1893.] On the Physiology of the Embryonic Heart. 465 



of muscarine poisoning, and the application of atropine failed to re- 

 store the rhythm. Probably any strongly alkaloidal body in such a 

 concentrated solution would produce a similar effect. 



i. Schmiedeberg' 's Digitalin. An embryo aged seventy-two hours at 

 30 C. had a heart rhythm of 132 per minute. To it 1 c.c. of normal 

 saline containing 0*000022 gram of digitalin was applied. During 

 the next eleven minutes the rhythm remained constant, after which 

 time 1 c.c. containing 0*00005 gram was added, which produced no 

 change in the rhythm ; then 0*0001 gram was put in, and after one 

 minute's action the frequency of the rhythm had fallen to 92 per 

 minute, but both the systole and diastole were strong. The rhythm 

 after six minutes' action rose to 104 per minute. After this another 

 O'OOOl gram was added, and the rhythm fell after two minutes' action 

 to 50 per minute. Tjie systole was typically perfect, but the diastole 

 was incomplete. The whole heart after two minutes' more action of 

 the drug became very pale and in a state of tonic contraction with 

 very feeble fluttering diastoles, which faded away, leaving the heart 

 stopped in a contracted condition. 



j. StropTianfhin (of Merck's manufacture). A seventy- two hoars' 

 embryo at a temperature of 32 C. had a heart rhythm of 132 per 

 minute. A dose of 0*00006 gram did not alter the rhythm. A 

 second dose of the same amount after twenty minutes' action reduced 

 the rhythm to 54 per minute ; both systole and diastole were regular 

 and complete. Five minutes after this the diastole became irregular, 

 and the systole was more marked than in the normal condition. 

 After another minute had elapsed the ventricle passed into a state of 

 tonic contraction with a few feeble beats, in which the diastole was 

 very weak. The auricles had a marked diastole and a weak systole, 

 and were engorged with blood. During the next five minutes the 

 auricle had a rhythm averaging 24 beats per minute, while the ven- 

 tricle remained in tonic contraction. Finally, forty-one minutes after 

 the administration of the dose the auricle stopped in diastole, the 

 ventricle remaining in tonic contraction. The auricles responded by 

 10 beats to a mechanical stimulus ; the beats did not extend to the 

 ventricle. Six minutes after this the auricle responded to mechanical 

 stimuli, the wave of contraction passing either from the ventricular 

 end to the auricle or vice versa, according to which end of the auricle 

 the stimulus was applied. 



In larger doses of 0*0002 gram the rhythm in a seventy hour 

 embryo at 33 C. was depressed from 120 to 102 per minute, the 

 systole becoming very strong and the diastole imperfect. After four 

 minutes' action the rhythm returned to the normal both in frequency 

 and force. To the same embryo 0*00025 gram was then added, when 

 after one minute's action the auricle dilated, giving small twitch-like 

 contractions, while the ventricle passed into tonic contraction. The 



