C 68 ] 
once between the mufcular Cells and the interftitial 
Air, no more than a pendulous Body can ceafe at 
once, after having been fwung beyond its Point of 
Reft. The Reafon is, that 2s long as the Heart re- 
mains warm, the elaftic Force of the interftitial Air, 
and that of the inflated Cells , will have the fame 
alternate EfFed upon each other, till the external 
Cold, and Want of the gradual Supply of the inflating 
Matter, caufe the Adion and Re-adion to become 
unequal, and fo by degrees fix both : But, when the 
Motion ceafes, it may be again excited for a little 
time by Pricking. This feems* to make a new Im- 
pulfe on the Matter yet remaining in the mufcular 
Cells, which, ading by their Expanfion, will com- 
prefs the interftitial Air, and receive a Repulfe from 
it for a few times faintly : But this Experiment will 
not anfwer, when the Heart is quite cold j but then, 
if warm Water be pour’d on it, there will be Motion 
again excited. This happens, becaufe the interftitial 
Air, before condenfed by the Cold, is now inftantly 
rarefied and expanded, and therefore prefies the muf- 
cular Cells ; which alfo being warmed, the remain- 
ing inflating Matter will exert itfelf in its turn, and 
fo continue an alternate Motion for a few times, till 
the Heart grows cold again. But this Experiment 
will not often anfwer 5 becaufe, altho’ the fame in- 
fccrftitial Air remains, it is a Doubt whether the Mat- 
ter of the Cells does not exhauft by degrees - 3 in which 
Cafe there can be no more Re-adion. I have two 
or three times obfdv’d, when the Skin of an Ox has 
been taken off, the mufcular Fibres continued to 
move in Spafms, and ceafed at Intervals 5 -then re-af- 
funied their Motion, going on thus till the whole 
Surface; 
N 
