142 Scientific Proceedings (119). 



the properties of the casein of milk are affected by heat so as to 

 have a marked influence on the precipitation of casein by acids 

 and on the hydrophyllic properties of the casein thus precipitated. 

 Apparently the addition of soluble calcium salts to milk helps to 

 restore the conditions existing in raw milk which govern the 

 normal rennet clot. All the interrelations of calcium and rennet 

 coagulation have obviously not been determined. A study of 

 these relations is at present in progress in this laboratory. 



Summary. 



It is shown that the partial fixation of the calcium salts of 

 milk by pasteurization or boiling is readily explained simply on 

 the grounds of the effect of heat on colloidal solutions of CaHP0 4 , 

 the calcium phosphate natural to cow's milk. 



It is shown further that the effect of heat in retarding the 

 rennet coagulability of milk is not related directly to the loss of 

 colloidal CaHPC>4 because the addition of colloidal CaHP04 to 

 dialyzed milk does not restore its coagulation by rennet, while 

 the addition of CaCl 2 or HC1 does restore this property. 



The phenomenon of rennet coagulation is discussed briefly 

 from the standpoint of the chemical and physico-chemical reactions 

 involved, and also from the standpoint of the possible bearing 

 which the addition of calcium salts to heated milk has on this 

 phenomenon. 



70 (1817) 



The velocity of development of the demarcation current in the 



frog's sartorius. 



By GEORGE EDMESTON FAHR. 



[From the Department of Medicine, University of Minnesota, 

 Minneapolis, Minn.] 



Urano and Fahr have experimentally established the fact that 

 the potassium ion is almost exclusively the only cation within the 

 muscle cell of the frog's sartorius. Overton has shown that the 

 demarcation current of the frog's sartorius may be inhibited or 

 have its sign reversed by replacing the lymph fluid surrounding 

 the muscle cell by a fluid containing K ions in place of the normally 



