140 
NATURE 
[ DECEMBER 10, 1896 
specific, z.e. that such serum can only counteract that virus 
against which the animal supplying the serum has been im- 
munised. Most snake poisons, however, are so similar in their 
chemical nature and physiological action, that it is hardly sur- 
prising that chemically similar poisons which, according to their 
action on the animal body, belong to one physiological group, 
should have the same antidote. In the former article the writer 
pointed out that there is one poison, daboia poison, which, as 
shown by Cunningham and Wall,! differs from cobra venom in 
its physiological action; and that therefore one could hardly 
expect that (a) animals immunised against cobra poison would 
become resistant against daboia venom, and vce versd, and 
that (4) a serum capable of acting as an antidote to cobra 
poison would also be capable of neutralising daboia venom, 
By a series of experiments performed at the Calcutta Zoological 
Gardens, in 1895 and 1896, Cunningham has supplied these 
@ prioré considerations with a sound basis of fact. He shows 
that a fowl immunised against daboia venom by means of an 
habitual cumulative treatment with that poison does not acquire 
a corresponding immunity from cobra venom ; and conversely, 
that the serum derived from the blood of animals which have 
been artificially immunised against cobra venom has no effect 
whatever as an antidote to daboia venom. The results are pre- 
cisely what had been anticipated by the writer from the perfectly 
distinct properties of the two poisons. It is therefore not 
possible, so far as our present knowledge goes, to establish a 
vicarious immunity against absolutely dissimilar poisons, and 
‘Calmette’s statement that a serum prepared from animals pro- 
tected against cobra venom is an antidote against the action of 
the venom of a// poisonous snakes requires some correction. These 
experiments then strongly support Behring’s law, and we must 
perforce adhere to the principle of the specificity of immunising 
serum : distinct toxins require distinct antitoxins. 
Fraser? has asserted that the serum or blood of poisonous 
snakes possesses antitoxic powers, and has explained the 
snake’s natural immunity from its own poison by assuming 
that it immunises itself by swallowing its own venom, and 
thus renders its blood antitoxic. In 1892, already the writer,* 
working in India with freshly-caught cobras, was unable to 
obtain any real antitoxic effects with the serum of a normal 
cobra. ~ Cunningham has since devoted full attention to 
this matter, and shows conclusively that the serum of a 
normal cobra, whether it be administered together with, 
before, or after the poison, has no antitoxic action whatever, 
and one must agree with him ‘‘that the natural immunity of 
cobras is perfectly distinct in its nature from the artificial im- 
munity which is established in other animals as the result of 
continued treatment with cobra venom, and that it is uncon- 
nected with any material of the nature of an antitoxin in the 
blood.”” Normal cobra serum has also no antidotal effect on 
daboia venom, although the cobra enjoys an extraordinary 
immunity against this venom. In the previous note it had 
already been maintained by the writer, that since a large 
number of innocent snakes are highly resistant against cobra 
poison, although they never ingest poison, it is almost im- 
possible to regard the natural immunity of venomous snakes 
as being due to habitual ingestion of their own poisons. 
All we can say is that a number of reptiles and amphibia 
possess a high degree of resistance as a natural property 
or character, independent of any process of self-protection, 
whether by swallowing or inoculation. In a few interesting 
experiments Cunningham, moreover, clearly shows that the 
inoculation of a poisonous snake with its own venom does not 
lead to the production of antitoxic substances inits blood. This 
is important, because it might have been assumed that, whilst 
normal cobra serum possesses no antidotal properties, serum 
derived from cobras in which self-inoculation had taken place, 
might have become antidotal. One of Cunningham’s cobras 
readily resisted inoculation with an amount of cobra venom 
sufficient to kill 1000 fowls, and yet its serum had no preventive 
action whatever on even the minutest dose of the poison. But 
what is stranger still : a fowl was inoculated with 3 cc. of serum 
from a cobra which had received *75 gramme of cobra venom. 
Considerable drowsiness followed, and sixty hours later the bird 
1 ** Indian Snake Poisons, their Nature and Effect,’ 1883. 
2 “ Report on the Results of Experiments on the Action of various reputed 
Antidotes to Snake-Venom.” (Calcutta, 1895-1896.) 
3 ‘*Tmmunisation against Serpents’ Venom.” 
