Koft P 1219178 (80)

Bibliotheca Osleriana No. 7570 describes a
similar MS on paper of larger size, completed
in 1815, on the same subject. These lectures
were delivered at guy’s Hospital. Osler writes:
Haighton was a pupil of John Hunter:
for his physiological experiments, which 
were certainly ruthless & numerous, he 
was called by his opponents “the merciless 
Doctor” (See T.J. Mathias, “Pursuits of 
Literature,” 12th Ed. 1803, pp. 419-20). A list
of his papers is in the DNB. Evidently an
able man and a capable physiologist.
[H.N.]
3390






Silas Stedman
1816



LECTURES
(on)
PHYSIOLOGY
BY
Dr. HAIGHTON.




1
INTRODUCTION.
At the commencement of a course of Lectures it is customary 
to give a general view of the plans that are
to be adopted, and the order that will be taken in
considering the subject proposed: to make the science
more interesting it is common to observe some of the 
facts, tending to display its utility, as well as to make 
it the more intelligible. I trust much need not be 
said to convince you of the important utility of
Physiology: as it is the business of the anatomists
to display the component parts of the animal body,
so it is, the duty of the Physiologist to display its
general functions: the one investigates the structure 
and the other the operations of the machine. The 
human body contains a number of different organs,
to explain their healthy operations and functions, is
the business of the Physiologist. The great advantages
of this delightful and interesting science are very 
apparent, even in its first stages, for by perfectly
knowing the Natural functions of different 
organs, we can without doubt, more easily describe
their unhealthy ones, and thus we are enabled
to moderate their inordinate actions, and know
how to assist them when weak and disabled hence 
in all ages, great men have applied themselves, 







2
particularly to this study. Besides the improvement
Physiology has derived from the constant exertions
of individuals, and by societies both here and abroad,
the Human Society proposed suspended Respiration
as a subject worthy of discussion, and this led to a more 
minute investigation of the Oconomy of the Lungs, 
as being the organs chiefly concerned in that case.
Digestion is no longer that intricate subject it was 
supposed to be by the ancients: it is now known
to be performed by chemical principles; by a fluid 
called Gastric Juice , which is secreted by the Arteries 
of the Stomach. We can also speak with equal 
certainty upon the functions of the absorbent system.
The great and deservedly formed Harvey demonstrated 
the circulation of the blood. The theory of 
optics has thrown great light when the Mechanism 
of the eye and our improved understanding 
of the theory of sound has much assisted us in our
knowledge of the Ear. We then have gained a great 
number of improvements in this science, but
although much hath already been done, there 
still remains many things to be developed by the 
inquires of future Physiologist. The Oconomy of 
the Brain and Nerves has not been clearly demonstrated.
Muscular action is not accounted 
for, and sanguification not yet satisfactorily ascertained





3
ascertained. The theory of conception is still involved 
in much obscurity; and it remains also
to discover the uses of the Thymus Gland and Spleen. 
I have made many experiments to ascertain the 
use of the Spleen which will be shewn in the 
course of these Lectures, together with the theory
derived from their results. Many have depreciated 
the knowledge of Physiology as being merely
hypothetical, but such as do this, do it as an excuse
for their own idleness, or to bring others on 
a level with their contracted understandings. It
has been said the cure of disease ought to be left to
Nature, and that the Physician should act merely
as a servant; but even in this limited view it is necessary 
to know when the powers of nature are sufficient 
to effect a cure, that he may administer
the proper assistances: he should be acquainted with
the effects of certain causes acting on the system: the 
progress and changes that might be produced by the
different remedies he is acquainted with. Persons
of respectable characters have been led to form a wrong
prognosis, from not sufficiently understanding
the cause of the complaint, and have paid their whole 
attention to the symptoms, while the original
disease has been neglected, as for instance, Anasarca 
is sometimes Idiopathic, and very difficult to cure





4
but it is at other times symptomatic only depending
on some other disease and in this case it will
disappear, immediately the original disease
is removed. A respectable Physician mended
a gentleman with Peripneumonia, and dysphnea 
under which he had labored some time 
without any relief; Anasarca soon after succeeded
when the Physician instead of a mending to the 
former symptoms, indiscriminately treated it with 
Hydrargyrus and Diuretics. Nature however triumphed 
over his practice removing the former
complaints when the latter was left merely as a 
matter of inconvenience, more than disease: this
was soon removed by punctures and the patient cured.
A physician filled for this purpose would certainly 
have considered the Peripneumony as the 
original disease and would have attended to it the 
anasarca was only symptomatic, arising from interrupted 
and difficult transmission in consequence 
of impeded Respiration. The object of this course of 
Lectures is to explain the Natural actions of the 
Human body, but whenever we digress it is with a 
view to illustrate them. The Human body contains a 
number of organs each of which is connected with, and
depending on each other, so that it is difficult to determine 
where to begin: we will endeavour 




5
to commence with the more simple Organs; some knowledge 
must be taken for granted. Nature points out to 
us which way to proceed: viz with that part of the organization 
of animals which is the most common, and found
in those of the simplest organic structure. Man of all 
animals is the most complex, and from him, there is 
a regular gradation down to the most simple. Have 
there any organ which is common to all animals?
Every animal has stomach or cavity for receiving 
of food and converting it into nourishment: this organ
is there certainly the most proper to begin with
and when we come to speak on the animal machine 
it will the first we shall consider: but before that 
it will be necessary to treat of the coincidence between the 
Animal, vegetable and Mineral kingdoms, and point 
out the distinguishing marks of each: we shall then proceed 
to consider the principle of Life, and the action of 
Life. It will be next in order to take a view of many
other animals with respect to their food before we consider 
the organs of Digestion, and that not from mere
fancy or whim, but from a difference in the structure
of their Masticating and Digesting Organs. Mastication
will be considered in many animals as far as it tends
to better illustrate that of the Human body; and this 
will lead us to the consideration of Deglutition and 
Digestion. Digestion is that change produced in the 




6
food while the Stomach contains it, and is performed by
the Gastric juice; hence we are led to consider the Stomach
and its office, both as the organ of secretion
and Muscular action, for by this the food is propelled
into the Intestines: the muscularity assists also in
vomiting. The Stomach is frequently liable to be affected
with this from causes situated at very distant and remote
part; thus pain in the Head often produces vomiting 
et vice versa. Consequently we shall then take 
notice of the Stomach as an organ of Sympathy. After 
the food has been sufficiently Digested, it has to pass
through the Alimentary Canal, and from this we shall
be induced to treat of the Muscular power of that Organ.
When the food has passed into the Intestines it has to undergo
a second change before it fitted for Chylification,
and the manner in which Nature performs this office
will be considered at large: which Chyle when completely
formed is taken up into the mass of Blood; and 
this is effected by the Absorbent System, or Vessels that 
arise from the Intestines by open Mouths. The food 
which we consume, contains very different portions
of the Nutrient principles it must therefore follow
that Nature has some resource to rid herself of those
parts which are not Nutritive and this leads us to 
speak of the Peristaltic Motion of the Intestines, and 
other means for evacuating the feculent matter.
 




7
We have said, that when the formation of Chyle is completed,
It is carried into the Blood hence we are induced 
to the consideration of the Blood; it is of the solid 
Blood that the Solids are supplied with which supplies
the waste and exhaustion and which is continually 
going on in the Stomach, as well as in the whole
system: but it cannot do this in a state of rest, it 
must be sent to every part of the body to convey nourishment;
this leads us to take a view of the circulation
of the Blood and we shall also speak of the 
causes which retard or accelerate it. The Heart as
being the principle organ performing that office
will form another interesting subject for consideration. 
The Blood after circulating for a short
time becomes unfit for the purposes of Life and
requires a change which is effected by the Lungs: to 
prove this we have only to open the Chest of a living 
Animal, and we shall see the Blood coming from
the different parts of the body, nearly black whilst
that which is going from the Lungs is of a bright red 
color. This change is produced by the air taken into 
the Lungs; and the properties of the air so far as they 
effect the change produced in the Blood as also the
effects of Suspended Respiration will be treated of.
Some remarks will be made on Animal heat, and 
Reference to Dr Crawfords experiments, some of which
  






8 
appear to be highly probable. The Blood is of two kinds.
Arterial and Venous of these therefore we shall next
enlarge upon: from the Blood a great number of 
Fluids are secreted, not Mechanically, but the Blood
appears to undergo a new mode of existence: this 
will lead us to consider the varieties of secreted fluids,
and of the Glands also which secrete them:
we shall then proceed to the Mind as giving voluntary 
motion to the Brain, and to the Nerves as
conveying the influence to parts intended to be moved;
we shall likewise consider how few it is concerned 
in the effects of Sympathy and shall take 
some notice of the proofs of Union between divided
nerves, and the kind of nature this Union is of: we
come next to speak of the moving powers of the body
the origin of Muscular Motion; after this we shall
take a view of some of the change occurring in 
the system, as those of Puberty and Menstruation
and the effects of its interruption: we shall then 
consider the organs of generation particularly, 
and after that the Phenomena which occur during
the act of generation and conception: with these 
remarks we shall finish the course, and I trust you 
only need be attentive to learn this science which is 
the grand basis for Medical information.








9
ON THE Animal and Vegetable KINGGOMS.
If we take notice of Nature, we find a wonderful 
diversity in its different parts, which often renders it
difficult to determine to which species each genus belongs:
the more readily to do this, Philosophers have 
thought proper to arrange the whole under three grand 
divisions: and under each of which will every part of 
nature be comprehended. The divisions are into the 
Animal, Vegetable and Mineral Kingdoms. In general 
every substance may be referred to each of these; but there
are some which cannot be well distinguished, so nice
are the gradations and shades between them. The Mineral 
is more distant from the Vegetable, than the Vegetable
from the Animal Kingdom; still there are many points
in which they agree for the Mineral asbestos very much
resembles a piece of wood, though it will not burn. Animals
and Vegetables have many points of coincidence
and in which they both differ from Mineral. They
have an internal organization a peculiar arrangement
of parts which are not in the latter: they both
have vessels distributed through them, as appears from 
their being injected: this is most conveniently done after
a few days, when all their vessels are nearly empty.
These vessels do not appear to have much communication
with each other. The Onion is one of the most easy







10
Vegetable to be injected: and the mode of doing it is to make 
an opening into the bulbous part, and then to introduce
the quicksilver which being a little pressed will 
readily pass into the vessels of the plant; and a fine injection 
may likewise be thrown in by a syringe without
much difficulty. As Animals and Vegetables have vessels
so likewise they have fluids passing through these for
their nourishment, which does not appear to be the case
with Minerals. By means of the Circulating fluids,
they have within them a power of growth. It is true
that Minerals increase in bulk, but this is effected by 
an external deposit, or an aggregation of particles.
In the mode  of Propagation, Vegetables come very near
to Animals: besides these coincidences they have others
more particular. Animals secrete, that is, they have a
power of forming fluids, different to the one passing
through them. The same takes place in Vegetables: they 
have particular Secretions, as Milk, Bile, Gum, &c.
and even Sugar is of this description. Almost every Vegetable
plant has one secretion, as the Poppy has a Secretion 
of Milk: some have more than one, as the Organe
and Lemon; they secrete an Acid and an Essential Oil.
Again with regard to Respiration these Kingdoms
resemble each other. Some Animals breathe by Lungs, and 
others by Gills, and some from the surface of their Bodies. In
like manner Vegetables have Air tubes, and pores on their Leaves.




11
Dr Ingenhous observed that air passed in, at the superior
and came out at the inferior part of the leaf which was at 
first hinted as by Priestly. Air in passing through Vegetables
undergoes a change as it does in the Lungs of Animals.
It becomes obnoxious to them in consequence of being 
impregnated with fixed air but this air is congenial 
to Vegetables, so that if you put an Animal nearly expiring 
for a long time amongst Vegetables they will 
revive the Animal and prolong its life by absorbing
fixed air: thus the Animal and Vegetable Kingdoms
counteract each other, viz, the impurities that would 
be produced by each of them singly. Another point of coincidence
is observed with respect to sleep: Animals
are well known to be affected with this, and the coralls 
of Vegetables to roll themselves up at certain times, and 
this act is not from an obstruction of light or heat for
the effect takes place in hot House. It was said that 
heat expanded the plant during the day, and when the 
Stimulus was removed, they of course collapsed; but 
this is not well founded, or they would not collapse 
at night in an equal temperature, as in hot House &c
Both Animals and Vegetables possess irritability, and
there is a susceptibility capable of being acted up on
by Stimuli, of some plants thus acted upon is the Sensitive 
plant, and it has a kind of Muscular action
and others have a particular motion when the Sun






12
shines upon them; so that the Vegetables seem to approach
to Animals in having the power of motion:
for a Polypus has but little more motion than the Vegitables
before mentioned. There is an American plant 
called Venus’s Fly trap, which has this kind of motion 
in a particular degree, and secretes a fluid on it surface,  
which induces the Flies to come above it, and as 
soon as they touch it, the leaf contracts upon them, and 
destroys them: any substance applied to the leaf will call
forth a similar effect. Some plants have a power of 
motion without any Stimuli being applied to them, and 
it is difficult to say whether this differs from the voluntary
motions of Animals. Further in their Instinct Animals 
and Vegetables seem to agree: no one will deny 
but that Animals possess this in a certain degree, but
its being possessed by Vegetables deserves our Notice. 
The bine of a kidney Bean will naturally stretch out
to grasp any body near to it, as if conscious of their own
inability to support themselves; and they will soon 
change their original direction in which they were growing,
if the stick he put in an opposite direction from 
them; they will strive to reach it and cling to it. If Trees
are planted so near a Ditch that their roots must grow
and spread out of the Earth, it is observed as soon as  they appear
upon the surface they dip down again; and in 
other instances, they are observed to seek particularly 







13
particularly the strata of the Earth that is next to them. A Cucumber 
if growing in one direction, and a wet sponge be applied
in an opposite one, it will change its course and grow
towards the Sponge. No Vegetable has the power of locomotion; 
neither has the Oyster, so that this will not distinguish 
them. There is an Indian plant called the walking 
plant which is observed to turn, and to completely 
change the direction of its leaves, but this depends on the 
Stimulus of light. Like Animals they have the power
Of repairing injuries. When an Animal is wounded
lymph is thrown out, this seems to be the means of bringing
the parts together again. Vessels shoot through the 
Lymph, and this unites them. In like manner when 
a Vegetable is wounded sap is thrown out; which answers 
the same purposes as Lymph in Animal.
The same coincidence is observed in the Animal and Vegetable 
Kingdoms in Propagation. The Polypus will propagate
its species by cutting it, and so will Vegetables
by slips, or by cutting them as in the Potatoes. The natural 
Propagation of a Polypus is by tubercles forming on its back
which after a time separate and become living Animals. 
According to the Lineman system, there are Male 
and Female plants, and they propagate by Sexual intercourse; 
on which are called Hermaphrodite flowers there 
are Male and Female organs; sometimes several Male to 
one Female. The Authors seems to answer to the Testes 




14
of the Animal, and the farina fecundating  to the Semen. In the
Female the Pisillum answers to the Fallopian tubes, and the 
Pericarp to the Uterus. The mode of receiving nourishment is
in some degree similar in Animals and Vegetables. Children 
are not nourished by a communication of vessels between
the Placenta, but Blood is taken up from it, similar 
to the root of Vegetables absorbing nourishment from the 
Earth. They agree also in other instances. Having pointed 
out the relation between Animals and Vegetables, a question 
naturally arises wherein do they differ, and how can 
we distinguish for a certainty the one from the other? 
Let us endeavors to draw a line of distinction from 
the manner in which they receive their food: if fluid it 
is absorbed by the roots of the Vegetables, and distributed 
thro’ their numerous tubes, for the nourishment of the 
plants; after having undergone some changes. On the 
other hand all Animals have one or more cavities, 
with which the food is received, called a Stomach, and here
the food undergoes an entire change, this we call  Digestion:
after the food is Digested, it is taken up by the Lacteals 
for the nourishment of the Animal; hence the grand
marks of distinction are, in the Vegetable the food is 
ready for nourishment directly it is received, where as in 
Animals it must undergo a process of Digestion, and
that in Animals the food is taken with the Stomach, and 
in Vegetables it is absorbed by the Roots.






15
On the difference arising between most
ANIMALS AND VEGETABLES,
By the addition of the Vital principle.
To ascertain this difference it will be necessary to inquire
first what Life is: Physiologist not being able to give a direct 
definition of it have made use of different analogies
to express their Ideas of it. Some have compared Life to the 
spring of a Watch, for they say tho’ every part of a Watch
is perfect, yet if it wants the Vital principle, or spring, it 
cannot go any longer: this comparison must appear faulty 
when you consider the spring of a Watch to be composed 
of matter, and that it acts on a mechanical principle.
Other have compared it with Magnetism, but with little
success. Some have compared it to Electricity, but this 
acts mechanically by a traction, and repulsion, in 
an uniform degree, whilst the actions of Life vary as 
much as the organs: hence all these comparisons 
are inadequate to the definition of Life: we cannot form 
any Idea of Life, but as connected with matter, and 
it exhibits great variety according to the kind of matter
which it is combined with nothing gives us an Idea
of it, as when combined with Animal matter. A distinction
must be made between matter and Life.
When an Animal moves we doubt not the existence 
of Life in it: but it does not follow, that when motion
ceases, as it does during suspension of Respiration





16
by hanging or drowning it could put it out of the
human power to restore Life, as that requires the power
of action. Some Animals and also Vegetables have 
no appearance of action; for instance the Egg and the 
Seed, yet these seem to possess Life. If an Egg which 
has received the influence of the Male is placed in a certain 
degree of warmth, a chick will be produced, now
warmth could not have had this effect if Life had not 
existed in the Egg, for suppose that it had not received 
the influence of the Male, putrefaction would be produced 
by warmth instead of Life. The heat therefore produced
by incubation does not impart Vitality to the 
Egg but stimulates and calls into action that vitality 
which pre-existed. The vital principle in an Egg,
may be destroyed by cold. If you expose an Egg to such
a degree of cold as to freeze it, and then place it under 
an Hen putrefaction will soon take place so that there 
seems some distinction between Life and action. If 
you attempt a definition of Life, the Intellectual faculties
cannot be admitted as essential to it for then almost
all Animals must be excluded. Those only are
are to be enumerated in the definition which are absolutely 
for the thing defined, and which could not exist without
them. Therefore the power of propagation must be 
excluded as well as the intellectual faculties for a man
has not a power until he has arrive at a certain age





17
and often Animals have it in common with him.
Sensation cannot be admitted into the definition of 
Life for Life remains during sleep, when Sensation 
and volition are absent. Involuntary action cannot be allowed
as essential to it, for we have reason to think it 
exists not in the Egg and reason have been given for supposing 
Life exists in it. Some have said that a power of 
resisting heat and cold, and of preserving temperature is 
a power definition of Life several experiments have been
made by Dr Fordyer which show that this power exists 
in a great degree in Man: the Dr heated rooms to different 
degrees of temperature and going with them gradually, one 
after the other, he fully proved that the temperature of his body 
was cooler than the air in the room and than the 
Urine he voided when in them: he carried these experiments
to a great height, and heated one room to within 
two degrees of boiling point in which an Egg and beefsteak 
were soon heated dry: during the time he was in 
the room, he observed some streaks of water running down 
his face, this might by some he imagined to be from the 
great heat of the body producing a larger quantity of 
perspirant matter than usual, but on the contrary it 
was proved to be owning to the condensation of heated air
in the room, which rested upon his body as colder 
medium. Amphibious Animals have this power
of resisting temperature in a slight degree. Serpents 





18
have it more than Frogs, Frogs more than Fish, but a Snail
has very little of it, and Worms and Leeches none. Birds have 
less of it than Beasts. Does it arise from Vitality or from a 
particular organization? From the latter because different
Animals are found to possess a resistance to variation of temperature
in proportion to their complicate structure. Some 
have rested the definition of Life on the power of resisting 
putrefaction. It is then so long as the Vital principle remains
that the cause producing putrefaction can have 
no effect, neither does a body become putrid as soon as 
Life ceases. Others define it, to the powers of resisting 
freezing but this definition has been before shown to 
be insufficient. Dr Hunter exposed two Eggs to Cold, one
of which had been frozen before and which again became 
so sooner than the other, this shows that Living matter 
has a power of resisting freezing. The difference then 
between dead and living matter seems to be this, as in
living matter there seems to be such a disposition to 
action that may be called forth by the application
of a proper Stimulus; thus the Egg and Seed have both
this particular disposition and action which may 
be produced in one by the application of heat, and 
in the other by the application of Earths; when we
speak of action we do not mean any peculiarity of 
action as of Muscles and Nerves, but of action in general:
we may here also distinguish action from 





19
motion, for inanimate powers may made to possess motion:
with respect to Stimulus no particular kind is 
meant, for that which may often prove a Stimulus to
one body, may not be so to another body but it is 
whatever has the power of exciting Animal and 
Vegetable matter to action. Thus then the disposition 
to action on the application of Stimuli we
offer as definition of Life. It is true that this approaches 
near to Irritability, but we do not confine
ourselves to Muscular action: we extend our
definition to all organized bodies. We shall now 
say something of the connection of action with the 
System. When action is begun it is necessary for 
the preservation of Life, that it should continue,
are we then to say that if action be suspended by 
Hanging or Drowning that we breath into the 
Nostrils the breath of Life? No, for after the 
suspension of action, there is a small interval 
between it and Death, the length of which depends
on various circumstances. A certain degree of action is only 
necessary for the continuance of Life, and in some instances
only a very small one. Maturation goes on in 
Fruits, if they are separated from the Tree, but if any 
part is bruised by accident so as to destroy its 
action that part will putrefy: hence it seems that 
action and Life are two very different things that they 





20
cannot exit separate long. The connection between Life
and action varies considerably, it being stronger in 
some Animals which are strong and growing and gradually
becoming weaker as they increase in size, thus it has 
been said, that the Polypus has been hatched, by pieces 
being cut off from old Animals of that species. Worms 
after being divided will unite and Live by bringing the 
parts in contact, and a Snail will Live after being decapitated. 
Some say a new head is produced; I have seen 
one Live three weeks after its head was cut off, and there 
seemed a considerable attempt at forming a new one.
Many Amphibious Animals will Live three or four hours 
after their Hearts have been taken out. If the large or Femoral 
Artery of a Dog be divided Nature will of her own
accord stop the hemorrhage. Many parts of a Man may 
be cut thru’ without injuring the Vital principle; but 
some parts being stronger will bear it better than others.
Parts may be much weakened and yet be restored to their 
natural action: care must be taken that the Stimulus 
applied be not too violent, otherwise the action produced
will be too great and mortification will ensue. 
It seems that Animals possess very different degrees
of Life, and Man less than most others, and is less retentive
of it. The reason seems to be his being endowed with 
a superiority of mental power to secure himself against injuries.







21
A COMPARATIVE VIEW OF,
Man, with Beast & Vegetables
IN REGARD TO THEIR FOOD.
We have hitherto considered matter as being divided into
three Kingdoms, Animals, Vegetables, and Mineral, and in
doing this, it appeared that the two former were endowed
with a power of growth, and had also various Secretions:
these of course must exhaust the nourishment
that is taken in for Food, consequently fresh supplies must
be frequently necessary. The principle causes of exhaustion
that must constantly arise from the various secretions,
has constituted a set of organs, for receiving and 
circulating the nourishment: various kinds of nourishment
are made use of, but it is derived from the Animal
or Vegetable Kingdoms. There are a number of 
Animals live only upon other Animals, some only 
upon Vegetables, and some upon both. This variety 
however does not upon inspection appear to arise
from any particular whim or fancy of the Animal,
but from a peculiar Instinct dependent upon the 
structure of their Organs for the purposes of Mastication 
and Digestion. Nature has constructed organs 
for these purposes by which each Animal is capable
of extracting nourishment from its peculiar 
food: so that by examining the particular formation 
of the Teeth, or Intestinal Canal, we can with certainty





22
certainty determine on what kind of food the Animal Lives.
Man is one of those, who live on both of them, or either.
Some digest Animal food with difficulty, while others
with equal difficulty digest Vegetable matter. Vegetables 
derive their food from Air and Water, but this contains
so little nourishment that few Animals can survive upon 
it. GoldFish seem to be of this kind, and it appears
that they are not supported by Animalcules that may
be in the Water, for they will Live in distilled water equally 
well, and are found not only to grow, but to discharge 
their faces. The Vegetables that are most nutritious, are
first those that abound in farinaceous matter as Grain
and Potatoes, second those which are impregnated with
Saccharine matter, as Sugar cane, Carrots &c &c. It is 
observed that the Blacks when they eat the Sugar cane,
are faster than at any other times: thirdly those which contain
Essential Oils and Gums. The Mucilaginous parts
of different Animals contain the most nourishment 
the dry part very little and Animal fat much more 
than Muscle: this points out to us an important question
What shall we say is the particular principle that gives 
nourishment to us? Some have contended it is mucilage 
but in my opinion it is better to call it the Nutrient
principle: to extract this principle from the food and 
to convert it into chyle is the business of Digestive Organs
and they are assisted by Mastication, the grosser 

 




23
parts passing thro’ the Alimentary Canal, Animals are 
Instinctively led to some kind of food, from a peculiar
organization, depending on their Teeth and Alimentary Canal;
Carnivorous Animals have sharp pointed Teeth to tear
their food in pieces, those that are fed on Grain and other 
Vegetables, have Teeth with broad irregular surfaces for 
Grinding their food more easily, and have a lateral motion
of the Jaws. The Teeth of Carnivorous Animals 
have the Enamel on the outside but in Granivorous 
it is mixed with the substance of the Teeth so that the 
surface will grow still more uneven. Man is so adopted 
in this respect as to be able to Digest both Animal and 
Vegetable food and this appears from the stomach and all 
the organs that have to do with the food. The Stomach of Granivorous
Animals is very large, as in Horses, Cows, 
Sheep &c &c. and for this reason, viz that Vegetables contain 
much less Nutriment than Animal matter, so 
a greater quantity is required to be taken in. The Intestinal 
Canal in these Animals is for the same reason
much longer, that the food may be a greater length of time
given for the extraction of the Nutrient matter.
Those Animals on the contrary which live on Animal
food have small Stomachs and Intestinal Canals.
Carnivorous Birds have very small, but strong and Muscular
Stomachs. The Human Stomach and Intestinal 




24
canal is between extremes. Hence it appears that 
Man was intended to Live on both Animal and Vegetable
food, tho’ he may be nourished by either. Among the Gentoos
whose religion forbids them eating of Animal food
Vegetable food is only eaten, but they are a weak and 
limited people. In Lapland where the soil is too barren 
for Vegetables, the Inhabitants live wholy on Animal 
food, and are very hardy and robust people: but in 
most countries they live on both, tho’ in different proportions,
generally most Vegetables are eaten in the 
warm climates, and the contrary in the cold. Animal 
food is necessary for those who are accustomed to hard
labour, and should be taken in proportion to that, but it
is not favorable to the intellectual powers for tho’ it invigorates 
the body, it clouds and stupefies the Mind. 
Before the food is taken into the Stomach it is necessary 
it should be first Masticated. Mastication is performed
by very strong Muscles and there is in the Human
Jaws, as well as in the Granivorous Animals 
a lateral Motion. On the articulation of the upper
Jaw with the lower one: there is a moveable Cartilage 
which allows this motion to the lower Jaw.
During the Mastication of food, several Fluids are 
mixed with it, as well to facilitate that motion or
process, as to assist Digestion. Ruminating Animals
have several Stomachs; they after Masticating their 








25
food a little while, deposit it, in the first Stomach or Pouch 
where it Macerates with a fluid contained therein, after
being sufficiently macerated, they have a power of regurgitation,
then they chew it again and make it pass
into the second Stomach, and then into the other Stomachs.
To illustrate this it is found that the Esophagus of a
cow communicates with her two first Stomachs, and 
the Animal has the power of passing the food into either 
of them at pleasure. Thus when the food has been triturated
a little, it is deposited into the first Stomach to 
Macerate, after Maceration it regurgitates and is again
triturated more minutely, and it then without
passing near the first passes into the second Stomach,
from that to the third, and then into the fourth Stomach
where it is Digested. The three first Stomachs do not
seem to have any power of Digesting the Food: but are
merely preparatory to that purpose. Liquids not requiring 
Mastication pass into the second Stomach at 
once, without going into the first: Birds have a peculiar
way of Masticating their food. Those of the Carnivorous 
kind do not masticate it at all: but only tear it in
pieces. The Birds which feed an Grain, have no Stomach
but receive their Food into a Bag called a crop, where it
is softened by Maceration. Ducks have not crops, but an 
Oesphagus enlarged. The food then passes into the Gizzard 
which is composed of two strong Muscles, and the food is 






26
ground down by the action of that organ. The sharp Pebbles, 
which the Birds, take in, assist in this process. The 
Pebbles or Sand taken in, are proportioned to the size of the Bird.
Thus the Ostrich takes in stones of one kind, fowls smaller
and small Birds only sand. If you open the Gizzard of a 
fowl, when it is triturating its food, the motion of it is 
very visible: and it may be easily heard. To prevent the bad
consequences which might arise from the sharper points
of the Pebbles against the Gizzard, it is line by a thick
horny substance that Pebbles assist in grinding the 
food is proved by keeping some Fowls from all sandy 
matter, Pebbles &c. when they grow very thin. Some have 
thought the Gizzard an organ of Digestion, as well as of
Mastication, but this does not appear to be the case, as 
the fluid necessary for Digestion has never been found. It
was observed that during Mastication, several fluids were
mixed with the food, and the principal one is Saliva. The 
Saliva is secreted by six Glands, each of which have a distinct
term in action in the Mouth. These Gland are very
liberally supplied with arteries, on account of the great
secretion from them. These do not secrete at all times
for Instance during Sleep, as you will often find the 
Mouth dry, when you awake, but a few motions of the 
Jaw by pressing upon them will make the Saliva flow.
Likewise smelling an agreeable Dinner will have 
this effect. 





