WI
E92h
1878
JEW TREATISE     .
Assimilation and Digestion
BHOWING THE
Oy^^^K[_
Different Solvent Juices and Fluids, /
Thier Origin and their Uses in the Human Sys-
 tem, the Glands from which they are Secre-
   ted, and their Relation to each other.
       BY THE AIJTHOR,

JOHN WESLEY EVANS, M.-D.,

   TJ^?New Canton, Pike Co., III.

)

M! /   r;\  ■-  /
 ■ it > ,    \,,&V ■
,s
      QUINCY, ILL.:
DAILT WHIG BOOK AND JOB PRINTING HOUSE.
         1878.
6 *L
*wv   .1 
RARY OF MEDICINE
NLfl  D01361b4 D
ARMY MEDICAL LIBRARY

        WASHINGTON

           Pounded 1836
Section
Number
.3.  7Sr^A3
       Fobm 113c, W. D., S. G. O.
3—10543    (Revised June 13, 1936)
NLM001381640 
 
NNI
 E92.*
 IBT8 
A Treatise on Assimilation and  Digestion.
  The subject of Digestion, though it has received
the attention and forethought of a great many of the
ablest minds of the world for  many centuries, I find
that, after all that has been written, the subject is yet
in its infancy, and nearly every author sheds some
new light upon the subject; and in my limited treatise,
 vhile I may receive the approval and. commendation
of a portion of the profession, yet I expect to receive
 he disapproval and disapprobation of another part of
the profession; for it  is  hard  to establish  any new
theory or principle without finding opposition at every
step of progress, and more especially in the medical
world.  In  this short treatise I shall endeavor to ex-
press my views in as brief and  few  words as I pos-
sibly can, as this  is a preliminary work.  I shall en-
deavor to conform to the principles already advocated
by the profession, as possible and consistent with my
views of physiological principles.   I shall approve
and adopt all theories that are founded on truth and
sustained by  correct reasoning, and disapprove  all
theories  not founded on truth;. and will give to the
medical world  all and any new ideas which will ad-
vance knowledge in general, and be a benefit to the
professional world and  a permanent benefit to the hu-
man family in this generation  and generations here-
after.
  The old established theory  is, that when food is
3 
4              A NEW TREATISE ON

taken into the system it is governed by laws of nutri-
tion, or that function  by which  the nutritive matter,
already elaborated by the various organic  actions,
loses its own nature and assumes that of the different
living tissues, to repair their losses and support their
strength.  Sometimes the word is used in a more ex-
tended signification, to express  the whole series  of
actions by which the two constant movements of com-
position and decomposition are  accomplished in or-
ganized bodies.   Nutrition, then, would comprehend
digestion, absorption,  respiration, circulation  and as-
similation;   the latter  being  (nutrition) properly  so
called, and being operated in the intermediate system
over the  whole  body, the  tissues attracting from
the blood the elements necessary for the reparation.
  The first principle involved in the development of
nutrition is Digestion, (from digere, to dissolve).  Di-
gestion is a function by means of which  alimentary
substances,  when introduced into the digestive canal,
undergo different alterations.   The object of this is
to convert them into two parts, the one  a  reparatory
juice destined to renew the perpetual waste occurring
in the animal economy, the other, deprived of its nu-
tritious properties,  to be  rejected from  the body.
This function is composed of a series of organic ac-
tions, differing according to  the particular organiza-
tion of the animal economy in man.  They are eight
in number, to-wit:  i. Prehension of food.   2. Mas-
tication.   3. Insalivation.  4. Deglutition.   5. Action
of  the stomach.  6. Action  of  the  small intestines.
7. Action of the large intestines.  8. Expulsion of the
fceces.  The first principle  involved:  prehension  of
food, which means carrying  food  to the  mouth and 
           ASSIMILATION AND DIGESTION.          5

introducing it into the mouth.  2d, Mastication, (from
I chew), the  action of chewing or bruising food  to
prepare it  for digestion, by the united action of the
tongue, cheeks and lips, which  push the alimentary
substances between the teeth, and by the motion  of
the lower  jaw it is cut, torn or bruised, and by the
 joint action of the above  named organs it excites the
salivary glands, which are the two parotid, two sub-
lingual and the two submaxillary glands.  The third
principle involved is insalivation, which is a secretion
from those three sets  of glands, called saliva.  Those
 glands manufacture the  saliva  from  the  blood  by
 means  of  small blood vessels,  or small  arteries, and
 the  balance of the blood is carried back into the cir-
 culation after the saliva is taken from it, by means of
 small veins;  this substance is as clear as water, but
 possesses  that peculiar property of dissolving almost
 any substance it comes in contact with.  The amount
 secreted, according to the report of some of the most
 popular physiologists, is about twenty ounces in twen-
 ty-four hours by a  healthy adult person of medium
 stature.  Upon inception of food into the mouth those
 glands throw out a sufficient amount of saliva through
 the  mucous membrane of the mouth to  partially dis-
 solve the food and hold it in a muco-soluble state, so
 that itacan pass down the oesophagus by the peristaltic
 action of the muscles of the oesophagus into the stom-
 ach, where it undergoes a chemical change and forms
 a new compound.  After the food passes the sphinc-
 ter of the cardiac muscle  into the  stomach, the food
 is passed back and forth  by an  involuntary muscular
 action of the stomach, to bring the food into direct
 action of the gastric juice, a fluid secreted by the mu- 
6
A NEW TREATISE ON
*cous membrane of the stomach; and the motions of
the  stomach, sometimes transversly,  and at  other
times longitudinally, not only produce a constant dis-
turbance, or churning of the contents of the stomach,
but  they compel them  at the same time  to revolve
about the interior from  point to point, and from one
extremity to the other.  In  addition to these move-
ments,  there is a constant agitation of the stomach
produced by the respiratory muscles, and the constant
action of the material taken  into the stomach acts as
an excitant for an effusion of the gastric juice, which
is eliminated by the mucous membrane of the stomach
to the extent of seventy-five  to eighty ounces in twen-
ty-four hours, according to the estimate of scientific
physiologists.   This gastric juice,  according to the
above  estimate, would  make about five pounds of
a  fluid avordupois weight, or in other words, over
half a gallon; a liquid almost clear, and containing a
very small quantity of solid material, but constituted
of very peculiar properties, combining a certain fer-
menting principle combined  with a peculiar  compo-
sition of chlorides, phosphates, potash, lime, soda and
magnesia, making  a substance which combines the
solvent properties of almost every principle displayed
in nature, and that will act upon all and any substance
which is placed in  it, dissolving it  into  its primitive
ingredients.
   The  peculiar  dissolving properties contained in the
gastric fluid, is not possessed by any other fluid.  It
has been analyzed and its primitive parts made known,
but why  it possesses these  peculiar  primitive prin-
ciples is a question not easily answered.  But certain
it is, that it  does contain certain solvent  properties, 
           ASSIMILATION AND DIGESTION.          7

and the admixture of it with the food assists to dissolve
the food, and forms a new compound, called chyme,
which is a muco-perulent compound, of the appear-
ance of milk in solution with other substances.  Some
physiologists say  that the process of chymification
goes on more rapidly when the contents of the stom-
ach are about 98 ° to 100 ° temperature, which is re-
quired  to  keep up the  solvent process,  which  is
retarded according to the depression of the thermom-
eter below the standard, so that at the ordinary tem-
perature of the atmosphere it is completely suspended,
to be renewed, however, with  an  increment of heat.
   The  next condition which specially affects the
time  required for the  process of solution in  mo-
tion :  This does not act  mechanically by way  of trit-
uration, as was once supposed, for food is found to be
digested when enclosed in metalic balls  perforated to
admit the access of gastric juice to the interior.  But
it answers the purpose of thoroughly subjecting the
whole of the alimentary bolus to  the agency of the
gastric  solvent by bringing each part successively into
contact with the  lining  membrane  of the stomach,
from the surface of which the fluid is effused.  The
removal of the matters already reduced or dissolved,
also has a most important effect in facilitating the so-
lution of the remainder.   This chyme will, of course,
vary greatly in composition, according to the propor-
tion of  the different alimentary substances  that have
entered into the composition of the food; and its ap-
pearance, also, is far from uniform, being sometimes
like gruel, and sometimes  more creamy; always,
however, having a strong acid reaction.   The effect
of the gastric fluid  upon the  several kinds of albu- 
8              A NEW TREATISE ON
minous matters, is to reduce them to a state of com-
plete  solution,  and at the same time to alter their
chemical properties so that  they, for the most part,
lose their distinctive attributes and are brought to one
uniform condition, that of albuminous, which seems to
be the state best adapted for  subsequent assimilation.
In this condition they seem to form definite combina-
tions with the solvent fluid.  Although the chyme, or
product of  gastric digestion, which escapes through
the pyloric orifice of the duodenum, contains much
oxidized matter in a state of actual solution, a consid-
erable proportion of it is still only reduced  and me-
chanically suspended, and the solution of the latter is
continued in the intestinal tube.  In  the farinaceous
part of the food, moreover, no great amount of change
has hitherto been effected, and  the sugar which has
been generated by the aid of the salivary ferment, is
probably absorbed  into the blood vessels nearly  as
fast as it is  formed.  Hence we  see that the process
of digestion, so far from being completed in the stom-
ach, has  only been carried one stage further.  Soon
after its entrance into the  duodenum, the chyme is
sujected to  the action of the bile, the pancreatic fluid.
  The next question to be determined, is: the quan-
tity of food to be  acted upon and taken into the sys-
tem, for  the support  of the system.  The  organic
compounds usually employed  as food by man,  are
partly derived from the animal and partly from the
vegetable kingdom, and they  may  be conveniently
arranged under the following heads:
  ist. Saccharine group, including all those substan-
ces derived from the vegetable kingdom, which are
analagous in composition to sugar, consisting of oxy- 
           ASSIMILATION AND DIGESTION.         9

gen, hydrogen and carbon alone, and having the first
two  present in the proportions to  form water.   To
this group belong starch, gum woody fibre and cellu-
lous  of plants, which closely resemble  each  other in
the proportion  of their elements, and which may be
converted into sugar by chemical process of a  simple
kind, whilst alcohol, which is derived from sugar by
the process of fermentation, has a composition  which
rather connects it with the next group.
  2d. The oleaginous  group,  including oily matters,
whether derived from the vegetable kingdom or from
the fatty portions of animal  bodies.   The character-
istics of this class lie in the great  predominence of
hydrogen and carbon, the small proportion of oxygen
and the entire absence  of nitrogen.
  3d. The albuminous group, comprising all those
substances, whether derived from the animal or veg-
etable kingdom, which are closely allied to albumen,
and through it to the animal tissues generally in their
chemical composition.   In this group a large propor-
tiou of azote is united with the oxygen, hydrogen and
carbon of the preceding.
  4th.   The gelatinous group, consisting of substan-
ces derived from animal bodies only, which are closely
allied to gelatine  in their composition.  These  also
contain  azote, but the proportion of their components
differ from that of the preceding.   There are many
other substances, however,  which,  though truly ali-
mentary,  and  consumed to a considerable  amount,
cannot be legitimately placed under either of the above
heads.  Such  are, for example, the vegetable acids.
The compounds of the  saccharine group cannot, with-
out undergoing metamorphosis, form part of the ani- 
10
A NEW TREATISE ON
mal tissue, as there are none  which they at  all  re-
semble in composition.  It has been shown, however,
that they are convertible within the animal body into
those of the oleaginous group, and may thus, like  the
latter, be applied to the  formation of the adipose and
nervous tissues.  But the amount of those substances
which  is thus employed is  a very small part of that
which is ordinarily introduced as food, and by far  the
larger proportion of them is made  subservient to  the
maintenance of the  heat of the  body by the  combus-
tive process.   The  sugar, which is taken in as such,
being dissolved and  absorbed into the current of  the
circulation, appears to undergo a speedy metamor-
phosis into lactic acid, which is  the form under which
it  is finally oxidized  and burned  off; and starch is
made capable of undergoing the  same change,  by
being first converted  into sugar.   During the diges-
tive process oleaginous  matters do not  seem  to  un-
dergo any change preliminary to their oxidation, save
their reduction to  a state of very  fine division.  We
shall presently see that a very considerable difference
exists between the saccharine and oleaginous matters,
in regard to their calorifying powers.  That none of
these non-azotized  substances  can  be made capable
of metamorphosis  or combination within the  animal
body, of taking the place of azotized substances, as
histogenetic or plastic compounds may now  be  re-
garded as one of the most certain facts in physiology.
The concurrent evidence of experiments and obser-
vations leading to the conclusion that in  plants alone
can any production  of azotized compounds take place,
and that animals are, in  consequence, directly or indi-
rectly  dependent upon  the vegetable  kingdom  for 
ASSIMILATION AND DIGESTION.
II
their means of subsistence.  If animals be fed exclu-
sively upon saccharine  or oleaginous substances  of
any  kind,  or in  any  combination whatever,  they
speedily show  symptoms of inanition, and  the only
assistance which such food affords in the prolongation
of life, is derived from its calorific power.
  The application of the  substances forming the  al-
buminous group  to the support of the animal  body,
by affording the materials for the nutrition and refor-
mation of its tissues, and also for the maintenance of
its heat:  The proportions of carbon, hydrogen, ox-
ygen and  nitrogen, of which  all  these  substances
are composed, appear to be identical, and they are all
capable of being reduced by the digestive process to
the condition of albumen.  Hence  it is a matter  of
little consequence, except as regards the proportions
of inorganic  matters, with which they may  be re-
spectively united, whether we draw our histogenetic
materials from the flesh of animals, from the white of
of eggs  (albumen), from  the  curd  of milk (caseine),
from the grain  of wheat (gluten),  or from  the seed
of the  pea (legumen).  Neither of these substances,
however, can long sustain life when it is used by it-
self, for it  has  been experimentally ascertained that
by being made to feed  constantly on the same sub-
stance—boiled white of egg, for instance, or meat de-
prived of the principal osmazome that gives it flavor,
an  animal  may be effectually starved; its disgust at
such food being such that even if this be swallowed
it is not digested.
  The  organized  fabric of animals contain,  as we
have seen, a large quantity of gelatin.  It seem cer-
tain  that this  substance may be  produced out  of 
12             A NEW TREATISE ON
fibrine and albumen, since in animals that are sup-
ported on these alone the nutrition of the gelatinous
tissues does not  seem to be impaired.  But it has
been  commonly supposed  that  gelatin, taken  in as
food, may serve for the growth  and maintenance of
these  tissues, even though it may be incapable of con-
version to the  albuminous type.   It is very doubtful,
however,  whether gelatin can render even this ser-
vice.   For all, our own knowledge of the history of
the development of the gelatinous  tissues would lead
us to regard them as secondary products, which take
their  origin  in fibrinous  blastema, and can only be
generated by  the metamorphosis  of protean  com-
pounds.  If these views be correct, it follows  that the
alimentary value of gelatin must be limited to its cal-
orific  power; its hydro-carbon being  separated from
its highly azotized portion, and  the former being ox-
odized and eliminated  through  the lungs, whilst the
latter  will pass off* by the kidneys.   And this view
is  confirmed by observations on the  result of inges-
tion of large quantities of pure  gelatin, this  being a
marked increase in  the proportion of urea in the
urine,  with  an  elevation of its  specific  gravity.
Neither leucine or glycine could be detected in the
fluid,  so that  gelatin seems  to  be subjected to the
same  metamorphosis that the protean compounds un-
dergo when they are taken in excess.  That gelatin
cannot take the place of the  albuminous compounds
has been  fully demonstrated; in so far, therefore, as
the only azotized principle contained in soups, broths,
&c, are  of the gelatinous character.' We must ac-
count these preparations as destitute of the power of
nourishing the body; and the peculiar nutritive value 
           ASSIMILATION AND DIGESTION.         13

which experience shows that such perparations pos-
sess in certain states of the system, must be attributed
to the albuminous  matters which they hold  in solu-
tion, and to the readiness with which their gelatinous
constituents are absorbed and applied to the  purpose
of calorification.
  The substances which cannot  be  arranged  under
either of the  preceding groups, are, for the most part,
of the non-azotized class, and as they mostly consist
of compounds in which the hydrogen and carbon are
not combined with their full equivalents of  oxygen,
they are made to contribute to the calorifying process
by undergoing oxidation within the system, so as to
be excreted  in the form of carbonic acid and water.
  By rules based on the foregoing data, then,  we may
estimate the relative value of different articles of food
for the two distinct purposes of tissue  formation  and
the production of heat.  For the proportion  of albu-
minous matter which any  substance may contain fur-
nishes the measure of its histogenetic value, whilst
the proportion of hydro-carbon uncombined with ox-
ygen, affords the  means  of estimating its  calorific
power when oxidized.  As  in almost every alimen-
tary substance, whether vegetable or animal,  the  two
classes  of compounds  are mingled; the percentage
of nitrogen which it may contain affords a tolerably
correct measure  of the amount of albuminous mat-
ter which it includes, and therefore of its histogenetic
value; where, on the  other  hand, the percentage of
nitrogen  is the smallest, that of hydro-carbon is the
largest, and  the proportion of the combustive mate-
rial is the highest.  It  is obvious that  the most eco-
nomical diet  will be that in which there is the most 
14             A NEW TREATISE ON

perfect  apportionment  of each  class of constituentis
to the wants of the system, and  these will vary with
the amount of muscular exertion put forth, and the
lowering of the external temperature.  Thus, for a
man of ordinary habits, and living  under a  medium
temperature, a diet composed of animal flesh alone
is the  least economical that can be conceived; for
since the  greatest demand for food in his system
is created  by necessity for  a  supply of carbon and
hydrogen to support his respiration.  This want of
non-azotized food in which these ingredients predom-
inate.   Thus it has been calculated that since fifteen
pounds  of flesh  contain no more  carbon than four
pounds  of starch, a savage with one  carcass and an
equal weight of starch could support life for the same
length  of time during  which another, restricted to
animal food, would  require five such carcasses to pro-
cure the carbon  necessary for  respiration.  Hence
we see the immense advantage as to economy of food
which  a fixed agricultural population possesses over
those wandering tribes  of hunters which still people
both the old and new  continents.   This mixture of
azotized and  non-azotized  compounds  (gluten and
starch) that exists in  wheat flour,  seems to be just
that which  is most generally useful to man, and hence
we see  the explanation of the fact,  that from very
early ages, bread has been regarded as the staff of
life.  There are  particular conditions  of  existence,
however, under which life may be advantageously sup-
ported upon animal food alone.  The Esquimaux, and
other dwellers upon the Arctic seas, find in the bodies
of the whales, seals, &c, whereon  they subsist, that
special  supply of the  very best  combustive material 
           ASSIMILATION AND DIGESTION.        15

which alone can  enable them to maintain their exist-
ence, where the thermometer is  for many weeks or
months in the year at 40 ° , or even lower, and where
the amount of heat which must be generated within
the body is four or  five times that for which a diet of
bread will suffice.  On the other hand, the general
experience of the inhabitants of warm climates seems
in favor of a diet  chiefly or entirely vegetable, and its
peculiar suitableness appears to consist in its affording
an adequate supply of the plastic  alimentary substan-
ces in combination with farinaceous matters, that give
the requisite bulk to the food without affording more
combustive material than the system requires.  The
quantity of starch which undergoes conversion, and
is introduced as sugar  into the circulation, being ap-
parently governed  rather by the demands of the re-
spiratory process than by the amount  ingested, and
the remainder being voided again unchanged.  The
mixed diet, to which the inclination of man in temper-
ate  climates  seems to lead  him, appears to be fully
conformable to the construction of his dental and di-
gestive apparatus, as well as to his instinctive propen-
sities.
   If, indeed, we take a comprehensive  survey of the
conditions of the  various races of man  at present in-
habiting the earth,  we  cannot help being struck with
his adaptiveness  to a  great variety of  circumstances
as regards climate, mode of life, diet, &c.  And we
scarcely  avoid  the conclusion  that  the Creator, by
conferring upon him such an adaptiveness, intended
to qualifv him for subsisting on these articles of diet,
whether animal or vegetable, which  are most readily
attainable in different parts of the globe, and thus to 
i6
A NEW TREATISE ON
remove the obstacle which a necessary restriction to
any one kind of food would have  otherwise opposed
to his universal  diffusion.  If we were to  bring to-
gether the  habitual  diet scales of the several races
of men which people the surface  of the globe, we
apprehend that the diversities which they would pre-
sent would be scarcely less strange than those which
exist among the regimens of the most dissimilar spe-
cies of mammalia.  In the various  devices  by which
man has succeeded in availing himself of these, and
in the various tastes  which have  led some to avail
themselves of articles of  food  which others would
loathe, we see the same wise  design as that which
has given to different tribes of animals their respect-
ive preference; and we deduce from  the whole  the
conclusion that man  is left by his Creator  at perfect
liberty to  select that kind of nutriment which he finds
most  suitable  to  his  tastes  and  to  his wants;  the
former, when  not absolutely vicious,  being  an  expo-
nent of the latter, just as the simple desire for food is
the exponent of  the need for it in the system.  When
the results of experience then  are  combined with the
teachings  of science, they seem to justify the  following
conclusions:   That a due adjustment of the albumi-
nous and  saccharine  constituents of the food to  the
varying conditions under which man  exists, is of the
first importance, and that the  question of the deriva-
tion of the first  two  of those constituents,  from  the
animal or from  the  vegetable kingdom, is one of a
secondary character, each  being capable of yielding
them in adequate  amount; and the only condition re-
quisite being that the articles of food  shall  be so se-
lected as to supply the needful quantity.   Thus a diet 
            ASSIMILATION AND DIGESTION.         17

