S. RANZI 307 



proteins treated with vegetalizing substances and the lower 

 resistance of proteins treated with animahzing substances. 



The denaturation induced by animahzing substances leads to 

 an additional denaturation induced by urea. The action of vege- 

 talizing substances is, however, a stabilizing action that opposes 

 the demolition by urea. 



In the experiment just described all vegetalizing substances 

 exert the same action of protecting from denaturation. All ani- 

 mahzing agents denature and predispose to denaturation (Table 



I)- 



Differences in Resistance to Demolition of Proteins 

 from Embryos Showing Different Malformations 



It is obvious that if the above phenomena are important in the 

 changes of embryonic determination, something must he ob- 

 servable in the embryo itself after treatment with vegetalizing or 

 animahzing substances. To examine this point we carried out the 

 following experiment. 



Fig. 14. Scheme of the experiments. Into tubes (1) and (2), 10 ml of 

 euglobulin a + b sokition was poured. To tube (1), 10 ml of IM KCl and 

 to tube (2), 10 ml of fluid (1.4 ml IM LiCl + 8.6 ml IM KCl) were added 

 and then stored one night in cold room; 5 ml of mixture (1) were taken 

 and put into tube (3), together with 0.6 ml of IM KCl; 5 ml of mixture 

 (1) plus 0.6 ml 30% urea represent the sample in tube (4). The same 

 procedures were followed for the mixture of tube (2) (vegetalized pro- 

 teins) and samples (5) and (6) were obtained. After 4 hours of matura- 

 tion, the viscosity was read by Ostwald viscosimeter at 14° C. Values of 

 readings are plotted on the column diagram under their respective tubes. 

 The lower column diagrams represent values obtained using iodosobenzoate 

 (left) and thiocyanate (right). In the iodosobenzoate experiment, tube 

 (1) contained the proteins dissolved in Weber and Edsall fluid plus 10 ml 

 of Weber and Edsall fluid; tube (2) contained the proteins plus 10 ml of 

 O.OOIM iodosobenzoic acid dissolved in Weber and Edsall fluid (the last 

 retained a constant pH in spite of the addition of iodosobenzoic acid ) . 

 In the thiocyanate experiment, the mixture of tube ( 1 ) was the same as the 

 Li experiments, while 1 ml of IM KSCN and 9 ml of IM KCl were added 

 to tube (2). It is evident that, with Li, the decrease in viscosity of tube 

 (6) mixture compared with tube (5) was less marked than the controls. 

 With iodosobenzoate and KSCN, the contrary is true. [Decrease of viscosity 

 of tube (6) in comparison with (5) is stronger than the decrease of (4) as 

 compared with (3).] (From Ranzi and Citterio, 1954.) 



