170 PHYTOTOXINS AND ZOOTOXINS 



produce decided therapeutic effects, although by no means all observers 

 are agreed as to its efficacy. l 



(The effects of the phytotoxins on the blood are discussed 

 under " Hemolysis " in the following chapter. Vegetable hem- 

 olytic poisons that do not resemble the toxins, e. g., glueosides, 

 etc., will also be found discussed under the same heading.) 



ZOOTOXINS 2 



SNAKE VENOMS 



This important class of poisons, first thoroughly investigated 

 by Weir Mitchell (1860), and Mitchell and Reichert (1883), 

 has recently aroused great interest through its relations to bac- 

 terial toxins and the problems of immunity. The poisons of 

 different species of snakes seem to have much in common with 

 one another, whether derived from the Elaperine snakes (cobras 

 and numerous other Indian and Australian snakes), or Viperidce 

 (including most poisonous American snakes), or Hydrophince 

 (the poisonous sea-snakes), although very characteristic differ- 

 ences exist between each. 



The essential anatomical differences between the different classes of 

 snakes are as follows : Colubridce, which include all the non-poisonous 

 snakes, have no mechanism for injecting poisons into their victims. 

 Colubridce venenosce are venomous snakes resembling in many particulars 

 the harmless Colubrines, but having short poison fangs, firmly fastened 

 to the maxilla in an erect position ; in this class are included the cobra 

 and the venomous snakes of Australia. Viperidce, or vipers, are char- 

 acterized by a highly specialized apparatus for injecting the poison ; their 

 poison fangs are very long, and the maxillary bone, to which they are 

 fastened, is so articulated that it rotates about a quarter of a circle when 

 the snake strikes, bringing the fangs into an erect position. The fangs 

 are canalized and pointed at the end like a hypodermic needle, and the 

 poison is forced through them under considerable pressure by a large 

 muscle that contracts over the salivary gland. Accessory fangs in vari- 

 ous stages of development are also present to replace any fang lost in 

 action. All the poisonous snakes of North America, with one insig- 

 nificant exception, belong to the vipers, and to a special class known as 

 the "pit vipers," because of the presence of a deep pit of unknown 

 function above the maxilla. The exception mentioned is the "coral 

 snake ' ' found on the coast of Florida, around the Gulf of Mexico and 

 in the southeastern states ; it is a member of the colubrine poisonous 

 snakes, of small size, and seldom causes serious poisoning. The poison- 

 ous vipers are the rattlesnakes (Crotalus), of which there are some ten 

 to twelve or more species, and Sistrurus, of which there are two species ; 



1 See Ingals, Jour. Amer. Med. Assoc., 1906 (47), 376. 



2 Full review and literature given by Faust, " Die tierischen Gifte," Braun- 

 schweig, 1906. Hemolytic Properties of Animal Poisons, discussed by Sachs, 

 Biochemisches Centralblatt, 1906 (5), 257. 



