ZOOGENY. 389 



Reptiles the trachea is therefore still in a membranous 

 condition, but in Birds and Mammalia, it is surrounded 

 by many rings, or is a repetition of the larynx. 



2232. In Birds even a kind of inferior larynx origi- 

 nates, which is provided with muscles and can produce 

 tones. 



2233. The ramification of the trachea into two 

 bronchi or branches is constantly progressing, and at 

 length these tubes divide into a great number of vesicles, 

 which together form the lungs. The lung, which was in the 

 commencement a simple saccular inversion of the integu- 

 ment, has now become a self-substantial organ, to which 

 the respiratory vessels have been subordinated. The 

 lung also divides upon each side into five lobes. 



b. VASCULAR ORGANS OF THE INTESTINE. 



Liver. 



2234. The self-substantial development of the vascular, 

 and its separation from the general, system, is most per- 

 fectly attained in the Liver. 



2235. In the liver, as being the vascular system, which 

 combines with the intestinal canal, the venous system 

 has become independent. The portal vein arises from 

 the intestinal canal, collects into one trunk, and again 

 ramifies in order to unite with the biliary ducts, which 

 are only a ramified saccular eversion of the intestine. 

 This conjunction is represented by the liver. 



2236. The liver as being a venous organ stands there- 

 fore in opposition to the lung, and produces, instead 

 of oxydes, a basic body, or the bile. The liver, as being 

 the venous system which has become free, is to be regarded 

 as the highest development or blossom of the vascular 

 system. 



2237. It is for the vegetative body, what the brain is 

 for the animal ; arid hence, therefore, the similarity of 

 structure and the sympathy between both organs. 