whose staple consists of potatoes or rice contains by
far too small an amount of albuminous matter in pro-
portion to farinaceous, but if to this be added a mod-
erate quantity of meat, the proportion is assimilated
to that which exists in wheaten bread, which may be
taken  as the standard for man's alimentation in all but
extremely  cold climates.   The  failure  of wheaten
bread  to supply what the system there  requires, de-
pends  on nothing else than its  deficiency in the olea-
ginous constituent; for, although such a craving for
fat meat is experienced by travelers in those climates,
as has led to the belief that it is necessary for their sup-
port, the same kind of difference should be made in the
winter and summer diet of the inhabitants of the tem-
perate zone.  For when the external temperature is
low  an ample supply of oleaginous  matter is indicated
and  may be  advantageously taken  in  the forn» of
butter, cocoa, fat meat or maze bread.  On the other
hand,  during the heat of summer, the  more  nearly
the  diet is assimilated to that of the  natives of tropi-
cal climates in the  substitution of fruits and farinacea
for oleaginous articles,  the less will be the liability to
disordered health in the autumn.  Experience teaches
that  it is not  a matter of entire indifference whether
the albuminous constituent be drawn from the animal
or from the vegetable kingdom, for the use  of highly
animalized diet has a tendency to raise, and that of a
vegetable diet to lower  the proportion of red corpus-
cles  in the blood, whilst by a due adjustment of the
proportion of  the two classes of components, the evil
effects  of the  exclusive  use  of either may be pre-
vented.  The  absolute  quantity of food  required for
the maintenance of the  human body in health,  varies
   2 
i8
A NEW TREATISE ON
so much with the age, sex, constitution and habits of
the individual,  and with the circumstances in which
he may be placed, that it would be absurd to attempt
to fix any standard which should  apply to every par-
ticular case.  The appetite is the  only sure guide for
the supply of the  wants of each, but its indications
must  not be misinterpreted.  To eat when we are
hungry is evidently a natural disposition, but to eat
as long as we are hungry may not always be prudent.
Since the feeling of hunger does not depend so much
upon  the state of  fullness or emptiness of the  stom-
ach as upon the condition of the general system, it
appears evident that the ingestion of food can not at
once  produce the  effect of dissipating it, though it
will do so after a short time.   So that, if we eat with
undue rapidity, we  may continue swallowing food
long  after we have  taken as much as will really be
required for  the wants of the system, and  every su-
perfluous particle  is not only useless, but  injurious.
Hence, besides its important ends, the  process  of
thorough mastication is important as prolonging the
meal, and giving time to the system so  that its de-
mands may be  abated in due time to prevent the  in-
gestion of more than is required.   There seems to be
a  sense of perfect intelligence conveyed to the en-
cephalic centre, which, in health, invariably dictates
what quantity of aliment is  naturally required for
purposes  of life, and which, if noticed and properly
attended to, would prove the most  salutary monitor
of health, and  an  effectual preventive of disease.  It
is not the sense of satiety, for this is  beyond the point
of healthful indulgence, and is nature's earliest indica-
tion of an abuse and overburden of her powers to re- 
            ASSIMILATION AND DIGESTION.         19

plenish the  system.   It occurs immediately previous
to this, and may be known by the pleasurable  sensa-
tions of perfect satisfaction,  ease  and quiesence of
body and mind.  It is when the stomach says enough,
and it is distinguished from  satiety by the difference
of sensations, the latter  saying  too  much.  Every
medical man is well aware how generally this rule is
transgressed; some persons making a regular prac-
tice of eating to repletion, and others  paying far too
little attention to the preliminary operations, and thus
ingesting more than is good for them, even though
they may actually leave off with an appetite.
  Although no universal law can  be  laid down for
individuals, however, it is a matter  of  much practical
importance  to be able to form a correct average esti-
mate.   It is from the experience afforded by the usual
consumption of food  by large bodies of men that our
data are obtained, and these data are sufficient  to en-
able us to predict with tolerable accuracy what will
be required by similar aggregations, though they can
afford no guide to the consumption  of individuals.
We shall first consider the quantity of food  sufficient
for men in regular active exercise, and then inquire
how far that may be safely reduced  for those who
lead a more sedentary life.  It is well known that  an
extraordinary improvement  has  taken place  in  the
health of seamen in the last few years.  At present
it may safely be affirmed that it would not be easy to
construct a diet scale  adapted to answer the required
purpose than the diet scale of the United States army,
which is from forty-one  to fifty  ounces in twenty-
four hours.   Of this  thirty-five  ounces is  vegetable
and  the  balance  animal;  and these can not be re- 
20
A NEW TREATISE ON
garded as superfluous, as there can not be any com-
plaint of insufficiency of food.  For this is  found to
be amply sufficient for the support of an able-bodied
man under the different conditions and exposures to
which a soldier is subjected.  The judicious admixt-
ure of the vegetable acids and canned fruit with the
other articles of diet has been found to be greatlv ef-
ficacious in warding  oft' scurvy, which used to be,
at one time, so greatly dreaded.  By diminishing the
amount of  alkali in the blood, and by  giving non-ni-
trogenous food, the scurvy is cured or prevented in
consequence of such  substances being acted on  in-
stead of the tissues of the body.  No other explana-
tion  can be given of the benefits which arises from
vegetable acids from  fresh vegetables, from sugar,
potatoes, &c.  The importance of a variety of food
need scarcely be insisted upon when the  number of
principles entering into the composition of the human
body is remembered.   The living body has no power
of creating  elementary substances.   It is obvious,
therefore, that the system must be supplied with food
containing  all the elements which enter into its com-
position.  In case of prisoners  the diet  should, of
course, be as spare as possible consistently with health,
but  it   should  be carefully modified in  individual
cases according to several  collateral  circumstances,
such as depression of mind, compulsory  labor, pre-
vious intemperate habits, and especially the length of
confinement. It  has  been  supposed  by some that
prisoners require a fuller diet than persons  at large;
this is  probably erroneous,  but more  variety is cer-
tainly desirable to counteract, as far as possible, the
depressing influence  of their condition upon the  di- 
ASSIMILATION AND DIGESTION.
21
gestive powers.   The evil effect of an undue reduc-
tion  in the  supply of food, and insufficient attention
to its quality, has, unfortunately, been  too  frequently
displayed in our prisons.   A notable example of which
will be hereafter alluded to.  It is not enough for the
healthy support of the body that the food ingested
should contain an adequate proportion of  alimentary
constituents; it is important that these should be in a
wholesome  or undecomposed  state.   Water consti-
tutes the natural drink of man, and that no other li-
quid can supply its place is apparent  from the large
proportion of the body that is  formed by  it;  the in-
fluence  which its presence exerts on the physical
properties of the various tissues into which it enters,
and the number a variety of purposes to which it  is
subservient  in chemico-vital operations of the living
body is unquestionable.  The  quantity  of water  in
the  different tissues  of the system amounts to two
thirds the weight of the entire system.   When we
examine into the uses of this large proportion of water
we find, in  the  first  place, that it serves  a purpose
simply mechanical, imparting to the tissues that su-
pleness and extensibility which characterize them in
their natural state, but which are completely removed
by drying them.   The  tissues  in which we find least
water are those whose functions  are most  purely
physical.  Thus we see that bone, whose  sole office
is to afford  an inflexible support, contains no more
than  ten to twenty per cent, of fluid; the principal
part even of this belonging to  the  softer tissues  im-
mediately connected  with its nutrition.    So in  the
cuticle and  its appendages, whose purpose is merely
protective, and  which  are partly dessicated by ex- 
22
A NEW TREATISE ON
posure to the air, the proportion of solid matter is at
least half.  But further, the presence of water is  es-
sential to the performance of all  those chemico-vital
processes by which the  integrity of the living body
is  maintained, and deficiency in  aqueous portion of
the fluids soon  manifests  itself in  a disturbance of
these operations, even though the constitution of the
solid  tissues may have not been affected.   As a gen-
eral  rule it  may be stated that  no chemical action
takes place between solid  substances, and that  they
require to be dissolved in water or some other men-
struum before they can be  made to affect each other;
and we find that this rule holds good constantly  in
the organized fabric alike of plants  and animals.   No
alimentary material can  be appropriated by the or-
ganism save in the liquid form, and hence it is that
animals, whose food is solid, are endowed with a di-
gestive apparatus for its  reduction  to the  state  in
which it may be absorbed by the  sanguiferous  and
lacteal vessels, which answer to the rootlets of plants;
this state being either one of complete  solution or of
very  minute division.  No other liquid than water
can thus act as a  solvent for  the various articles of
food introduced into the stomach.   Again, it is water
which continues to form the solvent of the nutritive
materials after they have  found  their  way  into the
current of the circulation,  and  have undergone that
assimilating process which prepares  them for being
applied to the  renovation of the solid tissues, and of
the vital fluid which courses in minute streams through
nearly every part of the  body, vivifying and  renova-
ting  the tissues  which  it  traverses.  Water consti-
tutes as much as  75 to 80  per  cent.  So  again  it is 
            ASSIMILATION AND DIGESTION.         23
the water of the blood which not merely brings to
the living tissues the materials of their development
in a state ready for appropriation, but also  takes up
the products of their  disintegration  and decay  and
conveys them by a most  complicated and wonderful
system of sewerage out of the system.  It is not dif-
ficult to understand, then, how seriously the chemico-
vital operations of the body  must be effected by a
deficiency  in  the normal proportion of this liquid,
more especially as some of the substsnces to be trans-
ported are of a difficult solubility; and we find  that
the demand for it, when it is withheld, soon becomes
even more pressing than the demand  for solid food.
   A very small amount  of putrescent matter in  our
food is quite sufficient to produce the  most pernicious
results, when that matter is habitually introduced into
the system, and these results, on  the one hand, mani-
fest themselves in the production of certain  disorders
which appear distinctly traceable to the direct action
of the  poison   so  introduced; whilst on  the other
hand they become apparent in the extraordinary aug-
mentation of the liability to attacks of such zymotic
diseases  as may, at the time, be  prevalent.   The va-
rious beverages employed by man, for the most part,
consists  of water holding solid  matter of different
kinds in solution, and it is not requisite, therefore, to
bestow any special attention upon them; but the  use
of alcohol, in combination with  water, and with  or-
ganic and saline compounds  in the various  forms of
fermented  liquors,  deserves particular notice, on ac-
count of the numerous fallacies which are  in] vogue
respecting it.   In the first place, it may be  safely af-
firmed that alcohol can not answer any one of those 
24             A NEW TREATISE ON
important purposes for which the use of water is re-
quired in the system;  and that, on the other hand, it
tends to antagonize many  of those  purposes by its
power of precipitating  most of  the organic com-
pounds whose solution in water is essential to their
appropriation by the living  body.   Secondly, the in-
gestion of alcoholic liquors  can  not supply anything
which is essential to the due nutrition of the system, for
we find not only individuals, but whole nations main-
taining the highest vigor and  activity, both of body
and mind, without ever employing them as  an article
of diet.  Thirdly, there is no reason  to believe  that
alcohol, in any of its forms, can become  directly  sub-
servient to the nutrition of the  tissues, for it may be
certainly affirmed that, in common with non-ozotized
substances in general, it is incapable of transformation
into albuminous compounds; and there is no sufficient
evidence that even fatty matters can be  generated in
the body at  its expense.   Fourthly, the alimentary
value of alcohol consists merely in its power  of  con-
tributing to the production of heat  by affording a pab-
ulum to the respiratory process; but  for this purpose
it would be pronounced, on  chemical  grounds  alone,
to be inferior to fat; and the result of the experience
of Arctic voyagers and travelers is most decided
in regard to the low value of alcohol as a  heat  pro-
ducing material.   Fifthly,  the  operation of  alcohol
upon the living body is essentially  that of a  stimulus,
increasing, for a time, like other stimuli, the vital ac-
tivity of the  body, and  especially  that of the nervi-
muscular apparatus, so that  a greater  effect may often
be produced in a  given time under  its use than can
be obtained without it, but followed by a correspond- 
            ASSIMILATION AND DIGESTION.         25
ing depression of power which is the more prolonged
and severe in proportion as the previous excitement
has been greater.  Nothing,  therefore, is in the end
gained  by their use, which is only justifiable where
some temporary emergency  can only be met  by a
temporary augmentation of power,  even at the ex-
pense of an increased amount of subsequent depres-
sion;  or where it  affords aid  in  the introduction of
aliment into the system, which nothing else can so
well supply. These cases, however, will be less nu-
merous in proportion as due attention is paid to other
means of promoting  health, which  are more in ac-
cordance with nature.  The physiological objections
to the habitual use of even small quantities of  alco-
holic liquors, rest upon the following grounds: They
are universally admitted to possess a poisonous char-
acter when administered in large doses, death being
the speed}r result, through the suspension of nervous
power which their introduction into the circulation in
sufficient quantity is certain to induce.  When habit-
ually used in excessive quantities, universal experience
shows that alcoholic liquors tend to produce a  mor-
bid condition of the body at large, and especially of
the nervous system.   This condition  being such as a
knowledge of its modus operandi on the body would
lead the physiologist to predicate the frequent occur-
rence of more chronic diseases of the same character
among persons advanced in life who have habitually
made use of alcoholic liquors in moderate amount,
affords  a strong  probability that they result from  a
gradual perversion of the nutritive processes of which
that habit  is the  cause.  The special liability of the
intemperate to zymotic  diseases, indicates that the 
26
A NEW TREATISE ON
habitual injestion of alcoholic liquors tends to prevent
the due elimination of the products of the disintegra-
tion of the system, and thus to induce a  fermentible
condition  of the blood.   Extended experiencd has
shown that, notwithstanding the temporary augmen-
tation of power which may result from the occasional
use of fermented liquors, the capacity for long endur-
ance of mental or bodily labor, and  for resisting the
extremes of heat and cold, as well as other depress-
ing agencies, is diminished, rather than increased, by
their  habitual employment.  On these grounds, the
author has felt himself fully justified in the conclusion
that for physiological  reasons  alone habitual  absti-
nence from  alcoholic liquors is the best rule that can
be  laid down for the great majority of healthy indi-
viduals, the  exceptional cases in which any real ben-
efit can be derived from their use being extremely few.
  After treating  on the course  of the food that  is
necessary for the support of the system in a normal
condition; the different actions it has to undergo be-
fore it is taken into the stomach; the chemical changes
it undergoes in the stomach;  the different kinds of
food that  enter into the composition of mas aliment;
the diffusion of food to man under different latitudes
and conditions in which he may be placed; the differ-
ent changes  in the food of different kinds, and the
attendant  circumstances  under which he be placed,
has been as briefly and concisely set forth as is pos-
sible in these few pages.   The next important  organ
of digestion which I shall refer to is  the Pancreas.  I
shall not  endeavor  to  give an anatomical or physio-
logical description, but merely its office and use in as-
sisting to dissolve the food  and encourage digestion. 
            ASSIMILATION AND DIGESTION.        27
It was a disputed point for many years what its office
really was, but after faithful research it was  demon-
strated  by scientific men that it did secrete  a fluid
which was essential to the decomposition of the food;
but we  will briefly say that the chyme, or product of
gastric  digestion, which escapes through the  pyloric
orifice  into the  duodenum,  contains much  azotized
matter  in  a state  of actual solution; a considerable
proportion of it is still only reduced and mechanically
suspended, and solution of the latter is contained in
the intestinal tube.  In the farinaceous part of the food,
moreover,  no great amount of change has  hitherto
been effected, and the sugar which  has been gener-
ated by the  agency of the salivary ferment, is prob-
ably absorbed in the blood vessels nearly as fast as it
is formed.   In the condition of the  fatty matters no
important change is  perceptible,  except such as re-
sults  from  the solution of the membranes, &c, that
enclosed them.   Hence we  see  that the process of
digestion, so far  from being completed in the stom-
ach, has only been  carried one stage further. Soon
after  its entrance into  the duodenum, the chyme is
subjected to  the action of the bile, the pancreatic fluid,
and that secretion from the glandular in the walls of
the intestine itself from  the glands of brunner.  Such
follicles present themselves along the whole extent of
the gastro-intestinal mucous membrane, but although
very similar in their appearance, in different parts of
its  length their  secretion is probably very different.
Along the course of the intestines, on the other hand,
it is doubtful whether they form any other secretion
than  that of protective  mucous.  Such follicles  are
not known to exist  in any other than the open state, 
28
A NEW TREATISE ON
and they seem to have a permanent character, con-
tinually discharging new broods  of epithelial  cells.
Various parts of the mucous membrane of the stom-
ach, and of the large intestine, are studded at inter-
vals with  shallow pits, or follicles, which, according
to observation, have the  form of closed vesicles dur-
ing fcetal life and early infancy, but gradually open so
that their  cavities become continuous with the free
surface of the mucous membrane, the columnar epi-
thelium of  which extends itself into them and they
remain in that condition during the rest of life.
  The pancreatic fluid will be  first  noticed.  The
structure of the  pancreas closely resembles that of
the salivary glands, for it consists of racemose clus-
ters of secreting follicles, which form the terminations
of the ramifying divisions of the  duct; each cluster,
with its blood vessels, lymphatic  nerves and connect-
ing tissues, forming a lobule, and the separate lobules
being held together by areolar tissue as well as by
the vessels and ducts.  Like the  salivary glands, its
development commences by a  sort of budding forth
of the  alimentary  canal  at a particular spot  upon
which a mass of cells has  previously accumulated.
The secretion of this gland strongly resembles saliva
in its general appearance, being clear and  colorless,
slightly viscid and  alkaline  in  its reaction.  It con-
tains a large proportion of solid matter, and the  na-
ture of its  animal principle is not precisely the same.
The albuminous ferment is not perfectly coagulable
by heat, and when precipitated by sulphuric,  nitric
and  concentrated  hydrochloric  acids, and by  the
metalic  salts, and when thrown down by these or by
heat, it is redissolved in an excess of the reagent, and 
            ASSIMILATION AND DIGESTION.         29
on the application of heat and this  solution it is  pre-
cipitated by ferrocyanide of potassium.  When boiled
with  ammonia it assumes an intense  yellow color.
The readiness with which this  substance  undergoes
change is  indicated by the  rapidity with which the
pancreatic  fluid passes into  decomposition, for even
after  a few hours exposure to the air it  gives off a
decidedly putrid odor.  Like ptyaline, this peculiar
constituent of the pancreatic  fluid possesses the power
of converting starch into sugar.   There  can be no
doubt, therefore, that it is subservient to the continued
digestion of the farinaceous  part of the food during
its passage  through the small  intestines.   It  shares
this office,  however, with the success of the enteritis,
which has  been shown to be possessed of this  con-
verting power.  It  has recently been  affirmed, and
strong evidence has been adduced, that the  essential
purpose of the pancreatic fluid is to promote  the ab-
sorption of fatty matters by reducing them  to the
state  of an emulsion, which  is capable of finding its
way into the lacteals.   That this fluid  possesses the
emulsifying power in a peculiar degree, may be con-
sidered as having been  fully demonstrated  by ex-
periments, for  mixing it with oil, butter,  or  any va-
riety  of fat, at a temperature sufficiently high to ren-
der the  fatty substance liquid, and then stirring the
mixture  a few minutes, an emulsion is produced bear-
ing a strong  resemblance to chyle.  This emulsion
does not cease to present its  peculiar aspect, although
left standing for some time;  whereas,  although  bile,
saliva, gastric juice, blood-serum  and other  animal
fluids have a certain  emulsifying power, yet after a
short time the oil particles run together again almost 
 30             A NEW TREATISE ON
 as if they had  been shaken up  with  water.   When
 fatty matters have been introduced into the alimentary
 canal they undergo no considerable change until they
 have  passed the orifice of the pancreatic  duct, and
 oily emulsion being then for the first time found in the
 intestinal canal, and the contents of  those absorbents
 only having the opaque  whiteness  of chyle, which
 originate in  the intestinal villi below  that  orifice.  So
 again, by putting a  ligature  round  the pancreatic
 duct,  the digestion of  the oleaginous matter  is  so
 completely prevented that it is found in the lacteals.
 This  position is further strengthened by the  fact as-
 certained by chemical observation, that there is a close
 relation between disease of the pancreas and the dis-
 charge  of fatty matters per anus.  That the diges-
 tion and absorption of fatty matters will take place
 after the pancreatic duct has been tied, (sufficient time
 having been given for the evacuation of any pancre-
 atic fluid  which may have been in the alimentary
 canal  previously to  the operation),  and even in the
 lower part  of  the small intestines into  which  these
 substances have been conveyed by ingestion, after it
 has been completely separated by a ligature from the
upper part into which the pancreatic  fluid has been
 poured. It further appears from these experiments, that
 a mixture of the pancreatic fluid with  the bile and
the succus  entericus possesses  a  more  energetic
emulsifying  power than the first of these  fluids alone;
 and it seems probable  that, as  in the conversion  of
 starch,  so in the  emulsification  of fat  the intestinal
 fluid performs  a very important part.   It would not
 seem  unlikely that  the  qualities  of these fluids, like
those  of the saliva, may vary in different animals, and 
            ASSIMILATION AND DIGESTION.         31
that the emulsifying power may be limited in the rab-
bit, or nearly so, to the pancreatic fluid; the  quantity
of fat which its natural food contains being  small,
whilst in the carniverous animals whose natural food
is more oleaginous, the provision for the digestion of
fatty matters may be more extensive.  Of the amount
of pancreatic  fluid which is daily secreted  by man,
we have no other data for forming an estimate than
those afforded by Frerichs, who collected from  an ass
in forty-five minutes, 387^ grains, and from a large
dog,  in  twenty-five  minutes,  46  grains.    These
amounts, however, were poured forth while food was
in the stomach and  digestion was going on, and it is
probable that at other times the secreting process is
nearly suspended.   The duodenum receives  not only
the pancreatic, but also the biliary secretion, and from
the constancy with which this fluid is poured into the
upper part  of the intestinal tube, or even  into  the
stomach  itself, in all animals which  have any kind of
hepatic apparatus, it seems a legitimate influence that
this secretion is not purely excrementitious, but  serves
some important purpose in the digestive process.   It
is not easy, however, to state  with precision what
this purpose is.   The result of many of the experi-
ments which have been made to determine it are  vi-
tiated by the  fact that the pancreatic duct, in most
cases, discharges itself into the intestinal tube  at the
same point with the  hepatic, and has  thus been fre-
quently involved in operations performed upon it, as
the most important constituents of bile.
  Regarding the organic compounds, we  have now
to consider our knowledge is far less definite and sat-
isfactory than  it is  respecting those which have been 
32              A NEW TREATISE ON
already passed in review, and this arises from several
causes, among which may be more particularly men-
tioned the great facility with which  they are  decom-
posed, both spontaneously and by the  operation  of
reagents, so that it  is by no means easy to say, in
many instances, whether a given substance extracted
from  the bile by analytical operations pre-existed in
it or has been subsequently found under the treatment
to which that fluid has  been subjected.   There  has,
consequently, been a discrepancy of opinion among
chemists with regard to constitution of this excretion;
some having regarded  as original components what
others have considered as secondary, and the number
of proximate  constituents  having been  ranked high
by some while others have reduced it  to some  four
or five.  The  biliary matter  is chiefly composed  of
two  substances, which  are regarded  as conjugated
acids formed by the  union of one and the same acid,
the true  choleic with glycine and taurine respectively,
and hence termed the glyco-choleic and tauro-choleic.
This choleic is a fatty, or rather a resinous, acid, from
which nitrogen is altogether absent,  while oxygen is
present in only a small proportion.  It forms tetrahe-
dral, or more nearly square octohedral, crystals, which
effloresce on exposure to  the air.  Its taste is bitter,
leaving a faint, sweetish  after-taste.  The acid reac-
tion of this substance is sufficiently strong to  redden
litmus paper and to enable it, with the aid of heat, to
expel the carbonic acid from  solutions of the alkaline
carbonates.   The  salts which it forms possess a bit-'
ter, and, at the  same  time, a  slightly  sweet taste.
They are all soluble in  alcohol, but water dissolves
only the chlorates of the  alkalies and the baryta. 
            ASSIMILATION AND DIGESTION.         33

