294 ESSAYS AND OBSERVATIONS 



15. Twenty three minutes pail twelve, 



I cut out the heart of another frog, and put 

 it in fountain-water. After twelve minutes 

 immerfion, I took it out of the water, when 

 it beat above 20 times in a minute. Having 

 put it in the water for five minutes more, 

 it ceafed from motion, and when taken out, 

 did not move except when pricked, and then 

 only performed one pulfation. 



16. Eight minutes paft eleven, I cut 

 out the heart of a third frog, and put it into 

 fountain-water. Eleven minutes after im- 

 merfion its heart beat 8 times in the mi- 

 nute, and four minutes after this it vibrated 



I I times in thirty feconds j but the motion 

 was confined to about one third part of the 

 heart next its apex. Twenty minutes after 

 immerfion, it continued to move much in 

 the fame way; but in two minutes more, 

 obferving no motion in it, I took it out of 

 the water, and laid it on a table, where it 

 remained at reft, unlefs when touched. Soon 

 after this, however, it began to move ; and 

 at twenty five minutes after immerfion, it 

 made 9 pulfes in fixty three feconds. Four 

 minutes after this, it moved only thrice in 

 fifty feconds, and then ceafed altogether; 



unlefs 



