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minor operations, such as teeth extraction, especially in those in which the patient, being in the
natural upright position, can give the respiratory muscles full play, and completely fill the
chest.
Thus it is worth considering if the holding of a struggling animal, such as a dog,
might not so interfere with its breathing as to prevent the full dose being taken, especially as
the animal would not be likely to be held in its natural position. There is an indication in the
report that, in at least some cases, the holding of the animal did actually interfere with its
respiration. If it did so in one case it probably did so in many, especially as a dog's thorax is so
shaped, that to hold its fore legs together in front of it, would prevent the complete expan-
-sion of its chest, and so prevent it suddenly taking a fair dose of chlorof
o r m v a p o u r .
In animals, too, we have an absence of the desire to inhale freely. In at least
o n e r e p o r t e d c a s e t h e w i s h t o i n h a l e t h e c h l o r o f o r m f r e e l y c o n t r i b u t e d l a r g e l y t o t h e f a t a l r e s u l t .
In chloroform accidents in man, of the very sudden variety, considered to be due to
cardiac syncope, a certain set of conditions are present which are difficult to obtain in animals.
The subject is generally young or middle aged, with an expansile chest: the chloroform
is willingly inhaled, quietly at first, until semi-unconsciousness is produced, when the fauces and
glottis are insensitive: then, during struggling , with or without holding the breath, the patient,
often in an upright or semi-upright position, and having his arms fixed by the assistants, which
gives his respiratory muscles good purchase, gets one or two deep inspirations at the greatest
advantage, and so obtains the maximum amount of chloroform.
There is the desire to got under the influence of the drug the voluntary inhalation fol-
-lowed by the still steady conscious anxiety to inhale more, and then the involuntary deep in--
spiration, in the natural position in which a deep inspiration can be best taken.
All these are conditions difficult to obtain in experiments on animals, and it is only
under such conditions that the supposed cardiac paralysis has been produced in man.
The interval between the stoppage of the heart and the respiration is so short that these
points, trivial though they seem, may easily be of importance in modifying the result.
It has always been maintained by the advocates the syncope theory that it is only under
certain circumstances, and by a certain definite combination of factors, that chloroform sufficient
in quantity to paralyse the heart can be introduced into the blood, and that this particula
r combination of circumstances occurs very seldom—about once in every 1,000 or 2,000 admin
-istrations.
Thus as Dr. Snow pointed out years ago, the effect of chloroform on any given case
varies with the amount contained in the blood at any given time.
This depends upon the strength of chloroform vapour exhibited to the patient, the ease
with which it is inspired through the glottis , and the depth and frequency of the inspirations;
the amount actually absorbed depends upon the condition of the blood (its capacity for chloro-
- f o r m m a y v a r y ) , t h e t i m e i t s t a y s i n t h e l u n g s , t h e r a p i d i t y o f t h e c i r c u l a t i o n , a n d o t h e r f a c t o r s .