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.
On separating the coagulable albumins of the venoms of Colubridæ, by heating to 72° C., followed by filtration, we obtain a perfectly limpid liquid, which is no longer injured by boiling, and in which the toxic substance remains wholly in solution. The albuminous precipitate, when separately collected and washed, is no longer toxic. The clear liquid, after being filtered, is again precipitated by absolute alcohol, and the precipitate, redissolved in an equal quantity of water, is just as toxic as the original filtered liquid.
The venoms of Viperidæ, when coagulated, by heating them to a temperature of 72° C., and filtered, are almost always inert. The albuminous coagula, if washed, redissolved in water, and injected into the most sensitive animals, produce no harmful effect whatever.
The results of dialysis likewise differ when we experiment with the venoms of Colubridæ and Viperidæ. The former pass slowly through vegetable membranes, and with greater difficulty through animal parchment. The latter do not dialyse.
Filtration through porcelain (Chamberland candle F) does not sensibly modify the toxicity of the venoms of Colubridæ; on the contrary, it diminishes that of the venom of Viperidæ by nearly one-half.
By using a special filter at a pressure of 50 atmospheres, C. J. Martin has succeeded in separating from the venom of an Australian Pseudechis two substances: a non-diffusible albuminoid, coagulable at 82° C., and a diffusible, non-coagulable albumose. The former produces hæmorrhages; the second attacks the nerve-cell of the respiratory centres.