g24 ESSAYS anp OBSERVATIONS 
into a proper contraction, 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. r 
18. I cut out the heart of a fifth frog, 
and put it into a folution of opium in wa- 
ter five minutes before eight. After fe- 
ven minutes 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 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 
immerfed it in a folution of opium. Six 
minutes after immerfion, it had no mo- 
tion; but, when pricked, made one pulfa- 
tion. After lying five minutes more in 
the folution, it was quite dead. 
20. I cut out the heart of a feventh frog, 
and, at thirty-feven minutes paft nine in 
the morning, immerfed it in a folution of 
opium, as above, Forty-two minutes after 
nine, 
