KONINKLIJKE AKADEMIE VAN WETENSCHAPPEN 
TE AMSTERDAM. 
PROCEEDINGS OF THE MEETING 
of Saturday February 27, 1915. 
Vor. XVII. 
3G 
President: Prof. D. J. Korrrwee. 
Secretary: Prof. P. ZERMAN. 
Translated from: Verslag van de gewone vergadering der Wis- en Natuurkundige 
Afdeeling van Zaterdag 27 Februari 1915, Dl, XXIII). 
NED: IT EE EENES: 
S. pr Boer: “On the heart-rhythm”. (Communicated by Prof. J. K. A. WerrnHeim 
SALOMONSON), p. 1075. 
K. Kuieer Jr.: “The physiology of the air-bladder of fishes”. (Communicated by Prof. Max 
WeBER), p. 1088. 
Miss Apa Prins: “On critical end-points and the system ethane-naphtalene”. (Communicated 
by Prof. A. F. HOLLEMAN), p. 1095. 
JAN DE Vriks: “Systems of circles determined by a pencil of conics”, p. 1107, ; 
F. A. H. ScHRRINEMAKERS and Miss W. C. pr Baar: “Compounds of the arsenious oxide” I, 
js akiats 
Ernst Conen and S. Worrr: “The allotropy of potassium” I, p. 1115. 
H. A. VERMEULEN: “The vagus area in camelidae”. (Communicated by Prof. L. Bork), p. 1119. 
Physiology. — “On the heart-rhythm”. By Dr. S. pr Boer. (Com- 
municated by Prof. Dr. WeRTHEIM SALOMONSON). 
(Communicated in the meeting of Jan. 30, 1915). 
1. The a-v-interval and the refractory period. *) 
The normal heart-rhythm is caused by a system of different fac- 
tors, among which the irritability and the transmission of stimulation 
of the different parts of the heart are of great significance. I have 
now made a series of experiments on frogs, in which | have modi- 
fied these two principal properties of the heart by means of veratrine. 
I followed in my experiments this method: the heart was suspended 
on the point, after I had removed the sternum, cut open the peri- 
cardium and cut the frenulum in two. The single suspension was 
used, because I intended to note down, after the poisoning, during 
1) The experiments mentioned here were communicated by me in a lecture, 
held in the meeting of the biological section of the Genootschap ter bevordering 
der Natuur-, Genees- en Heelkunde at Amsterdam of November 19th 1914, 
71 
Proceedings Royal Acad. Amsterdam. Vol. XVIL. 
