302 EARLY DETERMINATION IN DEVELOPMENT 



It is necessary to discuss the nature of different conditions of 

 protein precipitation of embryos treated with LiCl or NaSCN. 

 There may be a difference in physicochemical properties of some 

 proteins or there may be a synthesis of some new proteins. In 

 order to check this point we extracted, following Lawrence et al. 

 (1944), euglobulin a + b* from frog eggs. By adding 1:1 IM 

 KSCN or IM LiCl and storing for one night in a cold room, we 

 plotted the salting out graph. Li+ induces precipitation at a lower 

 concentration of ammonium sulfate; SCN~ induces precipitation 

 at a higher concentration of ammonium sulfate (Fig. 12). That 

 is to say that the fibrillar proteins treated in vivo and in vitro 

 with NaSCN or LiCl show the same transformations. Therefore 

 we conclude that the difference in the salting out graph of em- 

 bryos treated with NaSCN or LiCl originates most likely from the 

 physicochemical conditions of their proteins and not from the 

 synthesis of new proteins. 



Moreover, it is possible to show that animalizing agents induce 

 a decrease in viscosity of solutions of protein particles which 

 under viscosimetric analysis appear fibrillar. The vegetalizing 

 agents induce instead an increase in viscosity of the same protein 

 solutions (Fig. 13). These changes in viscosity are related to 

 the shape of the particles in solution because they appear only in 

 solutions containing fibrillar proteins and not in solutions of glob- 

 ular proteins (Citterio and Ranzi, 1947). Moreover, both ani- 

 malizing and vegetalizing agents induce an increase in viscosity 

 of the globular protein solutions. The observation of the different 

 actions of animalizing and vegetalizing substances on jSbrillar 



* It is possible to extract euglobulin a + b from lyophilized eggs with 

 IM KCl. After delipidation with ether, if the solution is diluted to 0.3M, 

 euglobulin a + b precipitate and can be dissolved in IM KCl. This protein 

 does not show flow birefringence but appears highly anisodiametric in the 

 viscosimeter. Its axial ratio, taken with the viscosimeter, seems to increase 

 with dilution; moreover, starting from 0.50 reduced viscosity figures one 

 may reach values exceeding 1.00 (that is, an axial ratio of over 35.1). 

 After Lawrence et al. (1944), I termed this protein fibrillar folded by 

 assuming that its globular-shaped particles may unfold and are unfolded 

 along the walls of the viscosimeter while they appear folded in the axis of 

 the channel where flow birefringence is read. For discussion on other pos- 

 sibilities see Ranzi (1955). 



