Chap, ii.] PREGNANCY AND BIRTH. 1131 



month bile-pigment and bile-salts find their way into the intes- 

 tine. The quantity of bile secreted during intra-uterine life 

 accumulates in the intestine and especially in the rectum, form- 

 ing, together with material secreted by the walls of the alimen- 

 tary canal and some desquamated epithelium, the so-called 

 meconium. Human meconium is found to contain about 20 

 p.c. of solids. These consist of a considerable quantity of 

 cholesterin (-7 p.c), some fatty acids, bile salts with bile pig- 

 ments, both largely unaltered, and calcium and sodium salts ; 

 the ash is rather more than 1 p.c. Though bile contributes 

 normally to form the meconium, it is not essential, for a con- 

 siderable quantity has been found in the foetus in cases where 

 the liver has been absent. 



The distinct formation of bile is an indication that the pro- 

 ducts of foetal metabolism are no longer wholly carried off by 

 the maternal circulation ; and to the excretory function of the 

 liver there are now added those of the skin and kidney. Since 

 in man, and in many other animals, such substances as are 

 secreted by the kidney find their way at an early date into the 

 cavity of the amnion, the determination of the history of the 

 renal secretion is a matter of difficulty, for as we have seen 

 the amniotic fluid is derived in part at least directly from the 

 mother, and substances present in it may or may not have been 

 discharged into it by the foetus. The amniotic fluid varies not 

 only in quantity but also in specific gravity (1-002 to 1-086) and 

 in composition, and there does not seem to be any definite rela- 

 tion between its specific gravity and the quantity in which it 

 occurs, or between its specific gravity and the size or age of the 

 foetus. It may be said to contain on the average about 1-6 p.c. 

 of solid matter, of which about -2 are proteids, -8 extractives 

 and -6 salts. The proteids are serum albumin and probably 

 paraglobulin, mucin or a mucin-like body being also present. 

 Sugar appears to be sometimes present, sometimes absent. The 

 most important constituent is perhaps urea, which seems to be 

 always present. Since this is found at quite an early stage, 

 before any secretion from the foetal kidney could take place, it 

 may be thus considered as derived from the mother and com- 

 parable in origin to the urea found in serous fluids ; but since 

 urine containing urea is found in the foetal bladder at least as 

 early as the seventh month, we may conclude that during the 

 later stages of pregnancy, and possibly much earlier, part of 

 the urea of the amniotic fluid comes from the foetal kidney. In 

 some animals, ex. gr. ruminants, the cavity of the allantois re- 

 mains for a long time permanent and filled with fluid, instead of 

 as in man becoming at an early date obliterated in its distal 

 portion. In these animals the kidneys discharge their secretion 

 into this allantoic sac, and in the contents of the sac is found 

 the body allied to urea, allantoin, so called from its having 



