ZOOGENY. 403 



2350. Like the urethra, so is the trachea mem- 

 branous in Fishes, and in most Reptiles also. 



2351. Urinary bladder and urethra stand in sympa- 

 thetic relation with the trachea and larynx, and have 

 also similar diseases, such as catarrh, inflammation, &c. 



2352. The proper proof, however, of the urinary blad- 

 der belonging to the respiratory system resides in its 

 genesis. It proceeds from the allantois, which in Birds 

 is a decided organ of respiration, a branchia. 



2353. Out of this urinary bladder issue in the embryo 

 what have been called primordial kidneys, which shrink 

 or dwindle down at a later period, but have entirely the 

 structure of branchia?. 



2354. Here then is a sexuo-respiratory process, which 

 corresponds to the anal respiration, upon a higher stage, 

 of many worms and aquatic larvae, e. g. Holothurise and 

 Libellulae. This anal respiration is in its signification a 

 sexual respiration. 



2355. Even in'the acephalous Mollusca and Snails the 

 respiratory openings are almost always situated in the 

 proximity of the anus ; their respiration is still a sexual 

 respiration. 



2356. For the first time in Insects it becomes a re- 

 spiration of the trunk ; and for the first time in the higher 

 animals a truly animal, namely, a cephalic respiration. 



2357. The urinary system is a double system ; it con- 

 joins in itself the two highest galvanic processes, that of 

 secretion and excretion. 



2358. Secretion is an hepatic character, excretion a 

 pulmonic character. Secretion belongs to nutrition, 

 excretion to respiration. Excretion is an exspiration, 

 secretion an influx or infusion. Secretion is related to 

 excretion as water is to air, as liver to lung, as basis to 

 oxygen. 



2359. Secretion takes place, e. g. of bile and saliva, in 

 so far as the processes of the body, especially those of the 

 digestion, are promoted. Excretion is only effected in so 

 far as that the organs, into which what is secreted enters, 

 may obtain a tracheal signification, i. e. evaporation. All 



