SECT. 6] OF THE EMBRYO 943 



per day, instead of 1 740 mgm. However, this was a good deal more 

 than the highest point reached in pre-natal life. Fridericia did not 

 work out the percentage participation of protein in the total com- 

 busted material by actual measurements of the fat and carbohydrate 

 disappearing, as was done in later work (cf. p. 1 1 34) but knowing the 

 total heat output from Bohr & Hasselbalch's figures, and knowing 

 the amount of uric acid produced, and hence the amount of protein 

 catabolism and its heat, he calculated the latter in per cent, of the 

 former. Thus he was able to draw up the above table. It must be 

 remembered that the above data for the chick embryo were 

 Fridericia's own, and that other workers on uric acid formation in 

 the egg do not wholly confirm them, but nevertheless, a comparison 

 with these (Table 141) will show that the main conclusions to be 

 drawn are not affected by these discrepancies. The most probable 

 alteration which should be made in the table is a lowering of the last 

 value. Further researches should be undertaken to decide the point 

 at issue between Fridericia and Romenski. 



6*12. Maternal Diet and Embryonic Constitution 



On p. 248 I discussed the extent to which changes in the diet of 

 the hen could influence the chemical constitution of the egg and 

 thence perhaps of the embryo. In the case of the mammal it is 

 obviously impossible to trace the effects of the diet upon the con- 

 stitution of the egg, but something has been done on its effects on 

 the constitution of the embryos at birth. 



Reeb studied the effects of under-nutrition in rabbits upon their 

 offspring and found that the experimental rabbits produced embryos 

 41-2 per cent, lighter than the controls, containing 44 per cent, less 

 dry solid, and 61-9 per cent, less fat. The same results emerged, with 

 only minor differences, from work with dogs. Paton's guinea-pigs 

 gave the following results : 



Weight of young Average no. 



per gm. of mother of young 



at term (gm.) per litter 



Well-fed ... ... 0-350 2-7 



Under-fed ... ... 0-248 2-5 



Zuntz and Bondi worked with rats — the former confirmed Reeb, and 

 the latter reported that a rich fat diet caused an unusually high fat 

 content of the embryos. On cows, Eckles observed no effect of 



