292 ESSAYS AND OBSERVATIONS 



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 off a frog's head and deftroyed 

 the fpirial marrow with a hot wire, then laid 

 open its thorax and abdomen j and immerfed 

 it in a folution of opium at nineteen minutes 

 paft eleven. Eight minutes before twelve, 

 i. e. thirty three minutes after immerfion, I 

 obferved its heart beating very flowly : but 

 two minutes before twelve, when I took it 

 out of the folution of opium, it had no mo- 

 tion. After, this I opened the pericardium, 

 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 folution for five minutes more, 

 and, upon taking it out, found its heart quite 

 dead. 



13. After cutting off a frog's head and 

 deftroying its fpinal /narrow, I laid open its 

 whole abdomen, and immerfed it in a folution 

 of opium, twenty three minutes before one. 

 After it had lain Jixteen miitutes, I cut up its 

 f/fordx and pericardium ; and obferving the 



heart 



