320 ESSAYS AnD OBSER VATIONS 
cut the heart out of the body, and laid it 
on a plate, when ‘it gave two or three pul- 
fes. and never after moved, tho’ it was 
pricked once and again with a pin. 
No motion was produced in any of the 
other mufcles of this frog, by irritating 
them. 
12. I cut offa frog’s head and deftroyed 
the fpinal marrow with a hot wire, then 
laid open its ¢horax and abdomen, and im- 
merfed it in a folution of opium at nine- 
teen minutes paft eleven. Eight minutes 
before twelve, i. c. thirty-three minutes’ 
after immerfion, I obferved its heart beat- 
ing very flowly: But two minutes before’ 
twelve, when I took it out of the folution 
-of opium, it had no motion. After this I 
opened the fericardium, and irritated the 
heart two or three times with the point of 
a fcalpel, which always produced a few 
pulfations. I then put the frog in the fo- 
jution for five minutes more, and, upon 
taking it out, found its heart quite dead. 
12. AFTER cutting off a frog’s head and 
deftroying its {pinal marrow, I laid open: :. 
its whole abdomen, and immerfed it in a 
folution — 