27
ON THE STRUCTURE and FUNCTIONS OF THE
Stomach &c.
We now proceed to consider the action of the Stomach
on the food. After the food has passed into the Stomach 
it soon loses the character of Masticated food, and becomes
an uniform pulpy mass. If we examine 
an Animal soon after being fed, we find that part of 
the food which is nearest the upper orifice of the Stomach
to be little altered, but as is descends it becomes gradually 
more and more altered, and that nearest the 
Pylorus is the pulpy mass before mentioned from
the gradual change of the food in passing thro’ the Stomach,
it is evidently affected by that organ of Digestion. 
After the food is Digested it must pass thro’
into the Intestines to undergo a still further change,
which lead us to consider the Stomach as a Muscular 
organ, we find also that if any Material Injury is 
done to the Muscles, the Stomach will often be affected, and
from this we may consider it as an organ of Sympathy.
The better to understand the functions of the Stomach we
will first take a view of its structure, not however with
the Minuteness of an Anatomist, but so far as to assist
in illustrating its Physiology. The figure of the Stomach 
resembles as a bag pipe. It is situated obliquely in the
Epigastric region, and has two orifices by which the 
food enter and passes out. The Recipient orifice is 




28
called the cardiac, and the expellant, the Pylorus. The 
stomach we have said has a muscular power, by which 
it expels the food but from its oblique situation the gravity
of the food itself, will assist in its expulsion. The 
degree of obliquity is not great, and some might think
it would be advantageous if it was greater, as the food
would then pass more readily, but was this the case, it 
might be conveyed into the intestines before Digestion
be performed. The structure of the Stomach is not alike
in every part, and the vessels are not so minutely distributed
to some parts, as to others. The Stomach is 
covered by a smooth Coat called Peritoneum, in common 
with other viscera: when this is stripped off
we find a number of Muscular fibres, some longitudinal, 
some transverse, and others between both, 
when these are removed there appears a thick cellular 
membrane or substance, called the Villous Coat 
which is capable of secreting a fluid, hence those 
who admit the idea of Glandular structure to all 
secreting organs, might think it should be called a
Gland, but we do not find any Glandular structure
in the Stomach. It is a kind of Law of the Animal 
Oconomy that every part should be supplied
with Blood, from the large Arteries which end in the 
Villous Coat, and that this is the seat of Secretion appears
from the termination of arteries, for they are capable






29
of Secreting as well as Glands. As the Stomach is plentifully 
supplied with Blood, there must be veins to 
return the Superfluous Blood, and these terminate
in the Vena Portarum which supplies the Liver with 
Blood. The Stomach has likewise absorbents which 
have a peculiar termination, for instead of going to 
the Thoracic Duct, they terminate in red veins and 
this I have ascertained by Injection: and have found
it confirmed by eminent Anatomist. The Nerves 
of the Stomach are principally from the Par Vagum
and Intercostals, the branches of the Par Vagum are
distributed to the left extremity, and the Intercostals
to the right extremity of the Stomach. Now having 
considered the structure we are prepared to consider 
its functions, we will first briefly relate the different 
Theories that have been held respecting Digestion. 
Hippocrates supposed Digestion to be 
carried on by heat produced by the larger Viscera
which surrounded the Stomach, and as it were,
by Moisture. This is considering Digestion in a 
very confined ligtht. It will be proper however to 
mention an objection to it. The heat of the body of 
Frogs is very little above the temperature they Live
in, but Digestion is found to go on perfectly well
in them. But altho’ this is not a principal cause or 
agent, yet is certainly must assist in the process of  	





30
Digestion. Another theory was that it was performed
by a process of Putrefaction; but we do not find the 
smallest part of Digestible food putrefy, on the contrary
if food a little putrid, be taken into the Stomach,
it will be found to be meliorated more than 
otherwise. And some have asserted that if food quite
Putrid be taken into the Stomach, it would be rendered
quite sweet again. The theory next held up,
was that of Eristratus, who supposed that Digestion
was performed by trituration, and he took this Idea
from Birds and thought that Man did the same.
but the structure of the Human Stomach is such
that it would not perform this office: hence we
conclude Eristratus did not distinguish between
Mastication and Digestion. But a theory which prevailed
last century, and which still has its advocates 
is that Digestion is similar to Fermentation.
In the last Century all the Secretions
and other actions of the fluids, were attributed to 
Fermentation. Boerhaave exploded the opinions 
Respecting the Secretions, but at the same time
thought it had something to do with Digestion.
Several eminent Physiologist have entertained
this opinion, but they seem to annex a peculiar 
Idea to Fermentation very different to those of 
Chemists. A chemist would say that various







31
Cases are evident and evolved in fermentation, and 
therefore that the fermenting substances should be exposed 
to the air, and that different substances would 
be produced according to the different Ingredients
which were fermented, whereas the food in the Stomach
is excluded from Air, and that the substance 
produced by fermentation or Digestion is invariably 
the same. viz. Chyle, whatever Ingredients be
taken into the Stomach. The late Sir John Pringle
and Dr McBride made many experiments to support 
the theory of fermentation: they put many different 
substances into a Vessel, to which they added
warm water, and to render as they supposed the Experiments
more complete, they added a quantity of 
Saliva. They then exposed the Vessel to a degree of heat
very nearly that of the Human bodiy, for some time, 
and this they thought a mass similar to Digested food, but 
they forgot that the Stomach itself secreted a fluid, or they 
thought it was of no consequence in Digestion. The following 
experiments may however Illustrate the importance 
of this fluid. I fasted a Dog eighteen hours, and
then killed him, and on opening the Stomach I found a
quantity of Gastric juice, I collected half an ounce of 
this, and to a part was added twelve grains of roasted
Beef, and to another quantity in which was added
warm water with the Beef: I then put both vessels to 





32
a degree of heat equal to the Human Body. In the first 
vessel in eight hours the Beef was almost dissolved, 
but that in the other a very little altered; In twenty four 
hours the Gastric Juice, had entirely dissolved the Beef
without any appearance of Fermentation but the 
Water and liquor mixed, produced no alteration in 
the Meat, and a little fator was perceptible in it. It
is now pretty well ascertained that Digestion in performed 
by Chemical principles. Food has been introduced 
into metallic tubes and these into the Stomach
of Animals, on opening them it was found dissolved. 
Those who are advocates for fermentation, say that 
If the Gastric Juice has the power of dissolving Animal
substances, why is not the Stomach itself dissolved 
by it? The Stomach is in fact sometimes
dissolved by it, but not while Vitality remains. 
It may be asked, what are circumstances, which favour 
the action of this liquid upon the Stomach?
A healthy and vigorous Secretion at the time of 
Death, hence the Stomach has been found most frequently
dissolved in executed people: in them the fluid 
is already Secreted, and as soon as Life is gone, the 
fluid is capable of acting on the stomach, but those
who die after disease, having but a little appetite
and circulation, have consequently a very small
Secretion of fluid, which accounts for the Stomach


  




33
not being in a state of dissolution. The Gastric Juice 
will act upon Earth Worms, or Snails, if taken into 
the Stomach, but not while vitality remains in them.
Dr Stephen of Edinburgh has had an opportunity of 
repeating these experiments in the Human subject.
One was a German who gained his Livelihood by 
Swallowing stones for the amusement of the people 
he began at the age of seven years, and had at that time
continued it for twenty six years: he swallowed
six or eight stones at a time, some as large as Pidgeons 
Eggs, and passed them thro the Natural way, the 
Dr made this man swallow a silver sphere divided 
into two cavities by a partition and perforated by a 
number of holes capable of admitting a common 
size probe or needle; into one of these cavities he
put four scruples and an half of raw Beef, and into 
the other five scruples of raw Fish: in twenty one 
hours the sphere was voided, when the Beef had lost
one scruple and a half, and the Fish two scruples.
A few days after he swallowed the same sphere, which 
contained in one cavity eighty four grains of raw
Beef, and in the other one hundred and eighty grains
of boiled Beef. The sphere was discharged in forty 
three hours, the raw beef had lost twenty two grains
the boiled Beef twenty six grains: suspecting that 
if these things were divided, the solvent would have






34
better access and effect upon them, he produced another 
Sphere with holes large enough to admit common 
craw quills. In this he enclosed some Beef a little
masticated, and in thirty eight hours after it was voided 
quite empty, perceiving how readily chewed meat was
dissolved, he tried whether it would be dissolved without
being chewed, as soon, with this view, he put 
eight grains of Pork into one cavity, and the same
quantity of cheese into the other. The sphere was voided
after forty eighty hours, and not the smallest quantity
of Pork or Cheese was to be found. He again voided
the same sphere which contained some roasted Turkey
in one part, and some boiled salt Herring in the other, 
but not a part of either appeared, being both dissolved
observing that Animal substances, tho’ enclosed in tubes
were dissolved by Gastric Juice, the Dr tried whether it in
Vegetables would prove the same: he enclosed equal quantities
of raw Parsnips and Potatoes in a sphere which 
was voided in forty eight hours, and not a particle of 
either was found, pieces of apple and Turnip both raw
and boiled were dissolved in thirty six hours. He there 
enclosed live Leeches and Earth Worms, but found them 
entirely dead, and dissolved, hence if any reptile should
be swallowed there is no danger. Spallanzerni confirms
these Experiments, & says Digestion is performed by a Stomach,
however different the mode of Mastication. 





35
On the SOURCE OF THE Gastric 
FLUID OR JUICE.
He shall now proceed to make some further observations,
on the source of the Gastric fluid or Juice. In the 
Human subject, and in most of the Carnivorous kind, it seems
to be secreted from every part of the Internal surface
of the Stomach. It being almost equally vascular in 
every part. Some have said that the Asophagus has
yielded part of the Secretion, but this is erroneous for 
it has no Villous Coat; in the house rat this secretion
seems to be confined to the right side of the Stomach only 
which is Villous and secreting. In these Animals 
the Stomach is lined by a cuticle which is continued 
half way down, and when that ends the Villous Coat 
begins. The termination of one, and the beginning of 
the other is not confuted but distinct and marked
The Secretion being confined to the Villous Coat, the 
other being only slightly vascular. It must be supposed
that Digestion goes on slowly in these Animals, and 
it must be probable that one half of the Stomach serves
as a recipient, whilst the other performs the office of 
a Digestive organ. In ruminating animals there 
are four Stomachs, but they do not all secrete the Gastric
Juice, the three first seem peculiar to those as ruminating 
animals, but the fourth differs in structure
it being vascular, and by it the Gastric Juice secreted. 






36
It is this Stomach which is dried with Gastric Juice that 
is used in making Cheese and is called Rennet. It does
not appear that the Gastric Juice curdles milk by its acidity,
for if so we might suppose it dissolve the food like
other strong acids. Its properties and the manner in which
it acts on the food, cannot be discovered by any Chemical
process. When Infants throw up curdled milk, it is not 
from acidity in the Stomach for we see the Gastric
Juice has the power of curdling milk. In Granivorous 
Birds the Gastric Juice is secreted in the bulbous part
just above the Gizzard, or either by small Glands that 
have small Ducts, terminating in the internal surface
of the Bulb. This fluid is mixed with the food,
before it enters the Gizzard, and is afterwards triturated 
and Digested, at the same time. There is a similar apparatus 
in Carnivorous Birds for secreting the Gastric
Juice, but the Glands are small and more numerous; these 
Birds have not Gizzards, but a strong muscular Stomach
on the internal surface of which is the fluid discharged
by small excretory Ducts. With respect to the Granivorous
Birds it might be perhaps more properly said that the 
food is ground down and intimately connected with the
Gastric Juice in the Gizzard, but that Digestion is finished
in the Duodenum before the entrance of the Ductus
Choledoctrus communes, and Pancreatic Duct. In cold 
Blooded Animals, as the Serpent, the secretory part of the 





37
Stomach is very small in them it is difficult to say where
the Esophagus ends and Stomach begins, for they are both
nearly of the same size: the lower part of the Stomach is 
very vascular, and it is there that the Gastric Juice as secreted.
Digestion in these Animals must be very slow, for 
they swallow Animals newly as large as themselves, and 
the Stomach being so narrow, only one part can be acted 
upon at once; so that an Animal may remain in the 
Stomach some days before it is Digested entirely. The
Gastric fluid not only acts on Animal and Vegetable 
substances, but will also dissolve Metals, we know
that if crude antinomy be minutely divided it will dissolve in the 
Stomach. Chemical Analysis has shown that crude Sal 
Ammoniac and Muriatic acid are contained in this 
fluid, but does not explain its effects. It is best then to
say it is a strong solvent even for Bones, as we see in
Dogs. The Nausea excited by taking Copper is in consequence 
of its solution or that it resist fermentation, and is therefore
what Chemists call an Antiseptic. The Gastric 
Juice is subject to be changed in its properties by various
causes which may accidentally occur, and amongst
those the affections of the Mind may operate, thus when a person
if eating, is informed of any depressing news, his appetite
is immediately gone, or if he has been eating and the Digestive
process going on well, it is nearly or entirely stopped, hence
arise acid eructations &c. and hence hypochondriac people 




38
have eructations,  and other symptoms of Dyspepsia. The 
effects of the Mind on the Stomach are conversed by means
of the Nerves: the Par Vagum supplies the upper orifices 
of the Stomach the lower is supplied by the Intercosale Natler 
says if the Nerves going to the Stomach be torn, or cut thro’
the food will become putrid. In order to ascertain how far
the Nerves are concerned in Digestion Endeavored to interrupt 
the Nervous influence between the Stomach and 
the Head. To do this I divided the branches of the Par Vagum
of a Dog after he had eaten food, he died in two days and 
the food was only in part dissolved, now in health we know
the food will be pretty well dissolved in twenty four hours.
It appears therefore that the little Solution performed was 
by the Gastric Juice secreted before the division of the 
Nerves, and that after this none was secreted. To another
Dog, I gave a strong Emetic, and when it began to operate
I injected warm water into the Stomach so as to clean it 
Entirely; the Dog not being inclined to eat after the operation
of the Emetic, Food was forced down the Esophagus.
I afterwards divided the Par Vagum this Dog also died, and 
the food was not in the least acted upon. It appears then 
that the division of the Nerves either entirely prevented the 
Secretion of the Gastric Juice, or so far vitiated it, as to 
destroy its functions. In the next Experiment I divided 
only one branch of Par Vagum, and this did not seem
to produce any material difference in the functions





39
of the Stomach, but the Dog seemed rather uneasy at the 
Stomach, he eat well and his food was Digested. About six
weeks afterwards I divided a Nerve on the other side,
knowing that the first which had been divided, must be united
by this time; but it appeared from this division that the first
had not entirely recovered its functions. The Dog seemed 
very uneasy and depressed at his Stomach more than before
and his appetite was entirely gone. This however gradually 
returned, and by feeding him, upon milk, he became
able to eat things as before, but during this time he showed
many symptoms of Dyspepsia as Eructation, Emaciation 
&c. The inference to be drawn from these Experiments
is very evident that the Stomach cannot perform
its functions without the assistance of the Nerves, and that 
one will be restored with the other. Heat and Cold have 
evidently some influence on Digestion, but this limited
Heat must assist us, this is evident from putting 
two substances into two different portions of Gastric
fluid, and setting one in the Temperature of 100, while the
other is in the common Temperature of the atmosphere.
The former will be found first acted upon. Cold blooded
Animals, as Fish and Frogs have their Blood a little
higher in temperature than medium in which they 
Live, they do not Digest well, hence living Animals are
often found in their Stomachs, and they Live long without 
food, their Digestion, being so slow: In warm weather they 









40
eat heartily and Digest their food well, but in Cold weather
they become Torpid, and some eat no food at all. If in 
this state food be put into their Stomachs it will not be 
acted upon in the least. The Cold it seems destroys the 
Nervous Energy, in consequence of which the action
of the Heart and Arteries is much diminished, and the 
Blood in the Secretory Organs, being nearly quiescent 
They cannot perform their functions. This is a wise provision 
of Nature for in their Torpid state no exhaustion 
goes on in the system, therefore no secretions are wanted.
If a Torpid Animal, as the Hedge Hog or Lizzard, be put 
into a warm room, the influence of the Sensorium is first
reduced, and gradually in consequence of this, the actions
of the body are reduced. Food will now be wanted to supply 
the exhaustion of the Machine, and therefore the Gastric 
Juice is secreted. If the food be given to the Animal at this
time, he will eat it with avidity, and if no food be 
given he must die. Cold acts on the Nervous system
and produces Torpor and Sleep, different from Natural 
Sleep, for in Natural Sleep the Sensation and Volition 
be only suspended, but in Torpor no action whatever
is going on in the Machine. In Man and large 
Animals Digestion is not much altered by variation
of Temperature, for they can resist the effects of heat and 
cold to a very great degree.




41
ACIDITY IN THE STOMACH.
There is often some acidity in the Stomach during Digestion,
and it may be asked whether this assists or retards 
the digestive process, the latter may be said to be the case
and the acidity appears to be only accidental, for if we
examine the Stomach of an Animal in health, there is no acidity
found in it, what then does this arise from? Is it the 
same as would take place in the same substance out of 
the body? If this was the case, the more acid substances
taken in, the more acidity would be present or generated 
but this is not found to be the case; It seems then that the 
acidity in the Stomach depends upon some fault in the 
secretion of the Gastric Juices. Infants are very subject to 
acidity in the Stomach, and this has been supposed to exist
when it does not, as may be inferred from what has been
said in a former Lecture, respecting the coagulation of 
Milk. The acidity in the Stomach of children may be often
accounted for, by their being made to take an excess of food.
this for a time may increase the Secretion of the Gastric
Juice, but must finally weaken it, for all increased actions
are succeeded by Debility. The excess thus taken by Infants
is frequently made to regurgitate, and the Milk brought
rather in a coagulated state, but this coagulation is not
dependent upon acidity, but on the Gastric Juice itself.
Milk is always coagulated before it is Digested, and indeed 





42
this seems necessary for Digestion. The Rennet taken 
from the fourth Stomach of a Calf curdles Milk under
heat, and on the same principle does the Rennet in the 
Childs Stomach. Some have carried the Idea so far as
to say that Coagulation was universally necessary
for Digestion, but we may be nourished by many kinds
of food, which do not seem capable of it, as Broths &c.
Some kinds of food dispose the Stomach to acidity upon
very little disorder of its Secretions, more than others
as oily substances. Empyreumatic Oils become acid 
in the Stomach. The weaker the state of the Stomach the 
more it is subject to acidity, and therefore the less nourishment
is obtained, but how is this acid formed? Is it 
from an acetous change, into acetous fermentation, or 
from a diseased state of the Stomach, which disposes
it to a kind of acid secretion? So soon is this produced
in the Stomach that it is difficult to conceive how; can
it be a spontaneous change taking place in the food?
for it arises much sooner than it would out of the Stomach.
The theory of a French Chemist with respect to Acidity
being produced by taking oily substances into the Stomach,
was from its there becoming rancid. He said
that Acidity was produced by the extrication of fixed 
air, and that he would easily make rancid Oil sweet by 
the addition of this air, he supposed that the acid Eructations,
which is so common in these cases, is owning to the 






43
escape of fixed Air. I have not tried the experiment of making 
rancid Oil sweet, by the addition of fixed Air; yet was rancidity 
caused by the loss of it, that would not be sufficient to 
account for the quantity of acid discharged by eructation in 
disorders of the Stomach. This theory may stagger many,
but it is conceived that Air is secreted in many instances, 
as in Tympanites, and also after death from Putrefaction.
There is a disease which women are subject to after Delivery
called Tympanites Uteri; I found once a collection
of Air, in a circumscribed tumour for which I could not
account, unless it was Secreted there. In some fishes
as in Cod, there are Air cells, which do not appear to have
any communication with the atmosphere, but each
cell is vascular, and they appears to be an apparatus for
secreting Air. Disorders of the Digestive Organs arise
from three causes, first from the Indigestibility of 
the food taken in, second from want of sufficient 
Mastication and thirdly from the debility of the Digestive 
Organs. The last may be the effect of the 
two former, for the action of the Stomach being
increased by them, a proportionate degree
of Debility will necessarily ensue. Dyspepsia 
is usually the consequence of Distension, hence it  
is that the high living, as well as large Eating, are
certain causes to produce it.






44
[?ictions] of the Stomach.
After the food is Digested, it must be discharged from
the Stomach into the Intestines, there to undergo a further
change into Chyle, before it is taken up into the mass
of Blood. We come now to consider the power by which 
this is brought about; all motion depends on Muscles,
and of such structure we find the Stomach to be, in 
order that the Stomach may expel its contents, the fibres
must act in various and particular directions, we
shall first consider how the fibres are situated, and
then how far they perform their office. The Asophagus 
it has been observed is very Muscular, some of its fibres
running longitudinally and others transversely.
When the Asophagus enters the Stomach its Muscular
fibres expand so as to cover the Stomach on each side
the transverse intersecting the longitudinal at right 
angles – when these fibres are put into action, it is
evident that one will shorten the Stomach while 
the others act to contract it and it is by these principally 
that the office of expulsion is performed.
There appears some muscular fibres which pass in a 
direction between the two, but they are not very apparent
in most subjects, by these different fibres the 
food is expelled gradually lower and lower until it is
discharged. If you open the Stomach of a living Animal 






45
Animal the action is not apparent, but still it is 
evident. I have more than once opened Animals for 
this purpose, and have observed the action of the right
extremity of the Stomach to be greater than the left. 
I could perceive scarcely any motion, this may be 
accounted for by the Stomach becoming depressed 
about the middle, therefore until it arrives at the 
point, the food would descend by its own gravity;
about or a little below the middle of the Stomach, a
circular contraction appears, which gradually descends
to the lower Orifice of the Stomach, and someway 
into the Intestines. The contracted parts appears again
in the Stomach and Descends gradually 
as before. This motion resembles the creeping of a 
Worm, and is very similar to the Peristaltic motion
of the Intestines. I wished to know the effect 
of Stimuli and therefore made use of the Volatile 
Alkali, as a Chemical Stimulant, and a scratch
of a knife as Mechanical one, but I did not
find the Peristaltic motion at all increased by them,
the only effect was a local increase of action for a 
time. We find there is an agreement between the Digestive 
and Muscular part of the Stomach; this is a wise
provision of Nature, to prevent the expulsion of food, before
it is perfectly Digested. Sometimes the motion of 
the Stomach takes a retrograde course, beginning at 






46
the Pylorus, or rather Duodenum; this generally produces
vomiting. It is most natural to suppose the Stomach
would be employed, with respect to the act of Vomiting 
by contracting: that it begins at the Intestines is obvious 
from the matter Vomited. It was said by a foreigner and
confirmed by some Experiments in Edinburgh that the Stomach 
was distended in the act of Vomiting, by contracting
I could hardly suppose this and thought there was 
some fallacy in Experiments. I gave a Dog a scruple 
of Ipecacuanha, and when it began to act I opened him 
so as to lay bare the Stomach, but the Dog could not Vomit,
altho’ he seemed very sick; I threw in some Water thinking
there might be too little in the Stomach to enable
him to Vomit, but without success; and yet the Stomach 
appeared a good deal distended: a solution of Blue Vitriol
was given but Vomiting was not produced: it may be
argued against the Experiment, that the Stomach was for 
a considerable time exposed to cold, and consequently 
that its Irritability must be diminished; and it has 
been known that when an Intestine has been exposed a
long time to cold air, its Peristaltic motion has been 
destroyed. To obviate this objection, rather under different
circumstances, to the first Experiment after having
exhorted the Stomach, I procured an assistant to 
drop warm water upon it, by which means I preserved
natural warmth of the parts. In this case the sauces  




47
were irritated, Chemical and Mechanical Stimuli was applyed 
to it, and all other means, which are in the least 
calculated to produce Vomiting, but without effect. From 
the result I think there is a deception in those made at 
Edinburgh, and perhaps the Stomach was pressed upon, by
the false ribs, probably also the sudden inspiration before
vomiting might give the appearance of distention
to the Stomach. In the act of Vomiting in the Natural 
state the Diaphragm is depressed, consequently 
both it and the ribs make pressure upon the Stomach.
The Abdominal Muscles assist in the same intention.
From these experiments I think it is widest that no 
Power of itself can effect Vomiting. I thought this a 
fair opportunity to try, how much external assistance 
was necessary to enable the Stomach to expel its contents;
I therefore placed my hand under the Stomach 
as a fixed point, and the Dog instantly Vomited. It 
seems that tho’ the Stomach has not the power of performing
that sudden and violent action upon itself necessary 
to expel its contents, yet that the pressure of the 
Diaphragm serving as a fixed point will be sufficient. 
Drs Davenny and Hunter were of opinion that
the Stomach was totally inactive during the act of Vomiting.
Dr Hunters opinion was that Vomiting was
to the Stomach what expectoration is to the Lungs. It 
is well known that the Lungs are not Muscular, Expectoration 
 




48
[expectoration] is perform’d by a quantity of Air being inspired which 
being violently expelled by Muscles of expiration compressing
the Lungs suddenly, carries the Phlegm along with it. The Stomach
is Muscular, besides it appears, Air does not assist materially
if at all in the act of Vomiting, yet every little Air goes into the 
Stomach, and we often Vomit, without previous inspiration 
But can Dr Hunters experiment be refuted? The Stomach was 
said to be Muscular, but Muscles cannot act without Nerves.
We shall see, from these experiments whether the Muscular structure
of the Stomach be necessary for Vomiting, or if the Stomach 
is inactive as Dr A supposed. I gave a Dog an Emetic and Paralised 
the Stomach by dividing the Par Vagum  and Intercostal
Nerves; tho’ he became sick, he was unable to vomit. 
notwithstanding the usual pressure on the Stomach by the 
different Muscles. These and the Experiments before related,
prove, that the Stomach alone nor the Muscles pressing on it, 
are of themselves capable of producing Vomiting, but the powers
must be united. Some might draw an objection from particular 
Animals. Carnivorous Birds eat others with their 
feathers and indigestible parts, and what cannot be Digested,
they afterwards regurgitate, now these Birds have no Diaphragm,
but they have a Membrane which answers to it.  
Nature may provide some other means for their Vomiting
and here we shall inquire in what the structure of their Stomachs
differ from other Animals? They are more Muscular
almost approaching to a Gizzard.




49
ON THE STOMACH AS AN
Organ of Sympathy. 
I do not intend inquire into the doctrine of Sympathy,
but it should be understood what is meant by the term.
By Sympathy we mean Sensation or Action, in one part, in 
consequence of some impression made on different part
at a distance, the latter is called the impressed, the former
the Sympathizing, we are now to speak of Sympathy 
only as it is connected with the Stomach, sometimes 
the Stomach is Sympathizing, sometimes the Impressed 
part, when there is pain in the head, the Stomach
is often affected, et vice versa; when there is sickness 
of the Stomach, the head will be often affected with
pain: some kind of head ach depends on a morbid
state of the Stomach, but we may know which is the 
Sympathizing part, by observing which part is first 
affected, there is no part of the body except the Brain
which has such extensive Sympathy as the Stomach, 
every impression whether pleasant or
unpleasant is communicated by the Nerves,
which are distributed to every part of the body
hence the Brain may be said to sympathize
universally; that this is the case may be proved
by dividing a Nerve, when it will be found that
impressions made on such part do not produce
sensation, or in other words that the Brain does






50
not Sympathize with them. Nausea and Vomiting 
are produced by many Acute Diseases, or Inflammatory
Fevers, or Inflammation of any particular Organ
as the Kidney, or injuries of some parts, as the Brains
and this is no other than the Sympathy of the Stomach
When we have been long without food an uneasy 
Sensation is felt in the Stomach, which is called 
Hunger; this I call Sympathy of the Stomach with 
the Constitution, being in the latter instance an 
healthy Sympathy, while in the former it was a
morbid one. Some would explain hunger in 
another way; they would say the Gastric Juice having 
nothing to act upon produces uneasy Sensations,
by acting upon the Stomach itself. If this be the 
case why does it not produce the same effect, when 
there is food in the Stomach, for then it is in contact
with the Stomach, tho’ it be distributed thro’ the food.
besides it is a law that Fluids are never Stimulants
to the Organs that Secrete them; tho’ they may act
so to any other. The smell of food may be to an hungry 
person pleasant, but to one with a full Stomach
it would produce Nausea. This is a Sympathetic 
Action. The Mind often powerfully effects
the Stomach, Sickness often arises from Fear, or 
Dread, as for example, it being very frequent before
a Surgical operation is to be performed - hence the  
	




51
Stomach may be said to Sympathize with the
Mind, as well as with the Body. Something more 
may be said with respect to the Stomach producing
hunger. It is certainly a wise provision of Nature 
to make us mindful of supplying the system with 
nourishment, and much more adapted to reason than
if it had been left to reason to determine when that 
food was necessary. There are further causes for thinking
hunger an affair of Sympathy: Animals in a 
torpid state take no food; the Hearts excretions and 
secretions are nearly in quiescent state, therefore
no exhaustion is produced, and consequently no food
is required. In this state if you offer an Animal food
which is agreeable to him, he refuses to eat of it. 
the constitution not being in want, there is no Sympathy
in the Stomach, but when the various Organs have 
their actions increased, devour the same food with
avidity, which is a similar instance to people recovering 
from a Fever: when the constitution is left 
much reduced from the cause, the patient will eat
with great appetite and frequently every hour, we 
find also at such times the Stomach will Digest
a very large quantity of food: when the constitution is 
repaired, the inordinate appetite ceases. Such a disordered
state of certain parts, as to prevent the Nourishment
from getting into the system, produces also  






52
Sympathetic affections of the Stomach tho’ food be 
taken in large quantities; and of this kind is the 
Scuuchus Pylorus; people under this disease eat 
hardily, and yet are very hungry. This hunger 
induces them to eat more than they can Digest; and
they often Vomit back the food. A structure of the 
Esophagus produces the same effects but in this
case it is difficult to take food. Another Disease
producing Sympathy of the Stomach is that in the
Lacteals which inpairs their functions: I know a 
case of a Lady who was inclined to corpulency at the 
age of thirty, but afterwards become by degrees extremely 
emaciated; she eat enormously and sometimes 
Vomited her food from eating to excess, and yet she
was always hungry. On examination after her 
Death the Mesentric Glands were found obstructed
and their functions as assimilating Organs, much 
impaired. In the exhibition of many Medicines
the Stomach may be said to Sympathize with 
the Vascular system. A person in a state of Syncope 
may be instantly relieved by a Stimulant
received into the Stomach; this often must be produced
by Sympathy, for it takes place too quickly to
admit of a Stimulus being first taken into the system,
yet it is found they will act nearly as soon 
as if thrown with the mass of Blood: this effect




53
must be produced by Sympathy. I injected two
grams of Tarter Emetic into the Veins of a Dog, 
the jugular, and vomiting was soon produced, some 
might suppose this was an effect of an extraneous body
but on injecting a like quantity of water a similar 
effect was not produced. I afterwards repeated these 
experiments with the Solution and the like result
took place in half an hour. I wished also to know
if the Intestines were affected in the same way or 
not. I dissolved a few grams of Gamboge, and injected 
it into the Jugular Vein, and in about half an 
hour purging was produced, and soon after Vomiting.
When Urine was injected it made the Dog drunk.
These effects we cannot suppose be produced by the substances
taken into the system, and secreted on the surface of 
the Stomach and Intestines; we cannot account for 
them in any other way than by Sympathy. It has 
been questioned by Physicians, whether Bark acted
merely on the Stomach, or was taken into the system by
Absorption. We know many substances having been 
taken into the Stomach may be discovered in the 
Blood, and Secretions, by their smell, taste, color &c.
Thus Spt of Turpentine is readily discoverable in the 
Urine by its smell, and Rhubarb, by its color may be discovered
in the Blood. Bark being a Vegetable Astringent, 
may be easily discovered by solution of Iron 