The salts of choloidic acid are perfectly isomeric with
those of choleic acid, but it is that the former acid is
displaced even by carbonic acid, although with  the
aid of heat it  decomposes the carbonates.  Choleic
acid may be recognized wherever it occurs, whether
combined with its adjuncts as a  conjugated acid, or
metamorphosed into choloidic, by the excellent test
devised by its  peculiar reaction with  sugar and sul-
phuric acid; for if in the fluid suspected to contain bile
there be first added  a little solution of sugar, and pure
sulphuric acid be then added by drops, a yellowish
color is produced, deepening to a  pale cherry, then to
a carmine, and lastly to an intense violent tint,  if bile
be present.  This test may,  therefore, be  applied to
determine the presence or  absence of the  character-
istic  components of bile, and we shall hereafter  notice
some of the results of its application.
  When choloidic acid is distilled with  nitric acid it
yields the volatile acids.   The coloring matter of the
bile is a substance peculiarly difficult to obtain  satis-
factorily, owing especially to the very small quantity
in which it occurs, and to its extreme instability.   The
most frequent  form  under  which  it presents itself is
that  of a  brown  non-crystaline  powder,  devoid of
taste and smell; insoluble in water; very slightly sol-
uble in ether,  and  more so  in alcohol,  to which it
communicates a distinct yellow tint.   This substance
constitutes a large  part of most biliary  calculi, in
which it exists in a state  of insoluble  combination
with lime.   When it is dissolved in alkaline solutions,
these which are at  first a  clear yellow, become,  by
exposure to the air, of a greenish-brown tint, and it
is on this modifidation the  consequence,  probably, of
    3 
34
A NEW TREATISE ON
  a higher oxidation, that  the well-known changes of
  color which  occur in some of the animal fluids  are
  dependent.    The  yellow   alkaline  solution,  when
  treated with  nitric acid, becomes first green, then blue
  and then red; after  a considerable period  the  red
  again passes into a yellow color, but the nature of the
  substance is then entirely changed.  When  the  yel-
  low alkaline solution  is treated with hydrochloric acid,
  the pigment  is precipitated with a green tint;  this pre-
  cipitate  forms a red solution  with nitric acid  and a
  green solution with the alkalies, and appears to be per-
  fectly identical with the green modification of bile pig-
  ment.  When acids are added to the fresh bile, a green
  color is produced if  oxygen be present, but not if it
  be excluded.  Bile pigment is occasionally  found in
  the urine in  large quantities when its secretion  by the
  natural  channel is prevented, and it may be readily
  recognized  by the nitric acid test.  There  is much
  uncertainty in regard to the precise composition of this
'  substance, for the reasons already specified; the analy-
  sis  which have been made of it, however, indicate
  that it is remarkable for the enormous proportion of
  carbon which it contains.   The  only distinct  indica-
  tion yet obtained that the  characteristic components
  of bile are-performed in the blood, is afforded by the
  experiments of Kunde, who demonstrated by Pette-
  koffer's test, the presence  of biliary matters in the
  blood of frogs, whose livers had been extirpated.   On
  the other hand, there is much that indicates,-if it does
  not prove, that the function of the liver is not the mere
  selection and elimination of the elements of bile  from
  the blood, but that it exercises a most important trans-
  forming power, both over the  constituents  of the 
            ASSIMILATION AND DIGESTION.         35
blood and over those of the bile.   At present it will
be  sufficient to remark, that whilst a  chemical com-
parison of the elements of the bile and urine shows
that each of these  excretions is  the  complement of
the other, and that the mass of the blood, or of the
solid tissues, might resolve  itself into  these two sets
of compounds, various physiological  and patholog-
ical phenomena seem to indicate that the products of
the metamorphosis  of the tissues, which afterwards
become the components of bile, do not take the form
of these components until they have been acted upon
by  the liver and reduced to a state comparatively in-
oxious; for whilst there  is abundant evidence that the
constituents of bile, both its resinous acids and its col-
oring matter, may be  reabsorbed without serious  in-
jury, and whilst there is  strong  reason to  believe
that,  as  regards  the  resinous   acids, such reab-
sorption is  habitual,  there is  adequate  proof,  on
the other hand, that the retention  within the  circula-
ting current of the matters from which bile is formed,
owing to  structural  disease  or functional inactivity
of the liver, is attended with the most serious conse-
quences, and will, if prolonged, induce a fatal result.
  We shall here  limit ourselves to the consideration
of what mav be regarded as the best established facts
in regard to the uses of the biliary secretion  in the
digestive  process.   When its action  is tested out of
the body by mingling it with the different constituents
of food, it is found  to exert no change upon starchy
substunces while it is fresh, though when in a state of
incipient decomposition it acts upon them as other an-
imal substances do.   It has no action upon cane sugar
until it has  stood a considerable  length of time, but 
36              A NEW TREATISE ON
then it converts it into lactic acid.   This  change  it
speedily exerts,  as  do all other  animal substances,
even  when acidulated; and  though it will form an
emulsion with oleaginous matter, yet emulsification  is
less complete than that which is effected by the  pan-
creatic fluid alone; but the same similarity exists in
the salivary gastric juice, pancreatic juice,  biliary se-
cretion and the secretion from the mucous membrane
of the bowels.   When there is a deficient  secretion
of bile, or more food is swallowed than the  bile  pro-
vided for it can act upon, or the  character of the
biliary secretion itself has undergone any serious per-
version, there should be a much larger amount of pu-
trifactive fermentation than is normal, as indicated by
an  evolation of flatus  and very frequently by diar-
rhoea.   Further, the want of proper neutralization of
the gastric fluid will cause the  continuance of acidity
in the contents of the intestinal  canal which, in its
turn, induces a state of irritaition of its mucous mem-
brane and a perversion of its secretions, and it is  one
of the beneficial results of alterative medicines, em-
ployed to remedy this condition, that by augmenting
the secretion of bile they tend to  reproduce a state of
neutrality  in the contents of the  alimentary canal.
The presence of a proper quantity of bile in the intes-
tines  appears  to promote the secreting action of the
intestinal glandula, and also to contribute to maintain
the peristaltic  movement  of the walls of the canal.
This appears alike from the tendency to constipation
which is usually consequent upon the deficiency of
the secretion, and from the diarrhoea which proceeds
from  its excess, and is  confirmed by the  purgative
properties  which inspissated ox-gall has been found 
           ASSIMILATION AND DIGESTION.         37
to possess.  Notwithstanding all its uses, however, it
must be admitted that the prevention of the discharge
of bile into the alimentary canal is not attended with
the deleterious effects which might have been antici-
pated from it, for it has been found that if the bile duct
be divided and a tube be inserted  in  such a manner
as to  convey away the  secretion through a fistulous
orifice in  the abdominal  parietes, the  animals thus
treated may live for weeks, months or years, and suf-
fer  no inconvenience.  Of the quantity  of bile  daily
poured into the alimentary canal of man, we have no
other mode of forming  an estimate than  by observing
the quantity poured  out from the bile  ducts of ani-
mals.  In such experiments Blondlet found that a dog,
in which  he  had established a  fistulous opening for
the discharge of bile, secreted  about seven  ounces
in twenty-four hours.  The carefully conducted ob-
servations of Budder and  Schmidt indicate that the
rate of secretion is by no  means uniform, but that it
bears  a certain relation to the digestive process, the
quantity poured forth in a given time being  greatest
about ten or twelve hours after  a  full meal, and then
diminishing until it reaches its minimum, for which
about as many more  are required.  The secretion is
considerably diminished when  food  is  withheld  for
some time; the quantity poured out after ten  days'
starvation being only about one eighth of what  it is
when  at  its  maximum.  Still  it is obvious that, al-
though its rate is thus greatly influenced by the stage
of the digestive process, (which is formed from blood
that is charged with newly absorbed and imperfectly
assimilated matters), the excrementitious character of
the secretion  require that its elimination  shall  be con- 
38              A NEW TREATISE ON
stantly going on to a certain degree;  but a receptacle
is provided in man,  as in  most  others among  the
higher animals whose digestion is performed at inter-
vals, for the storing up of the fluid until it can be use-
fully employed in that process.  The intestinal orifice
of the ductus choledocus is closed by a sort of sphinc-
ter, and the fluid secreted during the intervals of di-
gestion, not being propelled with force sufficient to
dilate this, flows back into the gall-bladder  which di-
lates to receive it.   The presence of food in the duo-
denum seems to excite  the  walls of the gall-bladder
and of the biliary ducts  to a  contraction sufficiently
powerful  to propel their contents  into  the  intes-
tines in spite of the opposition of the  sphincter, but
whether this takes  place  through a reflex  action of
the  nervous system, or through the direct stimulation
of the muscular coat of the  duct by the passage of
alimentary matters over its surface, we  have at pres-
ent  no means  of  satisfactorily determining.   It will
be recollected  that the gall-bladder is usually found
distended with  bile in  cases of death  from starva-
tion, notwithstanding the diminution in the amount
secreted.   The fluid of the small intestines, which is
compounded by the intermixture of the biliary and
pancreatic secretions with the  salivary and gastric
fluids, and with the secretion of the  intestinal glan-
dula, appears  to possess  the very peculiar  power of
dissolving, or of reducing to  an absorbable  condition,
alimentary substances of every class, thus possessing
more of  the character of a  universal  solvent than
either of these secretions has in its separate state.  It
completes  the conversion of starchy into saccharine
matter,  and thus  enables  the former  to supply  the 
            ASSIMILATION AND DIGESTION.         39
blood with an important pabulum for the combustive
process, which is at once absorbed into the blood ves-
sels.  It emulsifies the  oleaginous matter, and  thus
renders it capable of being introduced into the lac-
teals; and  it not only restores to a state of solution
the albuminous compounds which may have been pre-
cipitated by the addition of bile to the product of gas-
tric digestion, but it also exerts a powerful solvent in-
fluence upon albuminous  substances which have not
been submitted to the previous agency of the  gastric
fluid; and it thus completes the solvent process which
had been very  far from perfected  in the"  stomach.
What is the precise share, however, of each of these
secretions in producing this composite result, can not
be stated with any degree of certainty, but it seems
probable that the secretions of the intestinal walls
have  a very definite share in it.  It is obvious that the
amount of each kind of alimentary substances than can
be thus  prepared in a given  time, will vary with the
amount of the secretion, by whose  agency this prep-
aration is specially affected,  and as there  are many
indications  that  the quantity of each that is taken up
in absorption is limited, and  that it bears a relation to
the wants  of the  system,  it" is probable that the
amount of the solvent,  or reducing  fluid, that is  se-
creted by each  glandular apparatus, is regulated,  as
we have seen it to be in the  case of  the gastric juice,
by the demand set up by the  nutrient operation, rather
than  by the amount of alimentary matter that is wait-
ing to be  digested.   The process of digestion  and
conversion are probably "continued during the entire
transit of the alimentary matter along the small intes-
tines, and at the same time the  products of that con- 
40              A NEW TREATISE ON
version are gradually being withdrawn by absorbent
action, so that by the time it reaches the caecum the
undigested residue contains little else than the innu-
tritious or insoluble component of the food, together
with the excrementitious portions of the bile and other
secretions.   Up to this time the contents of the canal
have an alkaline reaction, but in the caecum they again
become acid, and, it is supposed, that this change de-
pends upon the secretion of a fluid analogous to the
gastric juice,  by the large  and numerous  tubular
glands contained in the parietes of this part, whereby
the albuminous  matters, still undigested,  might  be
more  completely dissolved.   This  supposition  ap-
peared to derive weight  from  the fact that the caecum
is peculiarly large in most herbiverous animals; the
appendix vermiformis being also of greatly increased
dimensions, and sometimes double.   But from the ex-
periments and observations of Blondlet, it seems prob-
able that the acid of  the caecum is rather a product
of the transformation of saccharine substances in the
alimentary canal than a  secretion from its walls.  Still
as this lactic acid has a solvent power for albuminous
matters, which is equal, or nearly so, to that  exerted
by  hydrochloric  acid,  it is by no means  impossible
that it may be subservient to the completion of the
digestive process, in the case in question, since the
larger the proportion of the aliment composed of sac-
charine  matters, the  greater  will  be the importance
of a thorough extraction of its albuminous constitu-
ents.  The walls of  the lower part of the small  in-
testines are beset with elevated patches that are formed
by the aggregation of the bodies known as the Peye-
rian glandula.  Bodies  of a  similar kind, however, 
           ASSIMILATION AND DIGESTION.         41

also occur separately, and are known as the glandula
solitaire.  The glands of Peyer, when examined in a
healthy  mucous membrane,  presents  the  appear-
ance of circular, white, slightly raised spots, about
a  line  in  diameter, over  which the membrane  is
usually less  set with  villi, and very often  entirely
free from them.   Each of these  white spots, of which
a large number are contained in the agminated glands,
is surrounded by a  zone of openings, like those of
the follicles of Lieberkuhn, which lead into tubular
caecal.  The Peyerian  glands  must be regarded as
instruments for the elaboration of the chyle, which is
conveyed to them  by the  very delicate absorbents
that originate in the villi.  The  walls of the large in-
testines contain a considerable number of glandula
which closely resembles the glandula solitaire of the
higher part of the canal; these, however, are so much
more frequently open than closed  that the latter con-
dition was  not recognized until pointed  out  by Dr.
Baly.   It can scarcely be doubted that  these  are  se-
creting organs destined to pour the product of their
activity into  the  alimentary canal; but whether this
product be the peculiar mucous with which the coats
of the large intestines are covered, or consists of the
proper fcecal matter, or be something different  from
either, has not yet been determined.   The indigested
residue of the food mingled with the  products of se-
cretion that  have been  poured into  the  alimentary
canal, gradually acquires, in the large intestines, the
ordinary consistency of feces, through the continu-
ance of the absorbent process, whereby the superflu-
ous fluid is removed.  The changes ensue most rap-
idly in the flesh of fish and  hares, and less rapidly in 
42             A NEW TREATISE ON
that of poultry and other animals; the fragments  of
muscular tissue which remain aftter the continued ac-
tion of the digestive fluid, do not appear to undergo
any alteration in their passage through the re'st of the
intestinal canal, for similar  fragments may be found
in feces even twenty-four hours after the introduction
of meat into the stomach. - The cells of cartilage and
fibro-cartilage,  except those of fish, pass unchanged
through the stomach and intestines, and may be found
in the  feces.  The  intestinal tissues of these struct-
ures are converted  into pulpy, textureless substances
in the artificial  digestive  fluid, and  are not discover-
able in the feces.  Elastic fibres are unchanged in the
digestive  fluid;  fatty matters are  also unchanged;
fat cells are sometimes found quite  unaltered in the
feces, and crystals of cholesterine may usually be
obtained  from  feces,  especially  after the use  of fat
pork.  As regards  vegetable substances, Dr. Rawitz
states that he frequently found large quantities of cell
membranes unchanged in the feces; also starch cells
deprived of only  part of their contents.  The green
coloring matter was usually unchanged.  The walls of
the sap-vessels  and spiral vessels were quite unaltered
by the digestive fluid, and were usually found in large
quantities in the feces; their contents, probably, were
removed.
  Besides* the undigested residue of food, the micro-
scope  enables  us to  recognize  the brown coloring
matter of the  epithelium  cells and mucus-corpuscles
and various saline  particles, especially those  of the
ammonaco-magnetisan phosphate, whose crystals are
well defined; most  of which are derived from the se-
cretions.   The quantity of fcecal matter which is daily 
            ASSIMILATION AND DIGESTION.         43

