NAJA HAJE. 319 
doses the persistent presence of a certain amount of antidotal material within the system is secured. This 
must serve to convert any normally minimal lethal doses which may be subsequently administered into 
sublethal ones, and, as the development of antidotal material bears a direct ratio to the amount of venom 
entering the system, the successive administration of progressively increased doses of venom must lead to 
corresponding rise in degree of immunity. 
"4. The serum of the blood of artificially immunized animals contains the antidotal material on which 
their immunity depends, and hence the introduction of such serum into the system of non-iumiunized and 
susceptible animals must tend to counteract the toxic effects of snake-venom upon them. 
" 5. But in cases of artificial immunity the quantity of antidotal material in the system appears to corre- 
spond closely with the amount of venom to which immunity has been established — there does not appear to 
be any r considerable manufacture of antidote in excess of the quantity necessary to neutralize the toxic action 
of the amount of venom in relation to which immunity has been established. 
" 6. Consequently, so long as crude serum is employed as an antidote, in any case in which a non-immunized 
animal has received a given dose of venom, it must be necessary, in order to neutralize the normal toxic 
effect, to employ the entire or almost entire serum-contents of the blood of an animal which has been 
immunized up to the point of resisting a corresponding dose, or, if smaller bulks of serum are to be efficient, 
to employ serum from animals in which a relatively very excessive immunity has been established. 
"7. It follows from this that, whilst treatment with crude serum may be efficient in dealing with cases in 
which minimal lethal, or slightly supra- minimal lethal, doses of venom have to be counteracted, it is not 
likely to be of any practical value in, dealing with doses of larger amount. 
" 8. The relative immunity conferred by the introduction of the serum of immunized animals into the 
system differs from that following the introduction of venom in being very transitory — it depends on the 
introduction of a ready-made antidote and not on the local manufacture of an antidote within the system. 
" 9. Artificially established immunity to the action of colubrine venom does not imply the presence of 
any immunity to the action of viperine venom, and vice versa. 
" 10. The excessive immunity of venomous snakes to the action of snake-venom is not dependent on the 
presence of any antidotal material 'within the system of the same nature as that which is developed within 
the bodies of susceptible animals under the influence of such venom." 
The immunity to the venom of snakes claimed by certain sects and tribes of men as 
the result of the ingestion of the poison is a subject of considerable interest. Not a 
few travellers and others of unquestionable reliability have recorded that certain 
peoples of the African continent and of other parts of the globe resort to the practice 
of drinking the venom of snakes, of eating the poison-glands, and even the snakes 
themselves, to secure for their persons an immunity from the deadly results usually 
following the bites of these animals. 
Professor Fraser made a series of experiments with the object of determining 
whether serpent's venom is inert or nearly so when introduced into the stomach of an 
animal. He administered cobra-venom to a cat, gradually increasing the doses up to 
eighty times more than a minimum lethal dose, with no evil result. Under this treat- 
ment the cat was found to have become protected against cobra-venom, and so much so 
that one and a half the minimum lethal dose of the poison could be injected subcuta- 
neously with impunity. Moreover, it was discovered that its blood-serum was definitely 
antivenomous, and the still more remarkable fact was ascertained that her progeny had 
acquired protection through her milk. Experiments of a like nature were made on 