54
provided it entered the Circulation. A good opportunity
happened a few years ago to Mr Ralph
he had been some time under the course of Bark
and was suddenly attacked with Peripneumony 
which rendered Bleeding necessary, and on examining 
the Serum of this Blood by a solution of Iron
no trace  of Vegetable Astringency appeared. The 
action of Bark being Sympathetic is further
proved by the circumstance of a large quantity 
being taken previous to an ague fit, having better
effect than when more gradually taken; again
it has been inquired how Chalybeates acted
upon the system. I endeavoured to ascertain this 
by experiment. I gave a Dog an annu of Chalybeate 
Wine in Milk, after a time I opened him
and made two Ligatures on the Thoratic Duct, so
as to preserve some chyle pure. I afterwards examined
it by adding some fruit of Galls, but no alteration 
was produced in it. I gave another Dog
an ounce of Salt of Steel, mixed with his food,
after this trial upon examining the Blood, no Iron 
could be found. From these Experiments it appears
that these two important Medicines Bark and Steel 
produce their effects by acting Sympathetically on 
the Stomach, and not by their being taken into the Circulating 
Fluid



55
ON CHYLIFICATION.
Food is taken in to supply the exhaustion going on 
in the Body, but many changes must be produced upon 
it, before it is fit for the purposes required: after 
being Digested, the Nutritious part is to be formed into 
Chyle, this again is to become Blood, and lastly Blood becomes
a living solid. When Food is Digested, it has 
gone on but a small way to assimilation. The next
change it undergoes is that of being converted into
Chyle, which takes place in the Duodenum. When 
the Food enters the Intestine it admits all the Characters
of Digested Matter, which has been called Chyme, but
it soon after assumes a white appearance called Chyle,
this milky fluid is never founded in the Stomach.
We are now to consider what means are employed to 
effect this change. It must be brought about by the 
Duodenum or some fluid connected with it. We can
hardly suppose that the Duodenum can produce any
such alteration, by any Mechanical means of its own,
and therefore it must depend on some fluid contained in 
it. The Fluids found in the Duodenum are first the 
Mucous fluid, Secreted in the Intestine itself. It appears
at first view that the Duodenum is a Secreting Organ: it it
very Vascular and this Vascularity is determined to the
inner surface, and from this we presume that the




56
Secretion is carried on by it. Where there is Secretion carried
on, we do there expect to find Glandular Structure,
however this is not the case, as this is not absolutely Glandular
Structure, but it is found in the Intestines in great
abundance, more particularly in the Duodenum.
One set of Glands received their name from Bremier 
who first described, and likewise discovered them: they are
about the size of Pins Heads, and situated at the upper
part of the Duodenum. The secretion from these is more 
than sufficient to lubricate the Intestines, and probably 
therefore it assists in Chylification. Another set of 
Glands take the name of Aggregate from their being
Situated in Clusters, and others are called Solataria.
Besides the fluid secreted from these little Glands in the 
Intestines, there are other fluids, poured into the Duodenum:
which are Secreted by large Glands in the Intestines.  
There are others poured into the Intestines, which
are Secreted by larger Glands placed in the Abdomen, and 
their Excretory Ducts end in the Duodenum, not far from
the Pylorus. These are the Liver and Pancreas. The Liver
secreting Bile, and the Pancreas secreting a fluid called the 
Pancreatic juice. The Pancreas receives Blood from several
sources, and hence it is very Vascular, the Ultimate 
branches of Vessels terminate in Cells, and these again in the excretory
Duct that runs along the center of the Gland, and as was
Before said terminate in the Duodenum. The superfluous  




57
Blood is returned by the Veins. We shall speak of these fluids 
as they concern Chylification, and first of the Bile. The 
Bile was by many supposed to enter into the composition
of Chyle. I am not prepared absolutely to deny this, but 
am inclined to doubt it, at least it is not so obvious as
some have thought it. I first entertained doubts, of this, 
from the following Experiments. I opened a Dog, and 
thro’ the Intestines could be distinguished the process of 
Chylification. The Bile seemed to flow over the Chyle,
adhering so firm to the sides of the Intestines, that if you 
wished to collect it you must scrape it off with a knife.
Again if the Bile does enter into the composition of the 
Chyle, it must either change its properties, or some of 
its constituent parts. The coloring part of the Bile does
not mix with the Chyle, otherwise it would give a 
a yellowness to the Blood, which in a state of health is 
not found to exist. Bile is also very bitter: Chyle is 
sweet. It may be inquired what purpose the Bile answers.
It appears to act as a Stimulus to the Intestines, and thereby 
assist them in discharging their faces, and to which 
it gives colour. In Jaundice when the Bile is prevented from 
entering the Intestines in its usual form, or rather quantity
the faces are of a light color, or grey, and the bowels are constipated.
The Pancreatic Juice is Secreted by the Pancreas, and 
Carried into the Duodenum, by its Duct which terminate
there, in common with the Ductus Communes, and the  




58
manner in which they enter is somewhat peculiar. The two
Ducts enter the external coat of the Duodenum separately 
forming an acute Angle, but in their passage thro’ the
intestines they join the common Duct: there are however
varieties in their termination, and both ducts may terminate
in the Duodenum an Inch apart, hence it does
not appear necessary that the fluids should be mixed before
they enter the Intestine. The Pancreatic juice is said to 
have a share in Chylification. This is probable from
the change induced on the food in the Duodenum and 
not in the Stomach. It is not probable that the Bile, from
the Characteristic difference between it and Chyle, 
should be mixed with the Chyle; and it has been observed
upon opening a Dog. The Bile appears to flow over the Chyle
and not to unite with it. If the Bile was to enter into
the Chyle it would cause perpetual jaundice unless
it be proved that in this process it loses all its constituent 
properties. If Pancreatic Juice be obtained, and you
Crystalize it, some of the Crystals will be of a Cubic form 
and some of a Speculated form. The Cubic resembles common
Salt and the Speculated are found to be Sal Ammoniac,
Hence the Saline matter as it contains common 
and Ammoniacal Salt. It is detected by Nitrate of 
Silver and Muriatic Acid, but admitting that there is 
a Mineral Alkali, Muriatic Acid, and Ammoniacal Salt
in the Secretion, are they necessary to Chylification? We do




59
not know that they are, and the common Salt may be referred 
to what we daily take in. The Duodenum being brought forward,
two Ligatures may be made on the Pancreatic Duct,
so as to include the juice pure. It cannot be collected after Death
for the Duct then is always found empty. The Mucous of the 
Duodenum and Pancreatic Juice seem to be the principal 
agents in the process of Chylification: but how they act in producing
this change in the food, we cannot say so far we know 
that it is not long taking place. This has been found by keeping
an Animal fasting for some Days, and then giving him food
then on opening the abdomen two hours after, Chyle has been 
found completely formed. In the Intestines of Human Subjects
are found small projections, called Volvulu conniventes. Some 
have thought their use to be that of exposing a greater surface for
the absorption of Chyle, and this indeed is very probable others
have said that they are designed to assist the Peristaltic motion
of the Intestines, but their situation in different Animals
seems to [illegible] this. In the Whale, or Polypus they are 
longitudinal but in the human they are Circular. Herbivorous 
Animals have not these valves, but they have greater 
Length of canal. Vultures have rough villous proupes resembling 
thick, fur, at the Inferior part of the Intestine, 
when the Chyle is formed, the Valvulu Conniventes are discontinued. 
In Animals which dine entirely on Animal food, we do 
not find plaits in the small Intestines, but always something
in there stead. In the Human subject are small hair like 
 






60
processes which probably assist in Chylification. Great pains have 
been taken to ascertain the component parts of the Chyle, but
as yet this has not been accurately done. Experiments of this kind 
are liable to fallacy from the difficulty of collecting pure 
Chyle from those of Dr McBride, it has been formed to consist 
of Oil, mucilage, coagulable matter and fixed Air. It is not 
certain that these are the parts that compose it if they were by 
adding them together Chyle would be produced: but it has been
proved that it is impossible to form Chyle in this manner.
Chyle in its color resembles Milk, and in its properties is 
also said to resemble it. Milk is found to contain Sugar, bil,
Water and Lymph, but Chyle has not all these: that they vary 
Much in their properties is further evident from Milk undergoing
the same changes as the food. It must be coagulated and 
Digested, before it becomes Chyle. The Chyle has a mild and 
sweetish taste, and seems an heterogenous mass: it is
rather white but its colour may be changed, and probably 
feeding an Madder would effect this change. In many Birds
it is naturally transparent like Serum. When Chylification 
is completed, there are two operations set up in the 
Intestines: one to convey the Chyle by the Lacteals into 
the Mass of Blood, and the other to expel the excrementitious
part which has not been converted into Chyle. This will 
lead us hereafter to consider the Intestine in a Mechanical
point of view.
 




61
ON THE CONVEYANCE OF CHYLE INTO THE 
Mass of Blood.
Having traced the food to its formation into Chyle
we shall now consider its conveyance with the 
Blood, If we open an Animal a few hours after
it has taken food, we find adhering to the Internal
part of the Intestine a white substance as thick as 
Cream, and which adheres so firmly that it must 
be scraped off with a knife. This is Chyle, and when 
scraped off, we observe a rough surface which 
entangled it, and caused it so firmly to unite; this 
surface is called the Villaus coat of the Intestines, being 
composed of a number of hair like processes, they 
are not equally conspicuous being sometimes
flattened: they are easily seen by throwing in a 
fine Injection or are apparent in the Living Animals.
In either case they are distinct for they appear to be 
organized bodies, having each a Blood vessel, Nerve
and an absorbent pore; and by the pore being filled they
are kept erect, causing a sensation of roughness; as
by the Stimulus of Acids taken into the Stomach, the 
Papillae of the Tongue are kept erect causing a sensation
of roughness. So probably are the hair like processes
of the Intestines erected by the pressure of Chyle,
their proper Stimulus with respect to the Absorption 
of Chyle there are two opinions, one that it is performed 




62
by capillary attraction alone, or being combined with 
other powers, as Irritability, which was the opinion
of Haller: certain it is that the Lacteals, 
whose mouths have the hair like processes already 
mentioned, have motion or Irritability, on the application
of Stimuli. If when a tube, having one end 
inverted in a fluid, that fluid has a tendency to rise
in the tube, a little above the surrounding fluid, this 
can be attributed to nothing but what is called
Capillary attraction which takes place inversely as 
the size of the tube is in diameter. Many have endeavoured 
to support this Theory, by applying it to 
cases of capillary attraction, some of which are that
the position of the tube in the fluid is quite immaterial, 
whether perpendicular or oblique, that the attraction 
diminishes, as the size increases in Diameter
and that temperature does not effect this. They have illustrated 
this opinion by the analogy of Plants, but 
even in this instance all the laws of Capillary attraction
do not hold good. An experiment of Dr Hales has 
been brought to illustrate this opinion. That whether 
a Tree be immersed by its roots, or by its branches
that it regularly receives a supply of Sap: but this does
not depend on Capillary attraction; because the circulation
of the Sap depends upon, or is regulated by the 
degree of heat and cold. In the Summer we see the Trees





63
flower, flourish and are full of Sap. In the Winter
their leaves fall of; and every part appears collapsed
probably from the difference of heat: on the other hand 
there are evergreens which are always flourishing 
so it appears that the Sap vessels of the Vegetables have some 
action of their own independent of capillary attraction. 
Electricity has also been said to promote the 
growth of Vegetables, if not too powerfully applied. 
Some have endeavoured to comprehend the matter 
by saying that Chyle was carried on as far as 
the first pair of Valves, (for all the Lacteals that 
absorb Chyle have numerous vessels) by capillary 
attraction, and that power inherent in the Intestines
propelled it forwards. Haller was of 
this opinion. From the situation of the Lacteals
it has also been supposed that the Circulation of 
the Chyle, might be assisted by the neighbouring 
parts. The Lacteals ramify on the Internal part
of the Intestine, forming a kind of network, they 
then pass thro’ the Intestine, and do the same on 
the outer Coat. The restriction made on the Lacteals
by the Peristaltic motion of the Intestines, may facilitate 
the passage of the Chyle. It may be said it
would repel the Chyle into the Intestines, but 
whenever pressure is made on Vessels that have values 
their contents musts be progressive. Some have 




64
thought that the Mesenteric Arteries from their 
contiguity to the Lacteal, might assist in the 
same way, by their  pulsating action, but this 
assistance must be very trifling if any. That the 
Lacteals are Irritable and have a contractile 
power, is evident from experiments. If you open
a living Animal when the Lacteals contain Chyle
and by pressing on them, preventing any visa teyo 
The Chyle will be forwarded, and if a Stimulus 
be applied that motion will be increased. If the 
absorption of Chyle was entirely performed on the 
principles of capillary attraction, it would continue
after Death which is certainly not the case.
We must therefore look for some way, which is dependent
on Life: this appears to be no other than
the contractions of the absorbents and which seems 
to be performed in the same manner as a Leech sucks
Blood. The pressure of Chyle seems to stimulate
the Villi, and opens their pores: these by contraction
take in a portion of Chyle, which by a similar contraction 
is propelled. The Mouth or Pore then 
contracts again, and includes another portion,
which is forwarded in the same way. After it has been 
taken up by the Lacteals it is conveyed to the Mesentery 
the Glands of which answer to the Lacteals, as
Lymphatic Glands do to the other absorbent vessels. 




65
Before the Lacteal enters the Glands it divides into 
three or four branches, which end in separate Cells 
in the Gland. On the opposite side of the Gland the same
number of branches are observed to come out of it, and 
these join and form a single vessel. The branches 
which enter the Gland are called vasa deferentia, and
those passing out vasa efferentia. These Glands seem
to affect or perfect assimilation of the Chyle, for they 
are vascular, and formed to secrete, their structure
is cellular, and not made up of a convolution 
of vessels, as may be proved by injection. Probably the 
Arteries of these Glands deposit something which mixing
with the Chyle, prepares it for being carried into 
the Blood: and make it more fit for the purposes of 
Life. Glands are formed in great numbers, where
there are Lacteals, and particularly where these vessels
arise from small Intestines; they are much more
numerous where Lymphatic Glands pass. In Children 
the Mesenteric Glands are much larger than
in Adult, viz in proportion to their size, and it is 
known that they require more nutriment to support 
their growth. In many people they are very small,
and when these Glands are diseased which not infrequently
happens, especially in Children, Nutrition is very badly performed,
tho’ the appetite is good: this indeed may arise 
from mechanical obstruction, but more probably  




66
from the diseased state of the Gland. Mr Flewson supposed
that they assisted in forming the red particules of Blood, 
but we find that Turtles have but two Mesenteric Glands,
and yet a good deal of red blood. When the Lacteals have 
passed thro’ the Glands they become larger, which has given 
rise to division of them, into the vasa Lacteal, primi et
secondi generis. These unite to form larger vessels, which 
again unite about the first Lumbar Vertebrae, to form one 
large trunk called the Thoratic Duct. That part where the 
Lacteals enter into it is larger than the other, and is called 
recepticulum Chyli. The Thoratic Duct passes on to the left
side the Spine, between the Vena Azygos, and the Aorta
and is continued down under the Aorta: at the curvature
of the lower part of the Neck, it takes a turn downwards
and enters the Subclavian Vein, at its junction with the 
internal Jugular Vein. When we consider the great number 
of Lymphatics and compare their proportionate bulk, it 
seems hardly possible that all the fluid they take up should
be conveyed by it. This has led some to suppose there must be 
some other way, for the termination of the Lymphatics into
the Blood vessels, besides that of Thoratic Duct; such a
way however cannot be found. I have indeed found that
the Absorbents of the Heart pass at once into red veins, without
going thro’ the course of the Thoratic Duct and I 
have seen the same with respect to those of the Stomach
but these are not sufficient facts, on which we are to 





67
build any expectation of consequence. The proportionate 
smallness of the Duct may be accounted for in equal manner 
from absorption not going on, in any part of the body at the same
time. Those who suppose the Thoratic Duct is not the only 
way from the Lymphatics into the Blood, make this further
objection, that sometimes the Duct is obliterated in one part
without producing emaciation. Dr Chester met with a case 
of this kind, but when such obstructions are met with, it 
is found that there is a communication between the upper 
and lower part of the Duct by means of Collateral branches.
If an obstruction be formed near the entrance of the Duct
Into the subclavian Vein, it would give a great probability 
to such an opinion. I endeavoured to irritate 
such an obstruction by a Ligature, upon the Thoratic
Duct, of a dog, and Animal did not die from want 
of nourishment. Dr Munro could never make the experiment
without killing the Dog, and hence in this case I 
cannot draw a satisfactory conclusion; but altho’ I cannot
speak confidently in this instance, I can as to the termination 
of the absorbents into red veins, as before mentioned. 
This last fact may perhaps explain the speedy increase
of Urine, so soon after the fluid is taken into the Stomach from
its getting by red veins into the Circulation, and so conveyed
in a more direct manner into the Kidneys whose office is to 
secrete Urine from the Blood, than if this fluid had undergone
the process and the course of the Chyle. 




68
On the Peristaltic Motion of the
Intestines
We find the same connection between the Chylification
and Muscular power, as between Digestion,
and the Muscular power of the Stomach. Carnivorous
Animals assimilate their food, much sooner
than the Herbivorous, and have stronger Muscular 
fibres in their Intestines, and more strength, hence 
in those the excrementions maker is sooner expelled,
while in the Herbivorous the Circulation is slower
thro’ the Intestines, and more time is allowed for 
Chylification. The action of the Intestines in expelling
the feculent matter is called Peristaltic motion 
or action. This is difficult to describe to those who 
have never seen it, but it is not unlike the motions
of a Worm creeping along the Earth. It consists 
in a shortening and contracting of the Intestines, 
which begins at one part, and is progresive, 
and then begin at the same part it before
terminated at, and in this way extends thro’ the whole.
We can have no Idea of the gravity of the Intestines
assisting in their expulsion, the contraction of the Intestine
being so very numerous. The structure of 
the Intestine confirms the Idea, that they have two
motions, there being fibres in a longitudinal 
and circular direction, of which the latter are the
 




69
strongest. When the longitudinal fibres overact 
it causes an intussusception. The Intestines are
extremely irritable and their functions seem to 
go on longer than any part. Though their  Irritability
is very great yet it is probable they have 
but few Nerves, these not being necessary from
the will not having any power over them. Some
have denied their having any Nerves, but this
is certain that if you kill an Animal, and open 
it immediately, the Peristaltic Motion will
be clearly seen. The Irritability of the Intestines
may be greatly diminished by the application of 
cold. In making an Experiment upon the spleen 
of a Dog, I observed that part of the Intestine had
escaped from the abdomen, and the Peristaltic motion
had ceased from the exposure of it to the cold. 
Heat on the contrary will restore the motion. Opium
also diminishes the irritability of the Intestines
as likewise do the Astringent Medicines. The 
Irritability may be, as we before said, increased 
by Heat, and by presence of food. These Stimulate
the Intestines, hence a moderate degree of flatulency 
in the Intestine may be useful, or rather
necessary; but if there is too much Griping it produced,
by the Intestines being Stimulated, by over
Distension or by the violent contraction. Bile is 




70
the Natural Cathartic, and in jaundice there is a 
natural deficiency of Bile, and hence you have white 
Stools, and Costiveness, and again when there is too great a
Quantity Diarrhea is produced. Drastic purges act by determining 
a quantity of fluid to the surface of the Intestines, 
by stimulating the Glands, and thus producing an increased 
secretion, and in consequence the Peristaltic motion is increased. 
It was mentioned that the actions of the Intestines
might also be promoted by sympathy. In some 
Animal the Peristaltic motion of the Intestines is very 
weak and languid, and hence they are very difficult 
to be purged. It may arise in part from the thinness
of the Muscular fibres, and partly from the lenth of the 
Intestinal Canal. There is a difference in the Human
Subject with respect to the Torpidity of the Intestines. 
Some causes have a tendency to diminish motion 
among these are Opium and Astringents. Injuries
and Compression of the Spinal marrow may interrupt
the Intestinal Canal, when they happen low down.
The Sympathetic Nerve principally supplies the 
Intestines, and the lower down the Spine is Injured, 
the more likely is this Nerve to be affected, hence the disease 
will take place more or less, according to the situation
of the part Injured: and this confirms the
existence of Nerves upon the part. The retaining 
power of the Intestines may be diminished by the




71
Sphincter Ani losing its elasticity for after Death the size 
of the Sphincter Ani returns to its usual dimensions 
and hence its actions are different to Muscular Motion. 
Mechanical pressure, as in the strangulated Hernia 
may produce an inverted Peristaltic motion, and the 
same effect may succeed to Inflammation arising
from other causes this is followed by Vomiting, and often
the contents of the Intestines which have a stercorareous
smell and appearance. It has been said that the 
contents of the Intestine have often been Vomited in 
Strangulated Hernia, but these cannot with propriety
be called Faeces, until they have entered the large Intestines
and it will be presently shown that the contents of them 
cannot be regurgitated into the small Intestines. An
inverted Peristaltic Motion and its consequences may be 
produced by Malconformation. I have seen a small 
Intestines terminate in a blunt end, there being a 
space between the ending of one Intestine, and the beginning 
of another. When Bile is Vomited, it is brought 
up by an inverted Peristaltic Motion of the Duodenum.
When the remains of the food have been passed through
the small Intestines, in which it may be said that 
all the nutrient Principle is extracted they are propelled
into the large one, and are then called Faces. 
At the end of the small Intestines where they enter into
the large ones, there is a valve so constructed as to prevent
 




72
the faces from regurgitating. It has been a question
and is still one of no small importance to be discussed
how far nutrient substances thrown into 
the large Intestines, would nourish the machine?
Absorbents arise in great abundance in the large Intestines,
but what is taken up by them, cannot have gone
thro’ any assimilating process, I am therefore of opinion
that Life may be protracted for a while, but the Nutrient
matter not been assimilated, the patient must at 
length die from exhaustion. When the Faces have passed thro’
the small Intestines they must necessarily be discharged
as members of Society, it is necessary it should be done 
at particular times, and to retain the Faces until 
there is a convenient time for discharging them. There 
are at the extremity of the Rectum, a number of strong 
Muscular fibres, forming the Sphincter Ani, these may 
be said to have three powers, Elastic, Contractile and Tonic
powers. It is by its Tonic power that the Sphincter Ani
retains the Faces, in common without exertion. When the
muscles which assist in the expulsion of the Faces, as those of the 
Abdomen and Rectum above the Sphincter Ani, overcome
its Tonic and contractile power, and thereby cause a discharge
of them. Its elastic power is then necessary by which it is brought
back to its original state; In horse the rectum is inverted by discharging
the Faces, but is directly drawn up afterwards, This is 
not the case in Man if the parts are in an healthy state.	







73
ON THE SPLEEN.
We have finished what was to be said on  Digestion and Chylification,
But after food is Digested, there is usually some intervening 
time before more  food is taken in; during this time it
is natural to suppose that the Gastric juice is up plentiful
than when food is in the Stomach. It is a law in the Animal [A?nomy]
that Organs secrete in proportion to the Blood sent to 
them. We are now to consider how far the Spleen assists in determining 
Blood to the Stomach during Digestion, and thereby
promotes its secretions. The Spleen is an oblong body six 
inches in length, three or four in breadth and one or two in 
thickness, and is situated near the Stomach. It differs in shape
in different Animals. It is of an irregular form in Dogs, flat
and thin in Calves, and Globular in Birds hence whatever
be its use, it cannot depend upon its figure: the size is also 
various, I have known one weigh only an ounce, whilst 
others have weighed a pound or more, and this without any 
appearance of Disease; the general weight is about eight 
ounces. The colour in Infant is lighter than in Adults from 
the difference in the balance of the Circulation in the Arterial 
and Veinous system, there being most of the former in all
young people. The Spleen is not perfectly oblong but rather
of an oval figure, having one side convex, the other concave.
It is situated in the left hypochondria region, the convex 
Surface is turned towards the Diaphragm, and confined 




74
there by the reflection of the Peritoneum, whilst its concave
part is resting on the left extremity of the Stomach, hence the
Stomach always presses in some degree against the Spleen
but naturally in a much greater degree when full. The 
Spleen is very Vascular being supplied by a branch of the
Celiac and Splenic Arteries: the celiac is a short turn to 
arising from the Aorta, soon after it has entered the Abdomen
it then divides into three branches, Hepatic, Splenic, and 
Coronary before the Splenic arrives at the Spleen it gives off
some branches to the Pancreas and to the Stomach: those
going to the Stomach are one large one called Gastricadextia 
which goes to the right extremity, and greater curvature of the 
Stomach, and several smaller ones call vasa brevier, 
which ramify on the left extremity of the Stomach. Before 
the Splenic Artery enters the Spleen, it divides into a number
of branches, and they are large in proportion to the Spleen
if you inject by Arteries they terminate for minutely in
cells for the injection to pass but if you inject by the Veins,
the injection appears to become a mass, having a granulated 
appearance and retaining the shape of the Spleen. The Spleen
is at all times tender, and if great care is not taken the Veins
will be ruptured, but this granulated appearance when it is 
injected in the most careful manner is very different to the 
confused mass caused by the rupture of the Vessels. How is it 
that the Cells of the Spleen are completely filled by the Veins
and not by the Arteries? The ramification of the Arteries




75
as before hinted, are so much more minute, as not to admit
the warm injection used, for corroded preparations. But the 
orifices of the Veins arising from the Cells are so large that 
even common injection will pervade them. The Cells however
may be filled by the Arteries by a fine injection. No one doubts
the Spleen being Cellular, but the way many Anatomist have 
taken to prove this has in general been very unsatisfactory
They have after working the Blood out of it, distended it with 
air, and then made a section of it. Now almost every part
may in this way be made to appear Cellular: the most satisfactory 
manner is to inject carefully and afterwards
destroy the substance of the Spleen by corrosion. The more
clearly to prove the substance of the Spleen.  I had recourse to 
the following experiment. I made a small opening into the 
abdomen of a Dog, so as to let the Spleen hang out, when done
I could distinguish the Artery and Vein by their colour, I 
made a Ligature on the Vein, and the Spleen was increased
to about three times its Natural size: had this distension 
taken place merely from an enlargement of the Blood vessels,
it must have been in a gradual manner. The Vein
which returns the Blood from the Spleen empties itself
into the Vena Portarum, which carries Blood into the 
Liver for the Secretion of Bile. The Spleen is supplied
with numerous Absorbents, but they are not so evident 
in the Human subject as in some Animals. A proportionate
number of Nerves also and those entering round 
 





76
the Splenic Artery called the Splenic Plexus here there are 
all the parts constituting a Gland except an excretory 
Duct, which as yet has not been formed. Having premised so 
much with respect to the figure and structure of the Spleen
we come now to consider its uses: we see it supplied with 
a quantity of Blood equal to any Gland of the same size
but if it performed the act of secretion it must have an excretory 
Duct. Anatomists have puzzled themselves much 
to find out one, but have not been successful the use of this 
Organ has given rise to various opinions; some have been
so absurd as to suppose it had no use at all; others say
it is to supply the Liver with Blood, and so it does, but
it is highly probable it has something else to do, some other
function of a more important nature, for tho’ it is only
a quarter the size of the Liver, its Artery is larger. Some 
opinions on the use of the Spleen are so improbable and 
ridiculous that we shall barely mention them. It has 
been said by some to be a balance to the Liver, by others
the seat of Laughter, and others again say that of melancholy.
The ancients thought that Bile was prepared by 
the Spleen. Their ideas are too wild to require a refutation,
but the Moderns have delivered an opinion that 
requires more attention; amongst these is that of Mr Thewson 
he had particularly turned his attention to the red particles
of the Blood, which he examined very accurately with a
microscope, he found their shape was nearly flat. From  




77
the particular structure of the red particles he conceived
there must be an Organ for making them, and he wishes 
to make those Organs, whose uses were unknown subservient
to this office: he says that the central part of 
the red particles is formed by the Thymus Gland and the 
Vascular part by the Spleen. To prove that the Spleen performed 
this office, he examined the Blood going to it, and 
some which had passed thro’ it, he found that before it 
enter, the red particle had only Central part,
but after they had passed thro’, they were complete.
I examined the Blood under these circumstances,
but could not find any difference. Mr Hewson 
said that the Blood in passing thro’ lost its coagulating 
part, and that it goes to form the Vascular
part of the red particles. Haller says, that the Veinous
Blood of the Spleen does not coagulate. I collected an 
ounce of the Splenic veinous Blood, and found it to coagulate.
Dr Munro has investigated this opinion, and 
endeavoured to refute it: he observed that the size of 
the Spleen is not disproportionate to the quantity of 
red Blood, and yet they have very few red particles of 
Blood. But he principally thought he refuted Mr 
Hewsons opinion in discovering the Cells in which
the red particles were found to be. The large Cells of the 
Spleen were less than the red particles; but it is evident 
he never made use of a microscope. The present general 






78
opinion of the use of the Spleen, is that it is subservient 
to the Liver, in the secretion of the Bile. Haller says
very truly that the Blood circulating thro’ the Spleen
goes to the Vena Porta, and from thence to the Liver, but 
Blood is circulated thro’ the Stomach Pancreas, Omerteum, 
Intestines &c. and does the same but we do say
are those Viscera only auxiliaries to the Liver? Certainly
not, why then should it be said its use is to assist
in the formation of the Bile. Some say that Blood in 
its passage thro’ the Spleen undergoes a change to fit
it for the Secretion of Bile. We are told of several attractions
of this kind; Haller says it is alkalescent 
It is an Idea that Bile is a putrescent fluid and that 
alkalescents are susceptible of putrescency. Neither
of these appears to be the fact. I took Blood from the Splenic
vein, but could find no alkalescent properties, by 
the usual tests. If Bile and Blood be separately exposed
to air, the Bile first becomes putrid, again it
has been said that Blood circulates thro’ the Spleen
so slowly to render it putrescent. I took Blood 
from the Splenic and jugular Vein, and placed it in a 
temperature of 50° for a day, but no alteration took
place. The next day placing them in a temperature of 
90°, but still they were but little altered; on the third
Day putrefaction was observable in both alike. It seems
then that putrefaction was ten Days before it took place




