THE
MEDICAL EXAMINER,
AND
RECORD OF MEDICAL SCIENCE.
NEW SERIES. —NO. CI.—MAY, 1853.
ORIGINAL COMMUNICATIONS.
Zoonoma: or the Laic of Animal Life. A Lecture delivered
at the Smithsonian Institute, Washington, U. S., on March
the 8th, 1853. By Marshall Hall, M. D., F. R. S., Foreign
Associate of the “Acaddmie de Mddecine” of Paris, &c. &c.
Gentlemen,—I congratulate myself on the opportunity
afforded me, by your kind invitation, to unfold a principle in
physiology on which I have long meditated and experimented,
and which I have ventured to designate the Law of Animal
Life.
Many have been the attempts to define life. All have, I
think, proved abortive. I shall not, in my turn, venture to
attempt that in which so many have failed. My object will be
rather to describe than to define.
Life, then, may be justly viewed as consisting in a compre-
hensive system of action and re-action—of the action of certain
physical and chemical influences, and the re-action of certain
vital powers in organized beings.
Throughout the animal, and, indeed, the vegetable kingdoms,
the primary organic agents and re-agents are pollen and ova.
Life first consists in the reciprocal action of these upon each
other. Such is the very type and essence of life in its earliest
dawn. Harvey said—Omne vivum ah ovo. lie might, with
equal truth, have said, Omne vivum a polline; and with still
greater truth, Omne vivum a polline et ovo.
Each of them—the pollen, the ovum—was originally a crea-
tion. Their mutual and reciprocal action is a phenomenon
which the Creator has impressed on this portion of His works, as
the fiat of His will.
That this action is perfectly reciprocal, is proved by the
resemblance of the new being or offspring—be it animal or vege-
table—to both parents. The event is at present as inscrutable
in its nature and essence, as it is interesting to the physiologist
and philosopher as a subject of observation and new inquiry.
Why this seed of the Triticum Indicum, or Indian corn, on
which pollen has fallen, should, if planted in soil and exposed to
the genial influences of heat and moisture, become a noble and
useful plant; and this other, to which, from its mode of growth
and treatment, no pollen has been allowed to have access, shall,
under similar circumstances and influences, undergo decay and
decomposition, who can tell ? Why this egg, which has been
fertilized by pollen, should, under similar genial influences, be-
come a bird, and eventually soar into the regions of the atmos-
phere ; and why this other, unaffected by pollen, should pass into
a state of putrefaction, who can declare ? Who will attempt to
explain why those “divince particulse aurae,” which exist in the
form of pollen, can alone vivify these ova ? Who can say what
there is in these ova, and what there is in the appropriate pol-
len—for the two are equally essential—which develope growth,
and form, and life ?
Look at these ova and on these seeds. On this ovum and on
this seed no pollen has ever been shed. They will, though placed
in circumstances the most favorable for developement, only pass
the more readily into decay. But this other ovum, this other
seed, on which pollen, life-giving pollen, has shed itself, will,
under similar circumstances, germinate and pass into life, the
whole subsequent being being expressly imbued with the equally
inscrutable properties of the pollen, and of the ovum or seed.
What is the condition of this pollenized, this fructified ovum
or seed before active life begins ? Is life in abeyance ? or is it
in actual existence only in its lowest and imperceptible form ?
Have eggs and seed a temperature of their own, above that of
the medium in which they are placed ? And what is the condi-
tion of this of set of an animal or animalcule, (as the planaria,)
or of this plant ? Both will continue to live independently of
the original stem. Both may be multiplied and propagated by
new and similar offsets. Both are, as I have stated, equally
imbued with the properties, both of the original pollen and
ovum. All this is mysterious, inscrutable in its essence, consti-
tuting one of the arcana of nature, which may long, may for-
ever be hidden from us.
But the laws of life, and those of the material and inorganic
world, may be detected, and their detection and investigation are
amongst the most legitimate, interesting and important objects
of philosophical inquiry. At present I beg only to state, that
whilst pollen places the ovum or seed under vital influences, its
absence allows them to become the prey of mere physical or
chemical agencies alone.
The further essential and distinctive characteristic of organ-
ized beings, that in which they differ from the objects of the in-
organic world, is—membrane. Through this membrane, a special
function of transition takes place, constituting endosmosis and
exosmosis, or imbibition and exudation.
