Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/29/
DIGESTION. 
hypotheses and conjectures have been formed 
on the subject, there is none which seems to 
have obtained any credit with physiologists, or 
indeed to be entitled to much consideration.* 
The latest researches on the subject are those of 
Home, and of Tiedemann and Gmelin. Home 
examined the structure of the spleen, and, as the 
result of his investigation, informs us that it 
consists entirely of a congeries of bloodvessels 
and absorbents, and that there are interstices 
between the vessels into which the blood is 
effused, through certain natural orifices in the 
veins, when they are much distended. The 
conclusion which he forms respecting the use of 
the spleen is, that it is a reservoir for any super¬ 
fluous matter, which may exist in the stomach, 
after the process of digestion is completed, 
which is not carried off by the intestines, as 
serum, lymph, globules,and mucus; that these 
are conveyed to the spleen by certain communi¬ 
cating vessels, and are removed from it, partly 
by the veins and partly by the absorbents.-f 
The account of the structure of the spleen 
which is given us by Tiedemann and Gmelin 
is considerably different from that of Home. 
They inform us that it essentially resembles 
that of the lymphatic glands, and they conceive 
that it is to be regarded as an appendage to the 
lymphatic system. They suppose its specific 
function to be the secretion of a fluid which is 
conveyed to the thoracic duct, and being united 
with the chyle, converts it into blood.J There 
are many circumstances which render it pro¬ 
bable that the spleen, in some way or other, 
promotes sanguification, and we have some 
reason to believe, that there is an immediate 
and a ready communication between its arterial 
and its absorbent systems, but we conceive 
that the hypothesis must still be regarded rather 
as a plausible conjecture, than as a deduction 
from facts. 
There is moreover a circumstance which 
must not be overlooked in our speculations 
respecting the spleen, that we have some well 
authenticated cases, where it has been either 
originally wanting, or has been removed from 
the body without apparent injury.§ This argu¬ 
ment cannot, however, be considered as decisive, 
because it is well known, that in consequence of 
the extraordinary compensating powers of the 
system, certain organs may be occasionally dis¬ 
pensed with, which, under ordinary circumstan- 
* See Haller, El. Phys. lib. xxi. ; Soemmering, 
t. vi. p. 149 et seq. 
f Phil. Trans, for 1808, p. 45 et seq. and p. 133 
et seq., and for 1821, p. 35 et seq. pi. 3..8, 
t We have an ample and apparently correct ab¬ 
stract of the memoir of Tiedemann and Gmelin in 
the Ed. Med. Journ. v. xviii. p. 285 et seq. See 
also on this subject Elliotson’s Physiol, p. 108 et 
seq. ; also an essay by Dr. Hodgkin, appended to 
his translation of Edwards’s physiological work. 
§ Baillie’s Morbid Anat., p. 260, 1 ; works, by 
Wardrop, v. ii. p. 235. [Dupuytren observed an in¬ 
creased voracity in dogs from which the spleen had 
been removed.—Assolant, Dissertation du Rate ; and 
Mayo has in two instances remarked a considerable 
obesity in dogs after the removal of the spleen, 
but does not say whether this may not be attribu¬ 
table to the increase in the quantity of their food. 
In both instances the duration of the obesity was 
for less than a year. Mayo’s Pathol, vol. i.—Ed.] 
ces, appear the most essential to its existence 
and welfare. We may therefore conclude with 
respect to the pancreas and the spleen, that 
although there is reason to suppose that they 
contribute, in some way, to the function of di¬ 
gestion, we are still unable to ascertain the pre¬ 
cise mode in which they conduce to this end. 
Before we dismiss this part of our subject, it 
will be necessary to make a few observations 
upon a question, which has been proposed in 
relation to the digestive process, whether any 
part of the aliment passes through the stomach, 
and is taken up by the absorbents, without de¬ 
composition. It is obvious that this cannot be 
the case with vegetable substances of any des¬ 
cription, and with respect to substances of ani¬ 
mal origin, that form a part of the diet, although 
they approach so much nearer to the nature of 
chyle, yet it appears that they are not entirely 
identical with it, and that they must conse¬ 
quently be decomposed and assimilated to the 
general mass, before they can serve for the pur¬ 
poses of nutrition. There are indeed certain 
substances, that are received into the stomach, 
which would appear to form exceptions to this 
general principle ; these are the various saline 
substances, which are found in all organized 
bodies, as well as some others, which give their 
appropriate odours and flavours to the food, and 
also certain medical agents. There are some 
salts, which appear to constitute an essential 
part of the blood and other animal fluids, and 
as the same salts are introduced into the sto¬ 
mach with the food, we may conceive that 
they pass unchanged into the vessels. There 
are likewise certain substances which give their 
specific odour to the milk, and to other secre¬ 
tions and excretions, proving that they likewise 
pass into the circulating system without suffer¬ 
ing decomposition, and the same is the case 
with some of the medicaments.* 
IV. Theory of digestion.—We now enter 
upon the fourth branch of our inquiry, the mode 
in which we are to explain the action of the di¬ 
gestive organs upon the aliment. This has been 
one of the most fertile sources of conjecture and 
speculation from the earliest period, from Hip¬ 
pocrates down to our own times, and the ques¬ 
tion is one respecting which the greatest differ¬ 
ence of opinion still exists among the most 
intelligent physiologists.f V e shall not think 
it necessary to notice the opinions of the older 
writers, which were necessarily formed from 
very insufficient data, but shall select those hy¬ 
potheses which appear deserving of more par¬ 
ticular attention, either as having been supported 
by men of acknowledged eminence, or as 
* See the remarks of Fordyce, p. 122, 3 ; the 
results of the experiments that have been made on 
this point are somewhat contradictory ; but upon 
the whole there seems no doubt that, under certain 
circumstances, various extraneous substances may 
be taken up by the absorbents and recognized in 
the blood and other fluids. See Bostock’s Physiol, 
v. ii. p. 569, 0, note. 
t For an account of the doctrines maintained by 
the earlier physiologists, the reader is referred to 
the treatise of Fernei, De Concoctionibus, Physiol, 
lib. vi. cap. 6 ; Boerhaave, Prælect. not. ad § 86 ; 
Haller, El. Phys. xx. 4 et 5 passim ; and Blu¬ 
menbach, Instit. Physiol. §360.
        

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