202 INTERNAL SECRETION 



only. These results led Gottlieb to the conclusion that supra- 

 renal extract is a powerful stimulant of the vaso-motor ganglia of 

 the ventricle. 



The question as to whether the effect produced by adrenalin 

 upon the heart represents a direct muscular action, or is due to an 

 affection of the sympathetic nerve endings which reaches the 

 heart by way of the nervi accelerantes, has formed the subject of 

 much recent discussion. The following results are advanced as 

 evidence in favour of the latter hypothesis. 



According to Elliott, the cardiac action of adrenalin is not 

 observed in all animal species. The heart of invertebrates, as 

 the crab, does not appear to react to it in any way. 



Gaskell's experiments go to show that, in the heart of turtles 

 and birds, the auricle is provided with augmentary fibres, while 

 the ventricle possesses neither stimulatory nor inhibitory fibres. 

 Elliott found that, in the turtle, the effect of adrenalin is to 

 strengthen and accelerate the contractions of the auricle only, 

 the ventricle remaining entirely unaffected. When the heart is 

 undamaged, the acceleration probably affects the ventricular 

 rhythm only, though this has the effect of shortening the contrac- 

 tions. The isolated hearts of birds (pigeons) become very much 

 stimulated if adrenalin is added to the fluid circulating through 

 them. After separation of the auricles, the ventricular beat is 

 suspended for a time and adrenalin produces no effect upon the 

 activity of the ventricles, but portions of the auricle respond to 

 the action of adrenalin by accelerated contractions. As a general 

 rule, those parts of the heart react more readily to adrenalin which 

 are innervated, either wholly or in part, by the sympathetic 

 system ; thus the auricles react better than the ventricles. 



The effect of suprarenal extract upon the hearts of fish is to 

 produce a much stronger contraction of the ventricles. This is 

 clearly shown in the experiments which I carried out in 1899 with 

 the object of finding the curve of the cardiac activity of torpedoes. 

 The rhythm of the heart when in situ is rather retarded than other- 

 wise. The blood-pressure, which was taken at a branchial artery, 

 rose to very nearly twice the normal figure. A similar effect was 

 obtained with extract of the suprarenal bodies of animals of the 

 same species. 



By means of experiments with isolated hearts, Gatin- 

 Gruzewska and Maciag have recently discovered that the hearts 

 of cold-blooded animals are much less sensitive to adrenalin than 

 those of warm-blooded animals. The effect of adrenalin upon the 

 former is to increase the duration of systole and this is followed 

 by a slowing of the rhythm ; while in the case of hearts taken from 

 rabbits, the use of minimal doses is followed by stronger and 

 more rapid contractions. 



In the case of the embryonal heart, the effect of adrenalin 

 seems to depend upon whether or not it possesses a separate 



