LECTURE VII. 3 



or bears so great a proportion to the vesicular 

 one, or that of the air-cells, that the latter are 

 scarce distinctly visible without a close and minute 

 survey; but on. the contrary, in the Amphibia the 

 vesicular system greatly preponderates over the 

 vascular, insomuch that in some of the tribe, -as 

 in the Tortoises for instance, the lungs seem to 

 consist almost entirely of bladders or vesicles, 

 while the blood-vessels distributed through them, 

 and constituting their vascular system, appear 

 very slight in comparison. In Frogs the difference 

 is still more striking; for in these animals the 

 lungs, when in a state of inflation, exhibit the ap- 

 pearance of a pair of bladders, the internal part 

 or cavity of which is slightly subdivided into mi 

 merous cells, reaching but a little way down, or 

 in such a manner as to leave a large central, va- 

 cuity in each lobe of the lungs ; while the blood- 

 vessels are distributed in a very elegant and beau- 

 tiful manner between them. In many of the 

 Lizards the lungs seem even less complex than in 

 the Frogs; for in some of the smaller Lizards, 

 and particularly in the common Water- Newt, or 

 L. aquatica of Linnaeus, the lungs are merely a 

 , -pair of lengthened bladders, without any internal 



