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within the lungs is negative. (It is not probable that this difference is of importance, for
there is much evidence obtained by different workers which tends to show that the effects of
chloroform depend upon the amount of its reaching certain parts in a given time, the exact
mode of its introduction not making any essential difference. But direct proof on this point
will be adduced presently.) Further, in the experiments above described, the pericardial sac
was laid open, the heart was exposed, and recording apparatus was brought into connection
with it.
How far such abnormal conditions may invalidate the results obtained, as far as their
application to the ordinary inhalation of chloroform is concerned, has now to be considered.
I hold that they do not materially interfere with the applicability of the conclusions arrived at.
It seems to me that there is conclusive evidence showing that the action of chloroform, in the
respects above detailed, is essentially similar in the conditions under which my experiments
have been conducted, and during ordinary inhalation in the intact animal. I shall now proceed
to state briefly some proofs of this conclusion.
1. With regard to the possible influence of the presence of recording apparatus upon
the cardiac action, it is important to notice that the more considerable changes in the state of
the heart can be verified by direct inspection of the exposed heart without the use of apparatus,
t hough, of c our s e , s uc h a mode of e xa mi na t i on i s i ns uf f i c i e nt t o de t e c t t he f i ne r c ha nge s t ha t go
on. The broad fact of the occurrence of cardiac dilatation I have often verified by simple
inspection of the heart without the use of any recording apparatus. Hence it is plain that this
change is not dependent on any interference with organ from the application of the recording
apparatus; and, indeed, there can be no doubt that when the recording apparatus is used the
action of the heart can hardly be disturbed in any serious degree, for it continues to work
during long periods with very remarkable regularity and efficiency. Moreover, for compara-
ti-ve purposes (for example, the relative effects of chloroform and ether) the influence of the
apparatus cannot interfere, as it is constant.
2. I n r egar d t o t he openi ng of t he per i car di al s ac, I s hal l onl y r emar k her e t hat I have
been able to observe distinct changes in the heart, of the nature already described, even through
the intact pericardium.
3. With reference to the altered respiratory conditions present when the results
described in Part II. were obtained, I have made a number of experiments to compare
in the same animal the influence of a certain amount of chloroform ( a ) during the ordi
- n a r y i n h a l a t i o n o f c h l o r o f o r m i n t h e i n t a c t a n i m a l , a n d (b
) w h e n a i r c o n t a i n i n g c h l o r o f o r m
was artificially pumped into the lungs. The method adopted was the following:—A cat,
anæsthetised with chloroform, was fastened on a Czermak' s support, and the left carotid artery
wa s c o n n e c t e d wi t h a k y mo g r a p h , s o a s t o g i v e a b l o o d - p r e s s u r e t r a c i n g i n t h e o r d i n a r y wa y .
The animal was then made to breathe through the anæsthetic bottle, inspiring the air by its
spontaneous respiratory movements. This was done by connecting the bottle (a) with an air
-tight bag tied over the animal's mouth or nose, or ( b) with a canula inserted into the trachea.
The connection between the anæsthetic bottle and the bellows used for artificial respiration was
removed. With this arrangement the animal in breathing inspired atmospheric air through