£96 ESSAYS AND OBSERVATIONS 



a little, by a very faint kind of motion which 

 was excited in fome of its fibres. 



19. At thirteen minutes before twelve, I 

 cut out the heart of a fixth frog, and immer- 

 fed it in a folution of opium. Six minutes 

 after immerlion, it had no motion ; but 

 when pricked, made one pulfation. After 

 lying five minutes more in the folution, it 

 was quite dead. 



20. I cut out the heart of a fevfenth frog, 

 and at thirty feven minutes paft nine in the 

 morning, immerfed it in a folution o( opii/m, 

 as above. Forty two minutes after nine, 

 when I took it out of the folution, it was 

 without motion : but when touched with 

 the point of a knife or probe, it performed 

 one contraction, but with lefs vigour and 

 more llowly than the heart of N° 14. 

 Forty feven minutes paft nine, it began to 

 beat of its own accord. Two minutes after 

 this, it moved 6 times in the minute, but 

 much more feebly than N° 14. Six minutes 

 before ten, it beat only 4 times in a minute : 

 after this, it began to beat much fafter ; but 

 its motions foon returned to their former 

 llownefs. At ten, after having lain near a 

 minute without motion, it began again, of 



its 



