CHANGES IN THE MATERNAL ORGANISM 503 



till the end of pregnancy. 1 In other words, during the period 

 in which the needs of the embryo are small the amount of 

 protein katabolised is not counterbalanced by the food protein, 

 and the maternal tissues suffer loss ; in the later period, although 

 the daily amount of nitrogen fixed by the new organism is con- 

 siderably greater, the excreted nitrogen is more than counter- 

 balanced by the food nitrogen, and the maternal tissues gain, 

 or at least do not lose to such an extent as formerly. In the 

 human female, in whom investigations have been conducted 

 only in the last few weeks of pregnancy, a retention of nitrogen 

 has been invariably found. According to Zacharjewsky, 2 it 

 amounted to a gain of 0'873 grm. per diem in primiparse and 

 5'05 grm. in multipart. On a diet usually containing less than 

 20 grm. nitrogen per day, Bar and Daunay observed an average 

 retention of 6*54 grm. in three primiparae for eleven days in 

 the last month of pregnancy, a figure far exceeding that ob- 

 tained in the same women on the same diet a considerable 

 time after pregnancy. 3 



What is the reason for the increased katabolism of nitrogenous 

 substances during the ear her stages of pregnancy ? Hagemann 

 says : "In the transformation of maternal proteins into the 

 proteins of the growing uterus, embryos, and mammary glands, 

 some of the nitrogen-containing complexes of the molecules 

 lose their specific character, cannot be built up in the new protein 

 molecule, and are excreted in the urine." Ver Eeke suggests 

 that the loss of maternal blood may hasten protein katabolism, 

 and its reconstitution entail a sacrifice of nitrogenous substances 

 on the part of the mother. But it is not enough to say that the 

 loss of nitrogen is due to the inability of the cells to build up 

 protein synthetically, since no loss occurs on a sufficient diet 

 in the later stages of pregnancy, although the synthesis of new 

 tissue then reaches a maximum. Ver Eeke also states that the 

 greater katabolism in proportion to weight in growing than in 



1 Recently corroborated in the dog by Murlin (" Protein Metabolism in 

 Development," Amer. Journ. of Phys., vol. xxiii., 1908-9). 



2 Zacharjewsky, " Ueber den Stickstoffwechsel wahrend der letzten 

 Tage der Schwangerschaft," Zeitschr. f. Biol., vol. xxx., 1894. 



3 During the puerperium, the low diet administered to women entails 

 a loss of nitrogen to the maternal organism. Very variable times have 

 been noted in different cases before nitrogenous equilibrium was restored. 



