318 ESSAYS anp OBSERVATIONS 
10. I laid open the whole abdomen of a 
larger frog than any of the former; and, 
at twenty two minutes paft ten in the 
morning, immerfed it in a {olution of o- 
pium, as above. ‘1 hirty five minutes af- 
ter immerfion, .I took it out ot the folu- 
tion, and opened its thorax and pericardi- 
um. ‘The heart was vaftly red and much 
{welled, and its auricle greatly diftended 
with blood ; but both were without any 
motion: After two minutes, however, the 
heart began to vibrate at great leifure, 
{carcely performing nine pulfations in a 
minute; but the overitretched auricle 
made not the {fmalleft motion. During 
every /yfiole, the heart was remarkably 
paler, and, in the time of its relaxation, be- 
came much redder; which phenomenon I 
obferved likeways in all the frogs hearts in 
the above experiments, but more remark- 
ably in thofe frogs who had-been expofed 
to the action of opium. Another thing 
which i remarked in all thefe experiments, 
was, that the heart, during its /y/tole, be- 
care manifeftly fhorter, and was length- 
ened in the time of its relaxation. But 
te 
