270
(United States' Pharmacopaia), in some cases produced an immediate rise in the arterial
pressure, and even fugaciously registered itself in the respiratory rate, but perhaps more
frequently it failed in its influence.
The influence of injections of digitalis has been in a number of experiments very
pronounced in producing a persistent gradual rise of the arterial pressure with an increase in
the size of the individual pulse rate. In several instances death was apparently averted by its
injection, and I saw in one or two cases, where large amounts of the digitalis had been em--
ployed, sudden systolic cardiac arrest, indicating that digitalis, if in sufficient amount, is able
to victoriously assert itself in opposition to chloroform. Moreover, when I have given chloro--
form to dogs whose hearts were already under the influence of digitalis, there has seemed to be
a peculiar steadying or sustaining power combating the circulatory depression naturally
produced by the anæsthetic, and I believe that in all cases of weak heart in man a full dose of
digitalis before the administration of chloroform would greatly lessen the danger of cardiac
collapse.
With the nitrite of amyl four experiments were made; in some of these from four to
ten drops of the nitrite of amyl were injected in the jugular vein; in others the nitrite was
used by inhalation. No distinct effect upon the arterial press
ure was in any instance produced, and usually no alteration in the size of the pulse waves, although sometimes the pulse did
appear to be a little fuller.
Of all my experimental results, those which have been reached with strychnine have
been the most surprising. The injection of strychnine into the jugular vein usually produced
a gradual rise of the arterial pressure, and always caused an extraordinary and rapid increase
in the rate and extent of the respiration. Thus I have seen the respiration, which had practi
- c a l l y c e a s e d f o r t e n s e c o n d s , s u d d e n l y , u n d e r t h e i n f l u e n c e o f a n i n j e c t i o n o f t w o - t e n t h s o f a
grain of strychnine, become at once very large and full, and reach a rate of 130 a minute.
A series of elaborate experiments made upon the effect of the position of the animal on
the blood-pressure in the carotid and other arteries, has very clearly proved that the body of
the animal whose circulation has been paralysed by chloroform acts in a measure like a tube
filled with fluid. Thus, if the feet of the dog were raised vertically above the head, whilst
the l atter remai ned upon the tabl e, an i mmedi ate ri se of pressure occurred, even though the
heart had ceased beating entirely; provided that the head of the animal was kept upon a
level with the table. If, however, the head of the animal was depressed below the level
of the table for a distance equal to, or greater than, the length of the body of the
animal, a decrease of the arterial pressure occurred at once, although the animal was in a
vertical position. The phenomena observed were precisely such as would have been
produced if the canula had been inserted into a tube filled with fluid, instead of the carotid
artery, and the elevation and depression of this tube had registered itself on the recording
drum, in obedience to the ordinary laws of hydrostatics. The phenomena, were entirely in--
dependent of any beat of the heart, and were readily produced when the animal was dead,
provided the death had not occurred too long previously. Sometimes, even a very few minutes
after the cessation of the heart beat, it was impossible to produce the changes of pressure upon
the drum. This I believe to have been due to coagulation of the blood occurring very early