If this membrane be injured, or broken down, the materials of
organized beings are again immediately subtracted from the laws
of organization, and delivered over to the ordinary principles of
chemical action—decay, or eremacausis—from which that mem-
brane had preserved them, whilst it placed them under the do-
minion or modification of vital influences. Examples of this
fact are afforded by bruises of animal or vegetable tissues, which,
if slight, are repaired by the vital powers; but if severe, lead
to death or decay. How extraordinary are the changes which
almost immediately take place in bruised flesh, or in a bruised
orange or apple I
But I must hasten from these preliminary views, and pass on
to the more express subject of this lecture. All living beings,
from the serpent t.o the eagle, possess, in common, peculiar dy-
namic properties ; in all, these properties respond to appropriate
external and internal stimuli. On the reciprocal play, action and
re-action, of those forces and agents, life, with all its varied phe-
nomena, in all its varied forms, essentially depends.
These dynamics and these stimuli bear a relative proportion to
each other ; this proportion is inverse ; the higher the dynamic,
the lower the stimuli, and vice versa. Such is—the Law of Ani-
mal Life.
In the animal kingdom, two forms of dynamics exist; the first
has its seat in the nervous system, or, more definitely, in the spi-
nal and ganglionic sub-systems; I venture to designate it by the
term neuro-dynamic. The second has its seat in the muscular
system ; it may be designated myo-dynamic. The stimuli exist
in greater numbers, for they consist in physical and chemical
agents of the external world—such as air, food, "water, heat, light,
the galvanic influence, &c.
I must introduce the subject of the vital dynamics by showing
those who are not familiar with physiology, an experiment full of
the deepest interest; I place before you a frog, prepared for the
purpose, and you will observe how the most elevated principles of
philosophy may be illustrated by what you may deem the hum-
blest objects of creation. The physiologist knows and feels that
his science, elevated as it is, is included in the most insignificant
insect that lives—the caterpillar or the butterfly.
The nervous system consists in three sub-systems ; the first is
that in which the brain, or cerebrum, is the centre, and sensa-
tion and volition are the special functions ; I have removed this
centre and these functions from this frog, by removing the head,
and, with it, the very centre of the system, or sub-system, itself;
the creature is thus entirely deprived of sensibility; the idea of
suffering is excluded. It is also deprived of volition—all sponta-
neous movements are impossible.
Yet there is a source and power of movement remaining, for
you observe the effect of irritation of the integument covering the
toe or foot. This power resides in the spinal marrow, or spinal cen-
tre, and certain nerves proceeding to it and from it, termed
therefore, eisodic and exodic. I have designated this power neuro-
dynamic ; it was formerly termed the vis nervosa ; its English
appellation would he nerve-power.
The nerves which proceed to the centre of this spinal system,
arise from the skin. I have removed them from the left foot,
and you will observe that the same irritation which, applied to
the right foot, induced contraction of the muscles, is inoperative
when applied to this wounded limb; in effect, the origin of the
eisodic nerve has been removed with the integument
But I now irritate the spinal centre itself: you observe the
convulsions produced.
Lastly, I irritate these, the lumbar nerves; they are exodic,
and proceed to the muscles: again the limbs are violently agitated
by movements.
These, then, are phenomena arising out of irritation of the
nerves, eisodic and exodic, and the centre of the spinal system.
They attest the neuro-dynamic power of those several nervous
tissues.
But there is still a third sub-system of the nervous system;
it is termed the ganglionic, and it is connected with all that is
interior, or within us. I have here placed aside the viscera of the
frog, and with them the ganglionic sub-system belonging to them—
the heart, the stomach, the intestines, &c. If you were nearer,
you would see the heart pulsate, and the stomach and intestines
move by what is termed peristaltic action. These phenomena
are effectible through the medium of the ganglionic portion of
the nervous system, in which the neuro-dynamic must also reside.
But besides the power residing in the nervous tissues, there
is, as above stated, another dynamic. Its seat is the muscular
tissue ; for which reason it may be designated the myo-dynamic.
You observe the effect of a very slight galvanic influence passed
along this muscle ; the muscle is immediately vigorously con-
tracted. This is the vis muscularis of physiologists, the muscle-
power.
I must again hasten away from this explanation. I repeat
that these vital dynamics, and the physical and chemical stimuli
to which I have alluded, bear an inverse ratio to each other.