passed by an adult seems to average from four to six
ounces, but this contains seventy-five  per cent,  of
water, so that the solid matter thus evacuated is not
above one or one and a half ounces.  Of the degree
in which the bile, as a whole,  enters  into the com-
position of  the feces,  it  is difficult  to speak  with
precision.   Its coloring and its  fatty matter are un-
doubtedly present, but scarcely any traces of choleic
acid or of either  of its  conjugated compounds, or of
their soda-base can be detected,  so that the proper
biliary matter must either have  undergone  decompo-
sition, so as to be no longer recognizable, else it must
have been  reabsorbed.   The  latter is  the idea now
usually entertained, although Valentine has endeav-
ored to show that the proper fcecal matter is chiefly
derived from decomposed constituents of the bile.  A
more probable source for this, however, will presently
be offered.   The indications of the presence of bile
are  more distinct when the feces have  remained for
only a short time  in the  large  intestines,  and when
there has consequently been less time for its reabsorp-
tion.  In fcecal discharges which  result  from the ac-
tion of mercurials, or other medicine  which has  a
similar effect, large quantities of biliary matter  may
be detected very little changed.   Although it can not
be stated with certainty what  is  the precise amount
of the glandular apparatus connected with* the  intes-
tinal canal,  which is concerned in the  elimination of
that peculiar putrescent matter which give  the  feces
their characteristic odor, yet it may be stated  almost
with certainty that this matter is not derived from the
decomposition of the undigested  residue of the  food,
for  in the first place, this residue consists of matters 
44              A NEW TREATISE ON
whose very inaptitude for undergoing chemical change
is the source of their indigestibility; and it is scarcely
possible, therefore, to imagine that in so  short a  pe-
riod they should acquire a character so peculiarly of-
fensive.  But further, we, observe that feces matter is
still discharged, even in considerable  quantities, and
after the intestinal tube has been completely emptied
of its alimentary contents.  We see this in the course
of many diseases, when  food is not taken for several
days, during which time the bowels have been  com-
pletely emptied of their previous contents by repeated
evacuations; and whatever then passes in addition to
the biliary and pancreatic fluids, must be derived from
the intestinal walls themselves.  Sometimes a copious
flux of  putrescent matter continues  to take place
spontaneously,  whilst it is often produced  by the
agency of purgative medicine.  The colliquative di-
arrhoea which frequently comes on at the close of ex-
hausting disease, and which  usually precedes death
by  starvation, appears to depend not so much upon a
disordered state of the intestinal glandula themselves
as upon the general disintegration of the solids of the
body, which calls them into extraordinory activity for
the purpose of  separating the decomposing matter
which has accumulated in it to a most unusual amount.
That if albuminous or gelatinous compounds be heated
with solid  hydrate of potash, and the  heat be con-
tinued  until the  greater  part  of  the  whole  of
the nitrogen has been dissipated as  ammonia, and
hydrogen begins to be  given off, the residue, when
supersaturated with dilute sulphuric acid and distilled,
yields a liquid containing acetic and butryic acids, and
possesses in a very intense  degree the peculiar  and 
            ASSIMILATION AND DIGESTION.        45
characteristic odor of human feces.   The odor varies
according to the substance employed, and in this way
all varieties of fcecal smell may be obtained.  As the
action of caustic  potash  at  a  high temperature is
simply a limited or incomplete oxidation or combus-
tion, this curious result confirms the view which had
been previously put forth, that the proper foecal mat-
ter is the product of the imperfect oxidation which a
portion of histogenetic constituents  of the  food un-
dergo in the course of their  regressive metamorpho-
sis, being comparable  to  the soot  or lampblack of a
furnace or  lamp.   It  is further urged  by him that
the condition of feces differs  in many particulars from
that of substances in a state  of fermentation or putre-
faction, that their  peculiar odor is entirely unlike any
that is generated by  the  ordinary decomposition  of
organic compounds, whether azotized or non-azotized,
and that by contact with air  they themselves undergo
a sort of fermentation or  putrefaction in which  their
peculiar fetor disappears;  a fact, as he justly remarks,
which is  full of significance.  This  view is of great
practical importance, for if it be true that the intesti-
nal canal receives and discharges the products of the
secreting action of a glandular apparatus, whose spe-
cial function is the elimination of certain products of
decomposition from the blood, the facility with which
we can stimulate this  to  an  increased action by cer-
tain kinds of purgative  medicines,  gives us a  most
valuable means of augmenting its depurative  action,
seeing, as no medical practitioner  can  avoid doing,
how  frequently  Nature  herself employs this means
of eliminating morbific  matter from the  intestines,
as shown by the immense relief often given by an at- 
46             A NEW TREATISE ON
tack of diarrhoea.  We  may look upon this appa-
ratus as one which, like the liver or  skin, or kidney
and  spleen, may frequently be stimulated by medi-
cines that have a special action upon  it, and  through
which  some morbific matter may be got rid  of more
certainly and more speedily than through any other
channel.
  It  is  not intended by these  observations to  encour-
age the system of violent and  indiscriminate purga-
tion, but to show that  purgatives, judiciously admin-
istered, often constitute our best means of eliminating
injurious matters from the system.
  We  have passed  in review all the secretory glands
of the  alimentary canal: the parotis,  sublingual and
submaxiliary, which secretes the  saliva; the  pancre-
atic glands, which secretes the pancreatic juice;  the
bile,  secreted by the liver, next comes.   The spleen,
which is classed among the ductless  glands by a great
many  physiologists, deserves  more than a  passing
notice,  on account  of its size and obvious functional
importance in the requirements of the system. The
minute structure of the spleen has recently been made
the subject of careful research by many excellent  mi-
croscopic observers.  The following is a summary of
the most important  points they may be considered to
have determined:  The fibrous coat in  man  is com-
posed of white fibrous tissue, with an intermixture of
yellow or  elastic  fibres.  In many of the lower ani-
mals, however, it contains non-straited muscular fi-
bres, composed of fusiform fibre cells.   The  trabicu-
lar tissue consists of fibrous bands and threads which
arise from  the  inner surface of the fibrous envelope
and form a network that  extends  through the entire 
            ASSIMILATION AND DIGESTION.         47
organ, becoming connected  also  with the  fibrous
sheaths of the vessels which penetrate it.  These
bands are partly  muscular in the animals which have
muscular fibres in the external envelope of  the spleen,
but elsewhere they are simply fibrous.  The spaces
left by their intersection, which are by no means regu-
lar, either as to form or size, are occupied by the spleen-
ic corpuscles and  spleenic parenchyma.   In the trabe-
cule  of  the human spleen, Prof. Kolliker has dis-
covered  some peculiar fusiform  cells, round nuclei,
which are  probably to be  considered  as  contractile
cells,  not developed into their properly characteristic
form.  The peculiar spleenic corpuscles are whitish
spherical bodies,  which are embeded in the spleenic
parenchyma, but are connected with the smaller ar-
teries by short peduncles like grapes with their  fruit
stalks,  or   are  sessile upon  their sheaths.  Owing
to the rapid changes which they undergo after death,
and the influence of previous  disease and  abstinence,
they are seldom observed  in  the  human subject, but
are best seen in the perfectly fresh spleens of the ru-
minatia.  There  is no doubt of their invariable  pres-
ence in the healthy human subject, although this has
been  denied by many anatomists.  The size of these
corpuscles, when fully developed, varies  from  one
sixth to one third of  a line.  Each of them consists
of a delicate fibrous envelope, derived from the sheath
of the artery  to which it is attached, and  frequently
surrounded with capillaries  of  extreme minuteness.
The  remarkable discovery has recently  been  made
by Dr. Sanders, that the interior of the  malpighian
corpuscles is traversed by arterial twigs of consider-
able size. Many  observations of the author have shown 
48             A NEW TREATISE ON
that there is a special connection between the malpig-
hian corpuscles and .the lymphatics of the spleen, but
it may be considered as quite determined by the con-
currence of the most recent observations on this point.
The true spleenic parenchyma consists, in great part,
of cells which correspond in appearance  with those
of malpighian corpuscles, and which  are, like  them,
imbedded in a nearly homogenous plasma;  but two
other kind of cells occur in it which are  seldom met
with in the latter, and numerous free  nuclei are also
present.   Of  these two  kinds  of cells,  one  set is
smaller and the other larger than the  average of the
parenchymatous cells;  the former bears a strong re-
semblance to red corpuscles, but of a  paler  color.
These elements, like the contents of the malpighian
corpuscles, vary greatly in  their proportion  to each
other, from which it may be concluded that they are
in a state of continual development and degeneration.
They do  not  lie  collected  in large heaps, but form
small irregular groups of different sizes, which  are
clustered especially on the sheaths of the vessels, the
trabecular partitions and the membranes of the mal-
pighian corpuscles.   They are not  themselves  in-
cluded in  special  envelopes.  Besides the usual cor-
puscles and  granules of the  parenchyma, it contains,
dispersed through it in very inconstant amount, some
remarkable  colored particles, varying from the size
of small granules to that of blood  corpuscles, and
often  aggregated in  masses of 1-1000 of an inch in
diameter, having a distinct envelope which sometimes
contains as  many as twenty corpuscles.   These  are
probably blood corpuscles in various stages of degen-
eration, but  they are  by no means peculiar to  the 
            ASSIMILATION AND DIGESTION.        49
spleen, for they present themselves in many other sit-
uations, where extravasations of blood  occasionally
occur, and, as remarked by Dr. Sanders, from all the
circumstances  connected with them, they would  ap-
pear to be the  product, not of organic processes, but
of physical alteration in stagnant blood, and are only
more abundant in the spleen because more blood is
retained after death in its pulp than in the substance
of other organs.   Of the spleenic arteries it is chiefly
to be observed that their  branches form no anasto-
moses, but that  they subdivide  and  ramify like  the
branches  of a tree  with the malpighian corpuscles at-
tached as fruit.   Beyond their connection with these
the}'  enter into  the red spleen substance, and here
each  twig subdivides into a tuft of arteries still more
minute, which again subdivide into a close network
in the spleenic pulp.  Of  the veins  it is positively
nothing peculiar in their distribution.  The lymphatics
vof the spleen are few and  inconsiderable  in all, being
less  numerous than in other glandular organs, such
as the liver and  kidneys.  The nerves of the spleen
are very large in some animals, but the great  size of
their  trunks and  branches is chiefly due to the large
proportion of  ordinary fibrous tissue which enters
them.  That the ductless glands have some office of
importance to perform in the preparation and main-
tenance of the blood, cannot any longer be reasona-
bly questioned, and the determination of this point
may be fairly regarded as  a considerable  step in  the
investigation.   It is obvious,  from the very  copious
supply of blood which they receive during the period
of their functional   vigor,  and from  the  manner in
which this is distributed by the aianiLulijJ, vegaicles, 
50             A NEW TREATISE ON
that it must be subservient to some process of active
change; and the aspect of the contents of these vessicles
as well as of the substance in which they are imbedded,
indicates that cell-growth is rapidly proceeding at the
expense of the materials thus afforded.   But, on the
other hand, that the products of this cell-growth are
not substances which,  like those  of the  ordinary
glands, must be separated from  the blood either for
its purification or to serve some special purpose in the
economy, appears from the fact that they are not car-
ried off by ducts, but  are received again into the cur-
rent of the circulation.  This would be equally true
in the end were these products discharged by the lym-
phatics, but such an idea is inconsistent with our pres-
ent knowledge of the distribution of these  vessels;
and it may be considered next to certain  that  the
matters,  whatever their nature  may be, which have
been elaborated  by these glandular organs, are re-
ceived again through  the venous system;  so that after
having passed through the lungs they will be carried
by the systemic arteries through the system at large;
but the spleenic vein, it will  be remembered, forms
one of the roots of the portal  trunk,  and its blood
must pass through the liver before it enters the vena-
cava.   Whatever materials then are withdrawn from
the blood by the organs, are returned  to  it again in
an altered state, and that the change which they have
undergone is one that  prepares  them for higher uses
in the economy, may fairly be inferred from the  cir-
cumstances.  For, as  the  blood which has received
them is immediately transmitted to  the system with-
out having passed through any other  depurating or-
gan than the lungs, it appears fair to conclude that 
            ASSIMILATION AND DIGESTION.         51
the products which  it has taken  up in these  organs
are either combustic or nutritive, i. c, either serve to
maintain the functional activity of the lungs, or of the
system, or of the blood  itself.   Now,  that they are
not destined to prepare  a pabulum for respiration,
appears from the very small quantity of fat which  is
found in their substance,  except when their period of
functual activity has gone by.   On  the  other hand,
the albuminous nature of the plasma, and the fine
granular appearance which it presentsy strongly indi-
cate that a material is here in progress of preparation
which is to be rendered subservient to the formative
operations.   The peculiar  position of the  spleen  in
reference to the portal circulation, however, seems  to
mark it out as having some special function of a sup-
plemental character.  Two out of the  many theories
of its action which have been advanced, deserve par-
ticular notice in connection with  this point.
   Many experimenters have come  to  the  conclusion
that, whatever may be the other purposes answered
by the spleen, it serves as a diverticulum to the por-
tal circulation, so as to relieve its vessels from undue
turgescence, in virtue  of the readiness with which it
is distended with blood;  and this, under a great va-
riety of circumstances.   As the  portal system is des-
titute of valves, the spleenic vein has free communi-
cation with the whole of it, so  that the spleen  will
serve as a receptacle for the venous blood when the
secreting action of the liver is feeble, so that the por-
tal circulation  receives  a partial check.  That any
cause of obstruction to the hepatic circulation pecu-
liarly effects the spleen, has been proved  by experi-
ments; for  after  the vena portal had  been tied, the 
52             A NEW TREATISE ON
spleen of an animal which previously weighed only
two ounces, has been found to weigh a pound and  a
quarter, or ten  times as much.  Further, it is evident
that turgescence of the portal system is liable to occur
when the alimentary canal is  distended with food.  It
appears that the spleen has its maximum volume at
the time when the process of chymifaction is  at an
end, namely: about five hours after food is taken, and
that  it is small and contains but little blood  seven
hours later,  when no food has been taken in the in-
terval.  The spleen rapidly  increases in bulk  after
the ingestion of a  large quantity of fluid, which is
absorbed rather by the vein than  by the  lacteals.  It
has been further stated in support of this theory, that
animals from which the spleen has been removed are
very liable to die of apoplexy if they take  a  large
quantity of food at a time, but that if they eat moder-
ately and frequently they do not suffer in this manner.
Yet some physiologists say that the coats of the stom-
ach secrete from seventy-five to eighty-five ounces in
twenty-four hours.  From what?  Simply nothing.
  The next great  link  in  the chain of the animal
economy is, what office  does the spleen perform in
the animal economy?  Do not knozv,  comes  the an-
swer of the savants.  Now this important point I will
endeavor to explain.  Anatomists say there is a large
artery passing into the spleen and divides into a net-
work of small  arteries, and, in fact, unites  so closely
that it appears  that there is  a continuous chain from
the  spleenic arteries directly into the spleenic veins
and the blood;  after it passes out by those veins the
properties of blood are changed in a remarkable de-
gree.  Now this point  has  troubled me ever  since 
           ASSIMILATION AND DIGESTION.         53
I read Bronsay's  Principles of Physiology, when I
was a boy, until after strict examination I found, after
repeated trials, that there is  a direct communication
from the spleen to  the  coats of  the stomach, and
solved the great problem, the use of the spleen, and
where that great amount of gastric juice comes from.
My theory is as follows: The  spleenic artery con-
veys the blood into  the  spleen, which  manufactures
the gastric juice direct from the blood, and conveys
it by a large number of small arteries into  the inner
coats of the  stomach;  and  those  small follicles,  or
cells, or sacks, that are heretofore  mentioned, are
merely deputaries  of the gastric juice.  So that when
food is  received into the stomach it is there ready to
answer the requirements of nature.  The spleenic ar-
tery being  so much larger  than  the arteries which
 pass into  any  of the other  secretory glands, shows
that Nature  has wisely provided the means for  an
 abundant supply of the gastric juice.
   There has been many authors in different ages of
 the world who have made diligent search and enquiry
 to ascertain the source of the gastric juice,  but failed
 to find it from the  fact that they did not try in  the
■right way; and, likewise, to find the use of the spleen,
 and failed in  that for the same  reasons.  They were
 like the ruler who went  to the prophet, who ordered
 him to bathe in the river Jordan; and he was not sat-
 isfied, but  expected some great thing.  And in  my
 investigations  I followed the example of  others.  I
 tried to inject the  blood vessels of the spleen with al-
 cohol, ether, etc.,  when the vessels were already cold
 and corrugated, which only corrugated them more;
 but I did not despair. I continued my investigations 
 54             A NEW TREATISE ON
on  hogs,  beeves and other different animals, and  I
found, after repeated experiments,  that  soon  after
death the blood  vessels  were less  corrugated; and
acting upon that hypothesis, I continued my investi-
gations still further.  I found I could inject the  fluids
much farther in the blood vessel when it was warm than
when it was cold; and  I found that warm water, at
the temperature  of 98 ° to 100 °,  was  more easily
injected than when it was colder; so after repeated
trials, I killed a hog for pork, and I had a tub of warm
water and an injecting apparatus in  readiness, and as
soon as my butcher took the entrails from the hog  I
had him deposit them in  the tub of  warm water, and
had him cut the stomach open on the  opposite side from
the spleen, and I applied my injecting apparatus with
warm water colored red.  When the inner surface
was laid open, I immediately saw  that it was covered
all over with an emenation of gastric juice, which col-
lected in large drops and soon formed small streams,
and as it continued to flow I  soon discovered it was
tinted with red, and  finally it was as red as it was in
the vessel from which it was taken, and equally as
void of taste,  which gave  me conclusive proof that
there is a direct  communication between the vessels
of the spleen and the coats of the stomach; and the
gradual change in the conditions of  it, from the time
it  began  to flow until it ceased to  flow from my in-
jecting apparatus, showed to me that the spleen was
the fountain source,  and  those follicles were  the  de-
positories, for upon examination of them after my ex-
periment I found them empty.
   Under the  microscope the spleenic venous blood
presented remarkable differences from the blood of 
           ASSIMILATION AND DIGESTION.        55
the general venous system, as represented by the
blood of the  jugular vein and from arterial blood.
The red corpuscles did not form rouleaux, but in great
numbers were aggregated in thick irregular heaps,
or in smaller numbers forming little round or angular
flakes.  After some  days this firm cohesion of the
corpuscles diminished.   The  size of the corpuscles
varied extremely, but the majority were very small;
smaller, indeed, than the corpuscles found elsewhere.
The white corpuscles were very numerous; in one
case they amounted in number to a quarter or a third
of the colored particles;  they collected  also in heaps,
and seemed to be united by a fine molecular matter.
In some places they were mixed up with the red par-
ticles.   In size they varied greatly, being sometimes as
large as a red particle; at other times double the size.
Besides these there  were  cells  constantly  present,
larger than the  colorless corpuscles, and lay among
them in heaps of two or three together; they were
undoubtedly cells, and the cell wall could  plainly be
seen.  They were always spherical, transparent, with
a defined border, and  contained from four to ten
small, dark • outlined, strongly refracting  granules,
grouped in various ways, either centrally heaped to-
gether or forming a crescent, or without particular
order, and frequently changing their mode of arrange-
ment.   It is apparent upon strict examination, that
upon reception  of food  into the  stomach the manu-
facture of the gastric fluid is the  more rapid, and the
displacement of the red  particles of blood  is separa-
ted as before stated, and the serous portion is manu-
factured out of the blood and passes into the stomach,
as  before stated.   When  there is a deficiency of the 
56              A NEW TREATISE ON
red particles of blood, or a deficiency of perchloride
of iron in the blood, or when the spleen is inflamed
and cannot separate the iron from the gastric secre-
tion, the liver  fulfills the  office  of the  spleen;  and
again, when  the liver  becomes  engorged and indu-
rated, and cannot perform  the two-fold  office of gall
and gastric juice, the  pancreas  eliminates from the
dissolving property which the blood contains that  is
essential to dissolve the food.  When  this is  the re-
sult a cerebral disturbance is manifested by a general
atony of the  system, a white fur upon the tongue, a
weak, quick  pulse, a  grass-green discharge as the
symptoms become more aggravated; a reaction takes
place, fever sets in and relieves the sufferer by a  col-
lapse  of the  capiliary system.  The remedies which
will correct  the  secretions of the liver, spleen, sali-
vary glands and pancreas, and create a general equi-
librium in these secretions, will be given in my next
issue.   When the liver becomes inflamed a long train
of symptoms is the result.  Emaciated  appearance
of the face, drowsiness, jaundiced appearance of the
skin, pain under the right  shoulder  blade, numbness
in left arm between shoulder and elbow, and  an in-
creased  appetite for animal food;  the next symptoms
will be  thirst, yellowness of the eyes,  a  troublesome
hacking cough, caused by increase in  the size of the
liver, pressing against the diaphragm and making the
space too small for the lungs to expand and contract
in inhalation  and exhalation.  These  symptoms are
followed by  loss of appetite, furred  tongue, chills,
fever, and finally constipation of the bowels, followed
by diarrhoea,  clay-colored stools, general debility and
death.  So long as the alimentary matter remains  in 
            ASSIMILATION AND DIGESTION.         57
 the digestive cavity, however perfect may be its state
 of preparation, it is far from being conducive to the
 nutrition of the system as if it were in contact with the
 external surface.  It is only when absorbed into the
 vessels and carried by the circulating current through
 the very substance of the body, that it becomes cap-
• able of being appropriated by its various tissues  and
 organs.
   Among the higher  invertebrata, we  find the recep-
 tion of alimentary matter into  the  circulating system
 to be entirely accomplished through the medium of
 the  blood vessels,  which  are  distributed upon the
 walls of the digestive cavity.   But in the vertebrata,
 we  find an  additional set of  vessels  interposed be-
 tween the walls of the intestines and the sanguiferous
 system, for the  purpose, as it would seem, of taking
 up certain components  of the  nutritive  matter of
 which part, at least, are not in a state of perfect so-
 lution, and of preparing  them  for being introduced
 into the current of the blood.  These are the absorb-
 ents of the intestinal  walls of  which  those that are
 found after the performance of the digestive process
 to contain the white opalescent fluid  known as chyle,
 are  distinguished as  lacteals, while  the  remainder,
 like the absorbents of the  system generally, are known
 as lymphatics.  The  distinction  is a purely  artificial
 one, for the lacteals are the lymphatics of those parts
 of the intestinal walls  which they supply, as is shown
 by the fact that during the intervals of the digestive
 process they contain a transparent fluid, in all respects
 similar to the lymphatics of the other parts.   The ab-
 sorbents form a minute  plexus beneath  the  mucous
lining of the alimentary canal along its whole extent, 
58             A NEW TREATISE ON
but in the small intestines they enter the villi, at the
extremities of  which, indeed,  they may be said to
commence.  Those only are entitled  to the designa-
tion  of lacteals which originate from  the  intestinal
canal below the point at whieh the biliary and pan-
creatic ducts pour their contents into it; for above that
point the fatty constituents of  the  alimentary matter
are not in a state of sufficiently fine division to  enter
them, and the absorbed fluid is consequently pellucid
instead of possessing the milky aspect.   Thus, then,
we are to consider the lacteal  portion of the absorb-
ent system to  be  that  part of it which is especially
adapted  by its prolongation  into the villi for the re-
ception of an  oleaginous fluid, which we shall pres-
ently see to be taken up from the contents of the ali-
mentary canal, and to be prepared for entrance into
the absorbents by a  set of peculiar cells developed at
the radical extremities of those organs.   (For a gen-
eral structure of the villi of  the  intestinal mucous
membrane, see Carpenter's Human  Ph) siology, sec-
tions 228-234.) But the peculiar disposition of their
component structures must  here  be more minutely
noticed.   Each villus appears  ordinarily to  contain
but a  single  lacteal  tube, which occupies its center;
in the larger villi, however, two or even more trunks
are sometimes discernible.  The mode in which this
tube commences, near the extremity  of the villus, has
not yet been precisely made  out; but it seems prob-
able that it originates in a plexus formed by the anas-
tomosis  of branches into which  it subdivides.   This
much, however, is quite certain, that the lacteals do
not commence by orifices  on the internal surface of
the intestinal tube, as they were formerly supposed to 
           ASSIMILATION AND DIGESTION.         59
do.  Each villus is also furnished with a minute plex-
us of capillary vessels, which lies near the surface.
These sometimes pass between  a  single arterial and
venous twig, as in  the villus of the  hare, but are some-
times supplied by several distinct twigs, as in the villi
of man.   The different arrangement of the vessels,
the plexus differing in different animals.
  In regard to the degree in which  the function of
nutritive absorption is performed by the lacteals and
by the sanguiferous system respectively, considerable
difference of  opinion has prevailed.  When the ab-
sorbent vessels were first discovered, and their func-
tional importance was perceived, it was imagined that
the introduction of alimentary fluid into the vascular
system took place b}r them alone. A  slight  knowl-
edge of comparative  anatomy, however, might have
sufficed to correct this error, since no lacteals exist in
the invertebrated animals;  the function of absorption
being  performed  by their meseuteric  blood  vessels
only; whence it is evident  that  these do possess the
power of absorption; and  it  is scarcely  to be  sup-
posed that they should not  exercise this power in ver-
tebrated animals also, since  their disposition  on the
walls of the intestinal cavity is obviously favorable to
it.  On the other hand, the introduction of a new and
distinct system of  vessels would seem to indicate that
they must have some special purpose; and there can
be no doubt that  the  absorption of a particular kind
of nutritive matter is that for which they are designed.
That absorption is effected to a considerable amount
by the agency of blood vessels,  is  shown by the read-
iness with which aqueous fluids, and even alcohol are
taken up from the parietes of the stomach and are car- 
6o
A NEW TREATISE ON
ried into the general circulation.   Thus, in a case of
extroversion of the bladder, we may consider the san-
guiferous vessels then as affording the usual channel
by which  a large part of the  nutritive  materials are
introduced into the system;  but these are not allowed
to pass into the general current of the circulation until
they have been subjected to an important assimilating
process, which it appear to  be one great office of the
liver to perform, whereby they are rendered more fit
for the  purposes they are  destined  to  serve  in the
economy.   But the absorbing power which the blood
vessels of the alimentary canal posseses are not limited
to alimentary substances, for  it is through them, al-
most exclusively, that soluble  matters of every other
description are received into the circulation.  Absorp-
tion by the blood vessels is  a  simply physical  opera-
tion, depending upon  the  relative  consistency and
miscibility of the blood and of the liquids to be ab-
sorbed,  and upon  the  rapid movement of the blood
through the vessels.  Where  the contents of the ali-
mentary .canal are of  less  specific gravity than the
blood, and are capable of mingling with it, an  endos-
motic current will  be established  through the delicate
parietes of the blood vessels, and  then their  invest-
ment between the two liquids, the former passing to-
wards the other, and  in this mode albuminous, gela-
tinous saccharine, saline  and other soluble substances
may be caused to enter the  blood, if their  solution be
not too concentrated.  But if their density be equal to
that  of the blood,  or nearly so, little or no absorption
is likely to take place,  and  one purpose, which  is
answered by the very copious discharge of aqueous
fluid  into the  alimentary canal during  the operation 
             ASSIMILATION AND DIGESTION.         6l
  of digestion, is obviously the reduction of the density
  of the Solution to a  favorable point.   If,  again, the
  density of the contents of the alimentary canal should
  exceed that of the blood, an endosmotic current might,
  perhaps, be established in the opposite direction, but
  their dilution would probably be  effected so speedily
  that little of the contents of the  blood vessels would
  be thus drawn forth,  more especially as animal mem-
  branes  appear to have a special power of resisting
  the passage of albumen, whilst they give  free trans-
  mission to albuminose.   That the movement of the
  blood in the  vessels  will vastly increase the rate of
  endosmotic  absorption, is easily proved experiment-
  ally, and this it is which constitutes the main differ-
  ence between the living and the dead subject.
     The  mucous  membrane of the alimentary canal is
'  by no means  the only  channel through which nutri-
  tive or  other substances  may be introduced into the
  circulating  apparatus  from external  sources.  The
  lymphatic system is present in all animals which have
  a lacteal system, and the  two, as already pointed out,
  evidently constitute  one set of vessels.  The lym-
  phatics, however, instead of commencing on the in-
  testinal walls, are distributed through most of the vas-
  cular tissues of the body, and especially in the skin,
  but their number bears no proportion whatever to the
  vascularity of the several tissues, or to the  amount
  of interstitial  change which they undergo;  and it is
  remarkable that the  nervous centers should  be  en-
  tirely destitute of them, and that they belong rather
  to the connective areolar tissue than to the muscular
  substance  itself.  Their  origin  can not  be clearly
  traced, but  they seem in  general to form a plexus in 
62
A NEW TREATISE ON
the substance of the tissues, from which  the  conver-
gent  trunks arise, after passing, like  the lacteals,
through a series of glandular bodies.  We find in the
skin,  also, a  most copious distribution  of capillary
blood  vessels,  the  arrangement of which is  by no
n.eans unlike that of the blood vessels of the  alimen-
tary canal, and its surface is further extended  by the
elevations that form the sensory papillae, which are in
man)-  points  comparable  to the  intestinal villi, al-
though their special function is so different.   In  the
lowest tribes of animals, and in the earliest conditious
of the higher, it would seem as if absorption  by the
external surface is almost  equally important  to  the
maintenance of life with   that  which  takes place
through the internal reflexion of it forming the walls
of the digestive cavity.   In the adult condition of most
of the higher animals, however, the special function
of the latter is  so much  exalted as usually to  super-
sede the necessity of any other  supply, and the func-
tion of the cutaneous and pulmonary surfaces may be
considered as rather that of exhalation than absorp-
tion.  But there  are peculiar conditions  of the  sys-
tem  in  which  the  imbibition of fluid through these
surfaces is performed with  great activity,  supplying
what would otherwise be a most important deficiency.
It may take place either  through the  direct appli-
cation of fluid to the surface,  or even through  the
medium of the atmosphere, in which a greater or less
proportion of watery vapor is usually dissolved.  This
absorption occurs most vigorously when  the  system
has been drained of its  fluid, either by an  excess of
the secretions or by a diminution of the regular sup-
ply.   There  appears no doubt that if the  limb of a 
             ASSIMILATION AND DIGESTION.         6%
 person be placed in a liquid  for a certain time, it will
 be full of the  fluid through  the means of imbibition
 or by absorption,  and that  there  is a  close  corres-
 pondence in composition between the chyle of the lac-
 teals and the lymph of the lymphatics;  the chief dif-
 ference being  the presence of a considerable quantity
 of fatty  matter in the former  and of a  larger pro-
 portion of the assimilable substances which are equal-
v ly characteristic of both.   This evident  conformity in
 the nature of  the  fluid which these two sets  of ves-
 sels transmit, joined to the fact  that the fluid  lymph,
 like the  chyle, is conveyed  into the general current
 of the circulation just  before the blood is again trans-
 mitted to the system at large, almost inevitably  leads
 to the inference that the lymph is like chyle, a nutri-
 tious  fluid, and is  not of an excrementitious charac-
 ter, as maintained by some physiologists.  The  close
 resemblance between  the contents of the  lymphatics
 and diluted liquor sanguinis, seems to indicate that
 the former are partly  derived from the fluid  portion
 of the blood which has transuded through the  walls
 of the capillary vessels.  And we shall  presently see
 reason to believe that this transudation is partly  for
 the purpose of subjecting the crude materials which
 may have been taken  up  direct  into the  blood vessels,
 to an  elaborating  or  preparatory agency, such  as it
 seems to be the special object of the lacteal system to
 exert upon the nutritive substances which it serves to.
 introduce into the circulation.   But it seems  not im-
 possible  that there may be another source for the con-
 tents  of  the lymphatics.  We have already had to al-
 lude on  several occasions, to the disintegration which
 is constantly  taking  place  within  the  living body, 
64              A NEW TREATISE ON
whether as a result of the limited duration of the life
of its component  parts, or  as a  consequence of the
decomposing  action of oxygen.  It may be stated
then, as a general proposition, that the function of the
