All mammals exhibit the same symptoms after inoculation with lethal doses of venom. The same applies to birds; but in the latter the period of asphyxia is much longer, probably on account of the reserves of air accumulated in their air-sacs and pneumatic bones. They gape like pigeons that are being suffocated, rest the tip of the beak on the floor of the cage, and frequently have convulsive spasms of the pharynx, accompanied by flapping of the wings. Small birds and even pigeons are extremely sensitive to venom; fowls are more resistant. Frogs, thanks to their cutaneous respiration, succumb very slowly. I have seen some survive for thirty hours after being inoculated with a quantity of venom which, when subcutaneously injected into a rabbit, causes death in ten minutes. * * * * * Lizards and chameleons succumb very rapidly. Grass Snakes and non-venomous snakes in general withstand doses of venom that in proportion to their weight are fairly large; nevertheless, as indeed we shall see in the sequel, they do not possess any real immunity. It is only poisonous snakes that are unaffected by enormous doses of their own venom, as has already been shown by Fontana, Weir Mitchell, and Viaud Grand Marais. They are, however, quite capable of being poisoned by snakes belonging to altogether different species; strong doses of _Crotalus_- or _Lachesis_-venom are fatal to Cobras or Kraits, and, when several poisonous snakes are shut up together in the same cage, they are not infrequently seen to kill each other as the result of repeated bites. 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.