ZOOGENY. 391 



2247. The perfect organ of respiration is an air-organ 

 or lung ; combined with the tegumentary system, it is 

 a water-organ or branchia. 



2248. There are dermo-branchia or the branchiae pro- 

 per, as in the Worms, Molluscs, Snails, and Crabs. 



2249. Intestinal branchia in the Holothuriae, consti- 

 tuting in the higher animals a spleen. 



2250. The sexual branchiae are probably the primor- 

 dial kidneys. 



2251. The branchiae when united with the osseous 

 system are the branchial arches of Fishes, which subse- 

 quently separate into larynx and thyroid gland. 



2252. The self- substantial development of the integu- 

 ment into the respiratory organ is a lung. 



2253. When united with the vascular system or the 

 vegetative systems generally, the integument forms the 

 tracheal system of Insects. 



2254. The tracheae are spiral vessels as in plants. 



2255. The respiratory organ, united with the motor 

 system, is the lung proper, which is situated within the 

 thorax, and covered by ribs. 



2256. The proper lung divides also, like the intestine, 

 into two parts, into the cystiform, pharyngeal expansion 

 of the larynx, and into the pulmonic substance, which is 

 equivalent to the stomach, and wherein the analysis of 

 the air takes place. 



2257. The trachea, and especially the larynx, is more- 

 over an entire thorax, a ribbed skeleton upon a small 

 and membranous scale. In the larynx, the animal tho- 

 racic structure, consisting of ribs and muscles, resides 

 prognosticated. The larynx has originated from the 

 coalescence of branchial arches. The ribs are a repeti- 

 tion of the branchial arches. 



2258. The diaphragm is a formation, which admits, by 

 no reasoning from its anatomy, but only genetically, of 

 being explained. Originally, the whole body was only 

 an abdomen, upon the external surface of which the 

 branchiae were appended. A remarkable instance of this 

 is at once afforded by the Snails, and also the Fishes. 



