S. RANZI 



309 



Three groups of frog embryos at the stage of late blastula, 

 (stage 9) were allowed to develop in fresh water or in 0.05M 

 NaSCN or O.OTAf LiCl. At the stage of young gastrula (stage 10), 

 after 6 hours treatment, the embryos were carefully washed, 

 liberated from jelly, washed again in Holtfreter fluid, and then 

 lyophilized. The powder was extracted overnight in IM KCl. 

 Euglobulin a + b was taken in a solution of IM KCl and the three 

 solutions, (a) euglobulin of control embryos, (b) euglobulin of 

 vegetalized embryos, and (c) euglobulin of animalized embryos, 



100 



80- 



60 



■■•= 4 0- 





20- 



t-pypsin 



papain 



Fig. 15. The diagram shows the decrease per cent of viscosity induced 

 by urea (15% final concentration), trypsin (0.5% final concentration pH 

 7.9), and papain in the euglobulin a + b extracted from embryos: i, con- 

 trols; ii, developed in NaSCN solution; iii, developed in LiCl solution. (The 

 embryos used were taken from the same cultures as those used for the 

 graphs Fig. 10.) (From Ranzi, 1955.) 



were diluted in such a way as to reach the same optical density at 

 275 millimicrons in the Beckman spectrophotometer. With each 

 solution the following samples were prepared: (a) euglobulin 

 a -h b diluted 1:1 with the solvent (IMKCl); (b) euglobulin 

 a + b diluted 1:1 with 30% urea; (c) euglobulin a + b diluted 

 1:1 with trypsin (Merck) dissolved in IM KCl kept at pH 7.9 

 with Weber and Edsall fluid; (d) euglobulin a + b diluted 1:1 

 with papain in IM NaCl. After four hours incubation in the vis- 

 cosimeter bath, the viscosity readings were taken (Fig. 15), the 



