ACTION OF CHLOROFORM UPON THE HEART AND ARTERIES. 321 
when the respirations become shallow early in the administration, as is shown 
strikingly in the tracing given in fig. 6. 
While cases showing such a marked subterminal rise are uncommon, it is not 
unusual to find a subterminal arrest of the fall of blood-pressure, so that the curve 
remains for a minute or two at the same level, or shows a more gradual fall than 
immediately before and immediately after. Such arrest of fall, when unaccompanied 
by failure of respiration, may also be explained by the constricting action of the drug 
on the arterioles, acting either through the vasomotor centre or directly. This con- 
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Fic. 7.—Dog, weight 7000 g. Effect of inhalation through trachea tube of air nearly saturated with chloroform vapour. 
The uppermost tracing (A) is that of the blood-pressure ; the second tracing (B) is costal respiration ; the third (C) 
abdominal respiration ; the fourth, time in 10 seconds ; and the fifth, the signal marking when chloroform was admitted 
and stopped. 
In this experiment the heart failed before the respiration, and about 30 seconds later showed spontaneous recovery, 
which was, however, only temporary. There was no recovery of respiration. 
striction, although insufficient entirely to compensate for the continual and gradual 
weakening and slowing of the heart which is going on the whole time, interferes 
with the continuous and uniform fall of pressure, which would otherwise show itself. 
At a much later stage the ventricular contractions, although greatly weakened, 
produce large fluctuations of pressure in the arterial system, which is then com- 
paratively empty, owing to the accumulation of blood in the great veins and in the 
dilated heart cavities. 
