Medical Officers of the Army of India.
5
comes the stage of asphyxia with infrequent, primarily deep, subsequently brief
gasping respirations, anæsthesia, coma, and death, which, in acute cases, is pre
-ceded by violent general convulsions, a phenomenon which is generally absent in
chronic cases. Turning now to the symptoms attending intoxication by cobra-
venom, we again find a preliminary acceleration of respiratory movement, in
-creased nasal, lachrymal and salivary secretion, nausea and vomiting, paralysis,
especially of the lower or hinder extremities, slow and shallow respiration, coma
and death, preceded by general convulsions in acute cases and ordinarily occur
-ring without them in chronic ones. But in the case of poisoning by CO, there
appear to be no good grounds for doubting that the primary and essential action
of the gas is to induce a gradually progressive diminution in the respiratory pro
-perty of the blood owing to the gradual substitution of CO-hæmoglobin for
oxyhæmoglobin, and that the nervous symptoms are dependent on this and not
on any direct action on the nervous apparatus. But, if this be so, it is clear
that in the case of poisoning by cobra-venom the parallel series of nervous
phenomena which are present may have a like origin, and that their occurrence
affords no conclusive evidence that the toxin possesses any direct neurotic
properties. The mere presence of nervous symptoms does not prove that they
are dependent on any direct action of the venom on the nervous apparatus, and
the majority of those which are present are such as can be unequivocally shown
to arise in connection with progressive loss in the respiratory property of the blood,
so that the evidence in place of giving any decisive support to the theory of a direct
and primary neurotic action, is rather in favour of that of primary blood change.
But it is fortunately unnecessary to rest satisfied with such theoretical
considerations, as it can be readily demonstrated that cobra-venom does con
-spicuously affect the respiratory properties of the blood both within the body and
outside. It was long ago pointed out by Boag that the mixture of relatively
large quantities of snake-venom with blood produces an immediate effect on its
colour and coagulability, but, as Richards justly remarks, the value of this
observation as evidence for the occurrence of primary blood-change as the essen
-tial cause, of death in cases of poisoning by cobra-venom is minimised by the
fact that in the latter the proportion of venom to the mass of blood with which it
mingles is always very small and ordinarily excessively so. The average quan
-tity of dried material to be obtained from the venom ejected by a cobra at any
one time is only about 0.254 gramme, but this is amply sufficient to secure
the death of a man of 70 kilos in weight and whose blood probably amounts to
between 4,000 and 5,
000 grammes, or 16,000 to 20,000 times the weight of the
dried venom. The results of the following series of experiments, however, in
some of which only fractional quantities of venom acted upon relatively large
masses of blood, clearly show that the potency of the former as a factor of blood
change is such that the amounts which are liable to be introduced by a single