ORDER SAURIA. 181 



the crocodiles, attain to a remarkable size. The advanced 

 age to which they arrive is not surprising in cold-blooded 

 animals, which transpire with difficulty, easily dispense with 

 food, and possess the faculty of repairing such external losses 

 as they happen to sustain. 



In man and the more complicated animals of the verte- 

 brated division, circulation is a function of the first import- 

 ance. The blood, proceeding from the left ventricle of the 

 heart, spreads itself by the arteries through the whole body, 

 takes the capillary system in its way, passes into the veins, 

 returns to the heart, enters into the right auricle of that 

 organ, then into the corresponding ventricle, which, in its 

 turn, sends it into the pulmonary artery to be distributed 

 into the lungs, from which it issues by the pulmonary veins, 

 to repair to the left auricle and ventricle, and proceed from 

 thence in its round anew. In this course the blood evidently 

 describes a double circle, one in the lungs, the other in the 

 entire body. 



This is not at all the case with the reptiles in general, and 

 with the saurians in particular. The heart, as we have 

 already observed, in all these animals is so disposed, that at 

 each contraction it sends into the lungs but a portion of the 

 blood which it has received from all the other parts of the 

 body. Therefore the pulmonary circulation of the saurians 

 is but a fraction of the great circulation. This fraction is 

 more or less considerable, according to the genera, and pro- 

 ductive of effects more or less marked. But as we have 

 already enlarged on this topic sufficiently, and shown the 

 consequences of this sluggish circulation on the habits, pas- 

 sions, intellectual and physical constitution, we shall content 

 ourselves by remarking here, that the quantity of blood in 

 the saurians is very inconsiderable in comparison with that 

 of mammifera and birds. Hasselquist, who dissected a cro- 

 codile at Grand Cairo in 1751, reports, that the quantity 



