Fishes, which are particularly sensitive to the venom of Hydrophiidæ, readily succumb to inoculation with other venoms, such as that of the Cobra. At Saigon, in 1891, I made experiments upon the action of this latter venom on two specimens of the fighting fishes, that the natives of Annam rear in aquariums in order to witness their combats and make bets on them. The fishes died five hours after intramuscular inoculation with a dose which kills a pigeon in twenty minutes.
Many invertebrates, such as leeches, crayfish, and gastropod molluscs (snails), are killed by inoculation with very small quantities of venom.
C.—Determination of the Lethal Doses of Venom for Different Species of Animals.
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 | “ |