CHANGES IN THE MATERNAL ORGANISM 505 



absorbing nutriment it probably elaborates it into a form suit- 

 able for its incorporation in the new tissues. It is to tliis activity 

 that we may have to lo:k fcr an explanation of the negative 

 nitrogen balance at the beginning of pregnancy. In the later 

 stages the ectodermal covering of the viUi loses its vitahty, 

 and seems to act more as a semi-permeable membrane (see p. 488). 

 The cells of the new organism are now more fuUy differentiated, 

 and are capable of carrying on their own metabolic functions. 



d. The Nitrogen Excretion during Pregnancy. — The total 

 nitrogen excreted during the later stages of pregnancy is decreased 

 in' amount. It again rises distinctly in the puerperium (Boni/ 

 Siemens ^). The urea nitrogen was stated to be normal in 

 amount by v. Winckel * and Zacharjewsky, but more recent 

 observations prove that it is diminished in proportion to the 

 total nitrogen. According to Matthews,* it may fall below 13 

 grm. per day without any signs of insufficiency.* The ammonia 

 nitrogen, which is of interest in connection with the question 

 of acidosis in pregnancy, is relatively increased, but at present 

 no proof is forthcoming that it is absolutely higher than in the 

 non-pregnant state. The relative increase is due to the decrease 

 in the total nitrogen (Siemens, Matthews). In eclampsia, 

 Zweifel* has frequently observed an increase of the ammonia 

 nitrogen to 10 per cent, or more of the total, and, associated 

 with it, the presence of an organic acid in the urine. The 

 acidosis, at least in a certain number of the cases, is the result of 

 the eclamptic seizures. Further investigations of the conditions 

 when no fits have occurred are necessary before any constant 

 association of an acidosis with the disease can be affirmed. 



The uric acid excretion is within physiological limits. The 



' Boni, "I corpi purinioi nelle urine delle gravide e delle paerpere, " 

 Ann. di Oat. e Gin., 1906. 



^ Slemons, " Metabolism during Pregnancy," &c., Johns Hopkins Hasp. 

 Rep., Tol. xii., 1904. 



' V. Winckel, Studien Uber den Stoffivechsel, &c., Rostock, 1865. 



'' Matthews, " The Urine in Normal Pregnancy," Amer. Joum. Med. Sc, 

 vol. cxxxi., 1906. 



* There are, however, wide physiological variations according to the 

 N-content of th? diet. 



° Zweifel, "Die Eklampsie," Arch. f. Oyniik., vol. Ixxii., 1904. 