79
further that the Blood is not more than two minutes
circulating thro’ the Spleen, nor ever under half a 
minute. I proved this by tying it and then puncturing 
it, and observing often what time the vessel regaind
its usual size. Other have said that the Splenic Blood 
is more fluid therefore more fitting for diluting; but how 
is the Blood rendered more fluid? Does the Spleen take from 
it, its coagulating part? Or does it add more serosity 
to bring about dilution. This great fluidity does 
not however exist. To ascertain this I took away some
Blood from the Spleen, and some which had not passed
thro’ it, and examining the Serum of each, with its 
Crassamentum, I found the comparative part of each
nearly the same, and similar to Blood drawn from 
any other Organ. In the Arterial Blood, the Serum in
weight was to the Crassamentum, as 445 to 1000. I also
examined the Blood that had passed thro’ the Spleen, by 
chemical tests, and compared it with Blood taken from 
other parts, but found no difference from these experiments
I do not hesitate to say that Splenic Blood 
has no properties that can assist it in the secretion of 
the Liver. Ought not that Secretion to be different, supposing
the Spleen was necessary for the Secretion of the
Liver, if the Spleen was removed? But from experiment
and Chemical tests it is not found to be so. I took out the 
Spleen of a Dog, at first he appeared emaciated, but afterwards




80
afterwards he took food moderately well, and seemed to be
nourished as well as formerly. In about two months I 
strangled him, and another Dog at the same time whose
Spleen had not been removed Bile was taken from both
and carefully examined, but no difference was found, and 
to be more accurate I procured the assistance of Dr Babington 
whose skill in Chemistry need no praise from me. 
Hence the Spleen does not seem necessary to Biliary 
Secretion. But some say the Secretion is not altered, 
yet the quantity is, Mr Coleman took the Spleen from
a Dog and found he was costive for some Days, and this 
was supposed to prove that the Secretion of Bile was diminished. 
I tried the same Experiment and the Dog
had Diarrhea so that Costiveness seems to be only
accidental. At the battle of Deblingan a soldier had 
his side pierced with a Bayonet, he laid during 
the Night on the Ground, and when discovered in the Morning
the Spleen was hanging out of his side, and was do much 
enlarged, that the Surgeon thought proper not to return 
it, but removed it; no inconvenience was afterwards
found in the Animal functions, hence Mr Cline supposes 
it to be an Organ of convenience rather than of 
necessity. Many of those who think the Bile assists the 
process of Chylification, think that the Spleen assist in the 
following manner; when the Stomach is distended it presses
on the Spleen and accelerates the circulation thro’ it 






81
and a greater quantity of Blood being thus sent to the Liver, a 
greater quantity of Bile is secreted. Haller was of this opinion but I
from Experiment have found the contrary to be the case. It is necessary
to see what effect the pressure of the Stomach can have on the 
Spleen while in the body; but I endeavored to take it out of 
the body. I let out the Spleen of a Dog, and then made a Ligature 
on the Vein. I punctured it between the Ligature and the Spleen, this 
being done I pressed the Spleen in different degrees, and invariably 
found the Circulation impeded, after the first gush occasioned
by the Ligature was over. The fact then on which this opinion 
was formed seems to have no foundation, for pressure we see
retards the Circulation. From the knowledge of the fact I was 
led to theorize, and the conclusion I drew was as follows: It is
clear that if the Blood does not flow with freedom thro’ the Spleen
when pressed upon by the Stomach, it must pass in greater quantities
given off before it enters that Organ, viz into the Stomach and Pancreas
It is equally clear that the Stomach when distended must make more 
or less pressure on the Spleen, and that as the food is Digested. The Stomach
being less distended, the pressure will be lessened also. When 
the Stomach is most distended with food, there is the greatest
occasion for Gastric Juice. It was before shown that the pressure
on the Spleen by impeding the Circulations would necessarily determine 
more Blood to the Stomach so that its secretion would 
be increased. When also the Spleen has been removed, the Arteries
passing from the Stomach to the Pancreas have become less. It
was before observed that the Dog whose Spleen was removed,




82
become emaciated tho’ well fed, but whether this arise from any Assimilation
I do not know. In another Dog the experiment was 
made and emaciation continued only a short time. Now from 
what has been said, I am inclined to believe that the use of 
the Spleen is to assist in Digestion by determining more Blood 
to the Stomach, when distended with food, and thereby increasing 
its Secretion. I do not offer this as a theory not exposed to 
objection, but it appears to me more probable than any I am 
acquainted with. If this theory be founded on facts, there must 
be certain things which take place in all Animals, but 
when the Stomach is distended it should press upon the Spleen
that the Spleen is compressible, and in consequence more blood
is determined to the Stomach, I have made experiments to 
prove, and as far as I have examined I have found them to 
answer, but at present I have not sufficient tests to adduce 
in support of them. It also yet remains to be inquired, 
whether, or not, in all Animals, the Spleen be situated so as
to be compressed by the Stomach. Whether the Vessels ramify 
in that Viscus, in the way already mentioned, and whether 
the structure of it be such as to favour these circumstances
this would lead to an extensive inquiry, and would weaken
or confirm my opinion. Perhaps the use of the Spleen 
will never be well marked for as the Animals live either
with or without it, it seems to be rather an Organ of 
convenience than an Organ of necessity.





83
ON THE OECONOMY AND PROPERTIES OF THE 
Blood. 
By the Blood we mean that fluid circulating though the
Arteries and Veins, and propelled by the Heart. In Man
Quadrupeds &c we know that this fluid is of a red color,
and hence we are to consider this colour as essential to the 
Blood. The Blood in Lobsters is colorless like Water, and in
many Insects as the Caterpillar; whilst others have Blood
that is Green. When Blood is drawn from the Body, it 
appears an Homogeneous mass, bur soon after it loses its
fluidity and coagulates, and from this coagulation water
is effused. Thus the Blood divides into two parts, the solid
Blood called Crassamentum, and the fluid Serum. But 
are there not other parts in the Blood? If you expose the fluid
to heat, it will coagulate, and from this you may squeeze 
water, which by a great Physiologist was called its Serosity.
In the same manner the Crassamentum may be separated
into two parts, one of which is whiteish and solid, the other 
red. The white part which is separated from the Crassamentum
is called the Coagulable lymph, and the remaining red
parts, the red particles, the former being separated from the 
latter by ablution, hence there are four parts composing 
the Blood. Other substances as Neutral Salts, are occasionally 
found in the Blood, but we do not consider them as constituent
and grand parts. In different people, these four, differ much
in their proportion, and even in the same person, at different 





84
different times. In a strong man there is great solidity; in a
weak man, there is more water, and even the Crassamentum is 
of a lower texture. In females labouring under Chlorosis 
there is a very small proportion of red particles, and when Venesection
was performed so white was the Blood that it gave
no colour, to a white body immersed in it, after making
these general observations that the Blood is composed of different 
parts, we will now consider it in the aggregate and 
first what is the relative quantity of Blood in the system? Various have 
been the opinions on this subject. It would seem easy to ascertain
this by Bleeding Animals to Death, and then weighing
the Blood and the Animal afterwards; but this is not 
accurate for Animals die before their Blood is all lost;
and a great deal depends on the manner in which the Blood 
is taken away. Great quantities have been taken away in 
a gradual manner without endangering life, but if we
take a small quantity from the Aorta or any large vessel,
the Animal will die. A Man had aneurism which 
suddenly burst, and one pound of Blood was lost, and he 
presently died, and yet we take several pounds from other 
parts without danger, hence taking Blood from a living 
Animal will not lead to a relative knowledge of the 
quantity in the system. The result of Experiments of this 
kind fully prove this, for while some have said that the 
Blood is in proportion, as one to ten, others have said it is 
as one to twenty. While circulating thro’ the body the 





85
Blood is fluid, but if from the rupture of a Vessel it be extravasated
it soon loses its fluidy, while yet in the vessels, 
and becomes solid, as is the case in Aneurism; and this 
change takes place in consequence of its being nearly in a 
state of rest. In these tumors the Blood may circulate 
thro’ the direct line of the Vessels, but in the side extended
it becomes collected. It seems therefore that rest produces
coagulation. This is an important fact in the art of Surgery 
we may often avail ourselves of it in assisting nature in 
the stoppage of hemorrhage. Mr Bell says it is done by 
the contraction of the mouth of the Vessels, and this is natural
enough to suppose but from experiments I am 
convinced it is stopped by a consolidation of the Blood
itself. I opened the Cural Artery of a Dog, and it Bleed for a
short time, and then ceased forming a small tumor,
on Examination I found the Coagulation had extended
to the extremity of the Vessel, and pulled it up; but the mouth of
the Vessel was not at all contracted. The resources of nature in 
a Dog are surprisingly superior to what they are in the
Human subject, as the latter would have died under 
the experiment. The surgeon assists nature in the stoppage 
of Hemorrhage, either by Ligature or by Styptics; suppose 
a ligature to be made on a bleeding Vessel, in a few days
it is removed, but no Bleeding follows; what is the cause 
of this? Is it from the pressure of the sides of the Artery against
each other, by the pressure of the Ligature? It is  






86
true the Ligature obliterates the cavity of the Vessel
as long as it is applied, but in a short time it
Ulcerates, and no bleeding follows. If we examine
an Artery after it has been thus tied, we find that 
nature acts in the same way, as when no Ligature
is made, we find a coagulum of Blood, just above  
the Ligature, formed in the same way as in the Femoral 
Artery of the Dog. Now it seems that the
Ligature prevented the Blood from flowing at first
And the keeping it in a state of rest produced the 
Coagulation: which naturally plugged up the
Vessel; hence it appears that the Ligature may 
be removed after a certain time, without danger,
when sufficient has been allowed for coagulation to
take place. It sometimes happens that Hemorrhage 
does take place, although the Ligature may 
not be removed- now I ask the question, from 
what causes does this take place? Is it from the 
imperfect tying of the Vessel, or from the new
Coagulation of the Blood? It is very probable
that the Ligature has been made rather too tight 
so as to cut through the vessel, or at least to induce
a very speedy Ulceration of it. This suggest the 
propriety of making Ligatures with the atmost
caution, and using such as are broad and flat
for they do not then cu through or Ulcerate the




87
Vessel, so readily. The coagulum sometimes after
adheres to the Vessel, and even becomes organized
so as to be capable of being easily Injected. From 
what has been said it appears that a state of quiescence 
is certainly the most favourable for 
coagulation, and on the other hand a state of motion
and action tends most to pressure its fluidity.
A very little motion indeed seems to be
required to preserve its fluidity, as we see from
[from] the Circulation being kept up in Torpid Animals.
We ought to be cautious in the choice of 
vessels on which we make Ligatures, as we cannot  
with propriety make one on a Vessel, at a part
where another Vessel, is given off. Suppose there was
an Aneurism situated high up the Thigh, and 
a Ligature was made on the femoral Artery first
where the Profunda is given off; when the Ligature
Ulcerated away, an hemorrhage would come on 
and they would Die in consequence of it. A case of 
this kind happened some time since, A patient
was admitted into an Hospital with Bronchocele. 
The Surgeon thought that if the Blood 
could be intercepted which was going to the Tumor, 
he could cure the Disease; he accordingly dissected 
through the Hermo Mastoid Muscle, and made a
Ligature on the superior Guttural Artery, which  




88
is going to the Thyroid Gland, near whence its given
off, by the external Carotid, and he intended if this 
had succeeded to go on in the same way on the other
side. The Blood however constantly flowing through
the Vessels prevented a formation of a coagulum, where
the Ligature was made, and Ulceration taking place 
in the Vessel, Hemorrhage came on, and the patient
died. It happens often in Scorbutic habits that
though the Vessels be tied with the greatest care, that 
Hemorrhage will ensue, after some distance of time 
from the operation; this depends upon the Debilitated 
state of the Constitution. If a Ligature does not ulcerate 
off, until from ten to twelve days, we may safely 
say that the Surgeon has done his duty. But if 
an Hemorrhage was to take place in a day or two, after
the operation, we may conclude that the Ligature was 
improperly made. In a Scorbutic habit, if the hemorrhage 
ceases, we may perhaps prevent its return, 
by Nutrient Diet, Pork, &c. which give to the Blood, a disposition
to Solidity. But what are the powers and resources 
here of Nature? More credit has been given to 
Styptics than they deserve in my opinion, and we
should endeavour to know the power of each. In this 
respect we have always seen the resources of nature in 
checking the Hemorrhage, but we do not know so well
the powers and operations of Styptics



89
On Coagulation.
Mr Hewson made many Experiments, to ascertain whether
a transition from heat to cold, did not produce 
Coagulation, or at least promote it. He laid bare the 
Jugular Vein of a Rabbit, and made a Ligature upon
it, and then took out a part of it, containing Blood, and put
it into a freezing mixture: when taken out of the mixture
he found it not Coagulated, but it presently became
so after exposure to the Air: from this he was led to suppose
that the Air and Cold Coagulted Blood. Mr Hey
also took away Blood into two cups, one of which he put
into warm water at the temperature of 95° and exposed
the other to the atmosphere, at the temperature of 56°.
The cup which he put into the warm water had its 
Blood first coagulated, and hence he thought cold had 
no power in producing this effect. He also laid bare the 
Jugular Vein of a Rabbit and made three Ligatures
upon it, at an inch distance from each other; he then punctured
one of the portions of the Vessel, between the Ligatures,
after which he united the middle Ligature, so
that the Air might come in contact with the Blood contained
between the Ligatures, and he said that the blood 
coagulated in a short time. I also laid bare the Jugular 
Vein of a Dog and introducing Air, found it to lie on the 
surface, and not to mix with the Blood, and in half 




90
an hour the Blood was as fluid as it was at first,
hence the conclusion I draw is different from Mr Hey.
I know besides that Air is mixed with the Blood in the 
circulation, and produces no coagulation of it Mr Hewson
observed that Blood did not coagulate so readily 
at one time as at another, and likewise that the weaker
the Animal the sooner coagulation took place. This 
if it be true is of importance in Surgery, and would 
lead us in case of Hemorrhage to promote Syncope.
But Mr Hey has made experiments which seem to 
contradict Mr Hewson, he attended the slaughter of 
Sheep, and caught blood in three different vessels.
In the first directly after the knife had been plunged in. In the 
second a little time after, and in the third just as the Animal expired. 
He found that the Blood in the first cup coagulated soonest,
Or when the Arterial Action was strongest, that it separated 
the largest portions of Serum, and exactly the contrary
took place with regard to the Blood in the last cup. I have 
not yet repeated these Experiments myself. In making them
the Animal dies so soon that the Blood has no time to undergo
any material change. Now the better way would be to 
take an ounce of Blood from the Jugular Vein, when the Animal
is in health, and then suffering it to flow, take more afterwards
in about half an hour, and a third quantity at a still
greater distance, and then observe the respective time they both
would coagulate in. Under Inflammation the Blood is 




91
subject to great changes, and becomes more fluid, and assume
a buffy colour, from the red particles falling to the bottom in 
consequence of its slow coagulation. Mr Hewson endeavoured   
to ascertain the cause of this fluidity, he thought the Blood was
alternated by the action of these vessels; but the question is whether
it be alternated or diluted, that is, possessing more water. 
To ascertain this Mr Hey make Experiments on the Inflamed Blood
and found more water to separate from the Buff Blood, than 
any other, and hence he supposed that it was diluted, and not 
alternated. The change taking place in the Blood while circulating 
thro’ Inflamed Vessels deserves notice. Sometimes the change
is slow and gradual at other times sudden. Let us suppose the 
Pericardium the seat of Inflammation, if this at first be mild
it increases the liquid of the Pericardium, which is Secreted 
from the extreme vessels, but if it goes on with more violence,
we find a large thick crust, instead of this Secretion. Hence we 
find that mild Inflammation [pu???ed] out water, and that 
greater Inflammation gave coagulable Lymph: but sometimes
adhesions take place, from the great Inflammation
throwing out Lymph which afterwards becomes Vascular
this takes place in many parts, as in the Tunica Vaginalis 
tests. The Tunica Decidua which covers the Bourn, 
and retains it in its place in the Uterus, appears to be
nothing more than a coagulation of Lymph thrown out 
by the arteries of the Uterus. The Lungs are the most common 
seat of adhesion, which may either be partial 




92
or general, or confined to one Lung or extending to both. 
The older the adhesions the more extensive they become, and
the less inconvenience with respect to motion is experienced
from them; and they often assume the appearance of common 
membrane; but we find the Lymph in time becomes as Vascular as 
any other part; from the action of the Vessels of the 
neighboring parts, lengthening them and causing them to 
shoot thro’ the Lymph. This organization in the Lymph takes
place in a longer or shorter time, according to the extent 
of the Vascular surface in contact with it, and hence it must
take place in a short time in adhesions of the Lungs to 
the Pleura. I have known coagulable Lymph in this 
part organized in twenty four hours, as was found by injecting 
it. In the coagulable Lymph which plugs up
Ateries, in the stoppage of hemorrhage the progress 
of Vascularity is more tardy, from the extent of the 
Vascular surface lying in contact with the Blood, being 
less. Some say the consolidation of Lymph is slow
others that it is rapid, I think that the latter opinion 
is true. If a Vein be tied and exposed for a time
in that state it will Inflame, and the vasa vasorum 
throw out Lymph. If this Lymph was fluid it would 
be carried with the circulating fluid, but its being found
in Arteries and Veins would lead us to suppose that it consolidates,
as soon as effused. Mr Hunter had peculiar
opinions on the subject of the Blood, before he saw Vessels 





93
he said he saw Blood, and that is must exist of necessity before
vessels can be formed: but the principle by which it 
came from a solid to a fluid he said was its Life; though
at first he considered this change to be produced by the 
Stimulus of Death. Mr Hunter thought the Life of Blood 
favoured its coagulation, and that the union of living 
parts by Blood, was one proof of its Life. It was also
said to be vascular. When an inanimate substance is
not: but different opinions are held on the subject of Vascularity
of the Blood. It may it is said have a centre of 
ramifications though Mr Hunter once thought that
there was no proof of this, or it may become Vascular
by lying near Vascular parts. The Vessels being Stratum
super Stratum; but it is probably a passive medium
for Vessels to pass thro’. Another reason for the Life of
Blood was its disposition to solidity on its exposure, but 
we might as well say that saline matter was alive, because 
it crystallized. Again it was said to carry Life to 
every part of the Body, and if its course was interrupted
the part would die: but there is the same reason for food
to be alive. Not knowing the Essence of Life, we cannot 
speak of it with certainty in this Instance. Though it is 
probable it has something in it different from inanimate
matter The Blood being found fluid after Death, depends
upon the way in which Death takes place. If sudden there 
is not time for it to coagulate in hence it retains its

 




94
fluidity. A blow on the Stomach causing sudden death,
occasioned the Blood to be fluid. Mr Hunter also found it fluid 
in two instances hence he considered that the solids, dried first
and then the fluids. To ascertain whether this was the fact I 
struck down a rat by means of a large battery of electric fluid
passing the shock thro’ the head. I then opened the cavity of the abdomen,
and found the Inferior Cava to contain coagulated blood. 
I repeated the experiment on a larger scale, and with the same
Result: hence it appears that Mr Hunters opinion was not
Correct. The Blood supplies nourishment for the waste of 
the Machine. If a part be divided and then brought together
it will Unite and become vascular, thro’ the medium of the
Blood; but if not brought together it will Unite by the coagulable
Lymph, which is thrown out by the Inflammation
which ensues and the cut surface then being brought into
contact: this is called Union by the first intention and it 
may be said to be brought about by two modes, first by 
the Medium of the Blood itself, secondly by the Coagulable
Lymph. But there is a third mode, which is by Granulations.
This is performed by coagulable Lymph being thrown out and 
becoming Vascular. Also when a Bone is broken, the Vessels
are torn, they Inflame and throw out Lymph, and afterwards
a Calcareous or bony matter. Nerves and Tendons when divided 
Unite in the same manner, hence parts have the 
Power of assimilating Blood to their own substance some
Thing like Secretions. Dr Culler thought the Nerves, 





95
secreted a Nutrient principle, by which the parts were repaired.
Dr Morris thought that Union was produced by 
Means of Arteries and Blood. Parts having Life and strength 
in proportion to the quantity of Blood circulating in them
and have also the power of repairing injuries in proportion
to the Vigour of the Constitution. I proved this by the 
following experiments. I divided the Tendo Achilles of 
both Legs of a Dog, in one of which Legs the Artery had been
previously divided in that limb in which the Circulation
was free, the chasm made by the division of the Tendon 
was filled up in about a fortnight with a substance which afterwards
become tendinous. At the end of six weeks the 
Tendon of the other Leg was not united. I then killed the Animal
and examined both Legs. In that where the circulation 
was uninterrupted, I found that the Tendon completely 
formed, but in the Leg where the Artery had been divided
there was only a very small string, and that with difficulty 
preserved; from this experiment we see the Blood repairs 
injuries and that it may be present in a part insufficient 
quantities to support Life, tho’ not to form new
parts, for in latter case the Limb was preserved tho’ the
Tendon did not unite firmly. In a patient of Mr Clines
who had popliteal aneurism, the Artery was taken up 
and she had an Ulcer on her Leg at the same time, which 
as long as she lived showed no disposition to heal, this 
could not be impeded by any general weakness of the constitution 




96
constitution, for the Granulations in the wound made by the
operation, healed very soon. It could therefore only be owning 
to an interruption of the circulation caused by the Ligature
above. Now parts have vital power in proportion to the 
quantity of Blood circulating thro’ them. An injury done to a 
muscle is soon repaired, than for what one would be to the skin
or to a Tendon or a Ligament. As the power of repairing injuries
depends on the vigour of the circulation, it appears
that parts must posses this power in a greater or less degree,
in proportion as they are more or less distantly situated
from the source of circulation; hence Ulcers on 
the superior extremities heal more readily than those on 
inferior parts, from their being nearer the source of circulation.
Blood then is that fluid by which the injuries of the 
machine are repaired. Some have said that the Blood is merely
mechanical in the system, and circulates on the Hydraulic 
principles, and that any fluid circulating, will preserve 
Life as well as Blood. But from the experiments I have 
found this not to be the case. I opened the carotid Artery of a
Dog, and after he had lost a quantity of Blood, some Beer
was injected, I thought the Dog lived longer than if nothing 
had been substituted from the Blood, yet I am inclined 
to believe that this was merely fancy, for I made the experiment
and kept the Artery distended by injecting warm water, 
to supply the loss of blood, and could not observe that 
the Dog lived longer than might have been expected, if 





97
nothing had been injected. But though no other fluid will
answer for Blood; yet Blood taken from one Animal and 
conveyed into another will support Life. Dr Sower first 
introduced the practice into this country, about thirty 
years ago and which is called Transfusion. An Animal
has been bled almost to Death, and yet by transfusing
Blood has been restored. This has been frequently done.
I carried these experiments to a greater extent and found
them true, and found also that the Blood of different animals 
answered as well as the Blood from the same kind of Animals.
so completely of its Blood, that no Pulsation could 
be felt, and he was apparently Dead; but supplying 
him with Blood, contrary to the opinion of Mr 
Astley Cooper, he recovered. The experiment has been 
Made in France, and failed; this was probably from 
too great a quantity being introduced by which a 
Plethora was caused; but the abuse of a thing 
does not destroy the use of it. If may perhaps be 
advantageously employed to recover still born
fetuses, if had recourse to ten or fifteen minutes
after birth, and might be had recourse to, in subjects
who have died from a sudden loss of Blood. This appears
very probable, but prejudice will act against it.    




98
On the structure and 
OECONOMY OF THE HEART.
We have already considered the Nature Properties, and the 
importance of the Blood, but that the purposes of the Machine
be answered, it is necessary that the Blood shall be 
kept in constant motion. Hence we are led to consider the 
circulation of the Blood. If we open Vessels near the Heart,
and others at a distance from it, we shall find that the velocity 
of the Blood is greater the nearer it is to the Heart,
and diminishing in proportion to the distance from it: from 
this it appears that the Heart is the principal Organ, concerned 
in the circulation. We shall therefore premise 
something with respect to this organ, viz the structure of
it before we speak of the Circulation: we may define it 
a muscular cavity receiving vessels to propel and return 
the Blood. The Heart of Human subjects Quadrupeds 
and most Birds, have four Cavities, others as the Amphibious 
Animals, have three Cavities, Fish only two, and 
Oysters only one Cavity. The Leech and many Animals
have no Heart in them; there is a cavity for receiving 
the Blood by of one end of which it is taken in, and the other carried
out. The fluids in these Insects are carried and 
deposited from a kind of absorbent Vessel in the Stomach, 
and as we do not know how they are returned, we cannot 
speak of their Circulation. The Heart is situated in the 
Cavity of the Thorax, and is contained in the Pericardium 




99
It is chiefly retained in its situation by the reflection of the 
Pleura, which forms the Mediastinum; and is fixed also at
its base by the Vessels going from it. The Heart is placed somewhat 
obliquely; the base being the superior part and lying 
towards the right side and the apex the inferior part, and lying
towards the left side. The pulsatory motion is felt during 
the Systole or Contraction of the Heart between the fifth and 
sixth rib, from the auricles being distended forcibly and
from their situation at the basis. The apex is pushed forwards
the figure of the Human Heart is different from that of other
Animals, tho’ the situation and economy are the same. In 
Man the Heart is nearly of a conical form, but flat on one
side: in Brutes it is still more conical this difference is owning 
to the peculiar form of the Chest. In Man a line drawn
from Sternum to the Spine, is shorter than one drawn from 
side to side; and this structure confines the Heart, and it 
acquires a flatness on one of its sides. In Brutes it is the reverse
which gives room to the Heart and admits of its being more conical, 
as the Heart is the principal organ of circulation, it 
must have large vessels communicating with it, all of which 
communicate with the Heart at its base. The Human Heart 
itself is composed of four Cavities, two of which are called
Ventricles, the other two the Auricles. The Vessels communicating 
with the Auricles are Veins, and those with the Ventricles 
are Arteries. The Veins entering the Auricles are six in number
the two Cava entering the right, and the four Pulmonary  




100
the left Auricle. The Arteries only communicate with the Ventricles, 
the Pulmonary with the right, and Aorta with the left. The 
Veins bring Blood from the Arteries to the Auricles, and the Arteries
carry it from the Ventricles. If we consider the structure
of the Heart we shall see that this must be the case: it is an 
organ Muscular and Irritable in every part, but not equally 
so. There is also some difference in the capacity of the two sides
of the Heart, and  of course there must be a difference in the sizes 
of the vessels going from each. The Auricles are much thinner 
and less Muscular than the Ventricles, and the right Ventricles
less Muscular that the left. It may be asked why there is this 
difference? It seems a Law of the Animal Oeconomy that no part
shall be furnished with more of anything than is necessary for 
the discharge of its functions. The Auricles when distended with 
Blood by their contraction, force the Blood into the Ventricles
and as these be near, very little force is necessary, again the right
Ventricle being distended with Blood has to send it to the 
Lungs, the distance in this case is much greater; therefore more
Force is required: hence we find that the right Ventricle is much 
more Muscular than the right Auricle, but the left Ventricle 
has to send the Blood to every part except the Lungs, and here
therefore a greater force is necessary, and accordingly the left
Ventricle is formed much more Muscular than the right.
The Heart when cut open shows a particular Mechanism 
which determines the course of the Blood, to be such as we have
described. Indeed it is rather singular that the circulation 




101
of the Blood, was not sooner discovered on this account, considering
it has been in contemplation nearly two thousand years.
The valves are the parts which determine the course of the Blood
where the Auricles and Ventricles are communicating, there is
a membrane which projects into the cavity of the Ventricle,
and is so constructed as to let the Blood pass readily from the 
Auricle to the Ventricle; but should it offer to return, the 
Membrane would be raised up to obstruct its passage. The valves 
have different names, from some peculiarity in their structure,
tho’ they perform the same office. On the right side the 
valve is composed of three portions of membrane, and it 
is called Valvula Tricuspides: that of the left side is only of 
two portions, which projects in such a manner as to rememble  
a Nictre, hence they are called Valvula Nictralis. The outside 
of the Heart is smooth, but the inside is fascicular, and is composed
of Fleshy columns. What advantages arise from 
this kind of structure? It must be remembered that the contractions
and dilatations are not gradual like those of 
the Stomach and Bladder, but sudden and frequent. It 
seems then, that this disposition of the fibres makes the Heart
more capable of performing these sudden contractions.
From the muscular columns pass a number of fibres, called
Cord & Tendince, to be reversed into the Valves, and should the
Blood be regurgitated they would prevent the Valves from being 
Forced further from the axis of the orifice between the Auricle and 
Ventricle. Besides these there are others at the beginning of the  




102
large Arteries. The Aorta and Pulmonary in each of these there 
are three, and each of these are of a semilunar form and are 
therefore called Valvula Semi lunaris. They appear to be doublings
of the Internal wats of the Arteries. When the Blood is forced
from the Ventricle into the Arteries, the valves lie close
to the sides of vessel, but should the action of the vessels, 
drive the Blood back, they would meet in the centre, and by 
completely closing up the passage prevent its return. There 
are many means by which it can be proved that the Valves
perform this office, but by none better than by injecting
the Arteries, contrary to their course with plaister of Paris. 
Having premised these general observations with 
Respect to the structure of the Heart, we are better prepared
to speak of its oeconomy. There are some parts at 
which we must begin, but it is quite indifferent where it 
is like describing a circle. However we will say that all
the Blood sent from the Heart to different parts of the body
except the Lungs, by the Aorta and its numerous divisions 
and subdivisions. The ramifications are at last so
minute that they are called capillaries: these terminate 
in Veins by continuation of Canal so that we cannot 
know where the Arteries end or where the Veins begin. They 
may be called Veins as soon as the Blood begins to return.
The Veins unite and form larger branches, and at last 
unite and form two very large Vessels the superior and 
inferior Cava, by which all the Blood which is distributed  
 
 




103
distributed by the Aorta, is returned to the right Auricle of 
the Heart. The superior Cava returns the Blood from the 
Head and Thorax, and the inferior from the other parts of the 
Body. These vessels enter the Heart at acute angles with 
Respect to each other, which is favorable for the entrance
of the Blood from regurgitating into the Veins: It does contract
in some degree, and this is the cause of the Jugular Veins
and other large veins near the Heart pulsating but the Visa 
Tergo prevents its taking place at any considerable distance.
Besides in the Inferior Cava there is something like 
a Valve, of a crescent like form but from its size, it cannot 
prevent the regurgitation of Blood. It is called the Valvala 
Eustachii, and seems principally concerned in the fatal
circulation, and is often wanting in very young adults. 
The right Ventricle being filled contracts and drives the 
Blood into the Pulmonary Artery, and it is prevented 
from returning by the Valves already mentioned. The
Pulmonary artery divides into two branches, one going 
into each Lung, and there by ramifying conveys the 
Blood thro’ the Lungs. It is then returned by Veins which
terminate in four large vessels, called the Pulmonary 
Veins, they enter the left Auricle, forming nearly a square
but here a regurgitation in part takes place, not for want
of the Valves, but from the Visa Tergo, it seems to answer 
the purpose. The left Auricle being distended contracts 
and forces its contents into the left Ventricle and 




