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HARDWICKE'S SCIENCE^GOSSIP, 



essence that chamber of the mantle which covers the 

 branchiae in aquatic species, adapted for breathing 

 the atmosphere. A true lung, therefore, may only be 

 sought for in Vertebrates ; and, to commence with the 

 lowest class of fishes, we find under the spine and 

 within the general cavity of the body, a large, strong 

 membranous pouch inflated with gas which appears 

 to be secreted by its walls; ordinarily this swim- 

 bladder, as it is called, has no communication with 

 the exterior, but there are exceptions. 



In the Lepidosiren, or mud-fish, the transition from 

 the piscine air-bladder to the Reptilian form of lung is 



pulmonary development is well evinced in the lungs 

 of the frog {Rana temporarid). Here the triton-type of 

 lung is enlarged, and more especially is subdivided' 

 into delicate membranous chambers or cells, having, 

 blood-vessels in their walls exposed to the air that 

 passes through them by means of the very abbreviated' 

 air-pipe or trachea. The saccules, however, of a 

 frog's lung are, comparatively speaking, very large,, 

 and the extent of air-surface they present, though 

 vastly excelling that of the triton's lung, is much 

 smaller than that presented in the lung of a Mammal. 

 Wherein then is the difference between a Batrachiatr 

 lung, such as that of a frog, and a Mammalian lung,' 

 like, say, that of the mouse ? Chiefly in this, that 

 while the saccules of the former are few and large. 



M 



'¥ 



K 



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Fig. 147.— Lungs oi 

 Triion cristatus. 



Fig. 148. — ^Lungs of Raiia 

 teinporaria. 



Fig. 149. — Air Cells of the Lung of Rana; p, stellate pigment corpuscles. 



sufficiently obvious, but as we are here concerned 

 with our native animals, this mention of it will 

 suffice. The intimate principle of a respiratory organ 

 consists of a permeable membrane having blood-vessels 

 within its substance, exposed to the atmosphere chiefly 

 for the purpose of supplying the blood with atmo- 

 spheric oxygen for the sustenance of its vitality, and 

 for the general purposes of oxidation in all living 

 parts of the organism, but partly also for facih- 

 tating the escape of carbonaceous and other waste 

 from the body. The air-sac of a fish has very few 

 and scattered vessels in its walls, but if one of our 

 common newts, such as Triton cristatus, be dissected, a 

 large improvement upon the bladder of the fish will 

 be evident ; there are now two simple transparent 

 sacs communicating with a glottis in the floor of the 

 pharynx, an artery passes down the side of each sac, 

 and a vein collects the arterialized blood along the 

 opposite side. The breathing organs of the trjton 

 are therefore wholly devoted to the respiratory 

 function, while the air-bladder of the fish appears to 

 be chiefly an hydrostatic prgan. The next step io 



the lung-substance of the latter is a dense agglomera- 

 tion of an infinite number of minute air-cells. The 

 lung of the frog is obviously cellular, while a 

 Mammalian lung, when cut with a knife, apparently 

 presents a solid parenchyma, but no great magnifying 

 power is requisite to demonstrate the cellular 

 character of the latter. The lungs of birds resemble 

 more or less the Mammalian^type in structure. It is 

 impossible in this short paper to describe the collateral 

 development of other parts of the lung, such as the 

 increasing complexity of the trachea, the larynx, and 

 the various means for inflating and compressing the 

 lung. 



WRIGHTIA COCCINEA. 



READERS of Science-Gossip maybe interested 

 in the following brief review of a memoir, by 

 Dr. A. Tomes, of the Bengal Medical Service, orr 

 the fly-catching habit of Wrightia coccinea, which 

 has recently been issued amongst the Scientific 

 Memoirs by the medical officers of the army of 



