9] 



PROTEIN METABOLISM 



1119 



1400-1100 



Pigorini 

 Proteins of silkworm eggs 



ffl o 



reducing substances on acid hydrolysis, ovomucoid. Pigorini sub- 

 jected the eggs of the silkworm to three successive extractions, which 

 gave him the proteins of groups 

 A, B, and C, and then by co- 

 agulation of the extracts he was 

 able to evaluate the amount of 

 D. Fig. 339 gives the results. 



Monzini has estimated the 

 free amino-nitrogen in the silk- 

 worm egg at different stages 

 of development. Expressed in 

 terms of wet weight of egg, it 

 shows at first a not very well- 

 defined peak, and then declines 

 till the larvae emerge (see Fig. 

 340). Tirelli continued Mon- 

 zini's work, but his figures are so 

 irregular that it is impossible to 

 plot them, Russo extended the van Slyke method to the silkworm egg, 

 with the results shown in Table 155. x\ccording to his data the total 

 nitrogen per cent, of the dry 

 weight is variable, falling by 

 about 12 per cent., and then 

 rising by about 7 per cent. 

 There is every reason for sup- 

 posing a />non that no nitrogen 

 escapes from a terrestrial egg 

 such as that of the silkworm, 

 for the only form in which it 

 could do so would be gaseous 

 ammonia, and this would be 

 so perceptible by its odour in 

 the silkworm establishments 

 that it would be well known. 

 It is more probable that 

 Russo's estimations were not sufficiently statistical or accurate to 

 demonstrate a constancy in the total nitrogen of the egg. Ashbel, 

 it is true, has stated that ammonia is lost by silkworm eggs, but only 

 on the basis of erratic positive pressures in manometric experiments. 



Fig. 340. 