absorbent system is to take  up and to convey into the
circulating apparatus such substances as  are capable
of  appropriation  to the nutritive process,  whether
these substances be direcily furnished by  the external
world, or be  derived  from the disintegration of the
organism itself.  We have  seen in lacteals the select-
ing power is such that these vessels are not  disposed
to convev into the system any substances but such as
are  destined for this  purpose,  and  that extraneous
matters are absorbed in preference by the mesenteric
blood vessels.   The case is different with regard  to
lymphatics, for there is reason to believe that they are
more disposed than the  veins to the absorption  of
other soluble   matters, especially  when these are
brought  into  relation  with  the skin, through which
the lymphatic vessels  are very profusely distributed.
The alimentary substances taken up by the blood
vessels and absorbents seem very far from being cap-
able of immediate application to the nutrition of the
body, for we find that  they  are not conveyed by any
means directly into the circulating current, but those
that enter the  gastro-intestinal veins are submitted  to
the operation  of the liver,  whilst those  that are re-
ceived into  the lacteals are subjected  to a kind  of
glandular action wthiin their own  system; the newly
absorbed materials in both cases  undergoing consid-
erable changes, which tend  to assimilate them to the
components of the blood.   It will be recollected  that
all  the  veins  which return the  blood  from the ca- 
           ASSIMILATION AND DIGESTION.         65
pillaries of the gastro-intestinal canal, converge into
the portal trunk, which distributes this blood charged
with the newly absorbed materials, through  the ca-
pillary system of the liver.   The agency of this gland
was formerly supposed to be limited to the elimina-
tion from  the  blood subjected to  its influence of the
materials of the biliary secretion, but there is now ev-
idence that the blood itself is changed by its means
in a manner which indicates  an assimilating  as  well
as depurating  action.  The  blood  which  comes to
the liver from the alimentary canal is charged  with
albuminous matter in a state different  from  that of
the albumen of perfect blood, and the assimilation of
this would appear from the observations of the most
important  functions  of  the  liver.  The  saccharine
matters are brought to the liver  in the condition of
grape sugar, or of cane sugar; are converted by its
agency into liver sugar, a form of the saccharine prin-
ciple of whose presence the blood is much  more  tol-
erant than it is of any other.   From  the saccharine
componuds being brought to the liver, it appears that
fatty matter can  be generated; but as  the introduc-
tion of this substance into the blood vessels ordinarily
takes place through a different  channel, the action of
the liver would not appear to be essential to its assim-
ilation, and it has been found that oil can be  injected
into the general circulation  without  exciting any vio-
lent effort at  its  elimination.  The whole  absorbent
system may be looked upon as  constituting one great
alimentary gland.  The circulation  of nutritive  fluid
through the body has for its object, on the one part,
to  convey to  every portion of the organism the ma-
terials for its  growth and  renovation, together  with
    s 
66             A NEW TREATISE ON
 the  supply of oxygen which  is requisite for its vital
 actions, especially those of the nervo-muscular appa-
 ratus, and at the same time to carry off the parti-
 cles which are set free by the disintegration or waste
 of the tissues, and which are  to be removed from the
 body by the excreting processes.  Of these processes,
 the one most constantly in operation, as well as most
 necessary  for the maintenance of the  purity  of  the
 blood, is the extrication of carbonic acid through the
 respiratory organs,  and this  is made subservient to
 the introduction of oxygen into the system.  In man,
 as  in other vertebrated  animals,  there  is  a  reg-
 ular and continuous movement of the  nutritive fluid
 through the sanguiferous vessels, and upon the main-
 tenance of this the activity of all parts  of  the  organ-
 ism is dependent.  In common with birds  and mam-
 mals, again, man has a respiratory circulation entirely
 distinct from the systemic; all the blood  which has
 returned from the  body being  transmitted  to the
 lungs, and brought  back to the heart again before it
 is again sent forth for nourishment of the tissues and
 for the maintenance  of their functional activity.  The
 heart is placed at the junction of these two distinct
 circulations, which may be likened  to the figure 8,
 and it may be said to be formed by the  fusion of two
 distinct  organs—a pulmonary and a  systemic heart;
 for its right and left sides, which are  respectively ap-
 propriated to these purposes, have no direct commu-
 nication with each other, and seem  merely brought
 together for economy of material.   Each system has
 its own set of arteries or efferent vessels, and of veins
or efferent  trunks.  These communicate at their cen-
tral ex remity by the heart, and at their  peripheral 
            ASSIMILATION AND DIGESTION.         67
extremity by the capillary vessels, which are nothing
else than  the  minutest  ramifications of the two sys-
tems inosculating into a plexus, besides the systemic,
although  it has not an impelling organ of its own.
This is the portal  circulation, which  is interspersed
between the venous trunks of the abdominal viscera
and vena cava, for the purpose of distributing that
blood through the  liver, in  which organ  its newly
absorbed  materials  undergo assimilation, whilst  its
excrementitious matters are separated  by the secret-
ing process of the vena potarae, which is formed  by
the convergence of the gastric, intestinal, spleenic and
pancreatic veins, subdivides  again like an  artery, so
as to form a capillary plexus, which extends through
the whole substance of the liver and the hepatic vein,
collecting the blood.  This plexus conveys it into the
vena cava.  Thus  the  portal  circulation  is grafted
upon the  general circulation in precisely the same
mode as the respiratory circulation is grafted upon it
in mollusca and Crustacea;  and if the senus of vena
portae  had possessed contractile muscular walls,  it
would  have ranked as the proper heart of  the portal
system.  The really  arterial  character of  the vena
portae is well shown by comparing it with  the  aorta
of fishes, which is formed by the convergence of the
bronchial  veins, and then distributes the blood which
it  has  received from them  to the blood  generally.
That the movement of the blood through the arterial
trunks and the capillary tubes is, in man and in other
warm-blooded  animals, chiefly dependent  upon the
action of the heart, there can be no doubt  whatever.
It can be easily  shown by experiment, that if the ar-
terial current be checked, the capillaries will immedi- 
68
A NEW TREATISE ON
ately cease, almost entirely, to deliver the  blood into
the veins, and the venous  circulation will  be instan-
taneously arrested.  And it has also been proved that
the usual force of the heart is sufficient to propel the
blood not only through the arterial tubes, but through
the capillaries into the veins; even a less force will
serve to propel  warm water through the  vessels of
an animal  recently dead.  But  there are  certain re-
sidual phenomena, even in man, which clearly indi-
cate that it is not the  whole truth, and that forces exist-
ing in the blood vessels themselves have a consider-
able influence in producing both local and general mod-
ifications of the  effects of the heart's action.   There
are also indications  of the  existence of an influence
in which the  blood vessels do not  partake, arising
from those changes occurring between the blood and
the tissues, that  constitute the  process of nutrition,
secretion, etc.  Such, for instance, would appear to
be the interpretation of the fact  that whilst any varia-
tions in  the action of the heart  effect the whole sys-
tem alike, there  are  many variations in the circulation
which, being very limited  in their extent, cannot be
attributed to such central disturbances, and must be
dependent on causes purely local.   Of the nature of
these influences, and of the mode of their operation,
the most correct idea may  be obtained by  examining
the phenomena of the circulation  in  those  beings in
which the moving power is less concentrated  than it
is in higher animals; for we find that in plants, and
the lowest animals, as in  the earliest embryonic state
of the higher, a  movement of nutritious fluid  takes
place through a  system of  minute passages or chan-
nels excavated in the tissue, without any vis a tergo 
           ASSIMILATION AND DIGESTION.        69
derived from an impelling organ.   Ascending a  little
higher in the series, we meet with a system of vas-
cular trunks distributing the blood to these plexuses
and  collecting again  from them, and the  walls of
these trunks are so far endowed with contractility as
to assist, by a  sort of peristaltic movement, in the
maintenance of the current through them.  Still pass-
ing upwards, we find  this contracility manifesting it-
self especially in some limited portion or portions of
the  vascular  system  which  execute regular move-
ments of contraction and dilation, and this  tendency
to concentration is observed to increase until the whole
movement is subordinated to the action of the  prin-
cipal propelling organ, the heart.
   We shall now examine what agency in the human
circulation may be attributed to the heart, the arteries
and the veins respectively, and what other forces may
be fairly presumed to operate in the capillary circu-
lation.   We do not purpose  on entering in an ana-
tomical description of the heart,  or  the  action of the
heart in health, further than a brief expression show-
ing  the connection with the digestive apparatus.
   When the heart is exposed in  a living animal and
its movements are attentively watched, they are seen
to follow each other  with  great regularity.   In an
active, vigorous state  of circulation, they  are so linked
together that  it is not easy to distinguish  them into
periods, both auricles contracting and  dilating simul-
taneously, and both ventricles doing the  same.   Sys-
tole or contraction of the ventricles corresponds with
the  projection of the blood into the arteries, while the
diastole or dilatation of the ventricles  coincides with
the  collapse of the arteries.   The contraction of the 
70             A NEW TREATISE ON
ventricles and that of the auricles alternate with one
another, each taking place during the dilatation of the
other; but there is a period during which the auricles
and  ventricles of both  sides are dilating together.
This  occurs  during the first part of the  ventricular
diastole, for at the conclusion of the systole the auri-
cles are far from being  completely filled, and they go
on receiving an additional supply from the veins until
after the middle of the ventricular diastole, by which
time  they become fully distended  and immediately
contract.  The contraction of the auricles is synchro-
nous, therefore,  with  only the second stage of the
ventricular disastole, and their dilatation is going on
during the stage  of the ventricular diastole and their
dilatation  is going on during the whole period of the
ventricular systole.   Thus, whilst the entire period
that intervenes between one pulsation and another is
nearly equally divided between the systole and dias-
tole of the ventricles, the division is very unequal  as
regards the  auricle, scarcely more than one eighth
of the whole being occupied in their contraction and
the remainder being taken up by their dilatation. The
large veins  near  the heart  contract simultaneously
with the auricle and not whilst  it is dilating, so that
they can  have no influence  in causing  its distension.
The blood is expelled by the ventricular systole into
the pulmonary artery, which it distends, passing freely
through its semi-lunar valves, but as soon as this vis a
tergo ceases and  reflux might take place by the con-
traction of the arterial walls, the valves are filled out
by the  backward tendency  of the blood and com-
pletely check the return of any portion of it into the
ventricle.   The blood, after having circulated through 
               ASSIMILATION AND DIGESTION.         71
   the lungs, returns as arterial blood by the pulmonary
   veins to the left auricle, whence it passes through the
   mitral valve into the left ventricle and thence into the
   aorta through its semi-lunar valves, in the same man-
,   ner with that on the other side, just described.   The
   blood propelled from the heart is distributed  to the
   body in  general by a system of arteries which  may
   be likened  in  its  arrangement  to  the  trunk  and
   branches of a tree,  except  that  very frequent com-
   munications or anastimosis exist among these branch-
   es, so that by continued subdivision and inasculation
   their distribution comes more to resemble the capillary
   network in which they terminate.  Although  the di-
   ameters of the branches at each subdivision together
   exceed that of the trunk, yet there is but little differ-
   ence in  their respectiveness.  What difference does
   exist is  usually in favor of  the branches, and thus it
   happens that there  is a gradual  increase in the ca-
   pacity of the arterial system  from its center towards
   the capillaries, whose capacity is many times greater.
   There have been  many theories written by physiolo-
   gists of the passage of the  blood through  the  capil-
   laries, but one thing is certain: the blood  does  pass
   through, and with considerable regularity, and all the
   facts which bear upon the question of the  connection
   between nervous  agency and the  forces maintaining
   the capillary circulation, have an equal relation to the
   functions of nutrition and secretion in general.   The
   nervous system also influences these  by the control it
   exerts over the diameter of the blood vessels.   The
   venous  system takes its origin in the small trunks
   that are formed by the reunion of the capillaries, and
   returns  the  blood  from these to the heart.   The 
72             A NEW TREATISE ON
structure  of  the veins is essentially  the  same  with
that of the arteries,  but  the fibrous  tissue of which
their middle coat is made up bears more resemblance
to the areolar tissue of the skin than it does to the
true elastic tissue, and the muscular fibre-cells are
usually much fewer  in  number  and are  sometimes
wanting  altogether.   The elasticity  of the veins  is
shown by the jet  of blood which at  first  spouts out
in ordinary venesection,  when  by means of the liga-
ture a distension has been occasioned in the tubes be-
low it.  The movement  of blood through the  veins
is effected by propulsive force.  In  several portions
of the human body there are certain varieties in the
distribution and in the functional  actions of the blood
vessels which should not be omitted  in a  general ac-
count of the circulation.   Of  these  we have in the
first place to notice the apparatus for the  pulmonary
circulation,  the chief peculiarity of which  is that
veinous blood  is  sent from the heart through a tube
which is arterial in structure, while  arterial blood  is
returned  to the heart through a vessel whose entire
character is  that  of a vein. The movement of the
blood through these is  considerably affected by the
physical state of the lungs themselves, being retarded
by any causes  which can  occasion  pressure on the
vessels, and proceeding with the  greatest energy and
regularity when the respiratory movements are freely
performed.  The  portal  circulation, again, is peculiar
in being  a kind of offset from the general systemic
circulation, and also in being destitute of  valves; and
it may be surmised, with much  probability, that the
purpose  of their absence is to allow an  unusually free
passage  of blood from one part of that system to an- 
             ASSIMILATION AND DIGESTION.         73
  other during the very varying conditions to which it
  is  subjected.  Another very important modification
  of  the circulating system is that which presents itself
  in  the cranium.  From the circumstances of the cra-
  nium being a closed cavity, which must be always
  filled with the same total amount of contents, the flow
  of blood through its vessels is attended with some pe-
  culiarities.   The presence  of the atmosphere is here
  exerted rather to keep the blood in the head  than to
  force it out,and it may accordingly be inferred that while
  the quantity of cerebral matter remains the same, the
  amount of blood in the cranial vessels must  also be
  invariable.  This inference appears to derive support
  from the  experiments  of Dr. Kellie.  On bleeding
  animals to death, he found that whilst the remainder
  of the body was  completely exsanguine,  the  usual
'  quantity of blood remained in the arteries  and veins
  of the cranium; but that if an opening was made in
  the  skull  these vessels   were then   as completely
  emptied as the rest.   It is  not to be inferred that  the
  quantity of blood within the cranium  is not subject
  to variation,  and that in  the states of inflammation,
  congestion, or other morbid  affections, there is only a
  disturbance of the usual balance of arterial and vein-
  ous  circulation.
     The  nutritive fluid in its circulation through  the
  capillaries of the system undergoes great alterations
  both in its physical constitution and in its vital  prop-
  erties.  It gives up  to the tissues, with which it is
  brought into contact, some of its most important ele-
  ments  and at the same time it is made the vehicle of
  the  removal  from these tissues of ingredients which
  are  no longer  in the state of  combination that fits 
74              A NEW TREATISE ON
them for  their offices in the  animal economy.  To
separate these ingredients from the general current of
the circulation, and to carry them out of the system, is
the great object of the excretory organs, and it is
very evident that the  importance of their respective
functions  will vary with the  amount of the  ingredi-
ents which they have to separate, and with the dele-
terious influence which its retention would  exert on
the welfare of the system at large.   Of all  these in-
jurious  ingredients carbonic  acid is, without  doubt,
the one most abundantly introduced  into the  nutritive
fluid, and it is also most deleterious  in  its effects on
the system if allowed to  accumulate.   We  find, ac-
cordingly, that the provision  for the removal  of this
substance from the blood is one of peculiar extent and
importance, especially in the higher forms of animals;
and further, that instead of being effected by an ope-
ration peculiarly vital in its  performance, is secured
by being  made to depend upon simple  physical con-
ditions, and  thus comparatively little susceptible of
derangement from disorder of other processes.  All
that is requisite for it is the exposure of the blood to
the influence of the atmospheric air through the me-
dium of a membrane  that shall permit  the  diffusion
of gases; an interchange then taking place  between
the gaseous matters on the two sides, carbonic acid
being exhaled from the blood  and replaced by oxygen
from the  air.   Thus  the extrication of carbonic acid
is effected in a manner that renders it subservient to
the introduction of that element which  is required for
all the most active manifestations of vital power, and
 it is to these  conjointly, not in either alone, that the
function of respiration essentially consists. 
              ASSIMILATION AND DIGESTION.         75
    We shall now inquire into the sources from which
  carbonic  acid  is produced in the living body, and
  causes of the demand for oxygen.  The vital activity
  of the organism at large involve a continual change
j  in its constituent parts, and those which live the fast-
  est  usually die  the soonest and pass most readily into
  decay.  Hence, in the  very performance of the or-
  ganic functions which concur to effect the nutrition
  of the body, there is a constant source of disintegra-
  tion,  and one  of the  chief products of the  decay of
  the tissue, which is consequent upon their loss of vi-
  tality, is carbonic acid.  Thus the most  general ob-
  ject of the respiratory process, which is common to
  all forms of organized being, is the extraction of this
  principle of product from the  system, and the demand
  for aeration hence arising will vary with the activity
'  of the nutritive operations.   Now the rate of life, and
  consequently the amount of disintegration, in any or-
  ganized structure, depends in a great measure upon
  the temperature at which it is maintained, and thus it
  happens that the production of carbonic  acid  from
  this source at  the ordinary  rate of vital activity  is
  much more rapid in warm blooded than in cold blooded
  animals, and that the former suffer far more speedily
  than  the  latter from the privation of air.   But when
  the temperature of the reptile  is raised by external
  heat to the level of that of the mammal, its need for
  respiration increases, owing to the augmented waste
  of its tissues.   When, on the other hand,  the warm
  blooded animal is reduced in the state of hibernation to
  the level of the cold blooded reptile, the waste of its
  tissues diminishes to such an  extent as to require but
  a small exertion of the respiratory process to get rid 
76             A NEW TREATISE ON
of the carbonic acid, which is one  its chief products.
And in those animals which are capable of retaining
their vitality when they are frozen, or when their tis-
sues are completely dried up, vital  activity and disin-
tegration  are  alike  entirely suspended,  and  conse-
quently there is no carbonic acid to set free.  But an-
other source of carbonic acid  to  be set  free by the
respiratory process, and  one  which is peculiar to ani-
mals, consists in the rapid changes  which take place
in muscular and  nervous tissues  in  the very  act of
performing their peculiar functions; the development
of the muscular and of the nervous forces involving,
as the very condition  of their production, a change in
the substance of these tissues  respectively, in  which
change a large quantity  of oxygen is consumed and
a large amount of carbonic acid is generated.  Hence
in man, as in all animals in which the nervo-muscular
apparatus constitutes  the essential part of the organ-
ism, a powerful demand  for respiration is created by
its  activity,  the amount  of oxygen taken  in and of
carbonic acid  exhaled being determined by the de-
gree  in which this  apparatus is exercised.  Besides
these sources of carbonic acid,  which are common to
all animals, there is another which is restricted to the
two highest classes, birds and mammals; these being
distinguished by their power of maintaining a con-
stantly elevated temperature.  A  part  of this heat is
generated by the oxygenation of the components of
their  disintegrating  tissues,  the  metamorphosis of
which takes place  at a very rapid rate;  but  where
this is not sufficient, their power of maintaining their
temperature depends  upon the  direct combination of
certain elements of the food with  the  oxgen  of the 
             ASSIMILATION AND DIGESTION.         77
  air by the combustive process.   The quantity of car-
  bonic acid that is generated directly from the elements
  of the food, seems  to  vary considerably in  different
  animals and in different states of the same individual.
  In  the carniverous tribes, which spend the greater
  part of their time in a state of activity, it is probable
  that the quantity which is generated by  the waste or
  metamorphosis of the tissues, is sufficient for the main-
  tenance of the required temperature, and that little or
  none of the carbonic acid set  free in respiration,  is
  derived from  the  direct  combustion of the  mate-
  rials  of the food.  But  in  herbiverous animals of
  comparatively inert habits, the amount of metamor-
  phosis of the tissues is far from being sufficient, and
  a large part of the  food, consisting as it does of sub-
  stances that cannot  be  applied to the nutrition of the
I  tissues, is  made to enter into  direct combination with
  the oxygen of the air and  to compensate for the de-
  ficiency.   In man and  other  animals, which can sus-
  tain considerable variations of climate, and can adapt
  themselves to a great diversity of habits, the quantity
  of  carbonic acid formed by the  direct combustion of
  the elements of the food  with the oxygen of the air,
  will differ  extremely under  different circumstances.
  It  will serve  as the  complement  of that which  is
  formed in  other ways, so that it will diminish with the
  increase and will increase with the diminution of mus-
  cular activity.   It will  also vary in an inverse ratio to
  the external temperature, increasing with its diminu-
  tion and diminishing with  its increase;  the effect of
  external heat  being thus  precisely opposite in the
  warm blooded animals to that which it exerts on the
  cold  blooded.   In  all  cases,  if a sufficient  supply of 
 78             A NEW TREATISE ON
 food be not furnished, the store of fat is drawn upon,
 and if this is exhausted the animal dies of cold.  To
 recapitulate, then, the sources of carbonic acid in the
 animal body are three-fold:  ist.  The  continual de-
 cay of the tissues, common to  all organized bodies,
 which is favored by all that promotes their vital ac-
 tivity and retarded by every influence that depresses
 it; 2d, the metamorphosis peculiar to the nervous and
 muscular tissues, which is  the very condition of the
 production of their power, and which, therefore, bears
 a direct relation to the degree in which  they are ex-
 erted; 3d, the direct  conversion  of  the carbon and
 hydrogen of the food into  carbonic  acid and water,
 which is peculiar to warm blooded animals, and which
 varies in quantity in accordance with the amount of
 heat to be generated.                J
   The wonderful nature of the structural  arrange-
 ments which are made for  the  aeration of the  blood
n m an, and the completeness of the provisions where-
 by these are put into active operation, will be best un-
 derstood if,  for the sake of contrast, we first bestow a
 brief survey on the pulmonary apparatus.   The fol-
 lowing are the  points of  most  importance in the
 structure of the human lung:  The walls of the  bron-
 chial tubes contain distinct  longitudinal and circular
 layers of fibrous  structure, but  the latter alone con-
 tain muscular fibre  cells.  These tubes divide and
 subdivide like the  branches of a tree, still retaining
 their ordinary character, until  they come to an ab-
 rupt termination.  Beyond this boundary the tubular
 form of the air passages continued from  the bronchi
 is  retained  for some distance,  but  it  is gradually
 changed by the  irregular branches of the passages 
            ASSIMILATION AND DIGESTION.         79
and  by the  increase of the number of apertures in
their walls, which lead to the  air-vesicles.  Thus, at
last,  each minute division of the air passages become
quite  irregular  in  form, air-vesicles  opening  into
every part of them, and almost constituting their walls,
until they terminate almost without  dilatation in an
air-vesicle.  This terminal portion of the air passage
with its  surrounding clusters  of air-vesicles may be
regarded as forming a sort of lobule.  These  vesi-
cles  which communicate  directly with  the  bronchial
tubes  and intercellular passages  open into them by
large  circular apertures, and  they  are themselves
similarly opened  into by other vesicles, which  again
communicate with others beyond them, so that each
of the  openings in the air passages leads to a series
of air-vesicles  extending  from them to the surface of
the  lobule.   The vesicles which communicate  most
directly with the  air  passages are  more minute and
have a closer  network than those which lie nearer
the surface  of the lobule, an  arrangement which is
in beautiful harmony with the  relative facility of ren-
ovation of the air which they respectively contain.
It has  been computed by some physiologists that there
is not less than one half pound of air to each square
inch of surface when the lungs have been filled by
the deepest  possible inspiration, so that the whole
amount,  reckoning  on an  average  surface of  300
square inches for the male and 247 square inches for
the female, will be not less than 150 pounds for the
male and 123^ pounds for the female.  This force is
exerted in aid of the expiratory movement, and is di-
rectly  antagonistic to the  inspiratory, so that  the in-
spiratory muscles must overcome it in  order to  pro- 
8o
A NEW TREATISE ON
duce  complete  distension of the pulmonary cavities.
This distension is entirely accomplished by the action
of the muscles external to the thorax or partly forming
its parietes.  The lung  completely fills the cavity of
the pleura in the healthful state, at lesst so that when
this is enlarged a  vacuum would  be produced if it
were  not occupied by a corresponding enlargement
of the lung; and to effect this the  air rushes  down
the trachea and thence  passes into the  entire sub-
stance of the lung, which it fills out in every dimen-
sion.  This distension is much  more complete  than
any that  could  be  occasioned by simple  insufflation
from  the trachea, for long before  internal pressure
could overcome the resistance set up by the elasticity
of the lungs, and still more  by that  of the parietes of
the chest to the full dilatation of the  air  vessels, the
tissues of the lung  itself would  be almost certain to
give way. This has actually happened in numerous
instances, and it constitutes a very forcible  objection
to the use of any apparatus for artificial   respiration,
whose action  is that of insufflation.  The complete
dependence of the inspiration of the lungs upon the
enlargement of the cavity of the chest, is well known
by the effect of admission of air into the  pleural cav-
ity.  When an aperture is  made on either side, the
air rushes in at each inspiration of the  lung so that a
sufficient amount of change takes place for the main-
tenance of life.   It cannot be  too strongly impressed
upon the medical practitioner, and through him upon
the public in general, that the continued  respiration
of an atmosphere charged  in a far inferior degree
with the exhalation from the lungs and skin, is among
the most of all  predisposing  causes of disease, and 
              ASSIMILATION AND DIGESTION.         81
  especially of those zymotic diseases whose  propaga-
  tion seems to  depend upon the  presence of ferment-
  able matter in the blood.   That such is really the fact
  will appear from evidence  to be presently referred to,
  and it is not difficult to find a complete and satisfac-
  tory explanation of it; for  as  the  presence  of even a
  small  percentage of carbonic acid in the respired  air
  is sufficient to cause  a  serious  diminution in the
  amount of carbonic acid thrown off and oxygen ab-
  sorbed,  it  follows that those  oxidizing   processes
  which minister to the elimination of effete matter from
  the system  must be imperfectly performed, and that
  an accumulation of substances tending  to putresence
  must take place in the blood.  Hence there will prob-
|  ably be a considerable  increase in the amount of such
L  matters  in  the  pulmonary and cutaneous exhalation,
I  and the unrenewed air will become charged not only
  with carbonic acid, but also with organic matter in a
  state  of decomposition, and will thus favor  the accu-
  mulation of both  these morbific  substances  in  the
  blood instead  of effecting that constant and  complete
  removal of them which it is one of the  chief ends of
  the respiratory process to  accomplish.   It has been
  customary to consider  the  consequences of imperfect
  respiration as  exerted merely in promoting  an  accu-
  mulation of carbonic acid  in the system, and in thus
  depressing the vital powers and rendering it prone to
  the attacks  of disease.  But the deficiency of oxy-
  genation and  the consequent  increase of putrescent
  matter in the body, must  be  admitted as at least a
  concurrent agency, and when it is borne in mind that
  the atmosphere in which  a number of persons has
  been confined for some time becomes actually  offensive
      6 
82             A NEW TREATISE ON
to the smell in  consequence of the  accumulation of
such exhalations, and that this accumulation exerts
precisely the same influence  upon the spread of zy-
motic disease that is afforded by the diffusion of sewer-
atmosphere  through respired air, it  scarcely admits
of reasonable doubt that the pernicious effect of over-
crowding is  exerted yet more  through its tendency
to promote  putrescence in the  system  than through
the obstruction it  creates in the due  elimination of
carbonic acid from the blood.   For it is to be remem-
bered, that whilst the complete  oxidation  of the effete
matters will carry them off by the lungs in the form
of carbonic  acid  and water,  leaving urea and  other
highly azotized products to pass off by the kidneys,
an  imperfect  oxidation  will  only  convert them into
those peculiarly offensive  products which character-
ize the faecal excretions.
   Of the remarkable tendency of the  respiration of
an atmosphere charged with the emenations of the
human body to favor the spread of zymotic  diseases,
a few characteristic examples will now be given.   All
those who  have had  the widest opportunities  for
studying the conditions which  predispose to the in-
vasion of cholera, are agreed  that overcrowding is
among  the  most potent of these, and the Report of
the General Board of Health, on the late  epidemic,
contains numerous cases in which this was  most evi-
dent, of which the following may be selected:  In the
Autumn of  1849, a violent attack of cholera occurred
in the  workhouse in the town of Staunton, England,
where no cases of cholera   had previously existed,
and none subsequently presented itself  among the in-
habitants of the town in  general, though  diarrhoea 
            ASSIMILATION AND DIGESTION.         83
 was prevalent to a considerable extent.  The building
 was altogether badly constructed, and the ventilation
 deficient; but this was especially the case  with the
 school rooms, there being but  about 68 cubic  feet of
 air for each girl, and even less for the boys.  On No-
 vember 3, one of the inmates was attacked with the
 disease;  in ten minutes from the time of the  seizure
 the sufferer passed into a state of hopeless  collapse;
 within the  space of forty-eight hours from the first
 attack, forty-two cases and nineteen deaths took place;
 and in the course of one week sixty  of the inmates,
 or nearly 22 per cent, of the entire number, were car-
 ried off, whilst almost every one of the survivors suf-
 fered more or less severely from cholera or diarrhoea.
 Now in  the jail of the same town, in which every
 prisoner  is  allowed  from  819 to 935 cubic feet of air
 —and this  being continually  renewed  by an  effi-
 cient system of ventilation—there was not the  slight-
 est indication of epidemic influence.   Also the pene-
 tentiary at Columbus, Ohio, in the epidemic of 1849.
  Cholera is also produced by miasmatic influence, as
 demonstrated by the following cases:  In the Spring of
 1848 the author was living on Mill Creek, adjoining the
 city of Cincinnati, Ohio, and there was a pond drained
 into the  creek; the  weather  was warm, and there
 was an unusual amount of Diarrhoea and an increased
 number of patients in the  Commercial Hospital suf-
fering  from billious  diarrhoea;  the  next week the
cholera broke out to an alarming extent.   In 1850, in
Tuscarawas County, Ohio, there was a large pond
opened into the Tuscarawas river, and the same dis-
astrous results followed as at Cincinnati.  Also in
1850, there  was a large pond drained close  to the 
84              A NEW TREATISE ON
town of New Canton, Pike Co., 111., and in ten days
after the water was all let off about one half the peo-
ple were afflicted with cholera and a large  per cent.
died.
  The cholera epidemics here referred to as affording
the most remarkable examples of the influence of a
contaminated atmosphere in predisposing those habitu-
ally living in  it to the invasion of zymotic disease, yet
the evidence  is not less strong in regard to the uni-
form prevalence of ordinary fevers, etc., in the same
localities, the places in which cholera  was  the most
severe  having been almost invariably known as fever-
nests at other periods, and being distinguished by a
very high rate of mortality.  Thus it appears that in
all climates, and under all circumstances  and condi-
tions of life, the  purity of the  atmosphere  habitually
inspired is essential to the maintenance of that power
of resisting disease which even  more than the habit-
ual state of health is a measure of the real vigor of
the system.   For owing  to the extraordinary capa-
bility which the human body possesses of accommo-
dating  itself  to circumstances,  it  not unfrequently
happens that  individuals continue for years to breathe
a most unhealthy atmosphere without apparently suf-
fering  from it; and thus when  they at  last succumb
to some epidemic  disease, their death is  attributed
solely to the  latter, the previous preparation of their
bodies  for the reception and development of the zy-
motic poison  being altogether  overlooked.   It is im-
possible, however,  for any one  who carefully exam-
ines the  evidence, to hesitate  for  a moment in  the
conclusion that  the fatality of epidemics is  almost in-
variably in precise proportion to the degree in which 
            ASSIMILATION AND DIGESTION.         85

