SNAKE VENOMS 171 



the copperheaded adder (Ancistrodon contortrix) and the water moccasin 

 (Ancistrodon piscivorous). 



(The classification used above is the one followed in most publications 

 on poisonous snakes ; a more modern classification divides the snakes 

 (Ophidia) into several series, one of these including all poisonous snakes 

 under the title of Proteroglypha, and dividing this series into the three 

 families : (1) ElapiTice, including cobras, coral snakes, etc. ; (2) Hydro- 

 phince, the poisonous sea-snakes ; (3) Viperidce, including all snakes with 

 erectile fangs. 1 ) 



The source of the venom is probably in part the blood, since 

 snake blood has been found to contain poisons very similar to 

 some of those in the venom ; therefore these are presumably 

 simply filtered out by the venom glands, and not manufactured 

 by them. Other poisonous constituents of venom are not found 

 in snake serum, and therefore are probably manufactured by the 

 venom gland. Apparently many of the harmless snakes pro- 

 duce a poisonous saliva, since extracts of their glands are said 

 by Blanchard 2 to possess the properties of the venoms, and if 

 so these snakes are harmless chiefly because they lack an appa- 

 ratus for injecting the poison. As a rule, however, the venom 

 glands are much more highly developed in the poisonous snakes, 

 and are connected with a specialized injection apparatus ; in 

 structure they are compound racemose glands. 



Properties of Venom. As ejected, the venom is weakly 

 acid or neutral in reaction, and free from bacteria, contrary to 

 earlier ideas (Langmann). Its specific gravity is 1030 to 1077, 

 and it contains a large amount of solids, generally 20 to 30 per 

 cent, by weight. These are precipitated by alcohol, ether, tan- 

 nin, and iodin, but do not adhere to precipitates of phosphates 

 as do enzymes and toxins (Calmette). They do not diffuse 

 through dialyzing membranes. When dried, the venom can be 

 kept almost indefinitely without losing its strength, specimens 

 over twenty years old having been found unimpaired. Glycerin 

 and alcohol also seem not to injure it, but oxidizing agents of 

 all kinds are very destructive. Light impairs the power of 

 venoms, as also does radium (Phisalix 3 ). Eosin and erythrosin 

 also reduce the power of venom through their photodynamic 



1 For a full discussion of the characteristics of the poisonous snakes of 

 North America, see the monograph with that title by Stejneger, Report of U. 

 S. National Museum, 1893, Washington. A good summary is also given by 

 Langmann, Reference Handbook of Medical Sciences, vol. 8, p. 708. Con- 

 cerning poisonous sea-snakes, Hydrophidia, see Boulanger, Natural Science, 

 1892 (1), 44. The poisonous snakes of India are described by Fayrer, in " The 

 Thanatophidia of India," London, 1874. 



2 Compt. Rend. Soc. Biol., 1894 (46), 35. 



3 Compt. Rend. Soc. Biol., 1904 (56), 327. 



