903 



The firs! onibrvo gav(> ojily a few rather poor Iracings. t suppose 

 that its early stage of development, tlie effects of the shaking during 

 transpoi't and perhaps of a change of teniperatui-e may have been 

 the cause. From the second and third embryo 1 got a series of 

 satisfactory tracings. 



I may be allowed to show first the tracings from the last embryo, 

 whicli were obtained on a plate moving 20 mm. a second, an en- 

 largement of 1100 times, and a string of liigh resistance and sensi- 

 bility adjusted to a 30 mm. deflection for 1 millivolt. 



Looking at the tracings we immediately see that the heart action 

 was not entirely regular. The interval between two contractions is 

 not eqnal. The complexes occurring with every heart-beat also 

 showed a notable difference. In the first tracings we see two different 

 forms, alternating regularly. A little later an intermediate form 

 occurs a few times and in the last negatives we see only one of 

 the first complexes. As a point of interest we note the complete 

 absence of waves which might be identified as P- waves. 



The different complexes bear a decided resemblance to heteroge- 

 netic complexes occurring after stimulation of the right and left 

 ventricle. A contraction showing the form of a Z)-complex in which 

 there is a lesion of the right bundle, is followed each time by a 

 complex of the ^-type, where the contraction is caused by stimu- 

 lation of the right bundle or the right ventricle. 



Already in the fourth negative we see S-complexes which are 

 not followed by an ^4-complex. In the 5^^ negative we find for the 

 last time two complexes slightly resembling ^-types, but with a 

 much smaller amplitude and a few particulars that cause them to 

 be considered as intermediate or 6-types. After this we see only B- 

 complexes with a very slowly decreasing amplitude. The last tracings 

 become very irregular and show many small anomalous complexes 

 of different types. 



In the second embryo, measuring 26 centimetres, the thorax had 

 been opened by Prof. ' Treub, who was in doubt if the heart was 

 still beating. Here the contractions came in groups of 10 — 20 or 

 even 2 — 5 single beats, in the same way as was seen with chicken 

 embryos. 



The curves were traced with a velocity of 25 mm. per second ; 

 the sensibility was adjusted at 10 mm. per millivolt. 



All the contractions showed atypical complexes of the B-fovm 

 starting witli a descending curve, rising afterwards. Generally the 

 first contraction in a group was a rather small one, the next ones 

 being somewhat larger. The groups ended abruptly. 



