328 PROFESSOR E. A. SCHAFER AND DR H. J. SCHARLIEB ON THE 
If the chloroform be pushed until respirations cease altogether and the’ blood- 
pressure is reduced to a few millimetres of mercury, the only sign of life being the 
slow beat of the heart, adequate vagal excitation will: still cause inhibition, which 
under these circumstances lasts as long as the excitation; the removal of excitation 
being immediately followed by a resumption of the slow, weak beats. Such inhibition 
can be obtained as long as there is any perceptible beat (fig. 17). 
We have also re-studied the effect and dosage of atropine in preventing inhibition 
through the vagus. The results obtained are illustrated in the tracings reproduced in 
fig. 19. (See also fig. 10 for its effect on reflex vagal excitation.) 
If a dose of sulphate of atropine of 0°00002 gramme per kilo. be given hypodermi- 
cally in the dog, the effect upon the vagus is manifest about fifteen to twenty minutes 
Fic. 17.—Effect of moderate vagal stimulation in the 
last stage of chloroform anesthesia, the respira- 
tion having long ceased, and the heart beating 
slowly, feebly, and irregularly. The signal marks 
the period of vagal stimulation. (The alignment 
of the signal is a little too much to the left.) 
It will be seen that excitation of the peripheral 
vagus still causes arrest of cardiac action, which 
is at this stage probably entirely ventricular. 
after administration, and lasts about three hours. ‘The result of such a dose is in 
some cases to abolish for a time all vagal influence upon the heart (fig. 19, I.). But in 
most cases, although there is not complete abolition, nevertheless the strongest vagal 
excitation is unable to produce, in any stage of chloroform aneesthesia, complete cardiac 
arrest (fig. 19, II. to VI.). There may be, even with comparatively weak excitation, a 
slowing of the heart and a consequent fall of blood-pressure ; but it is no greater with 
strong than with weak excitation, and is never accompanied by respiratory arrest, unless 
in using a very strong excitation there is escape of current to the central end of the 
nerve. This peculiar condition, in which vagal excitation is unable to cause arrest, but 
only slowing and diminution in force of the heart, persists for nearly three hours, the 