104
here it is prevented from regurgitating by Valves, similar
to those of Pulmonary Artery. Thus we have traced
the Blood thro’ its double circulation. There are four cavities
in the Heart, but there are not four successive
contractions, there being two circulations going on at 
the same time. The two Auricles are filled altho’ sometimes
they contract and fill the Ventricles, which are
likewise contracted, so that the Auricles and Ventricles
contract together, but tho’ the actions are thus altered
the Auricles and Ventricles alternate with each other
this is observed to be the case on opening Animals, upon
each of the Valves is a small clot; called arpus 
sepamaideum; the use of which is most probably 
that of filling up the space between the Valves
for when these circular edges, as those of the Valves
are placed together, there will be a small space left
These bodies however do not seem to be of much importance
as they are often hardy discernable. The 
Blood which we have been tracing thro’ the Heart
does not all contribute to its nourishment. This organ is 
nourished by two Arteries, which from the manner of their
distribution are called Coronary. They arise from the Aorta
as soon as it has quitted the left Ventricle; these ramify thro'
the Heart, and then the Blood is returned, by the Coronary Veins
which terminate in the right Auricle. These Veins have 
Valves to prevent the regurgitation of the Blood from



105
the Auricle. So far have we considered the Blood mechanically  
as to its action, but where is the origin of this action or in what
does it exist? Most machines act from a power exterior to 
themselves, but as to the Heart, the very fluid which it is intended 
to convey, is that which first excites motion: If we inspect
the Heart of living Animals, we see a regular alteration of 
action, but soon the Lungs collapse, and the action of the Heart
begins to cease, first the left Ventricle ceases, and then the Auricle,
next the right Ventricle ceases and then the Auricle, which 	
continues its action some time after the other. Why does this take
place? Is it the last dying speech or confession of the Heart?
No, it may be better explained. The left Ventricle is most  
Muscular, and consequently empties itself more forcibly of its Blood 
and the left Auricle being weakened from the collapse of the 
Lungs and not receiving its supply of Blood, is not able to 
supply the Ventricles, consequently the Ventricles first fail 
and then the Auricles. The cessation of motion in the right
Ventricle, before its corresponding Auricle, is from its
greater Muscular force, emptying sooner than it can be supplied
with Blood by the Auricle; from the Auricle receiving
the Blood longest it retains its action longer, but 
if a Ligature was made to stop the Blood from flowing 
into the right Auricle, it would cease its action quite
as soon as the left. Hence it is not from any articular
vitality, that one part of the Heart continues to act, after 
the other, but from its receiving Blood the longer, which 




106
Seems to be the proper Stimulus to action. The Heart is Muscular 
and Nervous, and its action is involuntary, yet tho’ the 
will has no power over the Heart, still the passions have. If 
in the voluntary Muscles all Nervous communication is 
interrupted, all volition and sensation is lost, but the parts
may still possess irritability, and this the Heart has in a 
great degree: hence has arisen a question whether Nervous 
Energy be necessary to the action of the Heart? I think there 
cannot be the least doubt of this, though there is more Irritability
in the Heart than in other parts. We speak of 
the stimuli of the Blood exciting the Heart to action, and 
a deficiency of this from  a collapse of the Lungs causing 
a cessation of action. A redundancy may have the same
effect. The Heart may be so filled and overpowered with 
Blood, as to retard its natural action; a removal in part 
of this Blood would allow the Heart to contract as before.
Syncope may also arise from a defect of Blood in the 
Auricles, as happens from Bloodletting, but this is obviated
by laying the body in a supine posture, for 
that favors the return of Blood from the lower extremities: 
a deficiency sometimes happens from a rupture 
of the Auricle, and the Blood is suddenly discharged. 
Two pounds of Blood lost in this way would produce death, yet 
a much greater quantity may be drawn without injury in a gradual 
manner. From this principle bleeding from a large orifice
disposes to Syncope: but the operation of fear is often very great





107
On the Action of the Heart.
We have hitherto considered the Heart as inanimate, and 
receiving the passage of the Blood thro’ it, as depending on its
mechanical structure. Inherent of itself, depending upon 
a peculiar Stimulus to consider which will be our present
business: before we proceed, it will be necessary to 
establish some facts relative to the action of the Heart. If
we open the Chest of an Animal the Lungs will immediately 
collapse by the pressure of the external Air; at first we see
the action of the Heart very evident and then the action of 
the Auricles and Ventricles alternately in a very short time
we see the contractions of the left Ventricle to intermit and 
perhaps it contracts once to three times of the Auricle.
The length of the intermission is increased, and soon the action
of the Ventricle entirely ceases; after this the action of the 
corresponding Auricle seems disturbed, it first intermits and 
then ceases in a similar manner with the Ventricle. Now 
the right side of the Heart only is in motion, and in a few
seconds the same begins to take place in it, as did in the 
left. The right Ventricle first intermitting and then its 
action ceasing, and lastly the right Auricle ceases also.
From this it appears that the action of the Heart does not
cease in every part at the same time, but in the order above mentioned.
On this occasion many have supposed that the right
Auricle was most tenacious of life, and have endeavoured 





108
endeavoured to support the Idea, that the right side of the Heart possessed 
more irritability than the left. While the Lungs
are in action, the Blood has very easy transfusion thro’
them, but it is observed on opening the Chest, that external 
Air rushes in, and causing them to collapse. When
this has taken place, the Blood is prevented from passing 
thro’ them, with that freedom, it did before, consequently 
a less quantity of fluid is sent to the left side of the Heart,
which Nature intended as its proper stimulus. The Auricle
being much smaller than the Ventricle requires a less quantity
of Blood to make it contract, and therefore the Ventricles
cease first the Blood coming to the right side of the
Heart and not passing thro’ the Lungs has not of course its 
passage impeded, consequently the action of that side remains
the longest; this appears to be the reason but we should offer 
some proof. If we could so order that the left side of the 
Heart should be longest supplied with Blood we should 
then find the reverse of what has been stated to take place.
It would be proving as much as experiments can prove.
I opened the Chest of a Dog, having previously prepared ligatures 
to tie the Aorta, the only dissection necessary was 
to divide the Pericardium, where it covers the Aorta: this
being done the vessels were tied without further delay.
Pressure was made on the superior and inferior Cava, to 
prevent the Blood from passing to the right Auricle, and a 
small opening was made into the Vena Cava Inferior. 





109
Thus the left Auricle and Ventricle were prevented from 
receiving Blood, by the pressure on the Vena Cava. The opening
in the inferior Cava permitting the right Auricle
and Ventricle being emptied of the Blood, and the natural 
order of the circulation was in this way reserved. In this
case the right Ventricle ceased first to act, after it the
the Auricle on the same side, then the left Ventricle
and lastly the left Auricle. The Auricle will sometimes
contract two or three times while the Ventricle only
acts once, but this is only when the power of Life is 
ceasing. It may be accounted for in this way. The 
Auricle being weak cannot empty itself by its
Contractions, and therefore repeatedly contracts; but the 
Ventricle being more Muscular and Irritable has power
eno’ to empty itself, by one contraction. From what
has been said it appears that Nature has given the Heart 
great Muscularity, and that by the addition of Life it is 
rendered very irritable; it appears also that the Blood 
is the proper stimulus of the Heart. The action of the Heart
is weakened by a sudden diminution of Blood, as well
as by a sudden influx over distending it. Hence some
people using violent exercise upon the Muscles, pressing
upon the Veins, and causing them to return
their Blood in greater quantity by the Cava, into the right
Auricle may so fill it that its action cannot go on 
The mind acts in the same way by determining the  




110
Blood in large quantities to the Heart. Mr Hunter in part 
died from this cause. For by being, by some difference with
other surgeons, throw into a violent passion, more Blood 
was sent to the Heart in consequence, and this when the Organ
was previously diseased. This has been proved by experiment, 
a large quantity of Blood was thrown into the 
Heart of a Dog, and its action ceased, but on making a puncture 
into the Inferior Cava, so as to allow some of the Blood 
to escape, the action was directly restored, and on this principle
Syncope was explained. We know that a person
is much more liable to faint in an upright posture than 
in an horizontal one; for in the upright posture an equal 
quantity of Blood is not sent by the Inferior Cava, to the 
Heart, owning to the resistance given in its passage by 
its having to mount contrary to its gravity; but an Horizontal
position taking off that resistance favours two 
passage of the Blood. Besides the obstruction to the Blood 
in an upright posture, it may be added that blood drawn
from the arm necessarily prevents so much Blood passing 
by the Axillary Vein, and the superior Cava, so 
that in this case syncope arises from a deficiency, while
in the former it was from the greater quantity of Blood
The Heart is not as was observed uniformly in a state of 
action, but there is a momentary cessation between each 
contraction. There is some opinions relative to the cause
of this, which deserve notice. Galen thought the Blood 




111
acted by habit. Some have thought it a peristaltic motion. 
Boorhaave was of this opinion, and he endeavored to 
account for it, from the pressure of the Heart on the 
plexus of Nerves, situated between its basis and 
the Spine; when in a distended state, which he supposed 
produced a momentary Paralysis but such 
an opinion is to be regarded however, as an injudicious 
Hypothesis for it cannot be proved, nor yet
disproved by experiments, but what we know militates 
against it. Voluntary Muscles may be rendered
paralytic be pressure: but involuntary ones of which 
the Heart is ones will act sometimes after communication
with the Nerves, is cut off. The Heart will 
act a short time, after it is taken out of the body.
Besides when a part is rendered Paralytic by pressure 
its power of action is not entirely restored upon the 
removal of it. In addition to these observations, the softness
of the parts concerned, would not effect this purpose, 
and if they did, the irritability of the Heart
would cause it to go on. Notwithstanding the action
of the Heart does not appear to be so intimately 
connected with the Nervous influence, as most other 
Muscles. If we stimulate the Nerves going to the 
Heart its action is not increased, but this is not the
Case if we stimulate the Nerves going to the Extremities.
The Cardiac plexus of Nerves which supplies




112
the Heart is formed by the Par Vagum and great 
sympathetic Nerves: we have very good access to 
the former and if we stimulate it, no difference is 
perceptible in the Heart. Some have thought the 
Heart would act, as well without, as with the Nerves
but this does not appear consistent if we reason
from the Analogy of other parts. It is true that the 
great irritability of the Heart will cause it to act 
longer with the Nervous influence than any other
part; yet it cannot be continued for any length 
of time. Experiments have been made to determine
with what force the Heart acts, by placing 
weights upon it, but these experiments are rather
whimsical, and cannot with any certainly ascertain
the force. That this force is very great may
be proved by experiments. I compressed the Heart 
between my hands; when no force that I could
use, would stop its actions immediately. The force
varies in different Animals, and in the same Animals
at different times. The Pulsation of the Blood does 
not belong to the Heart alone, for the Arteries assist
in this office: we know that the motion of the 
Blood may be partially accelerated and this cannot
belong or depend upon the action of the Heart
but on a peculiarity of the action of the Vessels, of 
the part. There has been known instances where






113
the Heart has been frequently wanting in fetuses
yet the parts that were present had lived and were
nourished in every respect as well as those with perfect 
Hearts. I have dissected two Monsters where the
Heart and Lungs indeed where the whole of the 
upper part of the Body has been deficient, and  
for all this the other parts of the Structure, have been
as large as the generality of children are at Birth
This I think clearly proves that the Heart is not 
Essentially necessary for fatal circulation, and existence
But we are perfectly aware that such 
Monstrous productions must die immediately
they enter the World, for the want of Lungs which 
are required for Respiration. The structure of the Arteries
confirm the idea of their assisting in the circulation, 
and this more or less in proportion to the distance
the Heart is situated from the Arteries. The 
more minute the Arteries become, the more in proportion 
does their Muscular Coat increase; and 
hence it is we can account why the small Vessels
assist in propelling the Blood, more than the Arteries
do, which are evidently of a much greater magnitude 
we consider the Blood in its circulation precisely 
upon the same principles, as water passing through
an Hydraulic Machine. 





114
ON THE FOETAL CIRCULATION.
We are now to speak of the peculiarities which attend the 
Foetal Circulation. The Foetus has not only a Circulation
in common with the Adult, but also one peculiar to itself.
The peculiarities depend upon certain apertures and canals 
which do not exist in the Adult. Before we speak of these
it will be necessary to make a few observations relative to 
the connection between the Mother and the Child. The Uterus 
is well supplied with Blood from the Internal Iliacs. The 
Vessels of the Uterus after ramifying thro’ it deposit their
Blood in the cells of the Placenta. The Placenta is composed
of two parts, the Maternal and Foetal. The cells of the Placenta
is the Maternal part from these cells the Blood
is taken up by the Veins and returned to the Mother, having
no communication with the Foetus. In the Foetus, 
branches from the internal Iliac pass thro’ the Umbilicus, 
which take the name of Umbilical Arteries, and distribute
their Blood to the Foetal part of the Circulation. The 
Blood is then returned to the Umbilical Vein. It appears
then, that the vessels of the Uterus have no communication
with those of the Foetus, and this is further proved
by throwing in minute injection, but this subject will
be considered at a future time. The Umbilical Vein having
passed thro’ the Umbilicus going to the Liver, where it divides
into two branches, one called Ductus Veinasoes, which passes  



115
to the inferior Cava, and the other into the Vena Portarum,
which is going into Liver, and carrying the Blood for the 
secretion of the Bile: when the Blood has passed thro’ the 
Liver, it is brought by the Hepatic vein, into the Vena
Cava first before it enters the right Auricle. This is the 
Way all the Blood of the Umbilical Vein gets into the right
Auricle, either directly by the Ductus Venosus, or by the 
Hepatic Vein, after passing thro’ the Liver. In the right 
Auricle it mixes with the Blood of the superior and inferior
Cava. In the Adult the Blood is sent into the 
Right Ventricle, but in the Foetus one third passes into 
the left Auricle by an opening called the Foramen boele 
situated in the Septum dividing the left Auricle from 
the right. This Foramen is situated so obliquely as to 
answer the purpose of a valve and thus prevent the return
of the Blood into the right Auricle. The rest of the Blood 
being about two thirds of the whole goes into the right
Ventricle, and from there it is sent into the Pulmonary
Artery which circulates thro’ the Lungs; but in the 
Foetus it is not so for the Lungs not having performed their 
office of respiration, are in a collapsed state, and require
but little nourishment: by far the largest quantity of blood
passes by a large vessel called the Canalis Arteriosus, which 
goes from the Pulmonary Artery directly into the Aorta. The 
small quantity which circulates thro’ the Lungs is returned
by the Pulmonary Veins to the left Auricle. It does not in its 



116
passage thro the Lungs receive any healthy change as in the 
adult, but seems rather destined for the purpose of nourishment;
or for keeping the vessels pervious for future circulation
about one part in three passes in the course, and the 
other two by the Canalis Auriosus. The Blood in the left Auricle 
is sent into the left Ventricle, and from thence passes down  
the Aorta by the side of the Spine until it gives off the Umbilical 
Artery, by which the Blood is returned to the Placenta
so that the Blood is brought to the Foetus by the Veins and 
returned by the Arteries. The purposes answered by the peculiarities
of the Foetal Circulation cannot at present be 
entered into at large, from their depending upon some circumstances
relative to respiration. It seems however as the Lungs
cannot breathe that the Placenta performs that change in 
the Blood which the Lungs do afterwards for if the umbilical 
cord be pressed upon so as to prevent the flow of Blood
thro’ it, the Child will die. In ten or fifteen minutes after 
Birth several important changes take place, first
the Child has a struggle for breathing, afterwards inconsequence
of respiration the vessels and apertures shut up. 
but there are gradual changes. When Air is taken into
the Lungs they must be very much increased in size
and their vessels which were before coiled up, become larger and 
more pervious. The Blood passing now much more freely thro’ the 
Lungs than the Canalis Arteriosus, the quantity passing thro’ that 
canal will gradually diminish, and this, like all other arteries has





117
the power of adopting itself to the quantity of Blood passing thro’ it;
and by degrees it becomes obliterated. The Foramen Ovalis disappears 
about the same time, and from the same cause, though sometimes
this aperture does not entirely close. More Blood being 
brought by the Pulmonary Vein into the left Auricle than before
respiration took place, it becomes of course more filled, and gives resistance
to the passage of the Blood from the right Auricle thro’
the Foramen Ovalis and as the resistance increase the Foramen 
Ovalis becomes closed. The Umbilical Arteries being 
tied at Birth, the Blood that passes thro’ them must find 
some other course, which it does by the external Iliacs.
this accounts for the growth of the lower extremities after
Birth, being greater and nearer in proportion to the rest
of the Body than those of new born Children. The Umbilical 
Arteries having got rid of their Blood by their contractile power
soon become closed, but much more of gradual. I have 
known it pervious in a subject of sixty. It is the Vessel
which in the Adult is called Ligamentum Rotundam 
of the Liver. The Canalis Venosus, closes also in consequence
of these other changes. The Heart is not necessary 
in the Foetal Circulation, indeed it never is when
the Lungs are not in motion, and when the Lungs 
are wanting, the Heart is also. Several Monsters
have been known without having Heart or Lungs




118
On the Circulation of 
AMPHIBIOUS ANIMALS.
The word Amphibious is used in a very vague and indefinite 
sense. It is therefore necessary to explain what is meant 
by it. Those Animals which live near Lakes, and often
swim on them, have been called Amphibious, but these
have Hearts and Lungs, like other Animals. Toads, Frogs, Turtles
and Lizards have been more properly termed such
but even these strictly speaking cannot be termed Amphibious
Animals, for they may be drowned by being kept 
Entirely under water for a certain length of time. By
Amphibious Animals according to the true sense of the word
such as can Live in Air or in Water, for any length of time. 
We know of but one Animal of this kind, the Syrew, this is 
said to have a Heart and Lungs, like other Animals, and also
Gills like fish. It cannot live any more out of Water
than land Animals can in, yet they have a power of imbibing 
a property in the Water, which will produce the 
change in the Blood, as Air does in Land Animals.
What we have at present to speak of, is the Circulation of 
those Animals which can Live, a long time under Water
as Turtles, Lizards &c, they have very large Air cells that
enable them to live under Water a long time; but we shall
speak of this hereafter. In these Animals a part only of the 
Blood passes, thro’ the Lungs at each Circulation. Some therefore
Have thought the Circulation to be like that of the Foetus 





119
but it is not so; they have properly speaking, but three Cavities in
their Hearts for between the Ventricles is a large aperture of communication,
so that the Pulmonary Arteries, and the Aorta go off, at the 
same cavity. The Blood is returned from the Body into the right Auricle,
by one Cava only, and from the Lungs by the Pulmonary Vein
into the left Auricle. The Aorta is a great deal larger than the Pulmonary
Artery, so that part of the Blood that passed thro’ it in the former
Circulation must again pass thro’ it hence but a part of the Blood
Circulates thro’ the Lungs at each Circulation to receive its change
there. In the opening between the Ventricles is a Valve so placed
as to direct nearly all the Blood, that had circulated thro’ the
Lungs into the Aorta so that though a small quantity that had 
been circulated thro’ the Lungs may be sent there again, without
having gone thro’ the Body, yet it is but very little. Fish have but 
a single Heart viz one Auricle and one Ventricle; the Blood is 
brought into the Auricle by a Vein from whence it is propelled
into the Ventricle. From the Ventricle it passes to the Branchial 
Artery, which answer to one Pulmonary to the Gills, and after circulating 
thro’ the Gills it is returned by the Veins, which join
to form an Artery answering to an Aorta. In many Fish, as the 
Cod, the Branchial Veins are distributed over the Body without
being previously united into one large trunk. The Lobster, Oyster
Snail &c have but one Cavity in their Hearts, which has two Vessels
communicating with it, one by which the Blood is distributed
to the Body, the other by which it is returned from it. 




120
On the greater Circulation.
When we first spoke of the Circulation we observed it was doubled
there being a small one thro’ the Lungs, and a greater one thro’ the 
rest of the Body. We have finished what was to be said of the smaller
both in the Adult and the Fetus, as well as in many Animals, Fish 
&c. We have also considered the Heart as an Organ of Motion, and 
it now remains for us to take a more particular view of the greater
circulation. This includes the passage of the Blood from the left
side the Heart, and after pervading the system, its return to the 
right side. The first vessel considered in the greater Circulation 
is Aorta, which goes off from the left Ventricle, and passes thro’
the trunk in such a manner, as is most convenient for giving 
off branches to supply the different parts of the Body. The Ancients
thought the Arteries were to convey Air, they had an Idea that
they had a communication with the Air by means of Lungs.
The circumstances which gave rise to this opinion was that
the vessels were always found empty, or to contain nothing but 
Air after Death: hence they derive their name. Galen first discovered
that Arteries contained Blood by opening living Animals.
They accounted for the Blood getting from the left
side the Heart to the right by the Foramen Ovale. This Idea they 
probably took from examining the Foetus. It is now well understood
that the Arteries carry Blood, but why are they empty
after Death. There is always some Blood found in them, and 
the quantity depends on the action of the Lungs. The last






121
action of Life is expiration hence to Die and to Expire are synonymous 
terms; so that after Death, the Lungs are in a collapsed
state, in which the passage of the Blood thro’ them is interrupted,
thus the Blood is accumulated in the Vena Cava, and prevented
from getting into the Aorta thro’ the Lungs, which assisted
by the contractile power of the Arteries themselves causes them 
to be empty after Death. This reasoning is confirmed by facts.
A case is related of a person who was suffocated after a full inspiration,
and in whom on dissection, Blood was found in 
the Aorta. The same took place in some experiments made by 
Mr Coleman. The Aorta divides into two branches which subdivide 
into others, and these again into smaller and smaller,
until they end in Capillaries, which are the smallest vessels 
that carry red Blood, and in this manner Blood is carried to the 
remotest parts of the Body. In the Capillaries the Blood begins to 
take a retrograde motion, viz towards the Heart as those vessels
by continuation of canal, terminate in Veins, which return
the Blood to that Organ. That this is the course of the Blood is very 
easily proved by experiments. One made by Harvey was tying a 
ligature on an Artery and Vein, and this was the celebrated experiment
that led him to discovery of the Circulation of the Blood.
It was first made by Versalin, tho’ Harvey had the ingenuity 
& discovering the Conclusion from it. The Artery was observed
to swell on that side the ligature next the Heart, and the Veins to 
collapse, et vice versa. Some have made an objection to the 
experiment by saying that this phenomena do not always




122
take place. It is true that in many parts which have a Ligature
made on a vessel, no accumulation will take place, but 
it must be in those parts which have a number of anastomosing 
branches, given off from these vessels. For the same reason
there will be no collapse on the other side the Ligature, for the 
Blood will take a retrograde course as far as it can. A knowledge 
of the parts in which this will take place seems to be 
a matter of curiosity, but it is of real importance to every 
practical Surgeon. For instance if a Ligature be made on the 
Radial Artery, there will be a collapse between its owning to
the free communication between that Artery and the Ulnar.
This suggests the Idea that if the Radial Artery be at any 
time divided, a Ligature on the upper orifice would not stop
the Bleeding, and therefore a Ligature or pressure on the lower
orifice will be necessary. I once saw a case where the posterior
Tibial Artery was divided by a knife, plunged in thro’ the
Gastrocnemii Muscles. The Surgeon applied a ligature on the 
upper orifice of the vessel, but the Hemorrhage continued nearly 
as violent as before, and he thought that nothing could be 
done to save the patient, but amputating the Limb which he 
did; afterwards on dissecting the Limb no other cause for the
Hemorrhage could be found, but the lower orifice of the Artery
being open, which has a free communication with the 
plantar Arch, or anastomosing branches of the anterior
Tibial Artery and had this been taken up the Limb might have 
been saved; perhaps there is no proof of the circulation  





123
more striking than seeing it in the transparent parts as the web
of a Frog Foot. The Tails of Fish, Lizards &c. These may be so placed
under a Microscope that the Blood may be seen going by the Arteries
and returning by the Veins. The flow of Blood thro’ the Arteries
is not in an uniform manner, but by pulsations which however
are much more apparent in some Arteries than in others. In the
large ones they are very evident, in the small ones, less so, and 
in the Capillaries not at all for if these pulsated we should always
be in a state of pulsation. This is easily accounted for 
the Ventricles contracting sends a column of Blood into the 
larger Arteries, which contracting sends it forwards, another
column succeeds this, and is forwarded in the same manner.
The Arteries cannot empty themselves entirely by their own
action, so that if an Artery be divided at some distance from 
the Heart, the stream will be entirely interrupted by the action
of the Vessel, but will at the same time of the contraction of 
the Heart, be projected further. In the Toe very little Pulsation
is observable, in the distance to which the Blood flows, when
an Artery is divided. Harvey said there was some spongy substance 
between the terminations of the Arteries and the 
Veins, but no such substance can however be formed in the 
general termination of Arteries, but in some particular 
parts we find such. That no Parenchyma exists is proved
by injecting an Artery, in a transparent part as in 
the Intestines, or the Web of a Frog Foot, when it will be seen
that the Injection passes directly into the Vein Instances



124
of the Parenchymataus structure of the parts of the Corporacavernosa,
Penis, Clitoris and Spleen, in which the Arteries
terminate in cells: from which the Veins take their origin
by open Mouths. There are some Animals, that have 
the power of increasing particular parts at pleasure; such 
as Cocks, Turtles &c in these also the Arteries terminate in 
Cells. When the Animal is irritated these Cells are distended
for the increased action of the Arteries, but when the 
cause is removed the distension subsides. In general
we observe these terminations in parts where a slow circulation 
is required. It was formerly observed that the 
Blood was composed of different parts, viz, Serum Coagulable
Lymph and red particles; some vessels are so 
small as to admit only two of the former and exclude
the red particle, which has given rise to a division of the vessels
into Sanguiferous and Seriferous vessels, these have Veins
corresponding. The second termination of Arteries is said to 
be in the Seriferous vessels. This is a useful continuance for 
nourishing those parts, whose functions would be interrupted
of the red Blood, of such is the Transparent Cornea: tho’
this part cannot be proved to be organized by Injection,
yet it appears to be so from its often healing after wounds.
As after extracting the Cataract, the Tunica Conjunctive 
exhibits a specimen of both sorts of vessels. In the Natural
state it is transparent being supplied by Seriferous
vessels, but from Inflammation the vessels become 





125
Turgid, and admit red Blood so as to become uniformly 
red. This redness is not produced by extravasation or the formation
of new parts, but by red Blood being passed into Seriferous
vessels: this has been called by some error Luci, it is caused by 
some irritation as dust getting into the Eye, or it may be caused
by relaxation of the vessels: relief is obtained in two ways, when 
from irritation soothing applications are the most proper, but
when from relaxation Tonics are useful. And Leeches, Scarifying 
&c are beneficial and afterwards applying astringent lotions. 
Arteries terminate in open Mouths, and are the called exhalent 
these are found in almost every part of the body, both in its surface, 
and internal parts. The fluid passes off from them
slowly so that it is not evident at the time, but it is proved
by its being often accumulated in Cavities, as the Ventricles
of the Brain, Thorax and Abdomen in these a fluid is thrown
out to lubricate them internally, and thus obviates the 
effects of Friction by motion. It likewise facilitates motion.
The Cellular membrane necessarily has it, in order to
lubricate the parts, for the easier action of the Muscles,
and that it exists is often proved by its too great accumulation,
which constitutes anasarca. What becomes 
of this fluid? Nature has furnished the system with 
Vessels called absorbents, and these bear the same relation
to the Veins, as the Sanguiferous Veins, do to
the Sanguiferous Arteries. They take up the overplus 
of the Fluid, powered out by the exhalents, and 




126
these keep up a balance. When from any cause the action
of the Exhalents is increased or that of absorption
diminished, an accumulation of fluid take place, constituting
Dropsy. If pressure is made upon a principal vessel,
or Vein in a limb, there comes on a swelling of a Dropsy
like feel, which is owning to the Arteries depositing
to excess. Names have been given to these accumulations
in different parts, as that in the Ventricles of the 
Brain is called Hydrocephalus &c. The Exhalents
have another termination, viz, in the emunctories
of the skin, thro’ which the Perspiration passes. In 
some parts of the body, the fluid is not intended to be 
taken up, as in perspiration. The fluid carried off
by the Exhalents of the skin, is according to the Experiments
of Sanctionies, very great which relieves 
the system much, but there are some Organs in the 
Body which relieve others, as the Kidnies relieve 
the Perspiratory vessels, as for instance in cold weather
the Perspiration is diminished, and the Urine
is increased, so again in warm weather the Perspiration
is more and the Urine less. There is another termination
of Arteries, which is in Secreting Organs.
These are simple and complicated. Another termination 
is in Nutrient Vessels, by which Nourishment is given to 
the Vessels, conveying Chyle, or the Nutrient Principle



127
OF CIRCUMSTANCE AFFECTING THE
Velocity of the Blood.
The motion of the Blood in the large Arteries is greater than
is the small which is owning to the aggregate area of the latter
being greater than that of the former: for instance if we take an accurate
measurement of the Aorta first before it divides, and 
of the two Iliacs is greater than that of the Aorta the capacity of 
the Canal being enlarged, the velocity must necessarily diminish: 
in the further division of the Iliacs the same takes
place: therefore the velocity of the Blood in the Aorta, must be
consequently greater, than it is in the capillaries. Again the 
angles at which the vessels arise affect materially the velocity
of it; those near the Heart do not impede it so much, as 
those at a distance, where the angles are more acute. The Carotids 
go off at rather obtuse angles, the Intercostals at right angles,
the Iliacs from rather an acute angle; and the vessels of the 
extreme parts from angles more acute. This structure appears
in some degree to equalize the Circulation, for the 
resistance given to the force of the Blood, is in proportion to
the acuteness of the angles. Convolution of the vessels is another
circumstance affecting the velocity of the Blood; and it 
is in general found in these parts, where a slow circulation
is required as in the Brain; the more Convoluted the Vessels
are, the slower must be the Circulation thro’ them, for the convolutions
act much in the same manner as angles do.




