816 



REPORT — 1897. 



would represent a numerically expressible resistance. On this basis the folio-wing 

 calculations of resistances were made, using R. Tigerstedt's measurements of 

 velocity : — 



By this means the author proposes to measure the resistance through the 

 several organs and the entire vascular course. In this manner an idea can be 

 obtained not only of the amount of resistance in the various vascular paths, but 

 probably also several data for explaining the diameter of the blood-vessels, and 

 the thickness of their walls. For instance, for reasons into which it is not necessary 

 to enter here, it must not be concluded from the striking diflerence in length of the 

 aortic and renal path that the resistance of the aortic path is comparatively 

 greater than that of the renal path. The explanation is rather that the aorta has 

 a greater relative diameter than all the other organs, and is to be regarded not so 

 much as a pipe as an elastic reservoir with the function of an air vessel. 



4. The Coinparative Pln/siology of the Cardiac Branches of the Vagus 



Nerve. By Dr. W. H. Gaskell, F.R.S. 



5. On Rhythmical Variations in the Strength of the Contractions of the 



Mammalian Heart. By Arthur R. Cdsiiny. 



Periodic variations in the force of the contraction of the auricle and 

 ventricle occur after the injection of helleborein, as Knoll has pointed out. I 

 have observed them after a number of other poisons, and occasionally during 

 electrical stimulation of the dog's ventricle. The movements of the heart were 

 registered by a modified form of the Eoy Adami myocardiograph. These variations 

 seem independent of any inhibitory action, and occur only when the ventricle con- 

 tracts spontaneously in a different rhythm from the auricle, and so that during a 

 complete period the rhythm of the ventricle exceeds that of the auricle by one 

 complete contraction (Rw = l!,ff + 1). When the idioventricular rhythm gives rise 

 to a regular auricular one, no periodic variations are observed. The ultimate cause 

 of the variations is the alteration of the relation between the auricular and ventri- 

 cular systoles. When the As occurs in its normal position — during Yd — both A.* 

 and Yd are very complete, because the blood enters the ventricle freely, and the 

 latter has not to dilate against a negative pressure, nor the auricle to con- 

 tract against resistance. When the As occurs during the V«, on the other hand, 

 both are weakened, because the auricle has to contract against the systolic ventri- 

 cular pressure, and, on the other part, the ventricle contracts against the resistance 

 oflered by the blood current entering it from the auricle. At the same time the 

 auricle fails to supply blood to the ventricle during its relaxation, and the latter 

 is therefore incomplete. The exit of the blood from the auricle is hindered, and it 



