It is very difficult to specify, even within broad limits, the dose of venom necessary to kill a human being. The quantity of poison introduced by the bite of a venomous snake depends, as has already been stated, upon a large number of factors, and, very fortunately, this quantity is not always sufficient to cause death. Thus in India, that is to say in the region in which snakes are most numerous and most dangerous, the mean mortality seems scarcely to exceed 35 to 40 per cent., so far as it is possible to judge from official statistics. But, by experimenting upon animals, and commencing with known doses of venom, which has first been dried and then dissolved again in always the same quantity of physiological saline solution or sterile distilled water, we can determine exactly, _for each kind of venom, and for each species of animal_, the minimum lethal dose _per kilogramme of animal_. The entire series of data collected by investigators who have devoted themselves to this study may be summed up as follows:-- Minimal doses lethal in twenty-four hours for a _guinea-pig_ weighing from 600 to 700 grammes:-- _Colubridæ._ Venom of _Naja tripudians_ 0·0002 gramme “ _Bungarus cæruleus_ 0·0006 “ “ _Naja haje_ 0·003 “ _VIPERIDÆ._ Venom of _Vipera berus_ 0·04 gramme “ _Vipera russellii_ (_Daboia_) 0·001 “ “ _Lachesis lanceolatus_ 0·02 “ “ _Lachesis mutus_ (_Surucucu_) 0·02 “ “ _Lachesis neuwiedii_ (_Urutù_) 0·02 “ “ _Lachesis flavoviridis_ 0·007 “ “ _Ancistrodon contortrix_ 0·015 “ _Cobra_-venom. Dose lethal in twenty-four hours for different animals:-- Dog 0·0008 gramme per kilogramme Rabbit 0·0005 “ “ Guinea-pig 0·0004 “ “ Rat 0·0001 “ 150 grammes Mouse 0·000003 “ 25 “ Frog 0·0003 “ 30 “ Venom of _Bungarus cæruleus_ (Common Krait), according to Elliot, Sillar, and Carmichael.[15] Minimal lethal doses for:-- Frog 0·0005 gramme Rat 0·001 “ Rabbit (by subcutaneous injection) 0·00008 “ per kilogramme Rabbit (by intravenous injection, according to G. Lamb) 0·00004 “ “ Venom of _Enhydrina valakadien_ (according to Elliot and Fraser).[16] Minimal lethal doses per kilogramme:-- Rat 0·00009 gramme Rabbit 0·00006 “ Cat 0·0002 “ Venom of _Enhydris curtus_:-- Rat 0·0005 to 0·0006 gramme per kilogramme Venom of _Notechis scutatus_ (syn. _Hoplocephalus curtus_; the Tiger Snake of Australia):-- Rabbit (by intravenous injection, according to Tidswell) 0·00006 gramme per kilogramme Venom of _Vipera russellii_ (Daboia):-- Rabbit (by intravenous injection, according to G. Lamb) 0·00005 gramme per kilogramme