128
In Serpentine Arteries it is the same: also in the Uterus otherwise
Uterine hemorrhage would more often occur. This 
structure is very remarkable in the spermatic Artery of 
the Horse. It retards the Circulation in two ways, first
by increasing the resistance, and secondly by adding 
to the distance from the Heart. The collateral vessels
passing off from the Trunk of an Artery diminish 
the velocity of the Blood. It has been a question
how far the Nervous influence, affected the Circulation?
Some have supposed a great deal, and 
have produced the state of a Paralytic Limb, in  
support of this opinion, they say, they have a slow
Circulation and are weak; the Muscles becoming 
emaciated and pale: this however if examined closely
will not prove so strong an argument as it 
might first appear for all these symptoms will be
found when there is no interruption to the Nervous
influence, as in diseases of Joint; but I think that
a diminished circulation is not an immediate, but a 
remote cause of Paralysis. The Palsy prevents the
action of the Limb, and the Muscles being inactive
have not that quantity of Blood determined to them,
that otherwise would be; under these circumstances
they waste, become flaccid, and a less quantity of Blood 
is necessary for their support. The Arteries become small 
and weak, and this reason applies equally to a Paralytic





129
Limb, or a Limb with a diseased Joint if we observe
the change of the Circulation of a Limb recently Paralysed,
such as is produced for instance, by dividing the 
Nerves for the purpose, the above opinion would be entitled
to our credit: but we shall find that at first the 
action of the Artery, is not at all diminished, and it becomes
weakened gradually, as the Limb becomes emaciated 
It is a law in the Animal Oeconomy, that they increase
when there is much action required; not only because when 
they are in action they require a greater supply of Blood,
but the alternate contractions and relaxations of the fibres
impel the Blood forward and thus increase the circulation.
Thus we see that the fact induced in favour of the Nervous
influence, affecting the Circulation is not much to be 
relied upon. If also we have recourse to Experiments they
tend to prove that the Nervous Influence has not much
to do here. Fluid bare the Sciatic Nerve of a Frog, and put 
it first under a microscope, and then irritated the Nerve
by pinching it; but a person present observing the circulation
thro’ a microscope could not tell when the Nerve
was touched and when not. Again if the Nerves divided and 
a wound made in the Paralytic Limb, it will
heal quite as well as in the other not divided. The Arteries
being in a constant state of systole and diastole, they 
are subject to alterations which give a variety in the 
pulse. It is the diastole or dilatation, that causes the 






130
Pulse. When that is great we have a full Pulse, when small 
a quick and contracted one. Under Inflammation the capillaries 
partake of this motion from being more distended
hence the throbbing sensation at this time. If the Artery is impatient
of contraction, it gives a hard pulse, if still more 
impatient a quick one. The Pulsations of the Arteries in 
different parts of the Body are the same in number tho’
not in time: this is observed by feeling the Pulse in the hand
and foot at the same time. The natural frequency of the 
Pulse depends on the size of the Animal. In the Human
subject this differs at different periods of Life. In small
Animals the Pulsation is quick and in large Animals
very slow as in the Horses it is 40 in a minute, in a new 
born child it is 120. When two years of old it is 110, and so 
on, diminishing and grows larger at Puberty it is 70
and in old age 50 or 60. Therefore the Pulse in Children is 
no criterion in fever we must judge by the heat of the Skin.
Sometimes the regularity of the Pulse is distorted 
and now and then a Pulsation is wanting, this 
is called an intermitting Pulse, and shows some disease
about the Heart, and is owning to the Blood
not being thrown with sufficient force into the Artery
perhaps from ossification of the Valves, so that part
goes back again into the left Ventricle, and this prevents
the free circulation through the Lungs, hence the difficult 
respiration. This pulse is generally thought 




131
a bad symptom, but that depends upon the cause of it, 
if for instance it happens in Dyspepsia, Hysteria, 
Hypochondriasis &c. it is not very material.
The late Dr Manery at Chelsea had through his 
Life an intermitting Pulse, until within a year
or two of this Death, he lived at the age of ninety
six years, hence there are exceptions to an intermitting
Pulse being dangerous; though we are
to consider it as such, when it proceeds, from diseases,
exercise, food and many medicines quicken
the Circulation, much has been lately said of 
opium, which is thought to be universally a
Stimulant, but then it produces the following 
effect. I must consider it a sedative, I injected 
into the Circulation of a Dog, twenty drops of the 
Tincture of Opium in three ounces of water, the 
Pulse was brought down from one hundred and 
forty to one hundred and twenty, and gradually 
lower to sixty in a few minutes. The injection 
often did not produce this effect, therefore it is a 
Stimulant or a Sedative according to the dose given




132
ON THE VENOUS CIRCULATION.
The Blood after Circulating thro’ the Body by means of the Arteries,
is again brought back to the Heart, by other Vessels 
called Veins: they are easily distinguished from Arteries
in being thinner, and when cut thro’ they collapse, but the 
Arteries when divided retain their circulation from: they 
are evidently larger than the Arteries, tho’ when collapsed
they appear smaller: this arises from a difference of structure.
Arteries being more Muscular, and having an internal
Elastic coat, which Veins have not. The Veins have a Muscular
coat but it is not so distinctly seen as in the Arteries:
some have doubted this structure, but from their office we cannot
doubt its existence; and it is this which gives them a Tonic 
power: besides they are distended and contracted according to 
their contents. The Veins internally have a smooth membrane 
which differs from that in Arteries, by having Valves 
which are formed by doubling of it: by them the Blood is prevented
from flowing back. The Veins in general correspond
in number with the Arteries, and take the same course particularly
in the Viscera, and the only difference between them 
is that the Veins are larger. In some parts however we do 
not find them to correspond; there are two or more Veins to an Artery,
and these two Vessels are separately larger than the Artery, 
so that there is a difference with respect to number and size 
and consequently the Circulation must be slower than if 





133
they corresponded. This happens externally. The Veins, as well as the 
Arteries have free communication by Anastomosis, so that 
the Circulation will not be readily impeded tho’ pressure be 
applied. Veins are of two orders, superficial and deep seated
the latter follow the course of the Arteries, and have a free
communication with the superficial and therefore if these be
compressed others will be formed to return the Blood, we observed
in a former Lecture, that the Circulation of the Blood was 
performed by Pulsations; but in the Veins it is uniform, for as 
the Veins arises from the Capillaries, which are at a great distance
from the Heart, and possessed of very little Muscular
power, no pulsation is felt in them. In some Veins lying near
the Heart and Arteries, as the Jugulars &c an apparent pulsation
is seen corresponding with that of the Heart, but this 
does not arise from any power inherent in themselves. 
The Blood being interrupted by the Circulation and contraction 
of the Heart, the pulsatory motion is extended into the 
neighboring veins. The Blood does not move gradually
thro’ the Veins in every part alike, different positions retard 
or facilitate its motions, and in the viscera it is more 
rapid than it is externally. What is the office of the Valve?
Hitherto it has been but little understood, and we should 
first inquire where Valves are to be formed. Now Valves
are not found in every part of the Veinous system, in the 
internal veins there are none as in the Spleen, Pancreas, 
Liver, Viscera of the Thorax, and Abdomen, and the Coronary 





134
Veins: there are none in the Veins ramifying on the Dura Mater
or in the Vena Cava; but in the extremities there are Valves
and some think there are more Valves above the Heart than 
below it. Use of them. Some have supposed they have supported
the column of Blood, in the Veins, in the extremities;
this may be probable, but in the Vena Cava there are no Valves
in which the column of Blood wants support, therefore there
must be some other used. Now the extremities are subject to 
pressure, which if continued would throw the Blood into a 
retrograde stream, but the Valves prevent it. In some persons
particularly young people; the Veins are very large, producing
what are called Varicose swelling which arise from
debility, and may be much relieved by bandage, cold bathing
&c. Another cause retarding the Circulation thro’
the Veins is want of Exercise. Persons therefore leading a
sedentary Life, and whose muscles are consequently
inactive, are most liable to Varicose and Adamatous 
swellings in the legs. It is from this that the Legs of Horse
swell when standing in the stable without being Exersised,
for the Blood having to ascend and being deprived 
of any assistance from the Muscles and Tendons, it is 
not able to get forwards, and a swelling is the consequence
We are not to inquire in what manner Odema is produced. 
If anything retards the Circulation of the Veinous
Blood, as Debility in the part want of Exercise, or 
From any other cause as pressure on the Trunk of a Vein 




135
A resistance is given to the Blood in the Capillary Arteries,
and their action is in consequence increased, as is 
that of the Exhalents arising from them: in consequence
of this excitement of the Exhalents, an Aqueous fluid is 
effused producing Odema when partial, or Anasarca
when great. That this is the case is evident from Experiment.
If pressure be made on the principal Vein of a 
part, the contiguous Veins are at first inadequate to return
the additional quantity of Blood, and a swelling 
is the consequence; but as the Veins will become gradually
enlarged the Odema will disappear. Thus we may 
account for Dnapsics of particular parts, being produced 
by pressure from large Tumors, or enlarged Glands, and 
as all the Veins arising from the abdominal Viscera, terminate
in one common Vein, the Vena Portarum, what must 
be the consequence of a Schirrous Liver. The circulation 
must be retarded in the Vessels of the Viscera, and Water
be effused into the cavity of the Peritoneum from the increased
excitement that is produced in the Exhalents
and which constitutes Dropsy, as Ascites. Therefore in a 
case of Ascites we must attend to the Liver. When Scirrhous 
a Mercurine course is recommended, by which the action 
of the absorbents is increased, and the Scirrhous matter is
taken up, so as to allow the Blood to pass more easily thro’
the Veins. But an anasarca arises from another cause, as 
Hydrops Patons impeding the action of the Lungs, and the 
 




136
circulation thro’ the superior and inferior Cava. The Blood must 
pass thro’ the Lungs, before it is distributed to the other parts of 
the Body, and it follows of course that impediments to their functions,
must obstruct their circulation, and Water will be effused
and produce general Anasarca. But it is evident in cases of Dropsy
from a Schrirrous Liver, or impeded Respiration Diuretics 
can be of no use. In one case of Anasarca produced from pressure
many small Bleedings were successfully employed, tracing 
up the Disease, to an Inflammatory cause. It seems a law in 
the animal Oeconomy that there should be a difference in the 
balance of the Circulation at different periods of Life, which
gives a variation of color in youth and old age. In the 
former the complexion is more florid, and the latter more of a
purple hue: this arises from the Arteries in youth being
more pervious and the Veins less so. But in what difference
does this balance depend? It appears to me to arise from 
an alteration in the structure of the Veins. In youth they meet 
with a greater resistance to Arterial Blood, but in old age
they are larger and in youth they are smaller. Hence we can 
account for hemorrhage in old age, which is veinous
as the Hemorrhoids; in youth it is Arterial or Pulmonary,
and hence it is that old people have varicose and 
ulcerated Legs, which prove so obstinate to heal, but by 
giving a due degree of time to the Veins, by bandages &c
they will sometimes be relieved.



137
Of Respiration.
The Blood we have said is a fluid of great importance to
Life; we have taken a general view of its constituent parts 
and shall now further consider the changes it undergoes 
in the course of Circulation. The colour of the Blood 
in the large Arteries is very florid, in the small ones
less so, and in the large Veins near the Heart almost
approaching to Black when Blood loses its florid
colour it is then unfit for the purposes of Life;
a change is then produced in its passage thro’ the Lungs
by which it is restored to its former healthy state. 
It is not merely in consequence of the Blood passing
thro’ the Lungs, but it is brought about by the peculiar
action of the Lungs; viz by Respiration, the Lungs take 
in Air, which they retain for a few seconds, then 
expel it and receive Air again; so on alternately which 
alternate motion constitutes respiration. In order to 
understand the Animal Oeconomy of the Lungs in producing
a change in the Bloods we must first premise 
some general rule. The Lungs are two in number; one 
situated in the left side of the chest, the other in the right
hence they are called right and left Lungs. They are composed
of two parts, Air cells and Blood Vessels, and the latter
are of two kinds, the ramifications of the Pulmonary Artery
and Veins. The Cellular portion is much the largest




138
In the Human subject the Cells scarcely exceed the size 
of Pins heads, in many other Animals they are much larger: 
the Bronchial branches of the Lungs appear to be nourished
by the Bronchial Arteries, and the other parts chiefly by the
Pulmonary Artery. The Lungs are situated in a bay
called Pleura, which lines the whole cavity of the Chest,
[illegible] separate one Lung from the other by forming a
doubling or Mediastinum so that the Arteries and 
functions of one Lung may be impeded, by certain circumstances
and the other not. The Pleura not only forms a lag 
but a close covering and it being [p?????] in a very small
degree, prevents the Air from being pervaded, or diffused into 
the Cavity of the Chest. The Lungs have free motion in the 
Chest except at the root, where they are fixed, and where 
the Vessels of the Bronchia enter into the substance: this 
however is not the case in all Animals. In Birds the Lungs 
are fixed to the sides of the Chest and Spine: these also have no
Diaphragm, and therefore it appears there is some difference
in the manner in which respiration is performed; Mobility 
not being necessary to this class of Animals. Galen 
and some other Physicians say that Air was not only in the 
Cells of Lungs but in the Pleura also: this they endeavored 
to prove by Experiment. They asserted that if an opening was
made into the Cavity of the Chest, and a bladder applied to 
the aperture, it became distended with air; here it appears
they were not aware of the fallacy of Experiments which 
 




139
is very great, for if an opening be made, the air immediately 
rush in, which is during the action of inspiration, and hence 
the Bladder becomes filled. Harvey a much later writer was 
also of this opinion. It has been further said in proof of this
Hypothesis, that if an Animal be immersed under Water, and 
an opening be made between the Ribs, Air will rush in 
and cause Bubbles in the Water. The Lungs perform two
actions, Inspiration and Expiration. Inspiration consists
in receiving Air into the Lungs, and Expiration in evacuating 
it; after it has been received and undergoes its changes.
Many have agreed but not in a Physiological manner that
the Pulsation of the Pulmonary Artery distended the Lungs
and caused Inspiration. Some have supposed that the 
Lungs have a power of acting on themselves but if 
this was the case, Respiration would go on, when the cavity
was opened, which is not the case. It seems then 
that the Lungs are passive Organs, and that the Air is 
not drawn in them by a power inherent in themselves.
We should examine the structure of the Chest, and consider 
the action of the Muscles, and Mobility of the Ribs 
which are causes of the enlargement of the Chest.
The Diaphragm assists materially in this action, and 
also the intercostal Muscles. The ribs have different degrees
of Motion, in consequence of being more extensive as they
descend: after a full meal the Diaphragm is rendered
incapable of distending from the distension of the 




140
Stomach, so that the Intercostal Muscles, become the principal
Organs of Inspiration. The same occurs with the 
Diaphragm in Dropsical Patients, and in women who 
are laced tight: at other times the Diaphragm is the 
principal organ of action, as is the case when bandages
are applied in fractured Ribs. After Inspiration is
performed, the next action is Expiration. The actions
of the body are such as depend on the will, and such 
as are performed without our being conscious of them;
hence the division into Voluntary and Involuntary 
Muscles. Respiration partakes of both of these, and 
is called mixed action. What are the purposes answered 
by Inspiration & Physiologist say two, one 
is a free passage from one side the Heart to the other;
but this is casual, and not essential. We have said,
that the Lungs are composed of Cells, and Blood Vessels,
and that the former are alternately distended and 
collapsed. It is to be remembered that twenty 
eight inches cubic are equal to a pint of Air, and 
the heat existing in the Lungs about doubles the 
Bulk; and hence about a pint of Air is taken in, at
each Inspiration. The next and most important 
purpose of respiration, is the Change which is 
produced on the Blood, in its Circulation through 
the Lungs.




141
OF THE CHANGE INDUCED ON THE BLOOD DURING ITS
TRANSMISSION THROUGH THE LUNGS.
We are now to consider the change the Blood undergoes in its 
transmission thro the Lungs: it being different as to  
colour, previous to its entering these organs, to what it 
afterwards becomes, from passing thro’ them: in the first instance, 
it is of a purple colour, and afterwards becomes 
a florid red; but it will not be amiss to give an historical 
view of this subject, as by that means we shall then
better understand, the general changes, and improvement
in it. Physiologist and Experimental inquirers 
of the last century, were perfectly aware that 
a continual renewal of Air, was necessary to produce
this change, and made Experiments to ascertain 
how it was effected. Mayo and Boyle agreed that a 
certain portion of Blood was lost; and the other portion absorbed;
but if this was the case the presence of Air would
manifest itself in the Blood, which it does not; if it is so
it must be in a most intimate state of chemical combination.
Some have said that the elastic part of the Air was
absorbed, and that when this was lost Death ensued. But
as Chemistry was then in an imperfect state, we cannot expect
much accuracy on that point. This was the opinions
of Boyle and Mayo who had Animals in jars of Air, and 
finding it become diminished in quantity, conceived it to 
depend on the loss of Elasticity. Other Experiments were






142
also made to ascertain the effects of Air in the process of combustion
and here also it was proved that Air lost one of its properties, and 
underwent a diminution of its bulk: hence it was considered
that the process of combustion and respiration were analogous 
and instead of calling the matter given out Soot, as in combustion
they called it Fuliginous Matter. About the middle of last century
a repetition of Versalins’s Experiments were made by Hook.
He opened the Chest of a Dog, and made an opening into the Trachea 
to which he fixed a pair of bellows, in order to distend the Lungs
and by alternately distending and suspending their actions, he
got a clear idea of the manner in which respiration was performed:
he proved also by Experiments that the action of the Heart
corresponded with that of the Lungs. It was likewise about this time
that the changes which the Blood undergoes was first known; he 
then considered the change to be inconsequence of Nitrosluid Gas 
received into the Lungs, and imparted to the Blood. This conclusion
was natural enough though modern discoveries, have found it 
to be owning to fresh Air being given out, and the decomposition
of that taken in. Experimental Philosophers also discovered that 
a kind of Sooty matter was given off in the process of combustion
and concluded that something of this kind was given and in respiration
at this period the celebrated doctrines made their appearances 
which supposed a principle of Phlogistion or Inflammation 
in all their bodies. This Theory was made use of by 
Physiologist to explain the change made on the Blood, in the 
Lungs. It has been discovered by Dr Priestly, for which purpose


 




143
purpose he made a great number of Experiments on Blood with
Different kinds of Air: he found also that by pressing venous 
Blood into a sort of Phlogisticated Air, or Azrte, no change was produced,
but by putting it into common Air, it changed its color
to a florid red: this he attributed to the Phlogistic principle; he was
well aware that Blood and Air in the Lungs were not in actual
contact; Blood vessels being interposed he therefore interposed
between the Blood and Air membranous substances in which
case the Blood underwent a similar change: and thus he
found the result of his Experiments to coincide with what took
place in the Lungs. These Experiments altho’ very ingenious were
not altogether correct, as the coats of Vessels are different from Membrane,
and if a principle of Phlogistion be evolved, it is from
the Extremities of vessels, and not from their sides. We are now
since the discoveries of Larvursienr pretty well acquainted with 
the constituent parts of Air, but tho’ Philosophers agree in this,
they do not in the exact proportion of each part. They all agree
likewise that there is some part of the Air not essential to Life, and 
it is that part the Stathasions called Phlogisticated Air, or Azote 
by the French the atmosphere is then composed of three parts 
viz. Phlogisticated Air, Pure Aire, and Dephlogisticated Air: and 
some have said of a small quantity of fire, or fixed Air or Acrial 
Carbon. It becomes then necessary to examine the Air previous to 
any Experiments being made, for they will vary in proportion
to the degree of Pure Air. Dr Gordisor asserts that respiration
increase the proportion of fixed Air: that respiring 100 parts




144
of atmosphere Air, he found that it contained 80 Phlogisticated, 18 
Pure, and two parts fixed Air. That is retaining it in the Lungs
as long as possible, the fixed Air increased to 18 parts, and the Pure
Air decreased, the Phlogisticated Air retained its properties, so 
that it seems this last serves only as a medium for the two 
others. I found by Experiments, nearly the same result; some
have said that fixed Air, was resident in the Blood, and this 
was evolved while pure Air was absorbed: but those who 
reason thus, have not competent knowledge of the properties
of the Air: for fixed Air contains a portion of Pure Air and a 
Carbonaceous principle, and it is this principle only which 
exists in the Blood; which uniting with other properties forms
fixed Air. Dr Govdison contended that fixed Air was not destructive 
to Life, and that the ill consequences arising from 
the Air, being retained too long in one place; proceeded from 
a diminution of its purity. But I can refute these arguments
from actual Experiments, by suspending Animals a short time
in fixed air that proved destructive to Life; it will even extend its
deleterious effects to those Animals which inspire in Water if 
Water be impregnated with it, and altho’ combined with pure
Air, it will destroy Life. In order to make the change of the 
Blood in the Air, as concise as possible. I made many Experiments.
I first opened the Chest and Trachea of a Dog, and 
fixed to it an elastic bottle containing common atmospheric 
Air, and I injected it into the Lungs. The result of this was that 
the Blood coming from the Lungs was of a florid colour 




145
The Experiment was made a second time with pure Air
and found the Blood rather of a deeper purple than it 
was previous to its entering the Lungs. A third time the 
Experiment was made with that kind of Air which will
extinguish Flame: the result of this was similar to the last:
so it seems there is something separated or evolved from the 
mass of Blood, which is deleterious to Life, and it is that 
which the Philosophers of the present day call the Carbonaceous 
principle. In another experiment made by Dr Hunter 
when he conveyed the Blood from the Carotid of one Dog 
to the Jugular Vein of another, he observed the Blood to be 
more florid; as it flowed from an Artery he discovered it to 
be doubly Oxygenated; that is after having passed thro the Lungs
of one Dog, it was taken immediately from the Carotid and sent 
into the Jugular Vein of another, so thro’ the Lungs before it had
acquired the Carbonaceous principle. Some Animals are capable 
of supporting Life in bad Air longer than others, and 
this arises from the varieties in the Lungs. Those Animals
as Frogs &c, besides Cells have a kind of Bag that answers
as a receptacle for Air, and can while respiration is carried 
on by the Cells, live a long time without fresh Air.
But Man and Quadrupeds having Cells only and these 
very small cannot live without a supply of fresh Air.
The Otter and Whale cannot be said to be truly Amphibious 
for altho’ capable of remaining a long time under Water
they are frequently obliged to come up for Air. 





146
The source of Animal heat.
Besides the changing of the Colour of the Blood, we are now to 
consider what other offices are performed by the organs of respiration
we have many facts to prove they give heat to the body
and hence we speak of them as the source of Animal heat.
We are now to consider how far the last circumstance 
we mentioned is the source of it. It is first necessary to
understand what heat is, and to have some precise idea
of it. Some have said it is matter; others only a property
of matter. But as the Philosophers of the present day
consider it to be matter, we shall here speak of it as such.
We know that by beating two pieces of Iron together,
heat is produced; but this proves the mechanical production 
of it. Chemists have an extensive view of the
subject, and look upon it, as Elementary Matter, entering 
into the Composition of all bodies, either in a sensible 
or latent form. We must be precise in our definition
of heat. In common language we mean anything, 
when touched gives the sensation of heat, but we must 
not express the same term for cause, and effect. When we say 
Heat, we mean by it the matter of heat, and when we
Speak of temperature, we mean sensible heat. That 
does not always express its presence, either to the Thermometer, 
or Touch, as is evident from the mixture of Vitriolic 
Acid and Water: here it prevails in a latent form 



147
and therefore we cannot judge of the heat being absent,
because it does not manifest itself to our senses: now we 
could not a priori say that Carbonic Acid Gas was contained
in Chalk, wet by adding Sulphuric Acid to it, the former
is set loose in a sensible form. The Mixture of Snow and Sal
Amomniac does not generate cold, altho’ it gives the sensation 
to the finger; it is robbing the finger and all surrounding bodies 
of their heat, so as to obtain their Temperature. All bodies we
know by Chemistry are not disposed to combine with each 
other. Heat will more readily combine with one body than 
another and hence arose the Doctrine of Electric Attraction.
Many Experiments have been made to prove what these bodies 
are, we do not however intend to enter into a Minute
inquiry, what these bodies are, but so far only as to illustrate
the point in question. The Air thrown out has less 
heat, in combination, than that taken in; why? Because 
the Air expired is mixed with Carbonaceous principles,
which contains but little heat. But the contrary with regard 
to the Oxygenous part of the inspired Air. There is 
a process of double Electric attraction, which may be best
illustrated by a kind of diagram, as follows.
Venous Blood Blood [graphic] Oxygen Oxygen Gas
Carbon [graphic] Calorie 
We have observed there is a difference between Arterial and
Venous Blood that the latter contains more of the Carbonaceous
principle, and has a less attraction for the matter of heat.
Pure Air always contains a large quantity of heat in a 






148
latent form, not sensible to the Thermometer, and has a much 
greater attraction for it than fixed Air. The Blood in the Pulmonary
Artery is Venous and contains carbonaceous principles,
but in passing thro’ these Organs it loses its principle, and unites
with the oxygenating or accidifiable principle, which with heat
are the two properties of Pure Air. The consequence of the separation
of heat from the pure Air, is the extrication of Oxygen,
and the Blood afterwards being deprived of its carbon has a
great attraction for heat: hence it is that Arterial Blood, 
attracts the heat, and communicates it to the body; but 
altho’ this circumstance occurs, the Blood is not increased in 
temperature, after passing thro’ the Lungs, but on the contrary
is diminished about two degrees. Some have thought proper
to quibble at this, and have said, how can the Lungs be the 
source of Animal heat? If the Blood after passing thro’ them
is diminished in Temperature: the reason is the heat is present
in a Latent form. The Blood containing Latent heat in passing 
thro’ the Vessels receives the Carbonaceous principle
this extricates the heat existing in the Blood, and it is communicated 
to the Solids in a sensible form; by a kind of 
decomposition, and hence the degree of heat will be in proportion
to the Carbonaceous principle: from the preceding 
facts we might suppose that in proportion to the quantity
of Blood passing thro’ a part, would be the degree of heat but
this may not be the case for in passing too rapidly it may 
not be then decomposed and that heat does not depend





149
on the quantity of Blood, but in the degree of composition; this 
is evident from observing the effects which precede the operation 
on Tamoral Aneurism, or Popliteal Aneurism: after this 
operation the Leg becomes warmer and the reason is the principal
vessels being divided; the Blood circulates thro’ the collateral 
branches, and consequently much slower than usual. It 
becomes also of a deep colour from a greater proportion of Carbonaceous
principle being generated by their slow circulation
and by which heat is given out, is a sensible form. In a Man
whose respiratory organs were suspended they had for an 
hour and a half before been very much impeded, his 
body was in consequence very cold, and his face of a dark
purple colour, but on admission of Air, into the Trachea
his face became more of a florid colour, and the heat of 
Body was soon sensibly increased. In another case a 
Woman had an obstruction in the Larynx; she always 
felt cold, and on introducing a Thermometer under the 
Tongue I found the temperature at four degrees below
the usual standard. In an experiment made for another
purpose on a Dog, the Lungs were deprived of their Nervous
Energy, and the temperature was much lower 
than Natural. I found the degree of heat always increased 
by the actions of these Organs, and hence there seems to be 
an agreement between the extent of the respiratory Organs,
and the degree of heat in different animals. Those 
animals which have small Lungs and breathe but 




150
little, generate but little heat. This I proved by Experiment.
I procured Animals, such as Frogs, Snails, Eels, 
Leeches &c whose Lungs vary in structure, and examined their
dilative heat, I found that difference to be in proportion as 
the structure of these organs varied. The heat of the Human body, is the 
same in Winter as in Summer. In an Inhabitant of the Torred Lone 
as one of this Climate. Dr Crawford has made some Experiments
to prove this, or rather to explain it by immersing Animals in 
cold or warm Water. He found Animals in a cold medium
generate more of the Carbonaceous principle than in a warm one on
this [illegible] we explain the Blueness of the Face in Frosty weather
more Carbon being then generated. Now this Carbon decomposed 
more of the Air, in the Lungs, and this in proportion to its 
quantity, and hence heat is obtained according to necessity. 
An Uniformity of heat in Animals inhabiting different climates
is thus kept up. The Air thus gives out in proportion
to necessity, and the medium in which the Animal is. It has been
Anatomically discovered, that a Malconformation of the Heart
as when the Aorta and Pulmonary Artery arise from the same 
cavity, diminishes the heat of the body, for a part only of the Blood
can circulate thro’ the Lungs. The same effect is produced in 
Phthisis Pulmonalis; the Lungs are much affected and the 
transmission thro’ them is inconsequence imperfect.
The Blood by this means is only partially decomposed and 
hence occurs that Chilliness which patients are laboring 
under in this Disease. 