March 20, 1896.) 
4 Journal of Physiology, vol. xiil., 1892. 
NO. 1415, VOL. 55] 
(Address, Roy. Inst., 
died of typical cobra poisoning. The blood of the snake, there- 
fore, which had been killed a week after it had been inoculated 
with a large dose of cobra poison, contained enough unaltered 
venom to give rise, on injection into a fowl, to fatal intoxication, 
although the snake itself had shown no symptoms. In other 
experiments Cunningham obtained the same result, viz. ‘* that 
the serum of cobras treated with excessive doses of cobra venom 
has no protective action whatever, but may for some time cen- 
tain enough unaltered venom to give rise to fatal intoxication 
in susceptible animals.” Is it possible, then, that the natural 
immunity of poisonous snakes is due to the presence of the same 
antitoxic bodies which are called into existence in susceptible 
animals by a process of slow and gradual immunisation? Are 
not the conditions exactly parallel to those which we find in 
natural immunity from bacterial diseases? It is there quite 
exceptional to find that the serum of naturally immune animals 
possesses any bactericidal, immunising or antitoxic properties 
towards the bacteria or their toxins, from which the animals enjoy 
a natural immunity. We must come to the conclusion, at which 
both Cunningham and the writer have previously arrived, viz. 
“*that snakes as a group appear to be relatively insusceptible to 
the action of cobra venom, whether they be poisonous or 
harmless.” ; 
Cunningham further believes that there is good ground for as- 
suming that the degree of susceptibility, to some extent, runs 
parallel with that of respiratory requirement. Thus a Zamevis 
(Ptyas) mucosus, or “ common rat-snake,’’ may be submerged in 
water, without being the worse for such treatment, for about half 
an hour, and it may be exposed to an atmosphere containing a 
large amount of CO for at least two hours, without being in the 
slightest affected thereby. This parallelism between suscepti- 
bility to cobra poison and respiratory requirement, to some 
degree at least, holds good also for other cold-blooded animals. 
Thus the Varanus salvator is extremely resistant against the 
effects of cobra poison, and it is still more indifferent to sub- 
mersion, That immunity from intoxication with cobra poison 
does not, however, depend entirely upon a low degree of 
respiratory requirement becomes clear, as Cunningham distinctly 
states, when we compare the Zamenis with the Varanus ; for the 
former, which is much more rapidly drowned than the Varanus, 
possesses a far higher immunity than the latter. Certain 
Lacertilia, again, are as susceptible to cobra poison as fowls ; 
but Calmette is wrong in stating that a high susceptibility is a 
general Lacertilian peculiarity. The Ca/otes versécolor is quickly 
killed by cobra poison, but it is also rapidly affected by sub- 
mersion. Batrachia, however, which have a low respiratory 
requirement, are relatively insusceptible to cobra venom. 
Hence, although the natural immunity of these animals does not 
entirely depend on their low respiratory requirement, this 
property is a factor of great importance ; but however this may 
be, the natural immunity of poisonous snakes certainly does not 
depend on a process of self-immunisation. It would be inter- 
esting in this connection to study the natural immunity of 
freshly-hatched cobras, which, it is said, are venomous from 
their birth. AGT ACIS 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Oxrorp.—On December 1, Convocation decided to affix the 
University seal to a memorial to the Duke of Devonshire, Lord 
President of the Council, desiring that a central educational 
authority for secondary schools be created. : 
Dr. J. S. Haldane has been reappointed Lecturer in 
Physiology for three years from January 1, 1897. 
Messrs. E. E. Blackburn, E. E. Marsh, and F. A. Storr have 
satisfied the examiners in the second part of the examination 
for the Diploma in Public Health. 
The Hebdomadal Council has accepted an offer from Prof. 
Poulton to present a statue of Charles Darwin for the court of 
the University Museum. 
A bust of Sir Henry Acland is about to be placed in the court 
of the Museum as a memorial of his services to the Oxford 
Medical School. 
Mr. H. B. Hartley, of Dulwich College, has been elected toa 
Brackenbury Natural Science Scholarship, and Mr. L. K. Hind- 
marsh, of King Edward’s School, Birmingham, to a Natural 
Science Exhibition at Balliol College 
Mr. R. E. Thwaites, of Batley Grammar School, has been 