This is the case both primarily and secondarily; the first, by
creation ; the second, by a natural operation and effect; for if
stimulus be diminished, the dynamic becomes augmented : and if
the stimulus be augmented, the dynamic becomes exhausted, and,
in some degree, proportionately reduced, as natural events,
causes and effects. Thus the effect of hibernation, during which
the stimuli of air, food, temperature, and nutrition, are reduced to
their minimum, is to lead to augmented dynamic and excitability,
and to what may very appropriately be designated, vernation, or
the activity of spring; whilst the effect of the augmented stimu-
lus in the summer months, that is of augmented air, food, tem-
perature, and nutrition, is to exhaust or lessen the dynamic of
nervous and muscular fibre, however they may augment gen-
eral activity and power of mass, and prepare the way for the next
winter’s sleep.
By creation, and the operation of natural causes, then, the in-
verse ratio between dynamic and stimulus, in animated creation,
is—the Law of Life.
The attempt to invert this law in either direction, and equally
in either direction, is to destroy life. Unduly to augment the
stimulus when the dynamic is high; or unduly to diminish the
stimulus when the dynamic is low, is equally to interrupt the
vital actions.
I will again illustrate my subject by a reference to the inter-
esting case of hibernation:—If you take a bat from its winter quar-
ters, from its state of hibernation, in which its respiration is at
the minimum, and its dynamic at the maximum, and make it fly
about, and so augment the vital stimulus of respiration, it infalli-
bly dies! If, on the other hand, you take the same creature
in its condition of summer activity and of high respiration and
low dynamic, and deprive it of air, by immersion in water or in
an irrespirable gas, it dies, too. Invert in either way the inverse
ratio of dynamic and stimulus, and the result is fatal.
Low dynamic requires high stimulus; high dynamic, low stimu-
lus. The higher the dynamic, the more capable is the animal of
the further abstraction of stimulus, and vice versa. If, instead
of taking a bat from its summer activity, you take it in its state
of hibernation, and now immerse it in water for ten minutes, or
even longer, it is altogether uninjured. The bat taken in its
state of activity, and submerged in water, dies in two minutes
and a half.
Thus the hibernating animal dies if its respiration be augment-
ed whilst it can bear its suspension ; the same animal, in its state
of vernation, or of activity, can bear its respiration to be aug-
mented, but dies speedily if it be suspended I
I will illustrate this view by another order of facts :—the tad-
pole of the frog breathes in water, and feeds on water plants ;
the same tadpole becomes a frog, breathes in atmospheric air,
and feeds on insects ; it has become a higher breather—a higher
feeder. In the former state, the dynamic, in the latter, the
stimulus, is comparatively greater. The tadpole would die if
taken out of its element, the water ; the young frog would drown
if compelled to remain in it 1
These facts are the results of innumerable experiments. I
shall take occasion to revert to them hereafter.
Besides being inverse, to which there is no exception, the ratio
between dynamic and stimulus may be higher or lower. It is in
this manner that we are enabled to explain the modes of life.
As life in general is a result of stimulus into dynamic, we should,
without a provision of this kind, see all animals equally active or
inactive. Either the reptile would not creep slowly, or the bird
tribe would not soar into the atmosphere. But we observe, in
fact, that when the stimulus is cfo's-proportionately low, the animal
is of low activity ; and that when it is cZz's-proportionately high,
the animal is in the enjoyment of an intense degree of activity.
Throughout animated nature, as I have already stated, in all
the varied forms and modes of life, from the eagle to the serpent,
the dynamic and the stimuli are in an inverse ratio to each
other. Such, as I have observed and repeated, is the law of life.
In the bird-tribes, the quantity of air and food imbibed is ex-
treme, the degree of dynamic very low ; in the reptile tribes,
the quantity of stimulus is low, and the degree of dynamic high.
The following formulae may serve to express this general fact:
Stimulus, 8	4	2	1
Dynamic, 12	4	8
The degree of activity, or of inactivity, in all these cases may
be supposed to remain the same.
But to explain the greater activity of the bird, and the inac-
tivity of the reptile, a modification of the formulae is required,
which may be thus expressed :
Stimulus	1	2+1	4+2	8+4
Dynamic	8	4	2	1
In this manner, whilst the inverse ratio between the stimulus
and the dynamic, generally speaking, remains, that of the for-
mer may augment more rapidly as we pass int-o the more active
forms of living beings than that of the latter diminishes; and
thus the bird and the insect fly, whilst the reptile and caterpillar
creep. With higher stimulus, the animal becomes more bird-
like ; with lower stimulus, it becomes more reptile.
