464 



Mr. J. W. Pickering. 



[Jan. 26, 



saline was a stimulant; with 1 c.c. the frequency and force of the 

 heart diminished, systole becoming almost absent, while the heart was 

 finally paralysed in diastole. The addition of 0'03 gram of potassium 

 chloride restored the heart to almost its normal rhythm, the beats at 

 the same time becoming strong, both as regards systole and diastole. 

 A farther dose of nicotine depressed the heart, and again brought it 

 into diastolic stoppage, the systoles having become weaker and weaker. 

 There was no spasm. 



~ Atropine. Doses of O'OOl gram had, in a sixty hours' embryo, a 

 slightly depressant effect, and even after O'OOG gram had been ad- 

 ministered, the rhythm of the heart had only fallen from 96 to 72 

 per minute. In a seventy-two hours' embryo, with a heart beating at 

 116 per minute, 0'012 gram, after three minutes' action, had de- 

 pressed the rhythm to 80 per minute, while even after the administra- 

 tion of 0'275 gram the rhythm was strongly maintained at 64 per 

 minute. 



h. Muscarine Nitrate. To the heart of a seventy-two hours' embryo 

 at 35 C., which was beating with a rhythm of 90 per minute, 3 drops 

 of half saturated solution of muscarine nitrate were applied; the 

 rhythm remained constant for two minutes, after which period 2 

 more drops were added, and the rhythm kept constant at 94 per 

 minute during the next three minutes, after which period 4 more 

 drops were added, and the ensuing rhythm was 93 per minute; 

 2 drops of saturated solution were then added, which was so concen- 

 trated as to stain the embryo brown. During the following five 

 minutes the rhythm was constant at 84 per minute, each beat remain- 

 ing normal in direction and force. Two more drops of saturated solu- 

 tion caused slight irregularities, but the rhythm during the next seven 

 minutes averaged 72 beats per minute. Finally 2 more drops of satu- 

 rated solution were added, and during the following seven TniTmf.es 

 the heart's rhythm was 75 per minute. The whole experiment lasted 

 thirty minutes, and 10 drops of half saturated plus 9 drops of 

 saturated solution of muscarine nitrate were administered. A con- 

 trol experiment with the hearts of two frogs showed that the musca- 

 rine used stopped their beats, which were typically restored by atro- 

 pine. In a similar experiment, witnessed by Professor Halliburton, 

 with both embryonic and frogs' hearts, the rhythm of the former was 

 maintained at 136 per minute, while the latter was stopped and sub- 

 sequently restored by atropine. Identical results were obtained with 

 u ninety-six hours' embryo. In an embryo aged seventy hours at a 

 temperature of 30 C., which is subnormal in the chick, a rhythm of 

 92 beats was obtained after the application of 1 c.c. of half satu- 

 rated solution for the following nine minutes, after which 1 c.c. of 

 saturated solution was applied. This was fatal to the heart, almost 

 instantly coagulating the tissues. There were no typical phenomena 



