190 



FIRST LESSONS IN ZOOLOGY. 



pipe. In the bull-snake, the loud, hoarse hiss is due to the 

 presence of an unusually large epiglottis (Figs. 196, 197 I). 

 The fixed, stony gaze of snakes is due to the fact that the 

 eye is covered by a thin stationary capsule, the true lids not 

 being present. 



The proverb " deaf as an adder" is not founded on fact, 

 as snakes, like all reptiles, have internal ears. Their sense 

 of hearing may be dull; but certain snakes, as the cobra de 

 capello, are attracted by music. 



Most snakes resemble in color the 

 ground or soil they frequent; some 

 being, as the rattlesnake of the 

 Western plains, of the color of the 

 soil in which they burrow. The little 

 green snake is of the color of the 

 grass through which it glides ; oth- 

 ers are dull gray or dusky, harmo- 

 nizing with the color of the trunks of 

 trees on which they rest. The poi- 

 sonous coral-snake (filap*) of the 

 forests of the Southern States is, 



FIG. 197. Mouth of Bull- , -, -, , 



snake, seen from above; let- however, gayly and COllSplCUOUsly 



tersasmFig.l96.^Shufeldt. coloi , ed; indee( ^ j t cau afford to be 



brightly colored, as no birds dare to attack it. 



The poisonous snakes may always be recognized by their 

 broad, flattened heads, and usually short, thick bodies. 



The poison-gland of the rattlesnake (Fig. 198, a) is 

 a modified salivary gland. The two fangs are modifica- 

 tions of maxillary teeth, each of which has been, so to speak, 

 pressed flat, with the edges bent towards each other, and 

 soldered together, so as to form a hollow cylinder open at 

 both ends, the poison-duct leading into the basal opening. 

 When the fangs strike into the flesh, the muscles closing 

 the jaws press upon the poison-gland, forcing the poison into 

 the wound. The poison-fangs are largest in the most 

 deadly species, as the viper ( Vipera), the puff-adder ( 670- 

 tho), the rattlesnake, and fer-de-lance (Trigonocepltalus), 