With augmented air and food, other organs besides those of
respiration and digestion become stimulated to greater action.
There is especially a correlation between the rapidity of the
action of the heart and of the acts of respiration arising in a
peculiar and reciprocal manner out of the play of stimulus and of
the neuro-dynamic which resides in the spinal and ganglionic
sub-systems, and the myo-dynamic in the muscles which are
respectively under their dominion, and out of the law which
binds them together, which deserves to be distinctly described:
The blood flowing through the lungs exhales carbonic acid; this
is the internal excitor of inspiration acting on the fine branches
of the pneumogastric nerves spread over the lining membrane
of the lungs; the more rapid the circulation, the greater the
quantity of carbonic acid exhaled, and consequently the more
rapid the respiration. But this respiration brings the oxygen
of the atmosphere into contact with the pneumonic blood in its
turn, through the same pulmonary membrane ; this oxygen is
absorbed by the blood, passes into the circulation, and stimulates
the heart to augmented action, and augments the rapidity of the
circulation. This last has again, in its turn, a greater exhala-
tion of carbonic acid in the lungs, again augmenting respiration ;
&c. In proportion to the augmented stimulus the dynamic is di-
minished.
The changes which take place in regard to the ratio of dyna-
mic and stimulus are of two kinds : 1, structural; 2, physiological.
The former, in metamorphosis, is usually, if not always, upwards,
to a state of higher activity, to a state of higher stimulus with di-
minished dynamic ; the latter takes place in both directions, being
to one of higher stimulus in vernation, and to one of higher dy-
namic in hibernation. Activity on one hand, and repose, and,
especially, sleep, on the other, induce similar though les3 marked
effects.
I think I have said enough to convince you, gentlemen, that
there is, in this Law of Life, a most interesting and important
fact, a vast generalization. This generalization embraces three
great objects :	1, the scale of animated being; 2, metamorpho-
sis and perhaps mere development; 3, physiological changes.
I know of no law so general, so expansive.
I may now observe that it is of deep interest to trace the cri-
teria of the ratio between dynamic and stimulus.
In the first place, galvanism is a test of neuro- and myo-dy-
namic, just as nerve and muscle, in the animal in which these
dynamics are high, as the frog, become galvanoscopic or a
test of galvanism.
In the second place, in the animal in which stimulus is high,
the temperature and its measurer,—the thermometer,—become a
test of its degree, and, of course, of the inverse condition of the
dynamic.
Thirdly, the degree of activity or of inactivity denotes the rela-
tive condition of the two elements of the Law of Life.
Fourthly, it has already been noticed that, in proportion to
the dynamic, and in the inverse proportion to the stimulus, the
animal possesses the power of bearing the subtraction of sti-
mulus, the privation of air and of food, and is, in more senses
than one, endowed with tenacity of life. The length of time
during which an animal can bear the privation of air, or breathe
a given limited quantity of air, is proportionate to the dynamic.
In the fifth place, the quantity of respiration affords a mea-
sure of the stimulus. This is ascertained in various ways :
1, by the structure and extent of the lungs ; 2, by the number
of the respirations; 3, by the quantity of oxygen imbibed and
of carbonic acid exhaled.
In proportion to the surface of the lungs on which the me-
thgematous or blood-changing channels are spread, in proportion
therefore to the complexity of the structure of the lungs, is the
quantity of respiration. The fish has a mere gill; the batra-
chian has a vesicular lung, with or without subdivisions or inter-
sections, as we observe in the triton, or in the frog or toad,
respectively ; the lung of the serpent, the tortoise, the tribes of
the mammalia and of the birds, becomes more and more complex
and extended; in the insect and in the bird, the respiration is
extended over the system, not being limited to one organ ; in
the insect, indeed, each articulate segment is furnished with an
analogue of the medulla oblongata, as a central nervous organ
of the respiration. The dynamic exists in an inverse proportion.
In the sixth place, the quantity of food assimilated or respired
is a stimulus in itself, and in its proportion to respiration becomes
a measure and criterion of the degree of dynamic inversely. In
speaking of the quantity of stimulus as represented by the food,
we must bear in mind the quality as well as the quantity of that
food, and its convertibility into calorifacient and nutrient prin-
ciples. Insect food is perhaps of all kinds of food the most
stimulant, whilst vegetable food is the least so. It must also be
a question how much of the food is really made available, and
how much is excreted unrespired, unassimilated.
