ilEPTILES. 2(>7 



laginous, or osseous filaments, for their support, as in fishes. 

 Their teeth, in general, are fitted for retaining their food, 

 rather tlian for masticating, and the gullet is usually dilata- 

 ble. The food, in a few genera, is derived from the vegeta- 

 ble kingdom, but, in the greater number, animal food is ex- 

 clusively employed. A considerable quantity is consumed 

 at a time, but the intervals between the meals are remote. 



The circulation of this group may be considered as im- 

 perfect, since a part only of the blood is aerated, which 

 issues from the heart, and that portion, instead of proceed- 

 ing directly to the different organs, is again mixed with the 

 circulating fluid. The aerating organs consist, in general, 

 of lungs situate in the common cavity of the abdomen. 

 There is an imperfect larynx at the commencement of the 

 trachea, incapable of producing a distinct voice. The 

 lobes of the lungs are of unequal size, and the cells are of 

 much larger dimensions than in the warm-blooded animals. 



The kidneys are always present, either united into one 

 mass, or variously subdivided. The ureters either pour 

 their contents into a bladder of urine, which empties itself 

 into the cloaca, or they teiminate directly in the cloaca, the 

 urine passing into a lateral pouch until voided. The urine 

 itself varies much in quality and appearance in the different 

 tribes. In some it is pure uric acid, in others very diluted 

 urea. 



Althougli reptiles can secrete a limited quantity of heat 

 or cold, for their preservation in extraordinary circum- 

 stances, they usually remain nearly of the same tempera- 

 ture with the surrounding medium. They are remarkable, 

 however, for the facility with which they become torpid, 

 when the temperature sinks towards the freezing point. 

 So necessary, indeed, does a high temperature appear to 

 be, to the comfortable exercise of their several functions, 

 that wc find them chiefly inhabiting the warmer regions oi' 

 the rarth. 



