358 



ZOOLOGY 



SEUT. 



number of diverticula or air-sacs which are capable of being 

 inflated, causing an increase in the bulk of the animal which 



doubtless has an effect on assailants. 

 In the snake-like Lizards the right 

 lung is larger than the left, and in 

 the Amphisbeeuians the latter is 

 entirely aborted. In the Snakes a 

 similar reduction or abortion of the 

 left lung is observable. In the 

 Crocodilia and Chelonia the lungs 

 are of a more complex character. 



Fig. 1001.— Heart of I<acerta muralis, ventral 

 view. A, A. auricles ; Ap, pulmonary artery ; 

 As, As', subclavian arteries ; Ci, post-caval ; /. 

 jugular vein ; Ha, aortic aixhes (made up on 

 either side of two embryonic arches, 1 and ;?) ; 

 V, ventricle ; Vp, pulmonary vein ; Vs, sub- 

 clavian vein. (From Wledersbeim's Com2}arative 

 4natomT/.) 



being divided internally by septa 

 into a number of chambers. 



Organs of Circulation. — In the 



heart (Fig. 1001) the sinus venosiis 

 is always distinct, and is divided 

 into two parts by a septum ; its 

 aperture of communication with the 

 right auricle is guarded by valves. 

 There are, as in the Amphibia, al- 

 ways two quite distinct auricles, the 

 right receiving the venous blood from 

 the body, the left the oxygenated blood brought from the lungs 

 by the pulmonary veins. But a vital point of difference between 



y 



:.. 1000. — Lungs of Cliainzeleon. 

 T. trachea. (From Wiedersheira's Com- 

 jyaralive Anatomy.) 



