OF THE BARK OF EKYTHROPHLEUM GUINENSE. 
649 
From this experiment it is seen that after the primary slowing due to stimulation of 
the vagus-roots and the quickening due to paralysis of the vagus ends in the heart, a 
second slowing occurs. 
This second slowing might be due either to stimulation of the inhibitory apparatus 
in the heart or to weakening of the cardiac motor ganglia. 
The latter seems improbable, from the fact that each systole during this slow period 
instead of being weak is exceedingly strong, the pulsation in an artery being felt very 
powerfully when the finger is laid upon it, and the rise of pressure during it being very 
great, as shown by the oscillation of the mercurial column of the manometer. 
In order to ascertain more exactly whether the inhibitory cardiac ganglia were 
stimulated or not the following experiment was tried. 
Experiment XXXIX. 
A dog was chloroformed and 7 cub. centims. of a concentrated watery solution of 
casca were injected into the jugular vein. 
The pulse at the time of injection was 37 in ten seconds. In ten seconds after the 
injection it sank to 20. After the injection of 3 cub. centims. more the pulse rose to 37. 
After a further injection of 26 cub. centims. more in divided doses it again sank to 16. 
This number was, however, uncertain, as the tracing was a very imperfect one. 
The injection of 1 cub. centim. of liquor atropise, B. P., did not seem to alter the 
number of the pulse, but the injection of ^ a cub. centim. more seemed to cause it 
again to become quick. 
This seems to indicate that the slowing is due to an action of the casca on the inhi- 
bitory ganglia. The imperfection of the tracing renders the result somewhat uncertain ; 
but want of time prohibited us from repeating the experiment, although we greatly 
desired to do so. 
Experiments XL., XLI. — March 15. 
The effects on the capillaries of the frog’s web were microscopically observed in Expe- 
riment XL. after an injection of casca under the skin of the back, in Experiment XLI. 
when locally applied to the web. 
The capillaries were observed with oc. 2 obj. 4 of Haetxack. In the first case, i.e. 
after the drug had been injected, the results were purely negative. In the second, after 
application of a drop of strong casca solution to the web, the results were also indecisive. 
In the capillaries and also in the larger trunks the current was at first slowed, and in 
some permanent stasis occurred. When slowing only was produced, the partial arrest 
was followed by reaction, which did not exceed the original rapidity of the circulation. 
No dilatation or contraction of the vessels was seen to accompany the original slowing. 
Although the results of experiments on the frog’s web gave no definite information 
regarding the contraction of the arterioles under the influence of casca, yet no reasonable 
doubt can be entertained that in mammals they do contract ; for this is the only possible 
explanation of the exceedingly slow fall of the blood-pressure during the intervals 