151
ON SUSPENDED RESPIRATION. 
Having observed that the slow Circulation was favorable to 
the generation of the Carbonaceous principle, and that the Carbonaceous
Blood was carried to the Lungs, where it underwent
a double decomposition; that the Carbonaceous principle
was here evolved, and combining with the acidifying principle
of the Oxygen, was expired in the form of fixed Air, and at the 
same times Calorie was set loose from Oxygen, and the Blood
having lost its Carbon, required a new disposition to unite 
with the Calorie: but it was stated that the Blood not withstanding
this, was two degrees colder than before in the Lungs, nevertheless
it contained more latent heat, and in circulating
thro’ the small vessels of the Body, meeting with  a Carbonaceous 
principle, the latent heat was set loose in a 
sensible form, giving rise to Animal heat. If from any 
cause the evolution of this Carbonaceous principle be prevented
the Animal Machine must inevitably be injured. This 
leads us to consider the cause of Death from Hanging, and 
Drowning, and from Suffocation: first with respect to Hanging
various have been the opinions upon this; some have supposed
the Neck to be dislocated, and that Death was the consequence,
from the compression of the Spinal Marrow; but 
upon inquiring some doubts arose respecting this, being the 
cause; for Dislocation does not often happen, indeed very 
seldom; and if it did Death would not take place sooner 




152
than it usually does; it may however sooner in some 
case particularly in Corpulent Men. Finding this did
not stand the test of accurate inquiry; another idea arose
viz, that Apoplexy was the cause. There are some appearances
which are strongly in favor of this: the appearances
of apoplectic and executed subjects. In both the Face is 
bloated, and of a purple colour, indicating a great accumulation
of Blood. I have examined the Brains of Executed 
subjects, and never found them tinged with Blood,
or any extravasation to have taken place. We now proceed 
to consider how Death is caused by Drowning: some 
have thought it was occasioned by Water getting into 
the Lungs. When thus received it excites a distress in these
Organs, and they become convulsed to expel it, and hence
we find on examining the Lungs of Animals who have died
from submersion, a small quantity of Water, and that 
frothy. Haller firsts remarked this. To prove that this Water
is not taken in by mechanical pressure, but by mere
action of the Respiratory Organs, many Experiments
have been made. Dogs have been immersed in different
colored fluids, and the result of it has been that a quantity 
of it has been found in the Chest. Similar effects have taken
place by drowning a Dog, holding his Legs out of Water, 
and in this case it could not depend on its own gravity, 
and further to evince this on immersing a dead Dog, no 
Water was found in the Lungs. Nor is any Water found in 




153
the Lungs of a Fetus; the respiratory Organs in them not
being active. Another opinion has been, that it was not
the Water, that caused the Death of the Animal, but the 
obstruction given to the atmosphere Air. I made an Experiment
which seems to confirm this idea, for injecting
Water into the Lungs of a Cat, by means of an aperture 
in the Trachea, I found that the Animal lived, and that
by repeated convulsive efforts, converted the Water into 
the form of vapour an expelled it. I also opened the Trachea 
of a Dog and with a syringe injected two ounces of fluid 
into the Lungs; the Dog had symptoms of Dyspnea.
It seems then that it is not the Water that destroys Life, but 
the absence of respirable Air. The appearances are the same
as in other Animals, only there is a scarcity of Blood, instead 
of the Vessels being turgid, and this strongly militates
against the idea of apoplexy being the consequence of Drowning.
Similar effects are produced on the Heart as from 
Hanging. Lastly the consideration of Death being produced
by noxious Vapors, comes under our notice.
If an Animal be suspended in fixed Air, from whatever
source it may arise, Death is the consequence.
It seems here that Death is produced by the absence of respirable
Air, and by the Irritability of the Animal being 
destroyed. Now if we take a view of the causes of Death
we see appearances of each quite different, and no evolution
of the carbonaceous principle is caused in either. In the 







154
next place the means for restoring Life, under Suspended 
Animation or Respiration: this is to be effected by distending 
the Lungs with Air, and exciting the Heart and Arteries to 
action. There are various means for doing this, a common 
pair of bellows is often used; but if pressure is not made 
on the Esophagus; the Air will get into the stomach and not 
only deceive us in that respect but do much mischief 
there, and prevent the descent of the Diaphragm: for the particular 
mode of performing this see Mr Colemans treatise 
on suspended respiration; his operation is simply this; an 
elastic tube is passed down the Esophagus, thro which fluids
may be passed into Stomach, by means of a Syringe.
A curved tube is to be passed down the Trachea, by which 
the Lungs are to be filled by a pair of bellows. There may be at 
the time the Lungs are inflated an electric shock sent thro’
the Heart to excite it to action; but this should never be 
done in a collapsed state of the Lungs. If after the Electric 
shock, the Heart can be felt to beat, the Artificial respiration 
should not be withdrawn too quickly: observing whether 
the respiratory Organs would be able to carry on their 
action and to what degree they may be assisted by friction 
but even this, it would be injudicious to use in the first
instance, from the right side of the Heart being before distended. 
Its on this account that some people have proposed 
Bleeding; but as we cannot take Blood immediately
From the Heart, I think it had be better omitted; except in 




155
case of suspension by opening the Jugular Veins it may relieve
the accumulation in the Head and this should be 
little, or it would debilitate too much. A little Brandy 
may now be exhibited, and stimulating injections thrown
up the Rectum. Some authors have spoken a great deal
on the expediency of heat, I think this may be very necessary, 
but it is not what first should excite our attention.
External Stimuli are useless if the respiratory Organs
are not put into action, and they become injurious by 
preventing the return of Venious Blood, and thus adding 
a bar then to the Heart; which has already too much to 
act upon: but after this action is established simple friction
may be necessary, by supplying the right side
with Blood. The Body may be placed near the fire, 
and clothes dipped in warm water applied to it. Some
have conceived Emetics to be useful, but I think them
by no means so, and as their first action is to nauseate 
they tend to depress Life. If they would act as Stimulants
they might be of great use. Tobacco fumes and Enemas ought 
to be avoided as they are deleterious; and tho’ they may assist
in some instances, the restoration of Life is not to be attributed
to them, and I have seen very great danger arise from 
their use. In a collapsed state of the Lungs Electricity should 
not be used, for at that time the Blood cannot pass, and you 
excite the heart to no purpose. The Shocks should be weak 
and passed in an oblique direction of the Heart…




156
ECONOMY OF THE BRAIN. 
The Brain is that Organ of the body which is the source 
of Sensation. Quadrupeds have brain and consequently
are endowed with sensibility. We do not connect 
any peculiar ideas to the Brain for having Nerves pass
thro’ every part it may be called the Sensorium. The bulk of 
the Brain varies in different Animals: large Animals
have sometimes a small Brain, and in general the more 
perfect and complicated Animals are, the larger the Brain.
The Brain of Animals of many descriptions bear much
resemblance to that of Man; but as we descend in the creation
this resemblance is lost. The Polypus has no Brain
consequently no Heart, and no Sensation. The co-existence
of these Organs seems natural, as the Brain receives 
Blood from the Heart and imparts to it Nervous 
Energy. A fetus may have a Heart, and a 
Nervous system, without a Brain, tho’ it has Spinal
Marrow: Some have endeavored to ascertain the 
quantity of Blood sent to the Brain. The Vessels conveying 
it, are the two Carotids, and the two Vertebral Arteries, 
and from measuring the Diameter of these Vessels
it has been said that about one third of the Blood, of the 
whole body passes thro’ this part: but this is wrong. A large
quantity in proportion to its bulk, certainly passes thro’
this part, but I think this is not more than one fifth 




157
of the whole: sometimes such a quantity may not go into 
the Brain from pressure made on the Carotids externally
but this does not appear to disturb the functions of the 
Brain: from the general accumulation, between the 
Sella Tursica of the Sphenoid bone, where the circulus 
Arteriosus is situated, I have tied the Carotids of a Dog
and no ill consequence has followed. In this case the 
other Arteries cannot enlarge nor will the Boney 
canal thro’ which they pass allow it. The Circulation 
is retarded by the right Angles, at which the Carotids 
are given off, at the curvature of the Aorta, and by the 
Blood having to mount in opposition to its gravity
by the angles made by the Arteries where they enter the 
Cranium; by the convolutions of the Vessels, and lastly 
and chiefly by the difference in the structure of the 
Arteries themselves; they being in this respect more like
Veins. Notwithstanding the number and size of these 
Vessels the Brain is not very Vascular; form any of 
these terminate in red Veins, and others only carry 
Serous Blood, hence little Blood enters the Brain itself
although much passes into the Cranium. The Pia 
mater dips in, forming Sisrures, and convolutions in 
the substance of the Brain and Vessels accompanying 
these. Hence the Brain is perforated by the Vessels of the 
Pia Mater in an infinite number of places, like the 
Bones, by the Vessels of the Periosteum. The convolutions





158
convolutions enlarge the surface for Perforation. The Vessels
carrying the Blood arise from the Aorta oil [???curvature]
forming numerous convolutions and ramifying on the 
Pia Mater, previous to their entering into the substance
of the Brain. We do not find that red appearance that 
we do in other parts of the Body, and hence it seems that
only the minute branches enter the substance of the brain
the large ones terminating in Veins upon the Dura Mater
so that only a small portion of red Blood enters the Brain
itself. The Blood after circulating thro’ the Brain and 
Pia Mater is returned into Sinuses, which take the 
same convoluted course as the arteries. Thus it descends
agreeable to its own gravity, and prevents the
Brain from being incommoded, with any accumulation
as it would otherwise be. The internal Jugular Veins
form a very important part in the return of the Blood
but there are also external Jugulars, which return the 
Blood from the Head. It may be asked how the Blood
is returned by the Veins, where they ramify? Principally
on the sides of the Cranium; but it is found that 
the external have free communication with the internal
thro’ different foramina. Therefore if the Brain be oppressed, 
an opening into the external Jugulars would be
of infinite service. The Vessels communicating the external
Jugulars, and Facial Veins, are called Vasa Emissaria: 
they carry Blood out of Cranium and convey 




159 
it into Veins. When we remove a small portion of the 
Cranium, we perceive a pulsatory motion, which
has given rise to various conjectures. If we examine
closely we shall find the Pulsation sympathizing 
with the wrist and hence it has, with reason been
said to arise from the pulsation of the Arteries within
the Pia Mater; but independent of this there is a motion,
which exactly corresponds with the act of respiration:
for as Air is taken in, or expelled the Brain becomes
flattened or elevated. During Inspiration the 
Cells being filled, the circulation is free, but when expiration
is performed the Lungs collapse, and circulation
through them is impeded. This gives a temporary 
check in the admission of the Blood in consequence 
of which it is delayed in the Jugular
Veins, until an inspiration is again made, which 
explains the motion. There are ten pair of Nerves
arising the Brain, and thirty from the Spinal Marrow.
Besides these, there is another Nerve, the grand
Sympathetic, or Intercostal, which does not appear
to arise from either, but from the numerous branches
of others, and seems to be a Nerve of general communication
and sensation, rather than of a particular
origin communicating with vertebral Nerves
the pair Vagum and the sixth pair. Nerves are dense
and compact bodies, white inelastic, and connected 



160
together by cellular structure; in some parts being soft
and pulpy, and in other parts more compact: and from
these arises the various degrees of sensation. The pulpy 
Nerves, as the Ophthalmic, Olfactory, and Auditory, being 
more readily acted upon by impressing causes. 
With respect to Vision it is caused by the Subtle 
matter of Light, acting upon the Retina, and impressing 
upon the Mind the idea of the object seen. 
Hearing is not impressed upon the Mind, by the body
itself giving sound, but by a kind of tremulous motion
produced in the Air: by the sound, and the Nerves of these
parts being of a soft delicate structure, readily convey
the Sensation. The Sense of Smelling may be explained 
in a similar manner. A grain of musk for instance
will scent a whole room and yet it will not appear 
to be in the least diminished in bulk, although it 
must have sent off something to act powerfully 
on the Organs of Smelling.  Hence it appears a law
in the Animal Oeconomy, that the Nerves should be 
of such a structure as adopts them to receive the different
degrees of impression made on them by the variety 
of matter. Nerves are not possessed of Irritability
viz, they have no power of contracting inherent in 
themselves, tho’ by being stimulated a contraction will
be excited in the Muscles to which they are sent. This 
power is not generated by the Nerves, but proceeds from 





161
the Brain. I opened the Chest of a Dog, and divided the 
Phrenic Nerves, and then irritated it below the opening; I
found that the Diaphragm only contracted for a short time. 
The Nerves like the Arteries have free communication with 
each other; but the branches of communication are much larger, 
and are called Plexus’s. There is another structure peculiar 
to Nerves; they have a knotted appearance called 
Ganglion. The largest Plexus is the Axillary Venous opinions 
have been formed respecting these, or rather the 
use of them; some have supposed they possessed a Muscular 
power, or motion of propelling the Nerves influence 
further. Another supposes they answer as appendages 
to the Brain, and have a power inherent in them of 
generating Nervous Influence: but a similar objection 
may be made to these conjunctions, viz if there was any foundation 
for these ideas; the Ganglions, or Plexuses would
be found in those parts which are at the greatest distance
from the Brain, which is not the case. Mr Clines opinion
is that they serve only to enlarge the surface of 
the origin of other Nerves: and this opinion is I think
most reasonable. It is observed in proof of this, that 
many filaments of Nerves are going off at every Ganglion…




162
OECONOMY OF THE NERVES.
The Nerves may be considered in four points, first as the organs 
of Sensation; secondly as giving mobility to the Muscles; 3rdly as 
having on Influence over the Glands with respect to their Secretion, and  
4thly as being organs of Sympathy. In considering Nerves as organs of 
Sensations we must first make some observations on Sensation itself.
Sensation is the application of matter to a part which by means
of the Nerves the Sensation is conveyed to the mind; for instance if 
any thing be applied to the fingers, by means of the Nerves the sensation 
is conveyed to the Mind, and referred back by it to the part then
Sensation is produced. But the Mind may sometimes be deceived
for sensation may be conveyed to a part that does not exist,
thus after amputation the patient will sometimes complain of 
pain in the Toes; owning to some of the filaments going to the Toes
being in an irregular state, and the mind being long habituated 
to convey the impression: this is sometimes correcting the error, but 
at last it corrects the Sensation. Sometimes the mind refers the 
impression it receives to a wrong place, as in the stone, the pain is 
felt at the orifice of the Urethra. Again with respect to the internal 
part, we are not at all able to judge of the real pain; and the 
reference made to the Mind by these is often wrong; because they 
are not under its influence as the internal parts. Besides these 
there is another Sensation which conveys the idea of soreness, this 
however is nothing more than an inadequate quantity of 
Sensation. Before any Sensation is produced, there must be a    





163
communication of Nervous substance between the parts impressed 
and the Mind. There is a peculiar something in the Nerves which 
cannot be explained: but admitting the fact of their decussating 
each other, viz the Nerves arising from one side the Head being distributed
to the other side: it is upon this principle only that we can
account for Paralysis on one side, being produced by an injury on 
the opposite side of the Head. The irritation of the Tuniia Conjunctiva
from [illegible] a flow of Tears from the Lachrymal Glands: this arises from a
communication of Nerves: the fifth pair supplying filaments to 
both these parts: a branch being sent to the Lachrymal Gland. Light
irritates the Conjunctive membrane and excites the Pupil to contract
this also is from Nervous influence. It is necessary that this should be 
attended to in a Gutta Serena, for in this the Pupil is always dilated
and by irritating the Tunia Conjunctiva, it contracts. Another kind 
of Sympathy is that which we call setting the Teeth on edge; but 
this Sensation must be produced by different sounds, first acting 
on the Organs of Hearing and by means of Nervous influence
sent to the Teeth. It may still be asked how is this produced?
For the Portio Mullis, which is the immediate Organ of hearing 
has no nervous communication with the Teeth: but tho’
this is the case the Portio Dara sends off Bearuhes which communicated
with the Portio Mullis, and others also of the Teeth, and 
that is the Sensation produced. Another instance of Sympathy 
is the Inflammation of one Eye, irritating and inflaming 
the other, which arises from Nervous communication.
 




164
On the Secretions generally.
When we were considering the properties of the Blood,
we confined our observations to its important purpose
of supporting the Body; we are now to consider it, in another 
point of view. As forming the Secretions of these there are
a great number, some answering one purpose, some another
some are necessary to Health, and the support of Life, as Saliva
Gastric Juice, Pancreatic Juice &c others as the Fat, seem to 
answer more purposes as supporting the body, under distress
as well as constituting its beauties and form. Bile is answering
a very important end; being to act on the Intestinal
Canal, as its natural Cathartic: some others are of great use 
to facilitate motion, as the Liquor Pericardia, intestinal fluids 
&c. there are others which have answered their purposes as Perspiration, 
Urine, Exhalations from the Lungs, and Excrementious
Matter: these seem to benefit the machine only, by being 
thrown off from it. Some others seem destined for particular
purposes as for propagating the species as the semen, the fluid
from the vesicular seminalis, and prostate Gland. Females have 
also a Secretion of the Ovaries, and other parts: and likewise a 
peculiar Secretion; the Liquor Anmii: and the Milk for the nourishment
of their young, after birth. Particular Animals are 
found to have particular Secretions. Ants secrete an Acid fluid
the white of an Egg appears to be secreted from the vesicular membrane
which encloses it: this membrane is too vascular for the 




165
Blood to be at all intended for its nourishment, and a great quantity
of it seems sent to furnish this secretion. There are other Secretions 
belonging to particular Animals which are poisonous
as Rattle Snake, Wasp &c &c A natural Secretion may become
poisonous; this is remarkable in the Mad Dog, when the Salvia 
becomes poisonous. We must now distinguish Natural and Aritificial 
Secretions. The first are regular and constant; the latter 
are arising from accident, as Pus &c. but this is often poisonous
by being impregnated with Venereal or Variolas Matter.
Some Secretions resemble the Elementary parts of the Blood
as the Urine, Tears &c. &c. not that they are exactly the same
but differ only a little from them, and others again are
totally different; so that they would appear to be formed 
and not separated from the Blood; as the Bile &c. The 
properties of these fluids are various, and diversified as 
the Glands which secrete them. Secretions which at first
appear to be homogeneous, will by spontaneous separation
appear to be heterogeneous: thus Milk separates 
with cream, and what is call skim Milk under heat 
again separates into Butter: and another kind of Milk 
called Butter Milk is produced. These again may be separated 
by a process of Chemistry. Skimed Milk separates 
into Water, Sugar and Whey, and by the addition
of Rennet a solid Curd is obtained. We are quite ignorant 
as to the way that these fluids exist in the Body
that they do exist we cannot doubt, as every thing



166
is separated from the Blood, by the various offices of the different 
Glands. Every Secretion has its peculiar Organ or Glans: these 
Glands have different forms and hence a division of them into
Simple and complicated: of the first kind are the Mucous Secretions;
and the complicated are those with Arteries Veins, and 
Nerves, with Absorbents and Excretory Ducts. Of Glands there 
are a great variety, this term only refers to their figure, but 
we ought to refer to their Functions. Secretory Organs are 
sometimes membranous as the Stomach; this has no particular
Organ secreting the Gastric Juice but the whole 
internal surface is performing that office, and therefore we 
cannot properly refer the idea of Gland to figure. We know
that the business of this Secretion is to dissolve, and this it will
do more readily in proportion to its surface for its action
hence solution is more readily performed in the Stomach 
by this fluid, than if it was proved out by a few Excretory 
Ducts, and hence the Arteries have their two offices, that 
of supplying Blood, and answering as Excretory Ducts.
Another class of Glands, simple, are those which have Follicles
or Crypta. The Follicles do not secrete, but are receptacles 
only: the Secretion being performed by Vessels. The 
Tongue is a Gland of this kind. In the face about the Nose
the Lips and the Ears, we have a great number of these Follicles
which contain a Sebaceous fluid; these each have an outlet
but in those of the Cells there are none. The membrane forming 
these Cells secrete Fat, and the Absorbents take it up




167
and perform the office of Excretory Ducts. The Synovia is also taken
up by the absorbents. What we have already said respects simple
Glands, but others, are more complicated having Arteries, Veins, 
Nerves, Absorbents and Excretory Ducts, all connected and included
in one common membrane; of this kind are the Kidnies.
The Absorbents are few here in comparison to other parts. This division
of Glands into simple and complicated, arises more from 
their structure than their figure and is certainly more Physiological. 
Sylvius made a division of Glands into Conglobate 
and Conglomerate: the former applying to those which have a 
regular form, and the latter to those which are made up of a number
of small ones. The Vessels of the kidnies have one centre of 
ramification those of the Liver have two: the Lachrymal Ducts
are six or eight in number; and where there are a number of 
Ducts, these Glands have a receptacle for their Secretions; as 
the Female Breast, here the Ducts themselves are very much enlarged.
Secretion as those of the Semen and Tears are increased 
by the passions of the Mind, which cannot influence the principles
of Fermentation. In the Hepatic Duct the Bile is much 
Diluted, but in the Gall Bladder it is much more pure. It is not 
always necessary that Stimuli should come in contact with
the Secretory Organ; for instance if the Tunica Conjunctiva
be stimulated, the Lachrymal Gland will secrete abundantly.
In Winter the Secretion of Urine is abundant but in the 
Summer not near so much: more going off by Perspiration. 






168
THE SECRETION OF THE URINE.
We are at all times in the habit of taking in more fluids than
is necessary; consequently the Vessels, must be always in 
a distended state, if there was no outlet to carry it off.
The Exhalents are principally those of the Lungs carrying off
the more Watery parts of the Blood. Secondly the discharge of 
Perspirable matter, and thirdly the Kidnies, whose office we 
are now to consider. The Kidnies are two in number
situated in the Lumbar region, their figure is well known. 
As they give rise to a copious Secretion, they must necessarily
be well supplied with Blood. The Vessels carrying the Blood 
are the Emulgent Arteries, which pass off from the Aorta, the 
number of them is not always the same, being sometimes
two, three, or more: they enter at that part of the Kidney called
its Pelvis; but previous to their entering they divided into 
several branches, and in the substance of the Organ they
divide into Capillary Vessels; as the Arteries are large, the 
corresponding Veins must be larger. The Kidnies are also furnished 
with Nerves and Absorbents; but the latter are not 
so numerous as in the Liver. As the Kidney is an Organ
Secreting a large quantity of fluid, it is necessary that 
there should be a tube or canal to carry it off and this
is done by the Ureters. If we Examine a Kidney we find
it very different in different parts: one is called the Tubular 
and is whiteish, and the other being most exterior takes the 





169
name of Cortical. But in the Human Kidney these parts intermix 
with each other, and therefore the distinction is not exact. 
The Cortical part is very Vascular, and is the only part which 
Secretes. When the Emulgent Artery has ramify every minutely
it terminates in small Cells, called Corpora Globosa.
From the mammillary processes the Urine passes very slowly 
into the Infundibula, which are membranous cells; and 
the slowness of the Urines motion allows time for Calcareous
concrections to form in these parts. After passing from 
the Infundibulum the Urine passes into the Pelvis of the
Kidney, and is from this conveyed by the Ureters into the 
Bladder. Some have considered the Ureters as possessing 
Muscular power, I have not been able to discover this 
and hence other tests have been resorted to; some have 
stimulated the Ureters by pointed Instruments, and therefore
can deny it, however in subjects who have died and 
in whom Calculus Concretions have been found in the 
Ureters, I have found these distended. Now we see that
Muscular parts will recover their actions or dimensions
as soon as the obstructing cause is removed; but this I
did not find to take place, with respect to the Ureters.
From this and other reasons I am inclined to think that if 
they contain any Muscularity, it must be very inconsiderable. 
In the case of an Ovarian Dropsy, that burst the 
Water was effused into the Cavity of the Abdomen, and the 
Absorbents of that part, not being deceased took it up 

	




170
and a great Secretion followed. The Urine may be 
morbidly affected in various way; one is from Diabetes,
which is a Secretion of Urine not natural; but containing a 
Saccharine Matter. Experiments have been made to ascertain 
the quantity of this in twenty four hours; there is a 
great dryness about the Skin and fauces; the cause of this complaint
is not clear; for Medicines possessing different actions
have been found to cure, as steel, Bark, Aloes and Dovers Powders.
In Hypocondriacal people the Urine is rendered Pale,
and so it is in the cold stage of fevers: but when the constriction is
taken off a sediment is deposited. There are surrounding the 
membranous part of Urethra Muscular fibres, which are called
Sphincters, and which appear to act on two principles; first by 
their Tonic power they are capable of retaining the Urine, until 
the Bladder is distended to a great size; after the power is overcome
the Mind is called into Aid, in order to excite more forcibly 
the fibres to retain it: but suppose there is a great distension
the Levator Ani in that case, by drawing up the membranous 
part of the Urethra, against the Pelvis will narrow
the Pelvis Canal, and in that way assist the power of retaining 
it. Mr Cline recommends in case of inability to retain 
the Urine from Gonorrhea, Teriture Ferri Muriata 
gH + every ten minutes until it produces Nausea; the Aqua
Calcis and Bark will soon restore. Some have contended 
that there are other ways for Urine to get into the Bladder, besides
the Ureters: but this is the effect of Imagination. 




171
The Secretion of Bile.
We are now to consider the Oeconomy of that organ destined
to secrete Bile; previous to which it may be 
necessary to make some observations on the Nature of 
Bile itself. The Bile is a green fluid, bitter and pungent:
in the Gall Bladder it is concentrated, but when 
it is more diluted it is of a yellowish color, and hence
the yellow color in the jaundice. It has certain degree of 
viscidity; lathers under agitation, and possesses saponaceous
properties, which causes it to be employed by some
in the cleaning of clothes: there is reason to believe from 
these principles, that Bile possesses heterogeneous properties
it has often been the subject of Chemical Examination
and it was usual in this process to sublime it, and 
Examine the residuum. The science of Chemistry having 
become more extensive a knowledge of tests has become general:
and these have been employed instead of the old 
method by Heat. Vapour arises from Bile under heat 
impregnated with a degree of odour, which is the Watery
part and if we distill it, there remains a thick resinous
like substances. The Bile having great viscidity I wished to 
know, if it did not owe this property, as in other instances
to the presence of Mucous; with the assistance of Dr Batlington 
I made the following Experiments: when Mucilage is combined 
with water it will on the addition of Spirit of Wine





172
be separated, and the water be united with the Spirit.
This principle we applied to the Bile, and on the addition
of some Spirit of Wine, a green watery fluid was
separated, and left behind a mucous matter; probably
the mucilaginous matter is greater in the full bladder, rendering 
the Bile more viscid. The liquor thus obtained 
is evaporated, and the residuum was resinous; it is this 
Resin that imparts to the Bile its colour and taste: hence
then the odour, viscidity, colour and taste are accounted
for, but we spoke of a saponaceous liquor, which supposes
the presence of an Alkali probably the Mineral. For 
the Secretion of this fluid Nature has destined a large Organ
the Liver, which is situated in the Cavity of the Abdomen,
in the Epigastric Region, and right Hypochondrium,
and it is connected to the Diaphragm by reflections 
of Peritoneum. As the Liver performs a Secretory office
and all the Secretions being derived from Blood, in must follow
that this Organ must be plentifully supplied with 
Blood. In all Glands there are Arteries, which carry Blood
for the nourishment of the Organ, and for the Secretion.
But in the Liver there is a peculiarity in this respect, the 
Artery enters the Liver, at the Porta, and ramifies thro’ it,
and the Blood is returned by the Hepatic Veins, with the Vena
Cava. The Artery in this case does not supply the Blood for 
the purpose of Secretion; what vessel is it then? It is the Vena
Portasum, which serves in some measure to perform the  





173
office of Artery and Vein. The Chylopocitic viscera are 
supplied with Blood by the superior and inferior Mesenteric 
and Celiac Arteries; these ramify and terminate
in Veins, which ultimately terminate in one common
Trunk, called the Vena Portarum. The Hepatic Arteries, Vena
Portarum and others, are encircled in a folding of Peritoneum 
Which is call Glyssons Capsule. The Vena Portarum has
two terminations, one with the Hepatic Veins, the other for the 
Secretion of Bile, and we find that the Liver is formed of a quantity 
of Angular Crypto, not globular as in the Kidnies, and 
here the secretion appears to commence from these the Pori
Biliari begin, these are the commencements of the Hepatic duct
the branches which are at first small continue to enlarge and 
by smiting finally form the Hepatic Duct: the Bile is conveyed
by this duct from the Liver: it is then to go into the Duodenum,
but we have the Cystic duct communicating with 
this and the Gall bladder. It takes the Bile both from and to the 
Gall bladder as may be required. The Artery is thought by some
to assist in Secreting the Bile, and I believe it may do so,
sometimes but that is not its usual office. It is evident
that there will be sometimes a communication between the 
Blood in the Artery, and Vena Portarum, from regurgitation
as both end in the Hepatic Veins. When Bile is first secreted
it is first very Watery, but there are a great number 
of absorbents arising, and it becomes concentrated as it 
passes into the Hepatic Ducts, and it is still more so  




174
in the Gall Bladder. The Ductus Communis Choledochus, 
which is from the union of the Hepatic and Cystic
Ducts, and the Pancreatic Duct empty themselves into the 
Duodenum at one common opening. I have not been 
able to find Muscular fibres in the Biliary Ducts; but 
there may be Spasm at the end: because there we have 
a circular order of fibres: but these are in the Duodenum.
If Bile meets with a temporary obstruction 
only, it causes no inconvenience; but if it meets 
with a continued one, and is not carried into the Intestine, 
Jaundice is produced. A Gall Stone may be
the cause of the obstruction, any irritation of the fibres
of the Duodenum may cause a temporary Jaundice, 
from the obstruction of the flow of Bile. Jaundice 
generally arises from the pressure of stone, and 
not from Spasm as has been supposed by many 
Numerous conjectures have been formed relative 
to the opinions of how Bile gets into the mass of Blood.
Baron Haller supposed it got into the Blood by regurgitation; 
but Dr Munro and others thought
it was by Absorption. I believe it is in part by 
each. The use of Bile mentioned, when on 
the process of assimilation in a former Lecture. 



	




175
ON MUSCULAR MOTION.
There is in most Animals a power by which they can 
move one part upon another, and this is done by the 
actions of the Muscles. Some Animals have Muscles
which are remarkably distinct, others have them 
not so distinct, yet no one will doubt but that they 
possess Muscles, as the Flea &c. Anatomists are divided 
in regard to some parts, as in the Urethra, some 
say this is Muscular, because it is subject to spasmodic
action or structure; though this is not caused 
by Muscular action there, yet there are Muscles near, 
which may very probably cause it. The same takes
place in the Biliary Ducts; but the constriction is 
chiefly at the end of them. The same has been also
often said of the Gall Bladder, which we are persuaded 
is not Muscular. Some have said the Iris has 
no Muscular fibres, although there is contraction, and 
dilatation; but I have satisfactorily seen them 
in a grey hound. Some have carried their doubts so 
far, as to say, that there are no Muscular fibres in
the Uterus; but they certainly are very obvious here 
when the Uterus is enlarged from impregnation. A
Muscle is a bundle of fibres, they have Ateries, 
Veins, Absorbents and Nerves. Some have said, that 
what is called a Muscle is only a continuation of 




176
Nervous fibres; because if a point of a Pin is introduced
Pain is immediately felt. Muscles are 
ductile, but not elastic; they have a contractile 
power from Life and Energy. In general they are 
in an half extended and contracted state, which is 
for the most part most easy. They have the power
of lying in a short space, as in Animals when at rest.
This is owning to their Tonic power, which must not
be confounded with Muscular action. In order that
they should act, they must have health, or tone, and 
Life; also irritability to be acted upon, by the stimulus
applied and must communicate with the Mind, 
through the Medium of the Nerves. When a Muscle is 
in Tone it feels hard and firm. They are most firm 
in those people who are in the habit of using much 
bodily extension, also in parts much used by particular
employments as in Fencing, Boxing, Vaulting, and in 
Watermen whose Latissimus Dorsi are very large, and 
firm. They are also much weakened by want of use. 
Haller did not consider that Nerves were the immediate 
cause of action, but that Muscles has Vis Insita, 
as he termed it, in themselves. But it is, with more
propriety conjectured that altho’ Muscular fibres act, yet that
Nerves give that power of action. If a Limb is cut off, the 
Muscles will contract upon the application of stimulus, 
until the Nerves power is worn out; but to try






177
the Experiment fairly, I paralyzed the Limb of a Dog, by 
dividing the Nerves, then left it for a day, and Electricity 
would not rouse it: which arose from its want of Vis Nervosa:
but the Muscle has Life and Circulation, where there 
is the Vis Insitee? Muscles are not always shortened when
they act, but the endeavor to do so constitutes their action
Muscular parts can stretch, for instance, the Urinary Bladder
will distend to hold a Gallon, but if the cause of retention 
is removed it will contract on a spoonful. Exercising 
ourselves by action or costume, we give them precise power
we wish, therefore if we wish to raise anything apparently 
heavy, a large quantity of power is directed by the Mind
and if it proves to be light it is raised by a jerk et vice versa,
thus by habit we know what Muscular power is required.
Muscles are either voluntary or involutary. The Heart is 
involuntary, the Diaphragm and Intercostal Muscles are
so in part, but not wholly different kinds of stimuli excite 
the action of Muscles, as the Will, also fear. If a Man is shooting 
at a Mark he does it steadily, but if an opponent is in the act 
of shooting at him, his Muscles become involuntary. A person
by Anger may cause the pettish morose and surly disposition 
to be marked in his countenance. Muscles have the power of repairing
themselves: but we have reason to believe they do not repair 
themselves by their own kind. I divided the Stem Hyoidens Muscles
of a Dog and they contracted, after some years he was killed and the 
division was founded to be united by Ligament. 




