68 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
peripheral ends of a severed vagus, were required to arrest the heart; in 
the other instance, that is, under the action of the drug, 1 unit or a 
fraction of a unit of an electrical current of the same strength, was suf¬ 
ficient to bring about a similar result in the same animal. It is obvious, 
therefore, that sparteine induces a hyper-excitability of the cardio-in- 
hibitory centers, centrally and peripherally, which results in the slowing 
of the pulse rate. To the same stimulation, or better, perhaps, to a 
direct influence exerted on the cardiac muscle, may be attributed the in¬ 
crease in the size of the individual pulse-curves, this being an evidence 
of prolonged diastole, a greater filling of the heart with blood. These 
high pulse-waves appeared frequently proportionate to the decrease in 
cardiac rate. 
Fig. N. 
Tracing II.—The same, 1 minute after the injection. 
As regards the action upon the pulse sparteine resembles digitalis, 
though at no time was there observed the distinct dicrotic curves pecu¬ 
liar to the action of the latter drug. In one or two instances, it is true, 
was there noticed what might be called a kind of abortive systole (See 
Tracing II, Fig. F), but this was more probably due to some interference 
in the proper working of the registering needle in the manometer, and 
not to the action of the medicament. 
To the foregoing results may be added the observations of Fick,* to 
the effect that muscarine (a cardiac depressant) exercises little or no in¬ 
fluence on the sparteinized frog’s heart. The results, again, of my own 
experiments on the cut-out cardiac viscus of the batrachian are obvious, 
and point to one evident conclusion. It is apparent, then, that sparteine 
slows the pulse-rate through a double action: by stimulating the heart 
itself, whether its muscle or its contained ganglia, or both, and by excit¬ 
ing the extrinsic cardio-inhibitory centers as well. 
* Log. citat. 
