PHYSICAL AND LITERARYi 295 



unlefs that, when pricked with the point of 

 a knife, it gave one very faint pulfation. At 

 forty feven minutes paft eleven, it was quite 

 dead. 



17. I cu,t out the heart of a fourth frog, 

 and at thirty minutes paft ten immerfed it in 

 a turbid folution of opium in water of the 

 fame degree of heat with the fountain- water 

 ufed in the three laft experiments ^^. After 

 this heart had been immerfed ten minutes, 

 1 took it out of the folution, and laid it on a 

 table, but it made not the fmalleft motion ; 

 and when pricked with the point of a knife, 

 tho' it quickly recovered its fhape, yet it was 

 not excited into a proper contradion, as the 

 heart of N° 14. I continued to obferve this 

 heart from time to time for more than half 

 an hour, but it never made the leaft motion. 



18. I cut out the heart of a fifth frog, and 

 put it into a folution of opium in water 

 five minutes before eight. After feven mi- 

 nutes immerfion, I took it out, and laid it 

 on a plate, where it remained at reft. When 

 pricked with a knife, it did not perform a 

 full pulfation like N° 14. but_ feemed to feel 



a 

 * Vix. Neaily fixty degrees of i^«ir^«j&«V's thermometer. 



