ZOOLOGY. 



chambers. On this account, the mixture of arterial and 

 venous blood cannot take place within the heart itself ; 

 but the pulmonary artery and aorta are connected by a 

 small aperture near their origin. Through this aperture, 

 the venous blood contained in 

 the pulmonary artery is mixed 

 with the arterial blood con- 

 tained in the aorta. Thus, 

 in the crocodiles, a mixed fluid 

 is conveyed to the lungs and 

 through the system, as well as 

 in the other Reptilia. 



On account of this peculiarity 

 in the structure of the heart, 

 and in the course of the circu- 

 lation, the blood of the Reptilia, 

 being imperfectly aerated, is 

 cold ; and, as a consequence, 

 the movements of these animals 

 are sluggish, and their intelli- 

 gence of a lower order. " It 

 may be remarked, however, 

 that stupidity in reptiles is as- 

 sociated, as it often is in man, 

 with a venomous and rancor- 

 ous disposition; and that these 

 FIG. is.-Cm^ATioN IN REPTILES. Defects, both intellectual and 

 a, vena cava ; &, right auricle, moral, seem to depend upon an 



receiving venous blood from the ^^p-fp^- /yjn'rhtirm nf fho 



body; c, left auricle, receiving ar- iniper 



terial blood from the lungs; d, blood Corpuscles. (Dr. 



common ventricle, receiving mixed 7-7- ,, \ 



blood; e, pulmonary artery, con- a.ClugtltOn.J 



veying mixed blood to the lungs; rj^ ^ corpuscles of the 



/, aorta, conveying mixed blood r 



through the system. blood are oval and nucleated. 



46. Respiration. The cavities of the chest and abdomen 

 are not separated by a diaphragm. The lungs are large 

 and often extend into the abdomen. Their bronchi are 

 closed, and do not communicate with air sacs in the body. 

 In the serpents, there is only a single lung. 



