456 
4. 
These considerations induced Prof. HAMBURGER to suggest that I 
should enter upon a systematic investigation of the effect of various 
chemical and physico-chemical agents on the place of the chemism 
and their effect, restricting myself to the sinus venosus. 
The effect of salts and other substances on the heart as a whole, 
has indeed been investigated, but the matter then becomes too com- 
plicated to enable us to arrive at conclusions as regards the chemism 
of the sinus. The conelusions drawn from the study of the isolated 
ventricle or the auricle-ventricle system too cannot be immediately 
applied to the sinus. (See also summary on p. 464). In this connec- 
tion | may quote the opinions of HerING and Sakai as regards KCI. 
The former supposes that with respect to the frequency the ‘“nomo- 
tope”” centres are inversely proportionate with the “heterotope” ones. 
He supposes that KCl has a stimulating effect on certain “hetero- 
tope’ centres‘). Sakat on the other hand supposes that the sinus is 
stimulated into greater frequency by KCI. 
Method of Investigation. 
After some fruitless attempts to register the contractions of the 
isolated sinus, 1 have made use of ENGELMANN’s suspension-method. 
The fluid was driven through the heart from the vena cava inf. 
behind (below) the liver, mainly as suggested by Mines. The fol- 
lowing modification, however, seems to me of some importance. 
Besides one or both of the aortas also both venae cavae sup. were 
cut through at some distance from the auricle, so that the fluid 
could also flow away through these. If this is not done, blood will 
remain in the veins long after the experiment has begun. This must 
affect the frequency. If the fluid passing through the heart impedes 
automatism, such a vein will retain its former rhythm. Every con- 
traction of the vein is transmitted to the auricle, which will, there- 
fore, beat faster than if auricle and veins had been in contact 
everywhere with the same perfusion fluid. 
The difficulty is that auricle and ventricle are not supplied with 
so much fluid, and may under certain circumstances determine the 
rhythm; this can, however, be easily ascertained. Though | have 
constantly paid attention to this, I have observed it but seldom. 
The curves relating to these experiments have of course not been 
used for this publication. 
When the heart of large esculents had thus been treated, the 
pericardium parietale was removed, the frenulum was cut through, 
1) By ‘nomotope” centres Herne (Centralbl. f. Phys, Vol. 19. 1905, p. 129) 
means the places, from which the normal stimulus originates ; “heterotope” cen- 
tres are those from which it originates in abnormal conditions. 
