ZOOLOGY. 553 



3356. A Fish, respiring through the nose into two 

 swim-bladders, is an Amphibious animal, a Reptile. 



3357. In the Reptile, however, the thorax is still 

 subordinated to the abdomen. Its lungs traverse the 

 whole abdominal cavity, and its manner of breathing is 

 still similar in character to the abdominal function. The 

 lungs are simply two membranous bladders, like two 

 intestines, and admit also of being voluntarily filled with 

 air like the intestine is with water. This filling or infla- 

 tion of the Reptile's lungs takes place also by the abdo- 

 men being expanded at the same time that the mouth is 

 closed by the muscles of the fauces, and is therefore a 

 true process of deglutition. 



3358. Their inspiration is still therefore fish-like in 

 character, excepting that the air is drawn in by the 

 nostrils ; the respiratory process, however, and the respi- 

 ratory organ is constituted as in the perfect air-breathing 

 animals. 



3359. Reptiles may therefore be called Abdominal 

 animals, while the Fishes are Pelvic animals. 



3360. The metamorphosis of the branchial arches into 

 larynx is placed beyond doubt in the Reptiles. The an- 

 terior branchial arches frequently unite with the lingual 

 bone, whereby the latter obtains several cornua. 



3361. The thyroid gland also makes its appearance 

 here for the first time, while the branchial vessels sepa- 

 rate from the arches. Fishes have therefore no thyroid 

 gland. 



336.2. The circulation is complete. The venous and 

 also the arterial blood enters the heart. But both kinds 

 of blood are still mingled with each other as in Fishes. 

 Yet already, through the direction and arrangement of the 

 cardiac orifices, provision seems to be made for their 

 separation. 



3363. The rationale of this mixture of the blood ap- 

 pears to reside in the fact, that many of these animals, 

 and probably all of them in the ovum state, breathe by 

 branchiae. (This proposition, which was announced in 

 the 1st Edition, 1810. 305, and there based upon the 



