POISONS 71 



to be appreciably venomous. Man, it is true, is not 

 easily affected by the bite of these snakes, since, at 

 least in most of those which have a long maxillary 

 bone, the grooved fangs are placed too far back to 

 inflict a wound under ordinary circumstances. There 

 are, however, exceptions. A case was reported a 

 few years ago of a man in South Africa nearly dying 

 as a result of the bite of the Boomslang, Dispholidus 

 typus, the symptoms, carefully recorded, being those 

 characteristic of Viperine poisoning, an important 

 fact to oppose to the conclusions, based on the 

 physiological experiments on Ccelopeltis, which 

 appeared to disprove the theory that the Viperidae 

 may have been derived from Opisthoglyphous 

 Colubrids. 



Experiments made with the secretion of the 

 parotid gland of Tropidonotus and Zamenis have 

 shown that even Aglyphous snakes are not entirely 

 devoid of venom, and point to the conclusion that 

 the physiological difference between so-called harm- 

 less and poisonous snakes is only one of degree, just 

 as there are various steps in the transformation of an 

 ordinary parotid gland into a poison gland or of a 

 solid tooth into a tubular fang. 



The question whether all snakes are immune to 

 their own poison is not yet definitely settled. Most 

 snakes certainly are, and it is a remarkable fact that 

 certain harmless species, such as the North American 

 Coronella getula and the Brazilian Rhachidelus brazili, 