Seventhly, we have in the circulation a criterion of the kind
and character of life ; slow and with few methaematous vessels,
in the animal of low stimulus and high dynamic, it becomes
quicker with more crowded vessels as the stimulus is greater.
The structure of the lung and the degree of rapidity of the
movement of the blood globules, must be carefully noted: as
the former becomes more complicated and the latter augmented,
the quantity of stimulus is higher, and, I need scarcely say, the
degree of dynamic lower.
There is, indeed, no subject so replete with interest as the
circulatory apparatus—pneumonic and systemic—in themselves,
in the different orders of animated being, and in reference to
the law of life. The entire apparatus consists of—1, the minute
arteries ; 2, the minute veins; and, 3, the intermediate blood-
channels, or, as I have proposed to denominate them—from the
important fact that all the changes which take place in the
blood take place in them—the methsematous or blood-changing
channels. These vessels are specifically distinct, a distinction
on which I have insisted on another occasion.
I must now, Gentlemen, in the last place, bring before you
certain results of that law of life which I have thus very inade-
quately sketched. In doing this, I shall be compelled to repeat
some of the preceding remarks; but I prefer to do this to the
alternative of leaving my sketch incomplete.
The first remark I have to make in regard to the results of
the Law of Life, relates to the temperature of animals of high
dynamic and of low respiration, and consequently of low tem-
perature. Such animals are said to be of cold blood. This
expression is inaccurate. No animal is positively of cold blood.
The species of lowest temperature is still of a temperature
higher than that which would subsist absolutely without respira-
tion, and its blood is only low in temperature, without being
as cold as the surrounding medium.
Even amongst fishes some are high, others low, feeders and
breathers, with a corresponding temperature ; the trout can only
live at the surface of a limpid stream, breathing highly oxygen-
ated water, and feeding on the insects immediately on that sur-
face ; the carp, on the contrary, lives and breathes lowly, at the
lowest part of stagnant pools. The trout is, comparatively, a
fish of high stimulus—food and respiration—and temperature,
and of low dynamic ; the carp, of high dynamic and low stimulus.
The trout dies almost immediately if taken out of its crystal
element; the carp will live for days in wet moss, that is, out of
its own element, abundantly supplied with moisture, or in a limited
portion of water ill supplied with mixed atmospheric air.
As we rise in the scale of animated being, from the fish to the
reptile, from this to the mammalia, and from these to birds, the
respiration, and, with this, the temperature, also rises, the
dynamic proportionately falling ; the temperature of the fish and
reptile is slightly above that of the medium in which they dwell
respectively; that of the mammalia is about 98°, that of the
bird tribes about 102°, Fahr.
The temperature accurately coincides with the quality and
quantity of food, the quantity of respiration, and is, in effect,
the developement of an internal stimulus from stimulant ingesta.
With temperature there is also probably the evolution of the
galvanic agency.
The galvanic apparatus, the thermometer, the quantity of
food, the quantity of oxygen, the power to bear the abstraction
of these stimuli, or, in certain circumstances, their addition ; all
these are criteria of the place a given animal, in a given condi-
tion, ought to occupy in the zoological or physiological scale.
Growth, development, metamorphosis, nutrition, in ovo and
extra ovum, are other results of the play of vital powers,
dynamic and stimulus. With each of such changes in form, a
change in kind of life, or a metabiosis occurs.
Of these, hints have been dispersed in the preceding remarks.
If I have succeeded in giving you, Gentlemen, an adequate idea
of them, and of the other topics involved in the development of
the Law of Life, I shall feel much gratified. Pray accept my
best thanks for your kind attention throughout this imperfect
lecture.
Each part of my subject would afford scope for distinct dis-
cussion, and one object of my visit to the United States is to
secure to myself both the leisure and the opportunity for further
physiological inquiry in regard to it. In this object I know and
feel that I shall be assisted by the liberal and generous people
amongst whom it is my lot, for a time, to dwell, and by the noble
and free institutions, the objects of which it may, as on the pre-
sent occasion, be my proud privilege humbly to promote.
Of the Smithsonian Institute I can only most cordially say,
may it prosper, anl may it long be the means of the diffusion of
knowledge, and of consequent good to mankind I