REPTILIA. 



Fig. 343. 



to the pressure of the accumulated contents of that cavity, and there 

 would have been a disproportionate obstacle to the passage of the aerated 

 blood into the ventricle. This is obviated by providing the pulmonary 

 veins with a distinct receptacle, which is equally ready with the right 

 auricle to render its contents into the ventricle during the diastole of 

 that cavity. 



(1956.) Passing from the con- 

 sideration of the more perfect 

 Reptile circulation as it exists 

 in those genera which in their 

 adult condition possess lungs 

 only, to those which may pro- 

 perly be called Amphibious, and 

 are provided with both lungs 

 and gills throughout the whole 

 period of their lives, we must 

 still pause to notice one or two 

 intermediate forms, which, not- 

 withstanding that they lose their 

 branchiae at an early stage of 

 their growth, are evidently 

 closely related to the Perenni- 

 branchiata, as may be gathered 

 from the arrangement which 

 their blood-vessels permanently 

 exhibit. Such is the Menopoma, 

 or Great South American Sala- 

 mander, an animal met with in 

 the rivers and lakes of the South 

 American continent. In the an- 

 nexed figure, taken from the 

 Catalogue of the Hunterian Col- 

 lection, the principal vessels of 

 this creature are delineated as 

 seen from the dorsal aspect. The 

 lower jaw (fig. 343, a) has been 

 removed from the head, so that 

 in the drawing are exposed the 

 cut edge of the masseter muscle 

 (6), the tongue (c), and the opening of the larynx, into which a bristle 

 (d) has been introduced, one end of which is seen passing into the cavity 

 of the right lung : the bag of the pharynx (//) has been left entire ; 

 and upon this the main vascular trunks are supported. From the heart, 

 situated upon the opposite side of the esophagus, is given oif a large 

 vessel representing the bulbus arteriosus of fishes, which terminates by 



Circulation in 3/fenopotnu. 



