( 681 ) 
The following grounds may be adduced for this, partially borrowed 
from my experiments: 
1. P always appears with a definite interval of time before the 
mechanical change of the atria. 
2. P continues existing at the registration of an isolated atrium 
(Rana, Emys). 
3. P is absent when the electrogram is written of the isolated 
heart-ventricle of Anguilla vulgaris. 
4. P continues existing when a certain detraction of the ventricle 
does not show itself. This may be observed both in the patho¬ 
logical heartblock and in the heartblock called into existence 
by experimental causes, among others: 
a. by stimulating the N. vagus in the dog or the tortoise. 
b. by administering toxical materials like chloroform. 
c. by forming, resp. removing a ligature on the boundary of 
auricles and ventricles in Rana. 
5. P may be made to disappear temporarily, when in appropriate 
sample-objects a heartblock is brought about by stimulating 
. the N. vagus at the transition of the sinus to the atria, with 
which, it is true, the sinus-contractions are preserved, but the 
atrium-contractions with top P in the electrogram disappear. 
6. P does not arise from the sinus, witness the fact that a small 
top may be registrated before the appearance of top P, which 
* may be attributed to the sinus. 
7. Size and form of P depend upon the way in which the 
atrium is derived. 
If we consider the electrocardiogram of man and animal super¬ 
ficially, we get the impression that P has a very simple form. Under 
quite peculiar circumstances this shape has been seen to alter. On 
closer investigation, however, it has appeared to me that the electric 
phenomenon of auricles is practically a whole complex. This becomes 
clear at the registration of an isolated pulsating atrium. Yery fit for 
this purpose is one of the auricles of the heart of Emys. 
Thus the adjoined figure 1 renders the electrogram obtained by 
derivation of apex and basis of an isolated right atrium of Emys 
with the appertaining myogram registered by simple suspension 1 ). 
This image, in many respects, makes us think of an electrogram 
b The registration of the electrograms was brought about by means of Ewthovek’s 
string-galvanometer (Edelmann’s small model) according to the method pointed 
out before; see: Proceedings of the Kon. Akad. v. Wetensch. 31 Oct. 1908. 
46* 
