849 
P H Y S I 
chyle and foecal matter In the duodenum, has alfo been 
there mentioned; and we have only to add, that this re¬ 
paration, according to the recent experiments of Mr. 
Brodie, (Journal of Science, vol. xxviii.) depends en¬ 
tirely on the operation of the bile. 
To proceed, then, from this point. The firft queftion 
which naturally fuggefts itfelf is, How is this chyle car¬ 
ried into the circulation ? In the article juft mentioned, it 
was aflumed (on the authority of Hunter), that the laftenls 
and thoracic duft were the only agents that brought 
about this abforption. But late experimenters, particu¬ 
larly Majendie, have attempted to prove that abforption 
is not only performed by thofe veflels called lafteals or 
lymphatics, but alfo by veins. Their experiments have 
indeed been contradidted by fonie; on the other hand, 
they are fupported by fo many authorities, as certainly to 
fhake the Hunterian doftrine. At all events, we confider 
it proved, that, when the thoracic duft and its correfpond- 
ing lymphatic on the right are obftrufted, matters can be 
tranfmitted into the general circulation by the vena portae. 
But this, of courfe, does not prove that fuch is the regu¬ 
lar and natural paffage of the chyle. Again ; as far as 
regards the veins of the limbs, it is certain they have the 
power of tranfmitting poifons into the general circulation. 
This is proved by the following decifive experiment 
made by Majendie. He amputated the thigh of an 
animal, but kept up the circulation of the limb by intro¬ 
ducing tubes into the artery and vein. Then he placed 
poifonous matter in the cellular tifl'ue of the amputated 
limb; yet abforption took place, and the animal died. 
This queftion is much deprived of its embarraflment if 
we confider it under an extended view. Whatever 
veffels firft abforb, certain it is that the veins have the 
power (however acquired) of propelling the chyle when 
it is mixed with their contents. The vena cava carries 
forward that chyle which is received from the thoracic 
du£t; and this is in faff but an abforbent : hence we 
do not fee any thing furprifing in the faff: that a fmaller 
lymphatic may occafionally open direftly into a fmaller 
vein. Nor, fince we fee that veins in fome ftrudtures (as 
the corpora cavernofa penis) fuck up or abforb blood, can 
we be aftonilhed that they fhould exert this power on 
other fluids. Neverthelefs it cannot be granted that 
veins and abforbents are identical ftrudtures ; becaufe, as 
we have before ffiown, a power of changing their contents 
belongs to the former, which power is never obferved in the 
latter; and the minutenefs which feems to belong to abforb- 
ing veffels renders their exiftence fairly'’ inferrible in every 
fltuation where abforption has been met with. 
So far, however, from this opinion being general, the 
French phyflologifts exprefsly ftate their convidtion that 
abforption which they term imbibition, and exhalation 
which they term transudation, are merely the capillary 
attraction of tubes; and thatthis power is the fame before 
as after death. They have inftituted, in proof of this 
notion, a variety of cruel experiments, which go to fhow 
that matters injedted into the cavity of the abdomen, into 
the bowels, or into the cellular tiflue, pafs into the 
ftrudtures which are adjacent to them ; and further that 
this tranfmifflon goes on after death. Thefe experiments 
were quite unneceflary, becaufe, as far as regards the 
phenomenon in queftion in living bodies,difle£tions imme¬ 
diately after death might have difplayed them; and, that 
flefh abforbs by capillary attraction after death, any one 
might have learnt by confidering how copioufly fait is 
imbibed in the pickling of pork. 
With refpedt to the fluids contained in the abforbent 
vefiels, it is to be premifed, that thefe are of various kinds ; 
but the moft important one is that we have juft been 
fpeaking of, the Chyle. This fluid is formed equally 
w^ell from vegetable or animal food ; and it may contain 
flight heterogeneous mixtures without any ill confe- 
quences refulting therefrom. The chyle is perfect blood, 
with the exception of its colour, which leems to be 
acquired in the arteries or veins; fo that the converfion 
Vol. XX. No. 1373. 
