46(5 On the Physiology of the Embryonic Heart. [Jan. 26, 



auricle remained for six minutes feebly responsive to mechanical 



stimuli. .. , ot , .~ 



k Nitrite ofAmyl.A. ninety-six hours' embryo kept at 35 C. was 

 subjected to the influence of the vapour of 5 minims of nitrite of 

 amyl After one minute's action the rhythm rose from 96 to 124, and 

 after another minute fell to 112. After another minute it had fallen 

 to 104 and six minutes afterwards was at the normal. In a seventy- 

 two hour embryo at a temperature of 47, the rhythm was 124 per 

 minute. A dose of 1 c.c. of solution of amyl nitrite dissolved in 

 olive oil (strength being 1-5 c.c. of the drug to 10 c.c. of olive oil) 

 was given, and the frequency of the rhythm fell in one minute to 112, 

 but the beats were strong. Six minutes afterwards another c.c. of 

 the solution was introduced, and the rhythm fell to 104, but was 

 strong. Three minutes later another c.c. was put in, and the rhythm 

 rose to 112, but was very weak and irregular, and finally before death 

 the rhythm was reversed. 



Concluding Remarks. 



The observations here recorded show that the embryonic heart when 

 kept under favourable conditions reacts in a very delicate manner to 

 all those classes of stimuli which influence the adult heart. The ex- 

 periments on temperature show that its variations act directly on the 

 cardiac muscle, and thus confirm the opinion of Newell Martin* and 

 others who have arrived at the same conclusion from experiments on 

 the adult heart. 



The action of caffeine, morphine acetate, potassium chloride, vera/- 

 trine, nicotine, digitalin, strophanthin, and amyl nitrite is direct on 

 the contractile tissue of the embryonic heart. This greatly favours 

 the view that they act direct on the adult cardiac muscle. It will be 

 noted that many of the actions here described on the embryonic heart 

 are almost identical to those observed by others on the adult heart. 

 Notoriously so is the antagonism between veratrine and potassium 

 chloride, where my observations are identical with those of Kingerf 

 on the frog's heart. A similar antagonism exists between nicotine 

 and potassium chloride. The remarkable correspondence of my re- 

 sults with strophanthin on the embryonic heart with those of Pro- 

 fessor FraserJ on the frog's heart greatly supports the view of that 

 observer as to the direct action of strophanthin on cardiac muscle 

 without the intervention of any nervous mechanism, and, further, the 

 absence of diastolic stoppages in my experiments also supports 

 Eraser's view that that condition in the frog's heart is due to the 



Newell Martin, Phil. Trans.,' 1883, p. 663. 

 t Einger, ' Practitioner,' vol. 30 (1883), p. 17. 



t Fraser, 'Edinburgh Koy. Soc. Trans.,' vol. 36 (1890-91), Part II, p. 388, 

 et seq. 



