290 ESSAYS AMD OBSERVATIONS 



move, but more feebly than the auricle 



of N° 5. 



10. I laid open the whole abdomen of a 



larger frog than any of the former ; and, 

 at twenty two minutes pad ten in the morn- 

 ing, immerfed it in a folution of opium, as 

 above. Thirty Jive minutes after immerfion, 

 I took it out of the folution, and opened its 

 thorax and fericardium. The heart was 

 vaftly red and much fwelled, and its auricle 

 greatly diftended with blood j but both were 

 without any motion : after two minutes, 

 however, the heart began to vibrate at great 

 leifure, fcarcely performing nine pulfations in 

 a minute j but the overftretched auricle 

 made not the fmalleft motion. During e- 

 vtvyfyjlole, the heart was remarkably paler, 

 and in the time of its relaxation became much 

 redder j which ■phcenometion I obferved like- 

 ways in all the frogs hearts in the above ex- 

 periments, but more remarkably in thofe 

 frogs who had been expofed to the adion 

 of opium. Another thing, which I remark- 

 ed in all thefe experiments, was, that the 

 heart, during lis Jyjiole^ became manifestly 

 fliorter, and was lengthened in the time of 

 its relaxation. But to return \ at fix minutes 



paft 