an impure  atmosphere has  been habitually respired;
that an atmosphere loaded with putrescent miasmata
may afford a radius wherein a zymotic  poison under-
goes a marked increase in quantity and intensity, the pu-
trescent exhalations from the lungs and skin of the living
subject being at least as effectual in furnishing such a
radius as are the  emanations from faecal discharges
or from other decomposing matters.  That the habit-
ual respiration of such an atmosphere tends to induce
a condition of the blood which renders it peculiarly
susceptible  of perversion by  the  introduction of zy-
motic  poisons,  and which favors their  multiplication
within the system; and  lastly, that  by due attention
to the various means of promoting  atmospheric pu-
rity, and especially to efficient ventilation and sewer-
age, the rate of mortality  may be enormously de-
creased, the amount and severity of sickness lowered
in at least an equal proportion, and the  fatality of ep-
idemics  almost  completely  annihilated.   And  it can
not be too  strongly borne in mind that the efficacy of
such  preventive measures has been most fully  sub-
stantiated in regard  to many of the very diseases in
which the curative power of medical treatment has
seemed most doubtful, as for example in cholera and
malignant fevers.
  The function of nutrition  considered  in the widest
acceptance of the  term, includes  the whole series of
operations  by which the alimentary materials  pre-
pared  by the digestive process, introduced into the
system by  absorption, and  carried into  its penetralia
by the circulation, are converted into  organized tis-
sues* but in a more  limited  sense, it may be under-
stood as referring  to the last of these operations only, 
86
A NEW TREATISE ON
that of histogeneric or tissue-formation, to which all
the other organic functions, in so far as they are con-
cerned in maintaining the life of the  individual, are
subservient, by preparing and keeping in the requisite
state of purity the materials at the expense of which
it takes place.  It has been shown that the formative
capacity does not exist in the tissues alone, but it is
shared by the blood, which must itself be regarded
as deriving it from  the  original germ, for  there are
certain simple  kinds of tissue which  seem to  take
their origin  directly in its  plastic components. Of
others, which can not be said thus to originate in the
blood, the development is entirely determined by the
quantity of their special pabula which  it may contain.
And even of those tissues which  must  be  considered
as most independent and self-sustaining, the develop-
ment is not only checked by the want of a  due supply
of their appropriate materials, but it is modified in a
very remarkable degree  by the presence of abnormal
substances in the blood, which single out  particular
parts and effect determinate alterations in their  nutri-
tion in  such  a constant manner as to show the  exist-
ence of a peculiar elective affinity between them.  In
so far,  then, as the  process of nutrition is dependent
upon the due supply and normal state of the blood,
its conditions have already been sufficiently discussed,
and we have now only to consider it in its relation to
the  tissues.   The  demand for  nutrition  primarily
arises from  the tendency of the  organism to  simple
increase or growth.   Of this we have the most char-
acteristic illustration in multiplication of the first em-
bryonic cell by the simple process of duplicative sub-
division, whereby a  multitude of cells is  produced, 
            ASSIMILATION AND DIGESTION.         87
every one of which is similar in all essential particu-
lars to the original.  But after the different parts of
this homogenous embryonic mass have taken upon
themselves their respective modes of development, so
as to generate a diversity of tissues and organs, each
one of these continues to increase after its own plan,
and thus the child becomes the adult with  compara-
tively little  change but  that of growth.  An excess
of growth,  taking place conformably to the  normal
plan of the  tissue or organ, constitutes hypertrophy,
whilst a diminution, without degeneration or altera-
tion of structure, is properly distinguished as atrophy.
but growth is not confined to the period of increase
of the  body generally,  for it may manifest itself in
particular organs or tissues as a normal operation at
any subsequent part of life.   Thus, when there is an
extraordinary demand for the  functual activity of a
particular set of muscles, it is supplied by an increase
in the amount of their contractile  tissue; or, if one of
the kidneys be  disabled from  performing its office,
the other may be rendered capable of fulfilling  it by
augmented production of its own secretory tissue; or
if there be  an  excess of fatty matters in  the blood,
they  may be eliminated by an augmentation of the
adipose tissue throughout  the  body.  And  further,
even where there is no such manifestations of increase
there is really  a continual growth of all the tissues
actively concerned in the vital operations, and  this
even  to the very end of life, although it may be so
 far counterbalanced or even surpassed by changes of
 an opposite  kind, that instead  of augmentation in
 bulk there  is absolute diminution.  The evolution of
 the complete organism from its germ, however, does, 
88
A NEW TREATISE ON
not consist  in mere growth, for by such  a process
nothing would be produced but an  enormous  aggre-
gation of simple cells, possessing little or no  mutual
dependence like those which  constitute the shapeless
masses of the algae.  In  addition  to  increase there
must  be a development  that is a passage to a  higher
condition, both of form and structure, so that the part
in which this change takes place becomes  fitted for
some  special function, and is advanced toward  the
state  in which it exists in the highest or most com-
pleted of its specific type.  Thus the development of
tissue  consists in the change  from a simple mass of
cells or fibres into another form, as in  the production
from  the cellular substance of the  tooth-pulp, or in
the formation of bone  in sub-periostal membrane.
Again, the developmental change is seen in the pas-
sage of an entire organ from  a lower to a higher con-
dition  by evolution of new parts, or by a  change in
the relations of  those already existing, even though
the change in its texture  should consist of little else
than of simple  increase.  Thus in  the development
of the heart, we have the original single cavity sub-
divided,  first into  two,  and  at last into four  cham-
bers;  and in the development of the  brain, we find
the sensory ganglia to be the parts first formed,  the
anterior  lobes of the cerebrum to  be  evolved from
these, the middle lobes sprouting forth  from the back
of the anterior, and the  posterior from the  back • of
the middle, yet with all this there is no production of
any new tissue,' the new parts being generated at  the
expense  of  histological  components   identical with
those  of the pre-existing.   Now it is in the early  pe-
riod of embryonic life that the developmental process 
            ASSIMILATION AND DIGESTION.         89
is most remarkably displayed, for it is then that we
see that transformation of the primeval cells into tis-
sues of various kinds, which originates a special nisus
in  each part, whereby the production  of the  same
tissue in continuity with that first formed, comes to a
simple act of growth, and  it is  then, also,  that we
observe that marking out of all the principal organs
by the development of tissue in particular directions,
which makes all subsequent evolution  but a comple-
tion  or filling up  of  the  plan thus  sketched out.
Thus during the first few days of incubation in the
chick, the foundation is laid of the vertebral column,
the nervous centres, the organs of sense, the heart
and circulating system, the  alimentary canal, the re-
spiratory apparatus and many other  parts.   At the
termination  of that period the chick emerges in such
a state of completeness of development that little else
than increase is wanting, save  in the plumage and
sexual organs, to raise  it to its perfect type.
  The same may be  said of the human organism,
save that  the period of its development is relatively
longer, in accordance with the higher grade which
it is ultimately to  attain;  its earliest stages  being
passed through with rapidity.  The  completer evo-
lution of the generative organs of the  osseous skele-
ton and of the teeth, constitute the principal develop-
mental changes which the human organism undergoes
in its progress  from the infantile to the  adult condi-
tion • almost every other alteration consisting in simple
increase in form or structure.  And when the adult
type has been once completely attained, every subse-
quent  change is one rather of degeneration than of
development—of retrogression rather than of advance. 
OX)             A NEW TREATISE ON
The difference between the two processes of growth
and development is most  characteristically shown in
those cases in  which there is a partial or complete
arrest of one of them, without any corresponding im-
pairment  of the other.   The demand for  nutrition
arises not merely from the exercise of the formative
powers, which  are  concerned in  the  building up of
the organism, but also from the degeneration and de-
cay which are continually taking place in almost every
part of it, and the effects of which, if not antagonized,
would speedily show themselves in the complete  dis-
intregation.  We have  seen  that as each component
cell of the organism has to a certain degree an inde-
pendent life of its own, so has it also  a limited dura-
tion, and that its duration  bears an inverse ratio to its
functional  activity.   This  is  particularly  striking,
when we  compare the ratio of change in  the  organ-
ism of cold-blooded animals at low and at high tem-
perature,  for they live slowly, need  little nutriment,
give off but a small amount of excretory products,
and require a long time for the performance of the re-
parative process under the former conditions; but they
live fast, require a comparative large supply of nutri-
ment, give off a far greater  amount of carbonic acid
and other compounds resulting  from the waste of
tissue, and exhibited a far more rapid reparation of in-
juries in the latter state.  The constantly high  tem-
perature of man, as of other warm-blooded animals,
prevents the difference from  being displayed  in  him
in a similar manner, but it will be seen, when we con-
trast his different tissues with each other, and study
their respective histories.  For whilst there are some
which appear  to pass through all  their stages of 
           ASSIMILATION AND DIGESTION.         91
growth, maturiation and decline within a limited time,
there are others whose existence seem capable of al-
most indefinite prolongation; and others, again, which
are liable to have a period put to it at any time by
the direction of their vital force into other  channels.
Of these, belonging to the  first  category, a charac-
teristic example is presented by the overle, which,
if not fertilized within a limited  period  after its  ma-
turiation, speedily declines and decays;  and the same
law of limited duration doubtless extends to a large
proportion of such tissues as are actively concerned
in  the  maintenance of the organic functions; as, for
example, the corpuscles of the blood; the epithelial
cells of mucous membrane, which minister to absorp-
tion in one situation and to  secretion in another; the
cells forming the parenchyma of the ductless glands,
and many others.   The contrary extreme to this may
be found in those  tissues whose functions are rather
physical than vital, and especially in such as undergo
consolidation  by the  deposit of solidifying  matter,
either  in combination  with  the animal  membrane or
fibre, or in  its interstices.   Such tissues are with-
drawn from the general current of vital action,  and
there seems  to be no  definite limit to their duration,
except such as imposed by the chemical and mechan-
ical degradation to which they are subjected. This
appears to be the case with  the simple fibrous tissue,
especially the yellow, even in their soft  or unconsoli-
dated state; but it is far more obvious in the osseus
substance,  which  is chiefly formed by the  combina-
tion of calcareous salts with the fibrous animal basis.
Again, in the dentine and  enamel of teeth we have
examples of tissues that have once undergone a sim- 
92              A NEW TREATISE ON

