I9I3] Alfred P. Lothrop 463 



in the presence of enzymes from the liver and especially from the 

 blood. Spirochetes suspended in physiological salt Solution are 

 sterilized by a temperature of 45° C. in from seven to ten minutes. 



74. Studies on the chemistry of embryonic growth. I. 

 Certain changes in the nitrogen ratlos of developing trout 

 eggs.^^ Ross AiKEN GoRTNER. {Carnegie Institution of Wash- 

 ington; Biochemical Laboratory of the Station for Experimental 

 Evolution, Cold Spring Harhor, L. /.) The various nitrogen frac- 

 tions were determined in fresh trout eggs and in trout eggs at 21 

 days, 35 days, 51 days and ^2 days of development, using Van 

 Slyke's method. 



It was found that probably no nitrogen was either lost or gained 

 by the tgg up to the time of hatching. After hatching the loss 

 proceeds rapidly, until, twenty-one days afterward, 21.96 per cent. 

 of the total nitrogen in the tgg has been eliminated. During seventy- 

 two days of development the eggs lost 25.35 P^^" cent. of their dry 

 weight, 37.26 per cent. of this loss being due to non-protein (fats, 

 etc.), and 62.73 per cent. to protein (NX 6.25). During the proc- 

 ess of development the basic nitrogen increases at the expense of 

 the mon-amino acid nitrogen. 



There is selective utilization of the various nitrogen fractions 

 by the developing fish, as is shown by the nature of the nitrogen 

 that is lost. Only 25 per cent. of the expected amide nitrogen is 

 eliminated, only 50 per cent. of the expected arginin-reacting nitro- 

 gen, only 75 per cent. of the expected lysin-reacting nitrogen, none 

 of the cystin- or histidin-reacting nitrogen, only about one third of 

 the expected basic nitrogen, while the deficit caused by the basic 

 nitrogen is balanced by the elimination of mon-amino acid nitrogen 

 far in excess of the expected quantity — 83.30 per cent. of the total 

 nitrogen (expected, 57.65 per cent.). 



No appreciable amount of either urea or uric acid is formed 

 in the eggs during development. 



It seems probable that some of the energy of development (Ent- 

 wicklungsarbeit) comes from the shifting of the nitrogen ratios as 

 development proceeds. In the change from mon-amino acid nitro- 

 gen to basic nitrogen, the energy relations may be changed and heat 

 liberated, but at present this is only a hypothesis. 



" Gortner : Journal of the American Chemical Society, 1913, xxxv, p. 632. 



