LUNGS FOR RESPIRATION, 35 



birth, and long befoi*e most of the important tissues 

 of the body exhibit their characteristic structure, 

 some time before the intestine into which the secre- 

 tion of the gland is poured, is fully formed, the hver 

 not only possesses the structure it exhibits perma- 

 nently, but it performs its work, and probably in 

 much the same way as during later periods, when the 

 conditions under which life is carried on are so very 

 different from what they are during development. In 

 short, the hver seems to be fonned as a pennanent 

 organ almost from the very first, and fulfils two very 

 important functions. By its agency, certain matters 

 are separated from the blood, and converted into 

 two distinct classes of substances, one of which is re- 

 turned to the blood soon after its production, while 

 the other is carried away from the gland and poured 

 into the intestine. The material formed by the liver 

 and returned to the blood is sugar, and that which is 

 carried to the intestine is hile, of which part seems to 

 be effete, and at last escapes from the bowel, while 

 part is re-absorbed in an altered state by the intestinal 

 capillaries, and mixed with the blood. 



54. Lungs for respiration. — In another part of the 

 developing being organs are formed which are des- 

 tined to effect, withoiit a moment's interruption, 

 most important changes in the blood, from the 

 instant after birth until death. These organs are 

 the lungs, and as the blood traverses the capillaries 

 it takes up oxygen and gives off carbonic acid and 

 other constituents. 



55. The Kidneys for secreting. — The kidneys con- 

 tain bioplasm which selects various matters from 

 the blood. It undergoes change, and becomes re- 

 solved into certain constituents, which pass away from 

 the body altogether. These glands attain their perfect 

 form slowly, and are preceded by temporary organs. 



56. Cutaneous glands. — Glands are also found in 

 connection with the skin, whose ofiice it is to 



D 2 



