160 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, asin 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 Craspedo- 
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 C. 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- 