ilar consolidation, retaining their condition unchanged
through the whole remainder of life, under circum-
stances which show that if any nutritive change takes
place in them its  amount must be very small.   Yet
in both the osseous and dental structures of the young
there is obviously a determinate limit of existence, as
is shown in the rapid disappearance of a considerable
part of the laellas, first formed in  the cartilaginous
matrix; also in the death and removal which continue
to take in the inner and older portions of the shaft of
a round bone during the whole period of its increase,
and  in the exuviation, at a certain epoch, of the  first
set of teeth, which exuviation is usually preceded by
the  death and disintegration of their own  texture.
In hair, nails and other epidermic appendages, which,
when once their component cells have undergone con-
solidation by the deposit of horny matter in their in-
terior, may remain unchanged for centuries, we must
recognize the same principle of indefinite duration in
connection with  the annihilation of vital activity; the
chemical constitution of these substances being such
as renders them but  little  prone to be acted upon by
ordinary  decomposing agencies.    In  the case of
the  muscular  and  nervous  tissues, we  trace  the
operation of causes   that  differ from  any of those
already specified.  These tissues are subject, like all
others that are distinguished by their vital activity, to
the law of limited duration; when not called into use
they undergo a gradual  disintregation, or wasting,
which is not adequately repaired by the nutritive pro-
cess.   But their existence  as living structures appears
to be  terminable at any  time; the  exercise of their
functional powers for the development of muscular 
            ASSIMILATION AND DIGESTION.         93
 contractility, or of nervous force,  seems to invole as
 its necessary condition of the tissues, now reduced to
 the condition of dead matter, undergo those changes
 of blood  towards  the parts thus  called into  special
, activity.  During  the whole period of  active life a
 demand for nutrition is created  by every exertion of
 the  vital powers,  but more  especially by evolution
 of the  muscular and nervous forces.  The produc-
 tion, and of these may be considered as the great end
 and aim of the human organism, so far at least as the
 individual is concerned, the whole apparatus of or-
 ganic life being subservient to the building  up and
 maintenance of the nervo-muscular apparatus and of
 those parts, the bones, cartilages, fibrous textures, &c,
 of all the parts which minister to the former,  will be
 in proportion  to  the  energy with which they are
I called upon.  Of the mode in which the substitution
 of new tissue for that which has become effete is ef-
 fected  in process  of nutrition, our knowledge is at
 present limited.   There can be little doubt  that  it
- nearly always  takes place in  a manner closely con-
. formable to the first development of each tissue, whose
 term of life has expired, or whose vital energy has
 been exhausted, are removed  and disposed  of, our
 present knowledge is no less imperfect.  In the case
 of those  tissues which  are superficially nourished, a
 continual loss of substance is obviously taking place
 by the exuviation of dead particles en masse; this is
 the  case with  the  whole series of epithelial and  epi-
 dermic  cells, which are  thrown off with little pre-
 vious change, like the leaves of  trees, their decay not
 taking place for  the most part until after they have
 become detached from the organism.   But the fact is 
94             A NEW TREATISE ON
altogether different with regard to those whose nutri-
tion is instertial, especially the nervous and  muscular
tissues, for the decomposition of these would seem to
occur in their substance, its products being taken up
by the blood and subsequently eliminated from it by
organs appropriated to that purpose.  The evidence
of this is seen, as regards muscle, in the presence of
creatine, creatinine, inolite, and other undoubted pro-
ducts of regressive metamorphosis  in  the juice of
flesh.  As regards the nervous  substance, no such
definite proof  can  be at present afforded, since its
normal   constitution  has not  yet  been  sufficiently
studied to enable the products of its decomposition
to be distinguished.   There is one remarkable form
of disintregation  which is  common  to  nearly all  the
tissues, and  seems to occur as a normal alteration in
many of them at an advanced period  of life.   This
consists in the conversion of their albuminous or gel-
atinous materials into fat, thus constituting what is
known  as fatty degeneration.  That this change is
not due to the removal of the normal components of
the tissues and the substitution of fatty matter in their
place, but is the result of a real conversion of the one
class of substances  into the other, has  been already
pointed out; and there are certain facts  which indi-
cate that this  kind of degeneration  is  a part of the
regular series of processes by which tissues that have
served their purpose in the economy are prepared for
being removed by absorption.   In  the case  of  the
teeth—for the fangs of the deciduous teeth undergo
degeneration—when  the current of nutrition is di-
verted towards those which are to succeed  them,
their materials being slowly decomposed so as to be- 
           ASSIMILATION AND DIGESTION.        95
come soluble, and being gradually removed by ab-
sorption, nothing is left, at last, but the  crown of the
teeth.  On theother hand, the permanent teeth, which
are not to  be succeeded by others, when no longer
receiving their due  nutrition,  die and  are  cast out
entire.
  Among  the conditions of healthy nutrition a due
supply of nervous power is commonly  enumerated,
and it can not be questioued that the want of such a
supply is frequently the source of a perversion of the
normal operations.  This by no means proyes that
the formative power is derived from the nervous sys-
tem, and such an idea is at once negatived by a num-
ber of incontestable  facts;  yet it may be freely ad-
mitted that the right direction and application of this
power in nutrition may sometimes depend upon guid-
ance  and direction afforded by the nervous centres,
in the same manner  as  the  secreting process is cap-
able of being thus influenced.  We can scarcely ex-
plain in  any other  mode   that influence of mental
states upon the nutrient operations.
  Reparative  Process.—The nutritive operations
take place  with  extraordinary energy and rapidity in
the  process  of  reparation,  by which losses  of sub-
stance occasioned by injury or disease  are made good.
In its most perfect form, this process is exactly anala-
gous to  that of the  first development of the corres-
ponding  parts, and its results are as complete  in the
one case as in the other.   In  man, in the place of what
is lost by accident or disease, some lowly organized
tissue is formed, which fills up the breach and suffices
for the maintenance of a less perfect life.  Even thus
restricted, the operations of  this power are frequently 
96             A NEW TREATISE ON
most remarkable, and are  in  no instance, perhaps,
more strikingly displayed than  in reformation and re-
modeling of an  entire bone, when the original  one
has  been destroyed by disease.  That this power is
intimately related to that  by which the organism is
normally built up  and  maintained,  is evident,  not
merely from the  peculiar mode in which it is exer-
cised,  its tendency  being always to reproduce each
part in the form and structure characteristic of it at
the particular period of life, and not according to its
embryonic type, but also from the fact that it is more
effectual in the state of growth than in the adult con-
dition, and that it can do far more in  the  embryonic
state, when development as well as growth is taking
place, than after the  developmental process has ceased.
Thus it is well known to every practitioner how more
readily and perfectly the  lesions resulting from acci-
dent or disease are  repaired in childhood and youth
than they are after the attainment of the adult state.
Small wounds in persons of good habits of body,  and
in parts which can be completely kept at rest, readily
heal; and large wounds have been known to close in
the same desirable mode  beneath a clot of inspissated
blood.   That to induce the  most  favorable method,
the most perfect freedom from all pernicious agencies
should be required.
  Of the alterations in the conditions of the blood in
inflammation, the most characteristic  is the augmen-
tation,  either of the  organizable  or plastic fibrine, or
of the  organized  colorless corpuscles; the increased
production of these  two components seeming to bear
in some  degree  a relation of reciprocity, the one to
the other.  The increase  of fibrine may be considered 
            ASSIMILATION AND DIGESTION.         97
as the alteration most characteristic of a  previously
healthy and vigorous state of the system, and it is in
the inflammations which occur iu such subjects that
the effusions are  most  strongly  disposed to become
organized, and  show the least tendency to undergo
degenerative changes.   On the other hand, the in-
crease of the corpuscular element seems to occur in
cachectic or otherwise  unhealthy individuals, and the
inflammatory  effusions which partake  of  the  same
character, are far less  plastic, originally, and are  ex-
tremely prone to undergo degeneration, either  at  the
time of their effusion, or subsequently.   With this in-
crease in the proportion of fibrine and colorless cor-
puscles separately, or in combination, there is a dimi-
nution in the  proportion of the red corpuscles, albu-
men and salts of the blood.   None of these changes,
however, can  be legitimately regarded as  originally
or essentially characteristic of the inflammatory con-
dition ; they are, in fact, to be looked on rather as the
results of its establishment.   Constituting that series
of alterations in the  circulating fluid which is of par-
allel order to that which  occurs in  the solid tissues,
wherein the inflammatory action has been set up,  the
inflammatory state is further characterized by the ef-
fusion of certain of the components of the blood,  up-
on the surface or into the substance of the inflamed
tissues.  The  effusion  of pure serum cannot be  re-
garded as characteristic of inflammation, since it may
take place as  a mere  result of congestion,  especially
when this congestion is due to an obstruction to  the
return of the blood;  whilst again it may be due to an
altered condition of the albuminous constituents of
the blood which favors its transudation.  The so-called
    7 
98             A NEW TREATISE ON
serous effusions, which are poured forth in inflamma-
tion, do, in reality, contain fibrine in  solution, but this
fibrine may not manifest its presence by spontaneous
coagulation, until its passage  into the  solid state  is
favored by some  extraneous influence.  The  pres-
ence of fibrine  in  such an  effusion  is not in itself a
sufficient  proof of the existence of  inflammation, for
it has been shown by experiment that when the ob-
struction to the return of blood by the  veins  is so
great as to occasion an excessive pressure within the
capillaries, the fluid  which transudes may contain
enough fibrine  to render it spontaneously  coagulable.
The form of equdation which is most  characteristic
of inflammation is that which is known as coagulable
lymph.  It is much  to be desired that some other des-
ignation should be applied to it, since the term lymph
can only be applied to fluid  contents of the lymphatic
vessels.  The peculiar characteristic of this inflam-
matory exudation,  is its capability  of spontaneously
passing into the condition of an organized tissue,
either  fibrous or cellular, or  a  mixture of both, and
thus forming false membranes or inflamed surfaces,
or solidifying the inflamed part  by the intestinal pro-
duction of similar  lowly organized textures.   The
condition  of the  blood as  determining that of the
characters of inflammatory deposits in different dia-
thesis, correspond  very  generally  and closely with
those of the coagula found  in the heart and pulmo-
nary vessels after death.  Chemical observations fully
confirm this doctrine  by evidence  of another  kind,
that which is afforded by the different source of the
same specific disease in different individuals, accord-
ing to the previously healthy or abnormal  condition 
           ASSIMILATION AND DIGESTION.         99
of the blood.   There  can be no doubt  that a very
large proportion of what are called virus, especially
those of the erysipelatous type, are to be regarded
as owing their peculiarity to a deficiency in  the due
elaboration of the fibrine, and to the  low vitality of
the cellular components of the blood, both of which
conditions seems to be  favored  by the presence  of
those decomposing matters whose accumulation in the
blood acts in  man}^ ways so prejudicially on  the sys-
tem at large.  That the  equality of the exudation is
in some degree  determined by the seat  of tissue in
which the inflammation occurs, appears from the dif-
ferent character of the product of the  disordered ac-
tion occurring simultaneously in  different organs  of
the same individual, and apparently under the opera-
tion of the same cause.   Thus it  may happen that in
pleuro-pneumonia the two surfaces of the pleura be-
come  connected by  an  organized exudation of  a
fibrous character, whilst the effusion in the substance
of the lung is  rather of the  corpuscular  nature, and
speedily passes into supurative  degeneration.  The
mode in which  the intensity of the inflammation  ef-
fects the character of the effused lymph,  is two-fold.
For in the first place the  nature of the original effu-
sion is likely to vary according to the degree in which
the ordinary nutritive process is interpreted, since the
more intense the inflammation, the less will be the as-
similating force  of the part,  and the  more  will the
matters effused from the vessels deviate from the nat-
ural  plasma which would be drawn  from  them in
healthy nutrition; whilst on the other hand, when the
inflammation is less severe, its product will not differ
so widely from the natural one, and will, from the first, 
IOO
A NEW TREATISE ON
tend to manifest in its  development some characters
corresponding to those of the natural formations of
the part.   Various kinds of degeneration may take
place, according to the stage at which the develop-
mental process is checked, and among these in tissues
which have once attained an advanced stage of de-
velopment.  The most common is the fatty.  In per-
sons of that peculiar  constitution which  is termed
scrofulas, or strumous, we find an imperfectly organ-
izable or caco-plastic deposit, or  even an altogether
plastic product, known by the designation of tuber-
cular matter, frequently taking the place of the  nor-
mal elements of tissues, both in  ordinary process  of
nutrition, and still more when inflammation  is set up.
From  an examination of the blood of tuberculous
subjects, it appears that although the bulk of the co-
agulum obtained does  not consist of  well elaborated
fibrine, for it is soft and loose, and contains an unusu-
ally large number ot colorless corpuscles, whilst the
red corpuscles bears an unusually small proportion to
it; hence persons of a strumous diathesis, in their diet,
should keep in view this fact: that their system re-
quires such food as will produce the greatest amount
of iron in the blood.   Tubercle  is to be considered
whose production is dependent upon a  special  taint
in the blood; and just as the  normal lymph products
vary greatly in their degree of vitality, so that some
undergo a progressive  and others a retrograde  met-
amorphosis, so may tubercular deposits either retain
their original characters more or less completely, or
may undergo a  very early and  complete  degenera-
tion.  Now although tubercular matter may be slow-
ly and insidiously deposited by a kind of degenera- 
           ASSIMILATION AND DIGESTION.       IOI
tion of the ordinary nutritive process, yet it can not
be doubted that inflamation has a great tendency to
favor it, so that a large quantity may be  produced in
the lungs after  pneumonia has  existed for a  day or
two, that it would have required years to generate in
the previous mode.   But the character of the deposit
still remains  the same, and its  relation to the plastic
element of the blood is shown by the interesting fact
of no unfrequent occurrence, that  in pneumonia, af-
fecting a  tuberculous  subject, plastic lymph is often
thrown out.
  The ordinary process  of nutrition involve  a sepa-
ration  of certain of the  components  of the  blood,
which  are withdrawn  from it  by the appropriating
power of  the solid textures,  and  every such  re-
moval  may be considered in the light of  an act of ex-
cretion, so far as the blood and the rest of the organ-
ism is concerned.  The separation of certain matters
from the blood in a fluid state, either for the purpose
of being cast forth from the body, or of being em-
ployed for some special purpose within it, which con-
stitutes what is known  as secretion, is  effected by
an  agency of  the  same nature  with  that  whose
operation constitutes  the essential part of the nu-
tritive  process, namely, the production of the growth
cells.  Hence there is no other fundamental difference
between the two processes than such as  arises out of
the diverse destinations of the separated matters and
the anatomical arrangements which respectively min-
ister to these.  For the products of the secreting ac-
tion are all poured forth  either upon the external
surface of the body, or  upon  the lining of some  of
the cavities which communicate with it, and the cells 
102
A NEW TREATISE ON
by which they are separated from the blood usually
stand in the relation of epethelium cells to those pro-
longations of the skin or  mucous membranes  that
form either the projecting  fringes, or the  follicles  or
extended  tubuli of which  the  glandular  organs are,
for the  most  part, composed,  and are thus readily
thrown off from their free  surfaces.   Thus the act of
secretion essentially consists in successive  production
and exuviation of the cells  which minister to it; these
cells giving up by rupture, or deliquescence, the sub-
stance which  they have eliminated from  the blood.
Each group of cells is adapted to separate a product
of some peculiar kind, which  constitutes  its special
pabulum, and the rate of its production seems to de-
pend  upon the amount of that  pabulum supplied by
the circulating fluid.  The substances, at the expense
of which  the  secreting cells grow, may not  be  pre-
cisely those which are subsequently cast forth at their
death, for it is very probable that some  of them  at
least  undergo a certain degree of chemical  transfor-
formation by the agency of these cells; the  charac-
teristic materials of the several secretions not always
pre-existing as such in the blood, a  distinction  may
be drawn as regards this point, between those secre-
tions, the  retention of whose materials in the blood
would be positively  injurious, and those secretions
which are destined for particular  purposes within the
system, and the cessation of which has no immediate
influence on any other function than those for which
they are respectively destined.  The solid matter dis-
solved in the fluids of the latter class, is little else than
a portion of the nutritive  constituents of the blood,
either so little altered as  still  to retain its  nutritive 
           ASSIMILATION AND DIGESTION.        IO3
character, as is the case with the casein of milk, and
with the albuminous constituents  of serous fluid of
areolar tissue, and of serous and synovial membranes,
or in a state of incipient retrograde  metamorphosis,
as seems to be the case with the peculiar ferments of
the salivary,  gastric, pancreatic and intestinal secre-
tions.  On the other hand, the characteristic  ingre-
dients of the excretions  are very different in charac-
ter from the normal elements of the blood.  They are
all of them completely unorganizable, and they pos-
sess, for the most part, a simple atomic constitution.
Some of them, also, have a  tendency to  assume a
crystaline form, which  is considered to indicate their
unfitness to enter the composition of organized tissues.
With regard to  some of the chief of these, there is
sufficient  evidence of their existence in small quan-
tity in the circulating blood; it is also clear that they
exist there as products of decomposition, and  that
they are destined to be speedily as possible. If their
separation be prevented, they accumulate and com-
municate to the circulating fluid a positive deleterious
character.   Of this we have a  striking example  in
asphyxia, and the history of the  other three prin-
cipals of excretions, the spleen, liver and kidneys, will
furnish evidence  to the same effect.  As a general
fact, then, it  may be stated that the  materials of the
secretions pre-exist in the blood in  a state  nearly re-
sembling  that in  which they are thrown off by the
secreting organs; but that the materials of those se-
cretions which are destined to perform some particu-
lar function within the economy, are derived from the
substances which are appropriated to its general pur-
poses, whilst those of the excretions are the result 
IO4            A NEW TREATISE ON
of the destructive changes that have taken place in
the system and cannot be retained in it without injury.
  The composition and  uses of the principal secre-
tions which are elaborated for special  purposes with-
in the economy, have already been partly described
in connection with the function to which they respect-
ively minister, and the remainder will hereafter come
under notice in the same  manner.  It is here intended
to consider that important system of excretory ope-
rations, which serves to maintain the  purity of the
circulating fluid, by removing from it those products
of the disintregation  of the tissues which are not
capable of serving any purpose in the nutrition of the
system, and which  even act upon it as poisons; and
also by withdrawing the  products of the decomposi-
tion of those surplus alimentary materials, which, not
being required for the nutrition of the tissues, undergo
a retrograde  metamorphosis without  having  ever
undergone the process  of organization.  The process
of respiration, as already pointed out, is in part to be
regarded  as one  of an excretory  character, though
the peculiar manner in which it ministers to the re-
moval of carbon and hydrogen from the system, and
its subserviency to other purposes, necessitates its
separate consideration.  The true secreting processes
which are to be regarded as  more or less completely
excretory, are  the separation of the gastric juice from
the spleen, of bile from the liver, that of urine by the
kidneys, that of perspiration  by the skin, and that of
foecal by the intestines.  The sum total of these, with
the addition of the  carbonic acid and watery vapor
poured from the lungs, and of the indigestable matter
rejected in the form of feces, must  be equal to the 
            ASSIMILATION AND DIGESTION.       IO5
total amount of solid and fluid ingesta and of the ox-
ygen which disappears from the inspired air, the
weight of the body remaining the same.
  Under ordinary circumstances, the several parts of
excretory apparatus are limited each to its  own spe-
cial function; yet we see that there are certain com-
plimentary relations  between  them, which makes the
action of one to a certain extent vicarious  with that
of another.   Such a relation exists between the spleen,
liver and pancreas, on the one side, and the lungs on
the other side, for the more active the respiration, the
less active are  the other secretory organs; whilst if
the respiration be lowered, a  large proportion of un-
oxidized, or imperfectly oxidized, excrementitious mat-
ters accumulate in the blood, giving  rise to that aug-
mented production both of the biliary and  foecal se-
cretions.  The skin  actually assists in the elimination
of one of those azotized tissues, the removal of which
has  been,  until recently, considered as the special
function of the kidney.   Consequently, whenever the
due action of the skin as an excreting organ is inter-
ferred  with, it is  the kidney especially that will be
called on to take  its  place; whilst on  the  other  hand,
if it be thought necessary to  relieve  the  kidney, this
may be most effectually done by stimulating the skin
to increased  excretory activity.  The kidneys can
not be regarded to be inferior to any of the excreting
organs, but their function, also, consists in separating
from the blood certain effete substances, which are to
be thrown off from  it, and  has no direct connection
with any of the nutritive operations concerned in the
introduction of aliment  into the system.   The follow-
ing are the points in the minute structure of these 
io6
A NEW TREATISE ON
organs, which are of most importance in their physi-
ological relations:   The distinction between the cer-
ticle and medulary parts  of the  kidneys, consists in
this: that the former  is  by far the most  vascular,
and  the plexus  formed by the  tubuli uriniferi seems
to come into the closest relation with that of the san-
guiferous capillaries, so that it is probably the seat of
the greater part of the  process of secretion; whilst
the latter is principally composed of tubes passing in
a  straight line from the  former towards their point
of entrance into the uretor.
   The circulation of blood through the kidneys pre-
sents a very remarkable  peculiarity.  The supply is
derived in man direct from the arterial system.  But
although this  organ is supplied  from the venal artery,
yet  it  is not to its proper secretory apparatus that
the  blood  of that  artery is distributed in the first
instance, for  on  entering the  kidneys  this vessel
speedily and entirely divides itself into  minute twigs,
which are  the afferent vessels of the malpigian tufts.
After it has pierced the capsule each twig dilates and
suddenly divides  and subdivides  itself into  several
minute branches, terminating in  convoluted capillaries,
which  are  collected in  the form of a ball, and  from
the  interior of  the ball  the  solitary afferent vessel
arises, which  passes out of the  capsule by the side of
the  single afferent vessel.
   The kidneys serve as the special instruments for
depurating the blood of those  highly azotized  com-
pounds, which  are formed in the system by the de-
composition of the materials of the albuminous and
gelatinous tissues, and also by that of the non-assim-
ilated components of the food.   We have  seen, also, 
           ASSIMILATION AND DIGESTION.       IO7
that they serve for the removal of certain compounds,
of which carbon  is a principal ingredient, and these,
normally present in but  small amount, may undergo
a marked  increase  in disease,  especially when  the
liver or spleen is  insufficiently performing their func-
tions, or the  respiratory process is obstructed.  We
have  been  led to regard the kidneys as the emunc-
tory, not only for the  superfluous water of the system
but also for  those saline compounds which,  having
been introduced into the  system or generated within
it in larger amount than  is compatible with the nor-
mal constitution of the blood, or than is  required for
the reparation of the solids of the  body, or for  the
production of its fluid secretion,  are only fitted for
elimination.  Those soluble salts are most readily ex-
creted which produce a determination  towards the
kidneys, whereby an increased quantity of liquid is
filtered off through the outlet they afford.  And it is
in the same way  that the system makes an effort to
free itself from various foreign substances which have
been  introduced into it by absorption, and which
would be injurious if retained; the  rate  at which it
does  so being in a great degree dependent upon the
functional  activity of the kidneys.  It  does not  ap-
pear  that  the excretion  of  the organic  compounds
which are  formed within the system is augmented by
those diuretic medicines  which, by determining an in-
creased flow of blood to the kidneys, cause a large
amount of liquid to be passed off through them.  On
the contrary, it would seem as if by producing con-
gestion and inanition, they sometimes interfered with
the normal process of secretion.
  In the discussion of the liver I shall not attempt an 
io8
A NEW TREATISE ON
anatomical description, further than to state that the
hepatic artery sends branches to every  part  of the
liver, supplying  the walls of the portal  and  hepatic
veins, and of the hepatic ducts.  The hepatic  duct
forms, by its subdivision and  ramification, an inter-
lobular plexus, very like that of the portal vein.  The
conditions under which the secretion of bile takes
place, and one of the most  important of these is the
character of the blood with which the organ is sup-
plied, it exercises a depurative as well as an assimi-
lating power over  these; and  whilst it assists  in pre-
paring for nutrition those azotized substances which
are capable  of being applied to that purpose, and also
transform non-azotized matters into compounds, which
are more ready to undergo  combustion, and are thus
better fitted for sustaining  the heat of the  body by
respiration, it also eliminates certain substances whose
passage into the general circulation  would be inju-
rious.  The greater part of  the bile which  passes
into the intestinal canal is ordinarily destined for re-
absorption;  it seems fair to conclude that  the matters
which accumulate  in the blood, when the secreting
action of the liver is suspended, are  not in the same
condition with those which are received back  into it
after being submitted to that action, and that the liver
not only separates them, but exercises a certain trans-
forming agency upon them, it is known to effect upon
other constiuent of the blood which  pass  through it.
Bile is  a viscid,  somewhat oily looking  liquid, of a
greenish-yellow  color,  and very bitter taste, followed
by a  sweetish after-taste; it is readily miscible with
water, and its solution  froths like soap.
  The liver is an organ of excretion, designed to re- 
            ASSIMILATION AND DIGESTION.        IO9

