i6o The Naturalist in La Plata. 



as pyrethrum powder is to most insects, and even 

 go so far as to describe its effect as fatal to them ; 

 according to this, the smell is therefore a pro- 

 tection to the deer. In places where venomous 

 snakes are extremely abundant, as in the Sierra 

 district on the southern pampas of Buenos Ayres, 

 the gaucho frequently ties a strip of the male 

 deer's skin, which retains its powerful odour for an 

 indefinite time, round the neck of a valuable horse 

 as a protection. It is certain that domestic animals 

 are frequently lost here through snake-bites. The 

 most common poisonous species — the Oraspedo- 

 cephalus alternatus, called Vivora de la Cruz in the 

 vernacular — has neither bright colour nor warning 

 rattle to keep off heavy hoofs, and is moreover of 

 so sluggish a temperament that it will allow itself 

 to be trodden on before stirring, with the result 

 that its fangs are not infrequently struck into the 

 nose or foot of browsing beast. Considering, then, 

 the conditions in which 0. campestris is placed — 

 and it might also be supposed that venomous snakes 

 have in past times been much more numerous than 

 they are now — it is not impossible to believe that 

 the powerful smell it emits has been made protec- 

 tive, especially when we see in other species how 

 repulsive odours have been turned to account by 

 the principle of natural selection. 



After all, perhaps the wild naturalist of the 

 pampas knows what he is about when he ties a 

 strip of deer-skin to the neck of his steed and 

 turns him loose to graze among the snakes. 



The gaucho also affirms that the deer cherishes 

 a wonderful animosity against snakes ; that it be- 



