358 



ZOOLOGY 



SEC'T. 



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 Amphisbaenians 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, 





-As 



-Ac 



FIG. 1001. Heart of Lacerta muralis, ventral 

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

 As, As', subelaviaii arteries ; C'i, post-caval ; J. 

 jugular vein ; Ra, aortic arches (made up on 

 cither side of two embrj-unic arches, 1 and :.') ; 

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

 clavian vein. (From Wiedersheirn's Comparative 

 Anatomy.) 



being divided internally by septa 

 into a number of chambers. 



Organs of Circulation. In the 



heart (Fig. 1001) the sinus venosus 

 is always distinct, and is divided 

 into two parts b} r 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 



FIG. 1000. Lungs of Chamceleon. 

 T. trachea. (From Wiedersheirn's Com- 

 parative Anatomy.) 



