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78 O B S E R V A T I O N S ON THE
C H A P T E R XXV.
Whether the Nerves convey the Nouriihment to our Organs.
"T^HREE chief arguments have been employed by thofe who of late
have maintained that the nourifliment is conveyed by the nerves.
1. They pretend that the brain exifts before the heart.
2. That the limbs ilirink in the palfy, becaufe the nerves are fo difeafcd
as to be incapable of conveying the nouriÎhing fluid.
3. They fuppofe that a fecreted fluid is not fufficiently fubtile and moveable
for the purpofes of fenfe and motion, and, therefore, conclude that
the fluid which they admit the brain fecretes, mull ferve the only remaining
purpofe of nutrition.
BUT, on the firil of thefe propofitions, that the brain exifts before the
heart, I would obfcrve,
1. That it is contradi£ted by DrHaller, who, after the moft accurate obfervations
which have been made on that fubjedl, concludes, that there is
merely an evolution of the parts of the foetus, without the addition of any
new part
In
• Haller, Op. Minor, Tom. II. c, xv. p. 407. fays, « Didici ea ipfa exempla quae credebam refutare
' evolutionem, coiilirmare quam maxime Nihilque quidquam novi nafci.'
N E R V O U S SYSTEM. 79
In the egg, at the end of 38 hours from the beginning of incubation, he
could perceive the heart projeaing from the breaft; and, at the end of 45
hours, he could diftinguilh its auricle, ventriclc, and aorta, their motion, and
the blood beginning to grow red : And he obferves, that its parts and their
motion were not fooner diftinguiihable from their fmallnefs and pellucidity
only* To confirm wliich, we may obferve, that the lungs and other organs,
when firft obferved, were of fuch fize that they might eafily have
been feen long before, if they had not been pellucid But the head was
not diftinguiihable till the 41ft hour, the eyes not till the 51ft, at the
120th hour the brain was watery, and, fo late as the i68th hour, looked
like mucus; and, at the 131ft hour, fpontaneous motion of the foetus was
firft obferved J.
2. Nay, independent of the actual obfeiwation of Dr Haller, does not
the error of fuppofing the heart and veffels to be wanting whilll the animal
is growing, appear manifeft, if we alk ourfelves the following plain queilions;
Plow has the brain itfelf, from being fo fmall as to be invifible,
grown fo large as to be vifible ? By what channels did it receive its own
nourifliment? Or, by what means did the liquor, fuppofed to have been
conveyed by the nerves to other organs for their nourifliment and growth^
make its way into thofe nerves ? Are we to fuppofe the brain and organs
of
• Haller, Op. Min. Tom. II- c. ix. p. 369. 410. Cordis in univerfum primum veftigium vidi hora
38 rotundum aliquid depeitore eminens. Dein hora 42 et cor vidi et aortam et motum fanguiliis
rubiginofi ex corde. Hora 45 tres veficulas vidi et earum micationem, ut prima auricula fubfilirec,
inde ventriculus, demum aortae bulbus. Si cordis motus non prius oculis ufurpari poteft, caufa eft in
parvitate et pellucida natura ejus particulae. Non certe ideo nuUus in eo organo ante eum diem motus
fuit, cum ab ejus unica vi celerrimum incrementum primi diei pendeat.
-j- C. X. Pulmones. ' Primum mihi adparuerunt 120 hora .
' tuilTent confpici, nifi pellucidi fuiflent.'
n ita parvi, quin eüam prms po-
I H<.ller, Op. Min. Ovum 48. Horarum 41. Caput diftinguo, p. 412. ' Evolvuntur 0culi hora 51.
p. 361. ' Hora 120. Cerebrum aquofum. p. 361. ' Hora 131. Foetus primum motu fpon-
' laneo fe concuflit. p. 362. ' Hora ió3. Cerebrum mucofum ftiit.