Thes Fi TS TsOrrs ¥ 
happen not only in quadrupedes, but in birds 
and fifhes, but efpecially in the Wray-fifh; in 
the muicles of which there are very ftrong 
motions, when the nerves are irritated. 
On the foundation of thefe motions, which 
are produced in the mufcles, when their nerves 
are only difturbed or ftimulated, I determined 
to provoke the nerves of the entrails in the 
fame manner, in which I found very remark- 
‘able flefhy fibres. I had a mind to make the 
fame experiments on thofe nerves which reach 
to the kidneys, liver, {pleen, lungs, and genital 
organs; for I would fcarce prefume to affirm, 
that any remarkable contractions are produced 
in thofe parts, efpecially in the kidneys, by fuch 
irritation; and therefore one may penetrate 
much deeper, by that experiment, into the real 
ufes of thefe parts. But I have not yet been 
able to execute my purpofe, for want of time. 
It is therefore fufficient for me here to have 
hinted at thefe things in a few words, that 
others may have an opportunity of labouring 
further in the difquifition of them; for Nature 
muft be inveftigated by the joint labours of 
many. One man can make no great advance- 
ment in matters infinite. 
I beg leave to obferve here, that the motions 
of the mufcles, now mentioned, are not fo 
cconfiderable in animals which have warm 
blood, or rather they do not laft fo long, as in 
_ thofe that have the blood cold; as fith, and 
many other aquatic creatures, which have few 
or no feet, and in amphibious creatures in 
general. Hence I chiefly made my experi- 
ments on the Frog; for the nerves are very 
conipicuous in thefe animals, and may be 
eafily difcovered and laid bare. The {pinal 
marrow and the brain have this peculiarity in 
the Frog, that, like a fluid falt, they lie en- 
clofed in coats, and, being interwoven with 
blood-vefiels, are every where adjacent to them; 
fo that they are to be difcovered plainly even 
in the cavity of the vertebre, and in the fkull. 
The fpinal marrow glitters like pearl, and is 
difpofed, in the form of knots, all down the 
back, along the vertebre, where it appears 
very confpicuous. This native falt, mixed 
with an acid liquor, ferments very {trongly. 
Its fubftance anfwers very nearly to that gra- 
nulated and gravelly powder found in the head 
of the Shark, and fold in the fhops, and erro- 
neoufly taken by the ignorant, for the brain of 
the fifh; but this is nothing more than a ftony 
and gravelly fubftance, which is placed in the 
head of the Shark, as what is called the Perch- 
ftone is in the head of the Perch. I have like- 
wife found fuch a powder in the Wray-fith’s 
head, which fermented very ftrongly with an 
acid: and, therefore, I think that the alcaline 
falt, obfervable in the little tones called Crabs- 
eyes, is like this. But though that faline fub- 
{tance in Frogs is fluid, like water, it will not- 
withftanding be dried immediately by the heat 
of the hand or fingers ; but it never hardens 
to fuch a degree, but it may be very eafily re- 
duced to fine powder, with the tips of the 
fingers, The fame thing likewife holds with 
of +I NEES T.S. 123 
refpect to that calcarious fluid matter in the 
Wray-fith. Whether this falt has any medicinal 
virtue, I cannot yet fay; nor can it be known, 
except from experience. I return to the muf- 
cles. 
Another very delicate and ufeful experi- 
ment may be made, if one of the largeft muf- 
cles be feparated from the thigh of a Frog, 
and, together with its adherent nerve, prepared 
in fuch a manner as toremain unhurt. For if, 
after this, you take hold, Tab. XLIX. Fig. v. 
aa, of each tendon with you hand, and then 
irritate 6 the propending nerve with fciffors, or 
any other inftrument, the mufcle will recover 
its former motion, which it had loft. You 
will fee that it is. immediately contracted, and 
draws together, as it were, both the hands, 
which hold the tendons. This I formerly (in 
the year 1658) demonftrated to the moft illu 
trious the now reigning Grand Duke of Tuf- 
cany, when he gracioufly vouchfaied to pay me 
avifit. ‘This experiment may be repeated in 
the fame mufcle, as long as any part of the 
nerve remains unhurt; and we can thus make 
the mufcle contract itfelf, .as often as we 
pleafe. 
If we have a mind to obferve, very exadtly, 
in what degree the mufcle thickens in its con- 
traction, and how far its: tendons approach 
toward each other, we muft put the mufcle 
into a glafs tube, Fig. vi. a, and run two fine 
needles 64 through both its tendons, where 
they had been before held by the fingers ; and 
then fix the points of thofe needles, neither 
too loofe nor too firmly, in a piece of cork. 
If afterwards you irritate, Tab. XLIX. Fig. vi. 
c, the nerves, you will fee the mufcle drawing 
dd the heads of the needles together out of 
the places; and that the belly of the mufcle 
itfelf becomes confiderably thicker e in the 
cavity of the glafs tube, and ftops up the whole 
tube, after expelling the air. This continues 
till the contraction ceafes, and the needles then 
move back into their former places; and the 
belly of the mufcle, parting again from the 
tube, affords a free paflage for the air through 
its cavity. But if the mufcle be left to itfelf, 
or put into cold water, with all the apparatus 
juft now defcribed, we obferve it contracts it- 
felf by degrees not long after; and is finally 
fo remarkably bent, as to fill the whole cavity 
of the middle region of the tube. 
Having therefore duly confidered thofe expe- 
riments, which I have hitherto fet forth, and at 
the fame time attentively weighed the force of 
contraction or mufcular motion, which the mufcle 
re{umes every moment, when its nerve is again 
and again irritated: one may afk, whether any 
other communication be neceflary between the 
nerve and the mufcle, but only that fimple irri- 
tation on the touch or commotion? Butas a fimi- 
lar motion is likewife excited in the mufcles of 
animals which have hot blood, whofe nerves are 
ftimulated ; the fame queftion indeed may be 
likewife afked here, that is, whether in this clafs 
of animals alfo, any other communication be ne- 
ceflary between the brain and marrow, the nerves 
aa and 
