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to avoid its action on the heart, and if this dilution can be sufficiently provided for, observation
of the pulse is not absolutely necessary. Although I cannot agree with the Hyderabad Com
- m i s s i o n t h a t t h e h e a r t a l w a y s c o n t i n u e s t o b e a t a f t e r r e s p i r a t i o n c e a s e s , y e t t h e d i f f i c u l t y i n
maintaining the concentration necessary to paralyse the heart simultaneously with the respir-
tion is extremely great, and I should think that in ordinary chloroform administration such a
simultaneous paralysis can never occur.
As, in the great majority of my experiments, death was due to the respiration alone,
some experiments were made to find the condition of the medulla oblongata during chloroform
narcosis. This question was approached by an examination of the reflexes connected with it.
I found that these all ceased before the respiration, and returned (in cases where the animal was
revived) some time after spontaneous respiration had set in. The more concentrated the
mixture, the shorter the interval between their disappearance and that of respiration. The
first to cease to act was the corneal reflex, then that on the respiration from the nasal branch
of the trigeminus, then the swallowing reflex from irritation of the soft palate or of the superior
laryngeal nerve; and, last of all, Traube's active expiratory reflex from expansion of the lungs.
The reflex in dogs were not so carefully noted as in rabbits, but in general presented no
marked differences.
The respiratory centre, as Knoll has pointed out, is affected differently in different
stages of chloroform narcosis. At first it is acted on by the reflexes first from the nose then
from the trachea and lungs. Then the rapid stage of respiration sets in. This occurs after
di vi si on of t he vagi , and i s due t o st i mul at i on of t he vagus r oot s i n t he medul l a, and not t o
stimulation of the respiratory centre itself; for, if the latter were the case, the result would be,
as Marckwald has pointed out, respiratory spasms; whereas, after section of the medulla above
the centre and division of both vagi, chloroform breaks up the resulting spasms into regular
respirations exactly as weak tetanisation of the vagi does. Last of all, the centre is paralysed
by chloroform, and fails to respond to electrical stimulation of the medulla. The blood-pressure
was registered in several experiments in which the drug was administered in weak concentra-
tion, and I found that there occurred a slight rise and then a very gradual uninterrupted fall.
In very weak form (4 per cent.) chloroform caused no preliminary rise, but a slow fall from
the very first, though so gradual was the change in pressure that it could only be seen by
comparing the curves at intervals of ten minutes. No such sudden falls of pressure were seen
as have been noted by some critics of the Commission, which is perhaps to be explained by the
abundant and uninterrupted supply of air to the
lungs. I may remark that in those experi-
ments in which the movements of the heart were registered directly, they never showed any
sudden change, but gradually increasing weakness, which culminated in paralysis or passed
off, according as chloroform was continued or shut off.
For the sake of comparison a few experiments were made with ether, and the same
stages were observed as with chloroform, death occurring equally rapidly if undiluted ether
vapour was used, and being due to paralysis of the respiration alone or with accompanying
heart paralysis. In one case delirium cordis was observed after a minute and a quarter's in
-halation. Rabbits anæsthetised with pure ether vapour could not be revived by artificial res-