcdgc of organic chemistry, we see enough
to convince us that a series of the most refined and artificial
operations is required, in order to bring about the complicated and
elaborate arrangements of elements which constitute both animal and
vegetable products. Thus, in the very outset of this, as of every other
inquiry in Physiology, we
meet with evidences of profound intention and consummate art,
infinitely surpassing not only the power and resources, but even the
imagination of man [emphasis added].
II. -- NUTRITION IN VEGETABLES.
III. -- ANIMAL NUTRITION IN GENERAL.
1. Food of Plants. 19
2. Absorption of Nutriment by Plants. 21 021
3. Exhalation. 27 027
4. Aeration of the Sap. 28 028
 The remarkable discovery that
oxygen gas is exhaled from the leaves of plants during the day time,
was made by the great founder of pneumatic chemistry, Dr. Priestly. ...
Solar light is an essential agent in effecting this....
 During the whole of the night, the same leaves, which had been
exhaling oxygen during the day, absorb a portion of that element. The
oxygen thus absorbed enters immediately into combination with the
carbonaceous matter in the plant, forming with it carbonic acid. ...
This reversal at night of what was done in the day may, at first sight,
appear to be at variance with the unity of plan, which we should expect
to find preserved in the vegetable economy; but a more attentive
examination of the process will show that the whole is in perfect
harmony, and that these contrary processes are both of them necessary,
in order to produce the result intended.
The water which is absorbed by the roots generally carries with it a
certain quantity of soluble animal or vegetable materials, which
contain carbon. This carbon is transmitted to the leaves, where, during
the night, it is made to combine, with the oxygen they have absorbed.
It is thus converted into carbonic dcid, which, when daylight prevails,
is decomposed; the oxygen being dissipated, and the carbon retained. It
is evident that the object of the whole process is to obtain carbon in
that precise state of disintegration, to which it is reduced at the
moment of its separation from carbonic acid by the action of solar
light on the green substance of the leaves; for it is in this state
alone that it is available in promoting the nourishment of the plant,
and not in the crude condition in which it exists when it is pumped up
from the earth...
 Thus are the two great organized kingdoms of the creation made to
co-operatein the execution of the same design; each ministering to the
other, and preserving that due balance in the constitution of the
atmosphere, which adapts it to the welfare and activity of every order
of beings, and which would soon be destroyed, were the operations of
any one of them to be suspended. It is impossible to contemplate so
special an adjustment of opposite effects without admiring this
beautiful dispensation of Providence, extending over so vast a scale of
being, and demonstrating the unity of plan on which the whole system of
organized creation has been devised.
5. Return of the Sap. 32 032
Secretion in Vegetables. 38 038
7. Excretion in Vegetables. 43 043
IV. -- NUTRITION IN THE LOWER ORDERS OF ANIMALS.
V. -- NUTRITION IN THE HIGHER ORDERS OF ANIMALS.
VI. -- PREPARATION OF FOOD.
VII. -- DIGESTION.
VIII. -- CRYLIFICATION.
IX. -- LACTEAL ABSORPTION.
X. -- CIRCULATION.
XI. -- RESPIRATION.
XII. -- SECRETION.
CHAPTER XIII. -- ABSORPTION.
CHAPTER XIV. -- NERVOUS POWER.
PART III. THE
CHAPTER I. -- SENSATION.
CHAPTER II. -- TOUCH.
CHAPTER III. -- TASTE.
CHAPTER IV. -- SMELL.
CHAPTER V. -- HEARING.
CHAPTER VI. -- VISION.
CHAPTER VII. --
CHAPTER VIII. --
COMPARATIVE PHYSIOLOGY OF THE NERVOUS SYSTEM.
PART IV. THE
CHAPTER I. -- REPRODUCTION.
CHAPTER II. -- ORGANIC
CHAPTER III. -- DECLINE
OF THE SYSTEM.
CHAPTER IV. -- UNITY OF
[440 - Early concept of
"recapitulation"] It is remarked, in farther corroboration of these
views, that the animals which occupy the highest stations in each
series possess, at the commencement of their existence, forms
exhibiting a marked resemblance to those presented in the permanent
condition of the lowest animals in the same series; and that, during
the progress of their development, they assume, in succession, the
characters of each tribe, corresponding to their consecutive order in
the ascending chain; so that the peculiarities which distinguish the
higher animal, on its attaining its ultimate and permanent form, are
those which it has received in its last stage of embryonic evolution.
...  Nor is the human embryo exempt from the same metatnorphoses,
possessing, at one period, branchiae and branchial apertures similar to
those of the cartilaginous fishes, a heart with a single set of
cavities, and a brain consisting of a longitudinal series of tubercles;
next losing its branchiae, and acquiring lungs, while the circulation
is yet single, and thus imitating the condition of the reptile; then
acquiring a double circulation, but an incomplete diaphragm, like
birds; afterwards, appearing like a quadruped, with a caudal
prolongation of the sacrum, and an intermaxillary bone; and, lastly,
changing its structure to one adapted to the erect position,
accompanied by a great expansion of the cerebral hemispheres, which
extend backwards so as completely to cover the cerebellum. Thus does
the whole fabric arrive, by a gradual process of mutation, at an extent
of elaboration and refinement, which has been justly regarded as
constituting a climax of organic development, unattainable by any other
race of terrestrial beings. ... It must, I think, be admitted that the
analogies, on which the hypothesis in question is founded, are numerous
and striking; but great care should be taken not to carry it farther
than the just interpretation of the facts thethselves may warrant. It
should be borne in mind that these facts are few, compared with the
entire history of animal development; and that the resemblances which
have been so ingeniously traced, are partial only, and fall very short
of that universality, which alone constitutes the solid basis of a
strictly philosophical theory. Whatever may be the apparent similarity
between one animal and another, during different periods of their
respective developments, there still exist specific differences,
establishing between them an impassable barrier of separation, and
effectually preventing any conversion of one species into another,
however nearly the two may be mutually allied. The essential characters
of each species, amidst occasional varieties, remain ever constant and
immutable. Although gradations, to a greater or less extent, may be
traced among the races both of plants and animals, yet in no case is
the series strictly continuous; each step, however short, being in
reality an abrupt transition from one type of conformation to another.
In many instances the interval is considerable; as, for example, in the
passage from the invertebrate to the vertebrated classes; and, indeed,
in every instance where great changes in the nature and arrangement of
the functions take place.