458 
Number of contr. p. min. They show that the concentration of 
the salt was gradually increased or de- 
creased. Before passing on to another 
stage | waited till the frequency had be- 
come constant. Mostly this was already 
the case after 15 minutes except with 
weak concentrations. A return from low 
to high concentrations resulted in a rapid 
modification of the frequency (fig. 1). 
In these as in the following experi- 
0 af ments the temperature varied between 
Diagram II. Effect of excessive 
dose of CaCl, on the frequency each experiment. 
of the sinus venosus. 
13° and 17°, but was the same during 
Increase of the Cac, percentage 
of the perfusion fluid resulted in 
5 a slow but uniform decrease of 
TEMES tle frejuency (tig. 2), which lasted 
until the contraction-height became 
imperceptible. 
The deviation increased distinctly 
Fig. J. Transition at once from RINGER’s : a Ae 
at first (fig. 2) and decreased re- 
fluid without CaCl, to the same fluid 
with 0.005 ©/, CaCly. Effect after 5 min, gUlarly afterwards. In the two 
Time denoted in min. experiments with high concentra- 
tions the contractility had disappeared at + 0.3°/, CaCl,. 
The maximum contractility can of course not be determined with 
accuracy from these experiments. Probably 
CaCl,. 
ANNM; The tonus increases. This was not ob- 
it is not far from 0.1 °/ 
served regularly; probably owing to the 
UETRUUNUU CLUE diminutive size of the object and its 
delicate structure. At the highest con- 
ryt eae a d —__eentration, however, the sinus was strongly 
Fig. 2. Transition from RinceR’s el 
fluid with 0.005, CaCl, to 
the same fluid with 0.19, tracted into threads in which there was. 
contracted whilst the limp veins had con- 
CaCl, Effect after 5 min. hardly a lumen visible. 
Time denoted in half minutes. The osmotic pressure not being kept 
at the same height during the experiments, its influence was studied 
separately afterwards. The modification effected by it amounted to 
3 beats per minute at most. 