178
Of Menstruation. 
If we examine the structure of the foetus, and the Orblulb and 
their Oeconomy; we find, tho’ there are very different actions
set up in each, a foetus has the Organs formed for perpetrating 
the Races; but their actions are not developed. Those Organs
which are vital, and are immediately necessary to Life
are found to be perfect in the Foetus, as the Organs which carry 
on Circulation, Respiration; Glands &c. but those destined
for perpetuating the Species are not. This is a wise provision
of Nature, in consequence of which women never have Children
until they are able to take care of them. Some parts however 
which are not seen at Birth appear soon after as the 
Teeth which are necessary to perform the office of Mastication
they begin to come forward about sixth month; and the 
parts last formed are the Organs of Generation. About the Age 
of fourteen or fifteen in this country, changes take place, and 
this period is called Puberty. The softness and rotundity of 
the Breasts diminish, and give way to firmness and compactness;
at this period the body forms and assumes different characters
which mark its Sex: the increase of growth at this 
time is great, and the mind as well as the body is affected; by 
indulging in the Contemplation of the other sex. In Man we 
have a protrusion of Beard, and a great change of voice;
which at first is harsh and rough, but gradually softens into 
deep Manly expression. The Testes which were formerly situated





179
situated in the cavity of the Abdomen, have now begun to perform 
their office. An Eunuch who may be said to live in perpetual 
Infancy, has none of these changes taking place, he has the 
Bulk, but not the figure of a Man, his limbs are more wended 
like those of a Woman, and he seldom stands upright; there 
being a flexion of his limbs, which denotes a defect of Energy.
In other Animals the same cause produces the same effect.
A colt if Castrated never possesses the figure of a Stallion, 
he has not the fine arched Neck, Sonorous Voice, nor the piercing 
eye of these Animals; but becomes more like a Mare
in his appearance. In like manner the Ox does not possess
the figure of a Bull. The changes at the age of Puberty are so 
remarkable that many explanations have been offered for 
them, but they are vague and unsatisfactory; and the one 
most presumed upon is in my opinion the most fallacious;
this is that at the Age of Puberty Semen being absorbed
into the system is capable of producing these changes
which characterize this period. But if absorption was necessary
to produce those change, we ought to expect a continuance 
of causes to keep up the effect, and Castration
if performed at a late period of Life ought to throw the system
back into the same state it was in before Puberty
but this is not found to be the case; no change takes place in 
Man or other Animals castrated after this period, if we except
the before possession of propagating the Species. The changes
which take place in Females, are not less remarkable than 




180
those in Males and here the cause of absorption cannot be existing 
perhaps it would be more Physiological to say that it is the 
law of the Animal Oeconomy, and that these changes take
place in consequence. The changes in Females commence
rather earlier than in Males. A year perhaps in general.
The figure of the body is much improved in gracefulness 
and elegance; the Breast which may be considered as the appendages
of the Uterus are evolved. The Constitution sometimes
reaps great benefit and advantages in consequence. Epilepsia 
and Scrophula which have before this appeared, are frequently
now driven away; but the most remarkable change that 
takes place, is that of Menstruation, so called from the time of 
its recurrence; but from analogy it has been called Flowers
from their preceding fruit, as the Menses precede Impregnation
Sometimes the discharge has been called Catamenia, from 
the same cause of its periodical occurrence. This regularity 
is peculiar to the Human Female. No Animal besides
has regular discharges; but many as Bitches and Does
have Blood discharged at their particular season of procreation. 
The evacuation depends then on an accumulation
of Blood, which renders the Animal in a fit state to perform
that office destined it by nature. The general age of 
Menstruation is about fourteen or fifteen, there are exceptions
to this; some altho’ in good Health never Menstruate until 
their sixteenth year, and some again as early as twelve. I
know an instance where a Child Menstruated at six years





181
old, but no change had taken place in the Body, it was therefore
to be considered as a Morbid, rather than a natural Menstruation.
It also varies with respect to Climate; the warmer the 
Climate is, the sooner this discharge takes place. In the Indies
they generally menstruate as early as ten or eleven years 
of age, but in Lapland and cold climate this period is much 
later, and the discharge is very sparing at any time. There 
are many causes which may accelerate Menstruation, 
such as warmth, and the manner of living; Females who 
live luxuriantly Menstruate much sooner than those 
who live poor and labour hard. The periods of Menstruation
are not always Monthly; sometimes I have known 
them come on at three weeks, and in other instances as late
as five or more. This discharge having no coagulum is 
not like Blood; this is evident when the Menses have been 
retained by an imperforated Hymen. Sometimes Women have 
a flow of the Menses after conception, which in general is considered 
as a forerunner of Miscarriage. If this should coagulate 
and be attended with pain, it is then often followed
by Abortion. Before Menstruation comes on, Females have 
Characteristic symptoms, such as pain about the Breasts
shooting pains about the Loins, heaviness, head ach, and 
vertigo, all of which indicate the appoach. But as soon as 
the discharge appears the Woman is relieved. Sometimes
these Symptoms come on, and the discharge follows, and 
again recurring at particular periods, causing distension,




182
full Pulse &c. this indicates that the Secretion has taken place
but not discharged from an imperforation of the Hymen.
Here the simple operation of a Crucial incision will relieve
and the symptoms will disappear. Sometimes it happens 
that in young persons about seventeen, eighteen, or more, no
menstruation has taken place. A peculiaar change seems 
to have affected the constitution, there is great paleness, heat
a quick and rather hard Pulse with all the other symptoms
characterizing chlorosis; these manifest the want of Menstruation;
but this is also sometimes indicated by an accumulation,
distension or full Pulse, &c we should therefore 
carefully distinguish between the two causes of Amenorrhea.
In the latter case the functions of Chylification and Digestion
go on well, and the complaint is generally from cold
or some other cause: in this case of accidental obstruction
bleeding and emmanegogues will be necessary. Some have 
endeavoured in chlorosis to bring forward the Menstrual  
discharge, but this is the effect and not the cause. Electricity 
by being passed thro' the parts would cure the complaint,
but it is found necessary to strengthen the system with Bark
and steel. Perhaps witholding the Blood is wise in nature
when the Constitution is not able to bear it. In Chlorosis the 
patients should have some indulgence and not be too often
driven about which is too often the case, even with Medical 
Men. We must not consider every stoppage of Menstruation 
as Morbid, as after Marriage suppression of the Menses





183
is considered a sign of Conception, and Women generally
reckon from that time; and when there is a copious flow of 
Milk no Menstruation takes place, unless there is plethora: 
and it is always considered an objection to a Nurse
if she Menstruates. Some have supported that suckling precludes 
the possibility of Impregnation, and under this 
idea many women have continued to suckle their Children. 
This may in some degree be true, yet Women who 
while suckling have enjoyed themselves in the pleasure
of Coitu, have found themselves deceived in this particular.
There is a case mentioned by a German Physician 
of a woman menstruating only when she was pregnant
but we must leave their Physiologist to show how this was.
The proper seat of Menstruation is the Uterus, but where there
are sore or ulcerated legs it occasionally happens by them.
Some have had periodical Hoemoptoe, or Bleeding from the 
Nose or Intestines. Some have said the Vagine is the seat 
of Menstruation, so it may be, as these others are, but it 
is not the power seat. We may see what happens in 
providentia Uteri, we then can see from where it comes.
Another question is from what Vessels it comes. A few
have said it was from the Veins, but the more general 
opinion is that it is from the Arteries: and Anatomy 
seems to favor this opinion. Those who say the Veins
are the Vessels, ground their opinion, or the Veins being
more subject to congestion; so they are, but at what




184
period of Life? In regard to their being more liable to 
burst; this is in old people. But in the young these Hoemorrhagies 
are evidently Arterial, this is a strong objection
we consider that the balance of the circulation takes
place about the fortieth year, and according to this, their 
Menstruation should begin about the time it is ending 
and old Women only should Menstruate. There have been 
various conjectures on the cause of Menstruation, it has been 
said to be influenced by the moon, if thus, all Women would 
Menstruate at once, which is not the case. Other opinions have 
been general and local Plethora; suppose the first, drawing 
off a few ounces of Blood would prevent the appearance
of discharge, but it does not do so in an healthy patient,
but we know that when there is but little Blood made
we have Chloroses, and for want of general Plethora; but 
this alone is not sufficient. We suppose local Plethora
and it appears it is in part connected with general Plethora,
but more especially by Uterine or partial Plethora
its use is considered to treasure up a portion of Blood, for 
the Nourishment of the foetus, we may consider it as used
for this purpose, as far as it goes, but this is not sufficient
for its entire nourishment. We may consider it also to 
keep the parts in ready condition to form connection
with the ovum, and furnish it with necessary supplies
Impregnation can never take place till after Menstruation. 




185
ANIMAL IMPREGNATION.
Having finished what related to the Oeconomy of the different
organs most essential to Life, we come now to consider the 
means nature has provided for perpetuating the species; in doing
this we shall not enter into the manner by which it is performed
in different Animals, but shall confine ourselves immediately 
to the Human Species. In Man and in other Animals
the Race is propagated by mutual intercourse between the sexes. 
We shall therefore, in the first place consider the Seminal fluid
by which conception is produced, secondly, the other fluids which
are usually mixed with it, and lastly the conveyance of the fluid
into the Uterine system of the Female: first of the 
Seminal Fluid. The Testes are the organs, secreting this fluid
they are two in number, situated at first, within the cavity
of the abdomen, about the seventh month they begin to descend
into the Scrotum guided by the Gubernaculum. In some Animals
they remain in the Abdomen thro’ life. The Testes undergo 
great change at different seasons, in the Summer 
during procreation, they are very large, but in the Winter they
shrink to a very small size. We must consider them in 
the same order as other Glands, first taking a view of the Vessels
which supply them, with Blood, and next of their interior
or secreting structure. The vessels which carry the Blood to the 
Testes are the Spermatic Arteries, which arise from the 
Aorta near the Emergent Arteries. It would seem an 





186
objection to the general Law of Nature, that these should 
arise [from] at so great a distance from the part they are meant
to supply: but this is applicable to the adult only, and not 
to the foetus. The Spermatic Arteries pass thro’ the Abdominal 
ring dividing into two branches, one of which is 
going to the Tunica Vaginalis and the other to the Testes itself; previous
to their entering the Testes, they make several convolutions
this is more particularly the case in Horses which renders
the length of the vessels the greater, and the greater the distance
from the Heart, the slower the Circulation must be. It seems
that nature intended by this, that the fluid should be more 
elaborate, and better filled to form an offspring which in 
time is to produce a similar secretion. The Circulation 
thro’ the Artery is made slow, from its structure, which 
is like that of a Vein, and collapses in the same way as the 
Veins do when divided. In the Testes as well as other Glands
a considerable portion of Blood must be returned, hence 
there must be Veins, and the Arteries must have a communication 
with them. These Veins when we consider 
the size of them bear a much greater proportion to the Artery
than is general; there is mostly five or six in number
each as big as the Artery which renders the Circulation still
slower and more languid; this is further favored by position.
The Blood having to mount contrary to its gravity: these Veins
Freely Anastomose, and those on the right side empty the 
Blood in the Vena Cava, but those on the left side into the 




187
left Emulgent Vein. As the ultimate branches of the Spermatic 
Arteries, must have another termination, besides 
that of Veins, we must inquire what that mechanism is?
We are anatomically informed that the Testes are tubular 
they appear at first like a mere pulpy mass; but by maceration 
they may be enveloped, and a series of convoluted
vessels may be picked out, which somewhat resemble
a rumpled skain of fine thread. Now injection proves them 
to be hollow tubes, but to fill them, we must not inject 
in the course of the circulation, but in the contrary way 
hence they must be injected by the Excretory duct of the 
Testes, and not by the Spermatic Artery. Anatomists and 
Physiologists have puzzled themselves to discover the 
length size and number of these tubes; some have said that 
if drawn out, they would measure many leagues, others  
only a Mile; but Dr Hause has formed Calculation from 
which he says there are five hundred Tubes each being ten
feet long: he has also endeavored to ascertain their Diameter
by the use of micrometer, and by this he finds them to be about
the two hundredth part of an Inch in diameter: but 
tho’ this Calculation may apply to the Human subject, it 
will not to other Animals. Some Animals Secrete Semen very 
fast. When a Man is in company with Females under certain
ideas, if he was to examine, he would find some degree 
of tumor, not in the Testes, but in the Epididymis,
this probably is depending on a Secretion of the Semen  
  




188
from the Testes, and not being passed on, distension is the consequence.
This furnishes us with a sufficient proof of the Influence 
of the mind over the Seminal Secretion. When this Secretion
has been performed from the Artery into the tubes, there 
must be a way for its conveyance out of the Tubes. There is 
a set of tubes placed in a reticulated manner, thro’ which it  
passes, called the Rete; from there it passes to a set of vessels 
called Vasa Efferentia, these are about ten or twelve
in number, and partly from the Epididymis; one 
third of it being formed of these Vessels, and two thirds of 
the Membrane investing them: the Epididymis can 
be proved by Injection to be one canal only, but much 
convoluted. The Semen is then conveyed from the Tubiti
Seminiferi to the Rete, and from thence to the Vasa Efferentia,
And then to the Epididymis, and through the Vas
Deferens, which is formed from the latter: in then passes 
upward by the Vas Deferens, through the Abdominal
Ring, then on laterally, and then posteriorly to the inferior 
part of the Bladder; but before they terminate
they have a communication with the Vescicula Seminalis,
and these terminate together. The lower part of the 
Vas Deferens is much larger than it is above, and when 
cut open it is formed Cellular, or Convoluted. The Vesicula
Seminalis, when some care is taken to unravel them 
are found to be Tubes, with processes somewhat like the 
horns of stags. These are found to unite with the Vasa





189
Diferentia, and form two openings instead of four. The 
contents of the Vesicula Seminalis are partly as reservoirs 
for the Semen, and partly for a Secretion of their own,
but Mr Hunter went so far as to deny that Vesicula
Seminalis, were at all reservoirs of Semen. These bodies
are wanting in most Carnivorous Animals, but 
the Hedge Hog has them. They are wanting on Birds, but 
the Vasa Deferentia have enlargements at their ends, Horses
have them, but here they are mere bags, therefore in 
Horses I believe they have little or nothing to do with the 
Fecundating fluid, and are only reservoirs for their own
Secretions, which Theorists say, is to dilute the Seminal fluid. 
We have also the Prostrate Gland, which is composed of a 
series of cells and have Excretory Ducts, also we have 
sometimes Glands situated in the Membranous parts
of the Urethra called Cowpers Glands, but they are frequently 
wanting, so that we cannot think them of 
much service. We thus find that the Fecundating fluid 
is secreted from the Testicle of the Male; but before we can
trace this fluid into Uterus, there must be a certain 
state of the Penis; which is the Erection; we must therefore
consider the structure of the Penis. It has two Corpora
Cavernosa, and one Corpus Spongiosum; in the middle
of this is Urethra. The Corpora Cavernosa are of a 
very Cellular texture. The Corpus Spongiosum is that part
which forms the Glans Penis, and is a plexus of veins, that 
 




190
are much convoluted. It continues lower down than the 
Crura of Corpora Cavernosa; its termination is called
the Bulb. The Penis is supplied with Blood by 
four Arteries. The Pudendal sends off two, the superior 
on the Dorsum Penis to the Corpora Cavernosa; the 
two inferior to the Bulb and Corpus Spongiosum. 
The Blood passing into the Cells of the Corpora Cavernosa
causes the Erection, but the Blood communicates with 
the Veins, which are the Vena Magna, Ipsins Penis, and 
the Vena Ligamentous. The Blood when the Penis is in 
the common state, can easily return from these into the 
Iliac Veins; but under a certain impression of the mind
more is determined to these parts than can be readily 
returned, hence some say the distension is from a
spasm, this is a pretty soon to support a same
Hypothesis. Some say its from Mechanical pressure
but the Penis become distended before pressure is made.
This part is also very sensible having a number of 
Nerves supplying it; there are a pair of Muscles passing 
up, on each crus Penis, called Erectores Penis, but that 
is not the most proper name, as we can account for 
the Erection by other Means, there are also Ejaculatores
Urine, or Ejeculatores Seminalis, Levatores Ani, and 
Transverse Periner. 




191
Conception.
The Uterus undergoes various changes in consequence 
of Pregnancy, and contains substances which are not found
in it at other times. As the Ovum containing the foetus, and 
an appendage called the Placenta: and between the two
is the Navel string. The Water called the Liquor Amnii
and the Membrane surrounding the Foetus like a bag.
But an Ovum in its simple and advanced state is different 
in appearance. In its simple state the parts are 
not to be observed, but are afterwards more and more developed: 
before this it can scarcely be called an Ovum
In describing these parts we shall first begin with the simple,
and proceed to the more advanced state. Before an 
Ovum can be found in the Uterus conception must have 
taken place. In the Human Subject this is the consequence
of Sexual intercourse, in which something passes from 
the Male to the Female: this has varieties in the lower 
order of Animals, some of them having a spontaneous
mode of propagating: one of these possessing this power 
alone, was corked up in a Vial for a day, and 
it was found to produce several others. One Polypus 
alone being also [illegible] have before observed sufficient
for propagation: from its body several young ones
spring out, having apparently an aperture of free communication 
with the parent: after a time they fall 





192
off and grow, and in their turn send off others. There are 
some whose modes of propagating are very obscure, as 
in Insects in Water, when if water be corked up, these 
Animalcula form, and in Vinegar some of the shape of 
Eels are found, also in paste. Many Animals are Hermaphrodites, 
one having the parts of both sexes:
and here there is a double impregnation, two of them 
impregnating each other at the same time. It is 
not easy to distinguish how those living in shells 
have access to each other. There seems to be some 
Analogy between Animals and Plants, which are 
propagated by cuttings, for the Polypus may be
propagated in the same manner the one process you 
find similar within the other, as in the cutting of 
Potatoes each having an Eye. The farinaceous matter
of the Potatoes serving as nutriment for the Eye, until 
it can form a root, and draw its own food from the 
Earth. But if the Linnea System has any foundation
in truth, there must be another mode of Sexual intercourse,
and nature leads each to copulate with its 
species, as the Horse with the Mare, and when the 
Horse impregnates, the She ass, a Mule is produced. 
But with a few exceptions these Mules are barren. 
Before Impregnation takes place, one or both Testes in 	
the Male must be capable of secreting the Fecundating 
fluid called  Semen, and in the Female, one ovum in 




193
an healthy state, as is proved by spaying of Animals when 
one Ovum or one Testis is sufficient. There must also be 
a determination of Blood to the Uterus. In Women there 
is the Menstrual discharge, and it is said, they cannot 
be impregnated without it, but there has been instances 
of it. In Brutes, we find some discharge, but at 
no regular periods, it is most in hot weather, and we
find they then are most disposed for Impregnation,
keepers of Rabbits examine the Labia, to find if they 
are inflamed, and consequently fit for Impregnation
In Women altho’ there may have been no discharge yet 
there is a determination of Blood to the parts. The
Venereal Oestrum in Brutes is confined to the warm
Weather, the parts being shrunk in Winter, and developed 
in Summer: and the Ovaria in the Female are 
affected in the same manner. Coitus of the different 
Sexes is also necessary; yet in some as in Fish it can 
hardly be called Coitus. The Female seeks gravelly
situations, and discharges the Ova, the Male also 
seeks out similar situations and discharges its
Semen on it, but whether this is the part I know not. 
A person who had curiosity to watch a Carp in a 
pond, observed two of them approximated their hinder 
parts and formed an Acute Angle; something opaque
appeared and this was supposed to be the Fecundating 
matter. The Coitus of Frogs is remarkable for its






194
duration: the Female for many Days has a discharge of a shiny
substance with which the Male copulates, and sends out a 
similar fluid, which keeps them in contact. from this Tadpoles 
are formed which become Frogs. In some Birds no part of the Male 
passes into the Female, as in Fowls, which have no Penis. The 
fluid passes at once into the Female and Fecundates her. The 
Drake has a Penis like a Cork screw, and in most Animals there
is admission of the Male. The duration of Coitus is also different
In the Bitch it is of considerable time, from the alteration of the 
Penis of Dog, after a time it is involuntary. In Rabbits it is 
very short. We shall next consider where this Fecundating 
fluid passes to: different parts have been assigned to it; some 
say only to the Uterus; others say it is conveyed by the Fallopian 
tubes to the Ovaries; but it is not found by dissection
that this fluid enters the Fallopian tubes, except by Ruysh, who 
examined a Woman that was destroyed in the act of adultery
by her husband, and he affirms the saw it; not only 
in the Uterus, but in the Fallopian Tubes. No one else pretends
to have found it there, a few found it in the 
Uterus. Some say it is quite sufficient if it is exhaled by 
the Fallopian tubes, to the Ovaries, but this they have never
demonstrated, and is therefore to be doubted. It has been asserted
by Mr Hunter that he has found it in Uteri, but 
many others who have made experiments have not even
found it there. Baron Haller only mentions one case. The 
actual contact has been asserted to be necessary in the 
















195
Human subject in consequence of the Coitus of Frogs; but there 
it is out of the Body, and there is difficulty of its being affected
in the living body; nothing can be proved by analogy. There 
are others who take an opposite view and argue from the 
Linnaen system of Plants; the Ovaria being the real Capsule 
containing the Rudiments of the vegetable, and receiving 
impregnation from the pollen of the Anther: but another and 
better proof against actual contact is, that all the Eggs
a Hen lays are impregnated at once. It is difficult to form 
an idea how twenty Eggs can be impregnated at once, if 
Semen is to be conveyed by the Oviduct or Fallopian 
tubes, which are membranous bodies, and how can it pass
to every Egg? This does not appear at all likely. When impregnation
takes place, they are carried one by one to the Egg
long before the Shell is formed. When a Foetus is found in 
Utero there can be no doubt of Pregnancy, but there are 
other changes occurring in the Ovaria denoting it, and 
which are described by Stem and De Graaf. They found 
the Ovaria to consist of a number of vesicles, containing 
a substance of a Gelatinous consistence. When Impregnation
takes place the vesicle most formed, enlarges, projects
and bursting discharges its gelatinous contents which 
is grasped by the frinbriated extremity of the Fallopian
tube, and conveyed to the Uterus; but the vesicle remains 
behind and is filled by a fluid of a yellow colour, secreted
by the vessels of the parts, and which is called corpus 



196
Luteum: therefore when we find a Corpus Luteum we need not
hesitate in saying that impregnation has taken place. But
some have objected to this, and say that many have been 
found at different periods and no Foetus existing. If a Woman 
dies after Delivery a Corpus Luteum will be found; this 
not being a transiting circumstance; but remaining for 
twelve months. A Woman may miscarry at any period,
and on Examination no Foetus will be found, yet a Corpus
Luteum will remain. Another objection started is the 
number of Foetuses and Corporea Lutea are not always 
corresponding, but if we find two of them, and but one 
Foetus, she has miscarried and become Pregnant a second 
time. In general in Twins there are two Corpora Lutea, but 
sometimes only one, in which case the vesicle must have 
contained the Primordia of two Foetuses. When only one
Corpus Luteum, we find only one Placenta, and one set of 
Membranes, and two distinct Bags. We have thus an 
evident sign of Impregnation; and we want now to ascertain 
to what part the fecundating fluid is applied,
to bring this to the test of experiment is difficult; if we could
obliterate one or both Fallopian tubes, it would prevent
the course of the fluid: I therefore cut thro’ the Fallopian tube
of a Rabbit without doing much injury to the contiguous
parts; it lost all sexual disposition, and had an apathy
and dislike to sexual intercourse; after a time the Rabbit was
killed and the ovaria were found very much shrunk, and 






197
were not one third of their ordinary size. To produce the effect
of Impregnation, every link of the chain is required and concerned,
and if the Fallopian tubes are cut we injure the ovaries
and they are barren. But in dividing only one of the tubes, it 
had a strong tendency to prevent impregnation tho’ it now 
and then took place, and she became pregnant: after a time 
she was opened and a foetus found in one of the horns of the Uterus,
in the other none; but Corpora Lutea were found on 
both sides; this could not be by the fecundating fluid in 
the obliterated tube. Thus there may be an evidence of impregnation
without the contact of the fecundating fluid. In one case
the Female was admitted to the Male just before the tube was 
divided, as there must be time allowed for its passing, it was
done at different intervals even to forty eight hours: the vesicle
of De Graaf was ready to burst about the fiftieth hour, and 
to be taken up by the Fimbria, and conveyed to the Uterus
but it was the same as before there was no Foetus in Utero, 
tho’ a Corpus Luteum. If we wait until Conception has taken
place we find the Foetus in the Uterus. These facts raise some 
doubts about the necessity of actual contact, perhaps the 
fecundating fluid passes only into the Vagina or at farthest
into the Uterus, and excites a peculiar action by its specific
stimulus, the Ovaries are affected in a secondary
way; they enlarge, project as they advance, and burst, and 
their contents are taken up the fimbriated portion of the Fallopian 
tube; is carred by their Peristaltic motion to the Uterus


 





198
which forms a membrane over it called the Tunica Decidua.
The vessels from one to the other form the Placenta, a copious secretion 
is going on of Mucous, to close up the neck of the Womb
and thus prevent a premature expulsion of the young Foetus.
The Breasts enlarge to secrete the Milk, and this cannot be the 
effect of contact of the Fecundating Fluid: but it is only an
extension of the Sympathy I am contending for, as supposing
the Mother could not secrete the Milk, the majority of Children 
would perish, and this is a link of the chain. Sometimes
Women have twins, two vesicles of De Graaf may burst, and 
perhaps both fimbria act at the same time. We sometimes 
hear of superfetation, which is supposing the Woman is 
Impregnated, and some time after Impregnated a second time,
and two fetuses forming in Utero of different ages. This 
is common in Brutes, but very rare in the Human species. 
In Bitches the Uterus has two horns, and if the Human
Female had, it might often take place: but it has occurred
in a few instances. It has been supposed a Woman may 
have superfetation if she had two Impregnations before
the Astrum is gone off: there is a case related of a Woman in 
South Carolina who had two children, one white the other
black. She had a black servant in the house, whom the Lady
accused of frightening her one morning after her Husband had 
left her; this might do for the Husband! But it arose doubtless
from Superfetation. In whatever way Impregnation takes
place, the Foetus has no shape at first: the time the Foetus




199
is evolved is different in different animals; part after part is 
evolved until the whole is formed, it is then in due time
sent into the World. The result of conception being an Ovum
is what in common language is termed an Egg, which contains 
the principle of the Child; but there is a necessity for something 
else to be formed, for its nourishment. An Ovum is 
that substance in which the rudiments of an Animal are
contained, and this will apply as well to the Vegetable Kingdom
a Seed being a Vegetable Ovum which flourishes if thrown
into the Earth. These have different shapes, yet any peculiar
form is not necessary. Thus in Animals when an Ovum
has shape it is more like an Ovum, but there was a time 
when this had no determinate shape, as when the Vesicle
of De Graaf has just burst, and taken up by the Fimbra of the 
Fallopian tubes: but tho’ shapeless it is still an ovum
called by Ruyoh, Rudee Indigastaquamoris. Baron
Haller could not find anything in the Sheep before the seventh 
day that had shape or form, but is was as much an Ovum
before as then: the first stage is giving it form, by the formative
powers of the substance, making a Membrane we
find first an opaque spot, where the Foetus first begins to 
form and assume the character of an Animal: it progressively 
enlarges and adds part to part, until its shape 
and structure are complete, this may be easily traced, in the 
Human subject, something like Pins head is first observed
resembling a chasm of the Membrane: after some time 




200
it is of the size and form of a Maggot rolled up, next we find 
it the size of a Kidney bean suspended by the navel string,
but no distinction of parts except Black spots, for the beginning
of the Eyes: next form process for its extremities, and 
after a time the Fingers and Toes. Next the Sexual organs, 
features of the Face, and when everything goes on properly we 
have a perfect Child. But Nature is often diverted from her
course by some blunder in the evolution, and forms a Monster.
It was an old opinion that the Foetus was originally formed 
in the Ovum, but being transparent we could not observe
it, and we have no reason to credit it; for it is not so rational
as the formation of part after part: one of the first
changes is a cicatricula, next a swelling like a head, also
something like a Spinal Marrow, and the Eyes, organs of Sense,
and Vital Organs, and the extremities new parts being daily 
formed: so also in Flies, they deposit a Maggot which becomes 
a chrysalis, having previously crawled about, but now it
appears dead and changes its color, after a time an Animal
finds its way thro’ it, and is the Fly: here is evidently 
a succession of formation of parts, which we cannot say
were formed in the Chysalis. It is the same in Vegetables. 
A Bean put into the Earth shoots out and grows the stalks
bearing flowers and fruit, which could not exist in Miniature 
in the seed, hence I cannot agree with the Poet who 
say “The Acorn in its little form, contains the great Oak
within its Brains.” But Analogy will not lead us to 




201
much for which Rabbits are generally used for these inquires.
In these we can tell when the Vesicles of De Graaf burst and trace 
the substance into the Uterus, and by its evolution can say, how 
many Days have elapsed, but this in Analogy will not hold good
in the Human subject. In the Rabbit we have a proof of impregnation
in twelve hours; the Vesicle of De Graaf was about to 
burst in forty eight hours, and in fifty hours it burst, and in 
three days they all burst; but as yet nothing but Mucous can
be found in the Fallopian tubes, and these are the bodies that are 
afterwards to have form and shape; on the fifth day they are 
disposed to increase and on the seventh are as large as Peas.
On the eight the Vesicles are very apparent when put into spirits.
On the tenth day we observe a drin opaque spot and a daily progressive 
formation of the parts, until the new Animal is developed
which takes place at thirty days. This time bears the same
proportion to a foetus of three months; but at this time the 
foetus is of considerable size, one or two inches in length, and 
the extremities are apparent: thus Analogy misleads us. 
The Sheep goes five months, and here there is a considerable difference 
from the Human: when of the size of an inch its three
months, afterwards it has an increase of Solidity and bulk,
at five months it is capable of living by its own powers, if nutriment 
be applied to the Stomach. The Human Female contains 
the Foetus in Utero about forty weeks; at the end of this time
the Uterus is much enlarged, the Muscular fibres are obvious 
and by these means Nature acts in expelling the Child.
Finis.




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INDEX.
ANIMAL and VEGETABLE KINGDOMS



203
HEART its STRUCTURE and OECONOMY



























MS
B
314