652 
DE. T. L. BEUNTON AND ME. W. PYE ON THE ACTION 
of the vasomotor centre in the medulla. As casca acts on the vessels without this 
centre, however, it was natural to suppose that other vessels than those of the intestines 
might be affected ; and this the curves show to be the case. During the stoppage of the 
heart (Experiment XLII.) for half a minute the pressure fell only slightly. Now 
Ludwig and Hafiz found that when contraction of the abdominal vessels was produced 
by irritation of the vasomotor centre in the medulla oblongata, complete stoppage of the 
heart was followed by a rapid fall in the blood-pressure, the blood finding its way out 
of the arterial system into the veins through the vessels of the muscles. The slow fall 
after the administration of casca shows that the vessels of the muscles must be con- 
tracted as well as those of the skin and intestines. 
Action on Secretion of Urine. 
A detailed account of our experiment on the action of the drug on the urinary secre- 
tion, together with the accompanying effects on the circulatory system, will be found in 
pages 642 and 643. Underneath is a diagram showing the close dependence of the rate 
of secretion of urine upon the blood-pressure. 
'5 _g 
a S 
p a 
i j 
w| 
Remarks. 
The results of this experiment, as regards the vascular phenomena of blood-pressure, 
pulse, &c., have been already fully noticed. 
The action of the drug on the secretion of urine is seen to be very marked and cha- 
racteristic, and the dependence of the secretion on the blood-pressure is well shown in 
the accompanying chart. 
Thus the average rate of urine secreted before administration of casca being 5 minims 
in 10 minutes, an increase of 50 millims. in the blood-pressure caused by the drug 
brought the rate of secretion of urine up to 25 minims. When the action of the drug 
was further pushed there was first decrease and then total suppression of urine, the 
blood-pressure at the time of suppression being 200 millims. of mercury. 
Experiment XXX III. — March 31. 
