SECT. 6] OF THE EMBRYO 931 



the foodstuff provided by the maternal organism amounts to. We 

 cannot, therefore, enquire how many grams 100 gm. of raw material 

 hands over to 100 gm. of formed embryo in a given time. Con- 

 sequently the data we have on the absorption of material by the 

 mammalian embryo are fragmentary, and are almost entirely con- 

 cerned with the problem of how much the mother on a given diet 

 can afford to store away in the developing embryo. 



Thus Magnus-Levy calculated that the average daily deposition 

 in the human foetus for the last hundred days of its development 

 represents not more than 3-0 gm. of protein, 3-5 gm. of fat, and about 

 0-7 gm. of ash. His table was as follows: 



It is not possible to enter here into the question of whether the 

 absorption of raw materials by the mammalian embryo entails loss 

 from the maternal tissues or not. The question is a very complex one, 

 and reference should be made to the reviews of Magnus-Levy; 

 Feldman; Hoffstrom; Eckles; Harding; and MurUn, and to an anony- 

 mous one which, although now some twenty years old, is worth con- 

 sulting. Mention maybe made, however, of the interesting case studied 

 by Rubner & Langstein, where a 7-months embryo was born, and 

 was available for the study of the absorption and retention of the 

 food. The infant weighed 2050 gm. at birth, but 8 days afterwards 

 its weight had diminished to 1900 gm., though after that it began 

 to increase by about 28 gm. a day. When the experiments began it 

 weighed 2360 gm. During the next 11 days it retained 50 per cent, 

 of the nitrogen in its milk, though at this time, which would have 

 corresponded to the 8th month of pregnancy, the addition of protein 

 to the child amounted to only a half of that computed by Hoffstrom 

 for the foetus of the same age. The diet contained 126 Cal. per kilo 

 body-weight, of which 73 were used for heat production (973 Cal. 

 per sq. metre per day) and 53 were deposited in the infant. Altogether 

 42 per cent, of the Calories taken in with the food were retained for 

 growth. 



