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36 OBSERVATIONS ON THE L YMPHAT IC S
ter, but ferve alfo to take in from the air, wliich is mixed with the water,
fomewhat neccffary for life ; the precife nature of which, experiments do not yet
enable us to fpecify.
We may, however, obferve, that the colour and quantity of the red particles
of the blood, and the heat of animals, are connedted with the mode of their refpiration;
and that it is as conceivable that the craffamentum of blood immerfed
in ferum and inclofed in a bladder, or that blood circulating in the lungs of a
living animal, may receive or attrad fubtile matter from the atmofphere, as
that it may difcharge fuch into it.
C H A P T E R VI.
OBSERVATIONS on the LYMPHATICS of the SPLEEN in FISHES,
and on the USES in general of that ORGAN.
^ I "^HE late Mr Hewfon revived a very laudable attempt to afcertain by expe-
1 riments the itru£ture and ufes of the fpleen. He has defcribed certain
minute cells in the fpleen unknown to former authors, and fimilar cells in the
lymphatic glands.
In a former work, he had reprefented the red particles of the blood as confiiting
each of a central part or nucleus included in a veficular, together forming
a flat body, the ihape of which he compares to that of a ihilling. He contends,
that the cells of the lymphatic glands form the central parts, and tliat
thofe of the fpleen add the veficular.
His arguiticnts are^'nti'iii'erou», a.nd his concluiions are drawn with an air of
demonilration: Yet I ihall endeavour to prove, that neither his conclufions, nor
the fails on which they are founded, ought to be admitted.
1. It is perhaps not a little queilionable, whether two idnds of red particles
are diftinguilhable in the blood of living animals, very different from each other
in fize and iliape, to wit, the central, and what he calls the full formed flat
particles.
2. The appearance of cells in tlie lymphatic glands and fpleen I am well convinced
proceeds from an optical deception, of which Mr Hewfon had no fufpicion;
for I have found, that any organ of the body exhibits that appearance as
readily as thofe glands or the fpleen: nay, Mr Hewfon and Mr Falconer have
reprefented the particles of the blood about fixty times the fize of thofe cells,
within which, however, they pretended thefe particles are contained (5-).
3. Mr Hewfon tells us, that many central particles are to be feen in the
blood convcycd by the fplenic artery, but none in the blood of the fplenic vein;
whereas
(7) Sec: 1117 ObferTaiions on ihe Ncrvoos Syllcm, p. 73.
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o r THE S P L E E N F I S H E S . if
whereas I have not been able to difcöver any difference of particles in the fplenic
artery and vein either in a pig or in a ikate. Indeed in both, all the red particles
appeared to me to be uniform in fize and lhape.
4. Mr Hewfon tells us, that the blood of the fplenic artery coagulates readily,
but that of the fplenic vein fcarcely at all; hence he infers, that the lymphatic
part of the blood conveyed by the aitery is converted into the veficular
part of the red particles. But although I think I have obferved that the blood
of the vena portarum is lefs frequently coagulated, or fomewhat lefs difpofed to
coagulate, than that of the venae cavse, yet I cannot perceive that the blood from
the mefenteric veins differs fenfibly from that of the fplenic vein.
5. But his great argument, and which may be confidered as his argumentum
crucis, is, that the lymphatic veffels of the fpleen in living animals have been
obferved to contain the red particles of the blood completely formed. They
are therefore confidered by him as duds from the cells: and it is fuppofcd that
this circumftance as fully eftabliflies the ufe of the fpleen, as the finding bile in
the hepatic du<fl fliows the function of the liver (r).
As a full confutation of this noted argument, I muft point out three plain
fads.
Firft, That the lymphatic veffels of the fpleen are nowife remarkable for their
number or fize.
Secondly, That when the fpleen and its lymphatic veffels in a living animal
are firft laid in view, their contents are pellucid; and they only receive red particles
fome time after they have been expofed to the air.
The third fail, which I learned from repeated experiments many years be-*
fore Mr Falconer's book was publiihed, and which I mentioned in my leftures,
is. That the lymphatic veffels of any deep-feated organ, whether in the thorax
or abdomen, fimilarly expofed to the air and irritation, take up red particles.
Hence after opening the cavity of the abdomen of a livinir animal, and fome time
thereafter the upper end of the thoranV Jai!t, I have found many red particles
mixed with the contents of that duct. To inveftigate all the caufes of this fa£t
would be foreign to our purpofe: but one caufe readily preftnts itfelf; I mean,
" that the application of the cold air irritates and inflames the deep-feated organs
; and in confequence of the inflammation, there is an effufion of the red
matter of the blood into the cellular membranes, whcnce it is taken up by the
abforbent lymphatics; wliich too, affcded by the irritation, muft be fuppofed
to abforb with more than common vigour.
6. In fifties, and particularly in the flcate, Mr Hewfon has reprefented the
red particles of the blood much larger than in man ; and of courfe the cells of
the fpleen, in which thefe are faid to be completed, ought to be very eafily feen
with the microfcope: but this I have not found to be the cafe. Neither in two
or three ikatcs in which the circulation of the blood was going on, though in a
languid way, could I perccive any red particles in the lymphatics of the fpleen;
K whicli
(r) See M.Fidccn« on the Blood, Stc. feft, 103.
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