i82 ' REPTILES. 



The eyes of ferpents arefmall, compared to their length of body -, dif- 

 ferently coloured in different kinds ; yet in all nmalign, brilliant, and lively j 

 very mobile and projedling, and fo placed as to receive images from 

 the greateft fpacc their pofition admits. Their fight, therefore, may 

 juftly be efteemed fliarp and piercing. In feme, the upper eye-lid is 

 wanting, and the ferperrt winks only with that below j in others, the ani- 

 mal has a ni£litating membrane, refembling that of birds, which keeps 

 the eye clean, and prefcrves the fight. Thefubftance of the eye in all is 

 hard and horny j the cryftalline humour occupying great part of the 

 globe. 



The tongue is thin, long, and forky j compofed of two long flefhy 

 fubftances, which terminate in points, and are very pliable. At the root 

 it is conneded very ftrongly to the neck by two tendons, that give it a 

 variety of play. Some of the viper kind have tongues a fifth part of the 

 length of their bodies, which are continually darting out; but their 

 poifon is not in thefe. 



The gullet is wide, capable of being diflended greatly; at the bottom 

 of this lies the ftomach, which is not equally capacious. 



Serpents are furnifhed with very large lungs, in fome extending three 

 quarters of their bodies : thefe they fiill with air at once, but let it flovvly 

 cfcape. 



1 he heart, as in the tortoife, frog, and lizard, has but one ventricle; 

 and the communication between the blood which comes to, and that 

 which quits the heart, is independent of the lungs and of breathing. 

 H^ncethey are amphibious; but though all are amphibious, fome love 

 the water more than others, and probably the largeft kinds. Their blood 

 flows extremely flowly, pofTeffcs little warmth ; and hence they are in 

 certain degrees of temperature torpid. Thefe are ^he lelTer kinds j the 

 larger inhabiting climates where no fuch temperature is known. They 

 awake early jn Ipring, and, what is remarkable (as of all fleeping animals), 

 ■when the air is not equally warm as when they foifook it in autumn. 



The vent in thefe animals ferves for the emifilon of the urine and the 

 fseces, and they contain the necefi^ary parts for perpetuating the fpecies. 

 Thefe are double; but there are no external marks whereby to diftinguifh 

 the {exes. 



The body of ferpents is long, flender, and capable of bending in all di- 

 redtions, and even folds feveral times on itfelf : the joints in the back- 

 bone are numerous ; in fome amounting to an hundred and forty-five 

 from the head to the vent, and twenty-five more from that to the tail. 

 6 Thefe 



