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the thorax. As soon as chloroform was applied to a rabbit (except when the vapour was
greatly diluted with air), the animal began to struggle and the respiration became irregular
with expiratory gasps, or almost ceased for a few seconds. Very soon the stage of rapid
respiration described by Knoll set in. In those cases in which the air was saturated with
chloroform ( i.e ., in which all the air inspired passed through the chloroform bottle), this stage
only lasted from twenty to sixty seconds. In cases in which a lower concentration was used
it lasted much longer, sometimes for two hours, but in all the spontaneous respiration gra
-dually got shallower without getting slower, till it ceased entirely. The condition of the heart
at this moment varied with the concentration in which the vapour had been blown into the
l u n g s . O f s e v e n t e e n r a b b i t s c h l o r o f o r m e d w i t h s a t u r a t e d a i r , i n f i v e t h e w h o l e h e a r t c o n t i n u e d
to beat, in nine one or both auricles were in rapid motion while the ventricles were still, in one
the left auricle alone was paralysed, while in one the whole heart was in diastolic standstill.
In rabbits which were anæsthetised with a mixture of chloroform vapour and air, i . e
. , i n
experiments in which the stopcock on the water-bottle was partially open, the whole heart was
invariably found beating, but the more chloroform the mixture contained the weaker was the
heart beat. Even when only four parts chloroform-bearing air were mixed with ninety-six parts
pure air the respiration ceased, though only after from two hours to two hours and a-half
exhibition of the drug. With lower concentrations than this I could not obtain narcosis, and
did not attempt to find how long animal could be exposed to the vapour. Ratimoff found
that rabbits could be kept narcotised for six hours without the respiration ceasing. Paul Bert,
on the contrary, found that dogs died after two hours and a-halfs constant inhalation if the
narcosis was complete. Several dogs were chloroformed by the same method, and in all of
these, however concentrated the chloroform vapour, the respiration ceased, while the heart
could still be felt pulsating. A rather higher concentration was required to keep dogs narco
-tised than was necessary for rabbits.
In regard to the restoration of spontaneous respiration, in both dogs and rabbits, I found
that success depended not so much on the length of the interval between the cessation of the
spontaneous and the recommencement of the artificial respiration as on the concentration in
which chloroform had been given. In dogs inflation of the lungs was in cases.
In rabbits, on the contrary, it was impossible to restore life when chloroform-saturated air had
been used, however soon after paralysis of the respiration restorative measures were taken.
When a half-and-half mixture was used, three out of eleven animals could be resuscitated, and
with lower concentrations the proportion of recoveries increased till below 25 per cent. all
a n i m a l s c o u l d b e r e s t o r e d . I n o n e c a s e , w h i c h a 4 p e r c e n t . m i x t u r e w a s u s e d , a n i n t e r v a l
of three minutes elapsed before artificial respiration was begun, and the animal still recovered.
The chances of recovery after paralysis of the respiration, in fact, depend entirely upon the
condition of the heart, and therefore on the concentration in which the drug has been used.
if, as is the case in rabbits, the heart is very munch weakened by very concentrated adminis
-tration, it is impossible to restore the respiration. If, on the other hand, the heart is com
- p a r a t i v e l y u n a f f e c t e d , a s i n d o g s , o r i n r a b b i t s i n w h i c h t h e d r u g h a s b e e n a d m i n i s t e r e d i n a
more diluted form, the animal can always be revived provided the necessary measures are taken
within a reasonable time. The essential point is that the drug be given in sufficient dilution