SNAKE VENOMS 149 



in the southeastern states; it is a member of the coliibrine poisonous snakes, of 

 small size, and seldom causes serious poisoning. The poisonous vipers are the 

 rattlesnakes (Crotaliis) , of which there are some ten to twelve or more species, 

 and Sistrtirus, of whicli there are two species: the copperheaded adder (Ancistro- 

 don contortrix) and the water moccasin {Ancistrodon piscivorus) . 



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 includino; all poisonous snakes under the title of 

 Proterogiypha, and dividing this series into the three families: (1) Elapinw, 

 including cobras, coral snakes, etc.; (2) Ilydrophinije, the poisonous sea-snakes; 

 (3) Viperidic, including all snakes with erectile fangs. 20 



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 poison- 

 ous constituents of venom are not found in snake serum, and there- 

 fore are probably manufactured by the venom gland. Apparently 

 many of the harmless snakes produce a poisonous saliva, since 

 extracts of their glands are said hj Blanchard -- to possess the 

 properties of the venoms, and if so these snakes are harmless chiefly 

 because they lack an apparatus 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 ap- 

 paratus : 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 40 per cent, by weight. These 

 are precipitated by alcohol, ether, tannin, and iodin, but do not ad- 

 here to precipitates of phosphates as do enzymes and toxins (Cal- 

 mette). 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 unim- 

 paired. Glycerol and alcohol also seem not to injure it, but oxidiz- 

 ing agents of all kinds are very destructive. Light impairs the power 

 of venoms, as also does radium (Phisalix).-^ Eosin and erythrosin 

 also reduce the power of venom through their photodynamic action, 

 affecting the neurotoxic properties less than the hematotoxic compo- 

 nents (Noguchi).^* Cobra venom withstands even 100° for a short 

 time, but crotaline venoms are destroyed at 80-85°. 



20 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. Na- 

 tional jNIuseum, 189.3, Washington. A good summary is also given by Langmann, 

 Reference Handbook of INIedical Sciences. Concerning poisonous sea-snakes, 

 Ilydrophidia, see Boulanger, Natural Science, 1802 ( 1) . 44. The poisonous snakes 

 of India are described by Fayrer, in "The Tlianatopliidia of India."' London, 1874. 



21 Contradicted by Arthus, Arch, internat. phvsiol., 1012 (12), 1G2. 

 22Compt. Rend. Soc. Riol., 1894 (46), 3.5. 



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

 24, Jour. Exper. Med., 1906 (8), 252. 



