570 



REPTILIA. 



Fig. 257. 



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. 



(629.) Passing from the consideration 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 in- 

 termediate forms, which, not- 

 withstanding that they lose 

 their branchiae at an early 

 stage of their growth, are evi- 

 dently closely related to the 

 Perennibranchiata, as may be 

 gathered from the arrange- 

 ment which their blood-ves- 

 sels 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 annexed figure, taken 

 from the Catalogue of the 

 Hunterian Collection, the 

 principal vessels of this crea- 

 ture are delineated as seen 

 from the dorsal aspect. The 

 lower jaw (a) has been re- 

 moved 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 



