Not much is to be learnt from these figures; it would be of far greater importance to know the exact constitution of the proteid substances to which venom owes its physiological properties. Unfortunately, our knowledge of the chemistry of the albuminoid matters is still too imperfect for it to be possible for us to determine their nature. * * * * * As early as 1843 it was pointed out by Lucien Bonaparte that in the venom of _Vipera berus_ the most important principle is a proteid substance to which he gave the name of _viperin_ or _echidnin_, and which he compared to the digestive ferments. Later on Weir Mitchell and Reichert, and subsequently Norris Wolfenden, Pedlar, Wall, Kanthack, C. J. Martin, and MacGarvie Smith, showed that venoms, like diastases, exhibit a great complexity in composition; that all their characteristic toxic constituents are precipitable by absolute alcohol, and that the precipitate, when redissolved in water, recovers the properties possessed by the venom before precipitation. According to Armand Gautier,[8] venoms contain alkaloids. The latter may be obtained, in very small amounts, however, by finely pulverizing dried venom with carbonate of soda, and systematically exhausting the mixture with alcoholic ether at a temperature of 50° C. These alkaloids have yielded crystallized chloraurates and chloroplatinates, and slightly deliquescent crystallized chlorhydrates. The latter produce Prussian blue when treated with very dilute ferric salts, and mixed with a little red prussiate. They therefore represent reductive bodies analogous to ptomaines. Norris Wolfenden did not succeed in extracting these alkaloids from Cobra-venom, whence they had nevertheless been isolated by Armand Gautier. Wolcott Gibbs, and afterwards Weir Mitchell and Reichert, likewise failed to find them in _Crotalus_-venom. The toxicity of these bases is, moreover, but very slight, for the totality of the alkaloids extracted by A. Gautier from 0·3 gramme of Cobra-venom did not kill a small bird. It is therefore to the _toxalbumins_ that the toxic properties of venoms are essentially due. All venoms are not equally affected by heat. The venoms of COLUBRIDÆ (_Naja_, _Bungarus_, _Hoplocephalus_, _Pseudechis_) and those of the HYDROPHIIDÆ are entirely uninjured by temperatures approaching 100° C., and even boiling for a short time. When the boiling is prolonged, or when venoms are heated beyond 100° C., their toxic power at first diminishes, and then disappears altogether. At 120° C. it is always destroyed. The venoms of VIPERIDÆ (_Lachesis_, _Crotalus_, _Vipera_) are much less resistant. By heating to the coagulating point of albumin, _i.e._, to about 70° C., their toxic properties become attenuated, and they are entirely suppressed between 80° and 85° C. _Lachesis_-venoms are the most sensitive; their toxicity is lost if they be heated beyond 65° C.