O L O G Y. 
of food into blood chiefly takes place in the ftomach and 
duodenum ; the gaftric juice and the bile being the fecre- 
tions wdiich mainly bring about this important and fur¬ 
prifing change. 
The lower part of the bowels gives origin to the 
abforbents, which chiefly carry aqueous fluids. Ab¬ 
forption takes place, then, from the alimentary canal, the 
Ikin, and the lungs. But, befides thefe open parts, we 
have an interftitial abforption, which exilts in every 
ftrddture of the body, perpetually reducing into the blood 
the moft folid and diflimilar parts; fo that, as thefe are 
again fupplied by the fecernents, our whole frame under¬ 
goes frequent decay and renovation. But, whether fo 
often or fo generally as phyflologifts have aflerted, is not 
capable of demonftration. 
The curious faff, that abforption fcarcely ever takes 
place from the Ikin, unlefs this be abraded, might lead one 
to fuppofe, that the cuticle is not an abforbing furface, if 
particular cafes were not on record which plainly fhow 
the poflibiiity of cutaneous abforption ; and did not we 
fee that this phenomenon is eafily produced by fridtion. 
This laft fa ft was never well accounted for, till the 
ftruffure of the fkin was demonftrated to us by Mr. 
Chevalier (fee his “ Leftures on the General Struffure of 
the Human Body, and on the Skin in particular, 1814..”) 
This gentleman has (hown, that, though the fkin is not 
direftly perforated by pores, as was formerly fuppofed, 
yet that, in the delicate tubes, or furrows, which every¬ 
where abound in this ftruffure, a multitude of fmall 
tubes open in an oblique manner, of which fome are no 
doubt fecreting, others abforbing, tubes. Now, as thefe 
furrows are very minute and flender, we eafily infer that 
they do not admit extraneous matters until thefe are 
introduced into them by friftion, and fo immediately 
applied to the orifices of their abforbents. 
It is doubtful whether this aerial abforption which 
takes place in the lungs, is analogous to the funflions juft 
treated of; but, as it certainly belongs to the additions 
which the blood receives in its courfe, it fliould be 
defcribed here. The article Anatomy already contains 
a full account of the mufcular powers by which air is 
brought into the lungs: (fee vol. i. p. 612.) In that 
place it is Amply ftated, that, on the return of the air from 
the lungs, it is found altered, it being vitiated, or unfit 
to fupport combuftion; and, further, that this change is 
neceflary to the life of the animal. It is neceflary in this 
place to view the matter in a more detailed manner, and 
give a general hiftory of the conflicting opinions which 
are or have been entertained concerning refpiration. 
We fhall divide the confideration of this fubjeft into four 
heads. Firft, we fhall mention the quantities of air re- 
fpired. 2. We fhall defcribe the changes which chemiftry 
defcribes to have taken place in it. 3. The changes which 
are found to have taken place in the general mafs of 
blood, when fubjedted to this influence. 4. We lhall 
proceed to mention the inferences which may be derived 
from the preceding faffs. 
1. The bulk of air taken in at one infpiration has not 
been precifely determined. Borelli eftimated it at 15 
cubic inches, (de Mot. Animal.) Mr. Kite from 12 to 17; 
(Effay on Apparent Death, p. 24.) Dr. Goodwyn at 14 ; 
(Connedtion of Life with Refpiration, p. 28, et feq.) Mr. 
Davy from 13 to 17; (Refearches, p. 410 and 433.) and 
Drs. Jurine, Hales, Haller, and Sauvages, at 40 cubic 
inches. With the conclufion of thefe latter authors the 
accurate experiments of Dr. Menzies (on Refpiration 21) 
nearly coincide; and, as the methods which he adopted 
feem lefs liable to objeftion than thofe ot any other 
author, we may conclude with Dr. Boftock, that 40 
cubic inches is the quantity of air employed in an ordinary/ 
aft of refpiration. 
But there is great difficulty in arriving, by experiment, 
at certain concluflons reflecting the volume of air taken 
into the lungs in each infpiration; and this may arife 
from a difference in the ftate or capacity of thofe organs in 
4U different 