move from the blood those  hydro-carbonaceous  pro-
ducts of the disintregation  of the tissues,  which can
not be converted into sugar or fat so as  to be  pre-
pared  for direct elimination  by respiratory organs.
That in so doing this it  converts those excrementi-
tious matters into glycoholic and  taurocholic acids,
substances which have a certain utility in  the  diges-
tive process, and which, after ministering to that func-
tion are  capable of being re-absorbed and undergo-
ing  oxidation,  whereby  the  greater  part  of their
components  are carried off  in the  form of carbonic
acid and water by the lungs, the  remainder being
eliminated by the kidneys.  That  not only by the
separation of biliary matter from the blood, and by
the operation of this upon the alimentary  substances,
but also by the change in the constituents of the blood
itself,  the  liver aids  in  preparing materials for the
combustive process.   For  it  converts  all forms  of
saccharine  substances  derived from  food into  liver
sugar, the form which is most favorable to oxidation,
and it would seem  capable also of generating this
sugar from protein compounds, or from certain  pro-
ducts  of their decomposition, and it exercises a  simi-
lar transforming power upon fatty matter,  generating
the peculiar liver fat either  from other oleagenous, or
from saccharine substances supplied by the  food; or,
as  it  would  also appear,  from protein compounds,
or  from the products of the early stages  of their re-
trograde metamorphosis.   In all the foregoing actions
the liver is subservient to the respiratory function, but
in a mode very different from that formerly believed.
It is quite certain that if the whole of the  solid biliary
matter poured into the intestines were re-absorbed, it 
no
A NEW TREATISE ON
could furnish  but a  small  proportion of the total
amount of hydro-carbon  eliminated by the lungs and
the other excreting organs.
  The most important organ interested in the diges-
tion of alimentary substances, and the greatest organ
to disintregate from the blood, is the spleen, as we
have before  mentioned.   We may not give our views
as plainly and scientifically  as it will  be  treated  at
some future time, bnt we think that we may be able
to bring before the medical world that which will be
a  great benefit to the human  family at large.  The
simple structure of the spleen, as we before said, sep-
arates  the serous from  the resamentum  portion  of
the blood.   When the spleen becomes inflamed, and
the grape-like appendages  of the arteries are con-
gested with  cacen from the blood, there will be a sur-
plus of the  blood highly charged with gastratin  in
the vena patarum, and the hepatic artery, and become
assimilated by the liver into bile, and then pass into
the general circulation, until the system is surcharged
with bile and jaundice  is the  result.  . On the other
hand, when  the liver becomes inflamed from ulcers or
injuries by accident, or otherwise, and does not se-
crete a sufficient amount of bile  to  assimilate  the
chyme in the duodenum, then Nature makes  a  de-
mand upon the spleen and pancreas; and if the spleen
is inflamed and can not perform the office of the liver,
in addition to that it already has to perform,  then  the
pancreas is over-taxed, and has to perform the  office
of the liver and of the spleen, and the liver and chyle
is highly charged with carbon.  The  next demand is
made upon the  skin, lungs  and  kidneys;  if .they
fail to restore the equilibrium, then inflammatory
rheumatism is the result.
  The next  point we shall notice is the skin, which is
the seat of various secretions, each of which is pro-
vided with special organs; the only one which can be
regarded as truly excrementitious, is the transpiration
of  aqueous  fluid holding certain matters  in solution. 
ASSIMILATION AND DIGESTION.
Ill
The elimination of this fluid from the blood is effected
by the sudoriparous glandula, which,  seated rather
beneath than in the cutis, are diffused in varying pro-
portions over the entire surface of the body.   Of the
whole  fluid which passes off by the skin, only a small
portion can  properly said  to  be secreted by these
glands, a  large part, as in  the case  of the kidneys,
being the product of simple transudation.  It will be
this  part which will  undergo augmentation  when a
special determination of blood to the skin is produced
by external  causes;  and there  is no  more reason to
think that an increase in the amount of solid matter
thus excreted is induced by such agency, than that an
increase in the  solids of the  urine can be determined
by ordinary diuretics. Hence the debilitating effects
commonly assigned to profuse perspiration must be
attributed to some other causes, and these it does not
seem difficult to find.  Thus the  great fatigue which
is experienced  as a consequence of muscular  exertion
in a heated atmosphere,  may fairly be set down to the
diminished activity of the respiratory process at high
temperature, and  the colliquitive  sweating of hectic
fever is obviously not a cause but a  consequence of
the  debilitated state of the general system.   The en-
tire  amount of  fluid  which is insensibly lost from the
cutaneous and  pulmonary surfaces, is estimated at 18
grains per minute, of which n grains pass off by the
skin and 7 by the lungs.  The maximum loss by ex-
halation, cutaneous  and pulmonary  during  twenty-
four hours, is 5 pounds; the minimum, 2 pounds; it
varies according to the condition of the atmosphere.
The whole amount of cutaneous transpiration, sen-
sible and insensible,  is greatly increased by heat  and
dryness of the surrounding air;  the heat occasions
a determination of an augmented amount of blood to
the cutaneous  vessels, and of the fluid  which trans-
udes a large portion is carried off in the state of vapor.
The cutaneous excretion is in a great degree vica-
rious with the urine, in regard to the  amount of fluid 
112
A NEW TREATISE ON
 eliminated.   The share the skin has in the office has
 probably been  generally underrated.  There is  rea-
 son  to  believe that at least 100  grains of  azotized
 matter are excreted from it daily, and any cause which
 checks this excretion must throw an additional labor
 upon the kidneys, and will be likely to produce dis-
 order of their function.  The secretion of the skin is
 influenced by general  conditions of the vascular and
 nervous  systems, which are, as  yet, not fully under-
 stood.  It is quite certain that through the influence
 of the latter  the secretion may be increased or de-
 pressed by external causes having a tendency to pro-
 duce congestion and inflammation  of internal organs;
 a partial suppression often gives rise to febline symp-
 toms in man, and the decomposition of organic mat-
 ter in the blood, which it is its special office to elimi-
 nate. Hence the due maintenance of health requires
 that  the excretions should be promoted by the use of
 all natural means;  if the kidneys are in active order,
 the natural result should be to stimulate the  skin; if
 the lungs appear to be inflamed, increase  the action
 of the skin and kidneys; if the paroted, sublingual or
 submaxillary  glands  are inflamed,  stimulate  the
 spleen; if the spleen is inflamed, stimulate the liver
 and pancreas, and  vice versa when any organ is inca-
 pacitated from  performing its especial office in the
 animal economy, stimulate the  other  organs which
 will  relieve the  organ  affected, by performing  the
same office to a certain extent.
  In my next issue I will  introduce the therapeutical
 agents, with which the author has been the most suc-
cessful after an experience of over  thirty years' prac-
tice.   That the reader may find  some  new ideas ad-
vanced in this small work, that will prove a lasting
benefit to the human family, in relieving the suffering
and  pain to which they are  subject, is the heartfelt
desire of the author.            John W. Evans,
                         New Canton, Pike Co., 111. 
 
 
 
NATIONAL LIBRARY
NLM  DD13fllbM D
NLM001381640