940 16. CROTALIDA 
them industriously, with the result that we have never seen 
one strike more than one-third its own length. The strike 
however, is almost too quick to be followed by the eye, 
though the recovery succeeding it is slow. At the same time 
the snake strikes, its mouth is opened widely and the fangs 
are thrust forward so that the points are directed outwards 
at right angles with the vertical roof of the mouth. The 
mouth is kept tightly closed except during a strike, only the 
protruding and rapidly vibrating tongue shows, so terrify- 
ing to the average person. This tongue is a very soft and 
delicate organ, perhaps tactile in function. 
“The food of the rattlesnake consists chiefly of mam- 
mals. We found three snakes last summer by following up 
the excited calls of a number of birds in a rose thicket. The 
birds evidently had reason to fear the snakes, especially as 
they were of species which nest on or near the ground. We 
have never seen the rattlesnake climbing trees, though one 
individual was climbing through a brush thicket perhaps two 
feet above the ground proper. It is plainly of too heavy a 
build to be enabled to climb readily. It is hard enough 
work for it to squirm its way over the ground. We have 
never found any bird remains in rattlesnakes’ stomachs. 
“On Pine Flats, in the San Gabriel Mountains, a large 
lazy rattler was secured which showed a tremendous bulge 
about half-way along its body. Dissection disclosed a full- 
grown ground squirrel (Citellus beecheyi fisheri) which had 
been swallowed entire, as is always the case with whatever a 
snake eats. 
“In the San Bernardino Mountains, the junior author 
found a small rattler in the act of swallowing an adult 
meadow-mouse (Microtus). The victim was about half- 
way protruding from the snake’s mouth, and so tightly 
wedged in as to render the snake unable to get rid of its 
mouthful when we began to tease it and it wanted to. We 
