994 



The first descending part in such a complex was generally inter- 

 rupted bv a few short waves, after which the descent became 

 regular. The ascending part was less steep and ended in a blunt 

 summit. Before this last wave sometimes a small intermediate wave 

 could be detected. 



About 10 minutes later between the regular complexes as described 

 above, other anomalous ones appeared, of a much longer duration. 

 The number of these grew, and the form tirst ol)served disappeared 

 entirely. A\ last the tracing showed merely a series of conti- 

 nuously changing, very abnormal complexes. 



It is difTicult to explain these tracings. We know of course that 

 they are related to extremely abnormal circumstances. We have 

 before us a heart, very im|)erfectly developed, the halves of which 

 freely communicate, the ductus Kotalli still being largely open. 

 An embryo with such a heart is asphyxiated without the possibility 

 of a normal large or small circulation, as at the same time the circu- 

 latory system is entirely void of blood, and the heart cannot pump 

 any other tluid into the |)lacentary or proper circulatory system. The 

 consequences are not, even approximately, to be foreseen. We can 

 only consider one or two points. 



The normal stimulub for the heart starts near the right venous 

 sinus. Hut in the long run this necessitates the presence of blood 

 in the vessels. If this is and remains absent, the sinus node stops 

 its work. In «uch a case other parts of the auriculo-ventricular 

 bundle may temporarily continue the w^ork. In the embryo n". 3 

 we tind the evidence, that this occurs alternately in the left and right 

 part of the bundle, and later on only in the left part. The result 

 is a ventricular automatism. At last the left part of the bundle also 

 breaks down, but at this moment the overworked muscle contains 

 so much fatigue-products as to cause a "diathèse de contracture", 

 and to produce idiogonetic irregular ventricle contractions, originated 

 in the muscle-substance itself without ths aid of the bundle of His- 

 Tawara. In the larger second embryo, with the exposed heart these 

 irregular spasmodic contractions occurring at the same time as the 

 lengthened complexes could easily be seen. 



If the complexes produced by the second embryo may be con- 

 sidered as to be caused by a temporary ventricular automatism, the 

 small waves in the commencement of the first descending part of 

 the wave may be taken as recurrent auricular waves. As these 

 commence about the same time as the ventricular complexes, the 

 starting point of the stimulus ought to be situated not in the ven- 

 tricle itself, but somewhere between the auricle and the ventricle. 



