Chap. 30.] Secretion of Bile in Fijhes. ' 309 



A fact fo contradictory to the analogy of the other 

 fecretions cannot fail to excite Onr wonder and curio- 

 fity. Our curiofity we cannot hope to gratify, fince 

 the prefentilate of our knowledge, with refpect to the 

 nature of fecre.tion, gives us little room to expect a 

 difcovery of the advantages which are derived from 

 this br any other peculiarity in our frame; but our 

 wonder will be leiTened by confidering, that the fame 

 peculiarity takes place in certain animals, under cir- 

 cumftances ftill more remarkable. In fifties., a fingle 

 artery arifes from the ventricle of the heart, which 

 is entirely distributed on the gills ; from the- gills the 

 blood is gradually collected into a large vefTel, cor- 

 refponding to the aorta in man, and diftributing the 

 blood to every part of the body. From the bowels, 

 however, the veiTels flill again unite, and form a 

 large trunk, which, entering the liver, performs the 

 fecretion of the bile, in the third circle of the blood, 

 fmce it patted through the heart ; whereas in man the 

 blood, in palling through the liver, is only in its fe- 

 cond circle or courfe. 



Abforption, as was before remarked, is performed 

 by a fyftem of veflels quite diftinct from thofe con- 

 cerned in the circulation of the blood. Their appear- 

 ance, ftructure, and courfe through the body, have 

 been already defcribed. The ufes of the abforbents 

 in the animal ceconom/ are of the mod important 

 nature. By the abforbents all the nourifhment of 

 the body is conveyed from the inteftines towards the 

 heart ; and by the abforbents thofe particles, which 

 have become wfelefs in any of the organs, are taken 

 up, conveyed into the mafs of circulating fluids, and 

 ultimately difcharged from the body. The bones 

 themfelves afford evidence of the action of the ab- 

 forbents, as their component particles are continually 

 X 3 changing 



