PHYSICAL AND CHEMICAL PROPERTIES OF SNAKE VENOM 79 



CHEMICAL NATURE OF SNAKE VENOM. 



The venom of snakes is a secretion of a serous (namely, albuminous) gland, 

 which resembles in its phylogeny the parotid of the mammalian class, and is 

 composed of proteins, carbohydrates, salts, water, and certain occasional 

 admixtures of abrased epithelial cells or saprophytic micro-organisms. The 

 percentage of proteid substances, which are the main components of the 

 venom, is between 75 to 50 per cent, although there are certain proportionate 

 fluctuations according to different individuals or species. The amount of 

 fats and mucin is not very large, leaving the remaining percentage to water. 

 The salts found in venom are chlorides and phosphates of calcium, mag- 

 nesium, and ammonium, and are present only in small quantities. 



Our knowledge concerning the chemical nature of venom has passed 

 through many phases of evolution and is constantly moving forward. I shall 

 here attempt to give a brief resume of the investigations which supply the 

 principal facts upon which our chemical knowledge is based, as well as those 

 which once served to promote our knowledge. 



Lucien Bonaparte (1843) demonstrated that the most active principle of 

 Vipera berus is a protein resembling digestive ferments, and designated it 

 viperine or echidnine.^ 



S. Weir Mitchell and Reichert (1886) made very exhaustive studies upon 

 the venom of poisonous serpents, in which the chemical side of the problem 

 was also ably handled. 



According to their analysis there are in venom at least two distinct classes 

 of proteins — one including the globulins and the other the peptones. In 

 distinguishing these two kinds of proteins they refer to the facts that after a 

 thorough dialysis there appears in the dialyzer a large amount of whitish pre- 

 cipitate, which, after being separated from the fluid portion of the venom 

 by means of filtration, is found to belong to the globulin group. The filtrate 

 contains some proteins in solution, as it gave a proteid reaction. This latter 

 protein is found to produce no coagulation by brief boiling; not precipitable 

 by weak or strong mineral acids, or by solutions of ferri-chlorides or cupric 

 sulphate; precipitated, but not coagulated, by absolute alcohol;^ and if placed 

 in a dialyzer it is found to be readily dialyzable. Thus, from these general 

 reactions this was placed among the peptones. 



As will soon be detailed in tabulated form, the globulins which separated 

 from the venom solution by dialysis are again differentiated into three varie- 

 ties, all of which agree, however, in general properties in that they are insoluble 

 in distilled water, soluble in weak neutral saline solution, and soluble in 

 dilute acids and alkalies. They become turbid at about 60° C. and are 

 fully coagulated at a point a little above 70° C. 



The ways of preparing these three globulins are given below. For this 



1 He precipitated the proteins of the viper's venom with alcohol and found that the precipitate is poison- 

 ous -when redissolved in water. This differs from Mitchell's method for preparation of crotaline, 

 as the latter was precipitated not from the filtrate of the boiled venom but from the fresh fluid. 



" No effect upon the cobra peptone. 



