310 



EARLY DETERMINATION IN DEVELOPMENT 



viscosity of proteins diluted in IM KCl being 100. The values 

 show that the proteins from embryos treated with LiCl are much 

 more resistant to the action of urea and to proteolytic enzymes 

 such as trypsin and papain than are control proteins; the proteins 

 of embryos treated with NaSCN are less resistant to urea and 

 proteolytic enzymes. 



Another experiment was performed with these materials. The 



1.0 



0.5 





A NdSCN 

 Control 



Fig. 16. The optical densities (at 275 millimicrons) of the solutions of 

 Fig. 15 are assumed to be 100. After the readings, the proteins were precip- 

 itated with trichloracetic acid. The optical density after precipitation is 

 plotted on the ordinates. (From Ranzi, 1955.) 



solutions used for the viscosimetric test mentioned above were 

 precipitated by diluting 1:1 with 10% trichloracetic acid. The 

 optical density of the supernatant fluid was read at 275 milli- 

 microns in the Beckman spectrophotometer (Fig. 16). The data 

 show that, in the protein solutions of embryos treated with 

 NaSCN, a greater quantity of material remains in solution than 

 in the controls. In the solutions of embryos treated with LiCl a 



