2l6 



BACKBONED ANIMALS. 



of the Southern and Western States attains a length of 

 three feet, and is so fragile that the slightest blow severs 



it in sections. The 

 upper surface is 

 yellowish green 

 spotted with 

 black. 



Heloderma 



{Helodermidcs) . 

 The "Gila mon- 

 ster," or Heloder- 

 ma (Fig. 261), is 

 the largest lizard 



FIG. 2 6o.-Glass snake (Ophisaurus ventralis). of North America, 



attaining a length 



of three feet, and enjoying the distinction of being the only 

 poisonous member of the order. In appearance they are 

 repulsive, being covered with scales, the whole resembling a 

 flinty, faceted armor. The general color is black, marked 

 with yellowish-orange or white interspaces. The tail is 

 cylindrical and clumsy. Their movements are slow and 

 uncertain, resembling those of a young alligator. The 

 teeth are fissured, and at the bases of the grooves are the 

 ducts from which the poisonous saliva passes into the 

 wound.* After biting, the heloderma appears sluggish, 



* According to Mitchell and Reichert, the physiological action of 

 the poison is quite different from that of snake-poison. The latter 

 kills by paralyzing the respiratory center, while the poison of the helo- 

 derma paralyzes the heart. When injected subcutaneously it causes no 

 local injury, the effect being to arrest the motion of the heart, which 

 slowly becomes contracted, and the spinal cord paralyzed. It is not 

 necessarily fatal to human beings, though an American scientist, after 

 being bitten, was barely able to call assistance. In experiments tried 

 by Sir John Lubbock, a live frog when bitten died almost immediately 

 in convulsions. A Guinea-pig, bitten in the hind-leg, died in three 

 minutes, and young rats succumbed even more quickly. The specimen 

 kept in Ihe New York Zoological Garden thrived upon hard-boiled eggs. 



