RATTLESNAKE 649 



both of these instances the snake had swallowed its prey head foremost. 

 But a case has been reported by Dr. Barton W. Evermann (1915&) in which 

 a rattlesnake killed near Cascade Falls (west of the lower end of Yosemite 

 Valley) on July 15, 1914, contained an adult Mariposa Chipmunk which 

 it had swallowed tail first! "The head of the chipmunk was toward the 

 snake's head, and its legs, tail and fur all lay back toward the snake's tail, 

 smooth and in perfect order. ' ' 



Fig. 65. Sketch of head of Pacific Eattlesnake, showing important parts of the 

 anatomy which function in the bite and poisoning by this snake. The action of the 

 poison apparatus is as follows. As the snake moves its head forward to strike a victim, 

 be it man or animal, Muscle 1 (spheno-pterygoid) is contracted. This ptshes forward 

 the tooth-bearing bone preceding it and this in turn rocks forward the bone which carries 

 the fang and causes the fang to come in line with the strike of the head. After the 

 fang has entered the body of the victim, Muscle 1 relaxes and Muscles 2 and 3 (external 

 pterygoid and sphenopalatine) contract, drawing the fang more deeply into the flesh. 

 Then Muscle 4 (anterior temporal) contracts, bringing up the lower jaw and at the 

 same time compressing the poison gland so that the poison is forced along the duct, 

 through the fang, and into the flesh of the victim. Then the whole musculature of the 

 head and neck relaxes, the head and fangs are drawn away from the victim and the 

 fang is depressed again. This whole series of actions occupies but an instant. 



The fang is shown partly elevated. Normally it lies close to the roof of the mouth 

 and is covered by a membrane not shown in the dra\\'ing. When the fang is erected, 

 preparatory to biting, this membrane is folded down at the base of the fang and directs 

 the poison as it leaves the end of the duct of the gland into the base of the fang. 

 (Adapted from Noguchi.) 



A strong belief in many places is that the rattlesnakes "go blind" in 

 late summer and are then very dangerous and likely to strike without 

 warning. The basis of fact underlying this notion is that many of these 

 snakes molt in that season, and that for a time, just before the molt the 

 .skin overlying the eyes, which is likewise sloughed off, is clouded by the 

 secretion which loosens the outer skin preparatory to its removal. Another 

 widespread notion is that rattlers go about in pairs; we have never been 

 able to find any conclusive evidence on this point. 



The temperament of the rattlesnake is quite different from that of the 

 racers, and reflects in a way the differences in form between the two types. 

 The rattlesnake is generally quiet and slow, even lethargic, and is wont 



