302 EXPERIMENT STATION EECORD. 



The influence of acid on the inactivation of rennet by shaking, Signe and 

 SiciVAL ScuMiUT-XiKLSKN (Ztuclir. I'ltt/s. CItnit.. (i!) (I!)0!)), pii. '>.',7-~)'>(i, fig. /). — 

 Ilydroohlorie acid was found to provont the rendering inactive of rennet action 

 by shakinjr. while acetic acid had no intluence in this rej,'ard. 



The theory of the function of catalases, (). Loew (Anli. rin/.siol. [Pflih/cr], 

 I, is [I'.KJU). .\i). 10-1. i, PI). 5(!0-'>(i.'i). — A further discussion in rej^ard to the 

 existence and functions of the catalytic enzyni. 



The action of rennet on paracasein calcium, W. Van Dam (Ztfsfhr. Phifsiul. 

 Clfiii.. ill (IDOf)), Xo. 2, pp. L'i7-J63, flgn. 2). — The digestion of paracasein by 

 rennet is dependent upon the content of hydrogen ions in the media. Furtlier, 

 the rapidity of digestion is proportional to the hydrogen ions contained therein, 

 and in this respect resembles the rai)idity of coagulation. The rai)i(lity of 

 digestion and coagulation of paracasein lime runs parallel when different ren- 

 nets of the same acid content are employed. The author contends that para- 

 casein is digested by the chymosin and does not agree with Petry in regard to 

 the presence of a specific enzym for casein in rennet. Sodium chlorid acceler- 

 ates this digestion. 



The state in which calcium exists in milk, I*. Kona and L. Michaelis 

 Biochem. Ztschr., 21 {1909), No. 1-2, pp. ll',-122; ab.s. hi MoJk. Ztg. [Hildc- 

 nheim], 23 (1909), No. J,5, pp. 1270, i,27/).— Although from milk passed through 

 a bisque filter a portion of the calcium is retained, there is a possibility that 

 its state changes as the milk passes over and through the filter and that the 

 retained calcium is not necessarily present in the colloidal or suspended form. 

 In a study of the dissolved calcium a procedure which simulated as nearly as 

 possible natural conditions was devised, by dializing milk against other sub- 

 stances of almost the same composition but of lower or higher calcium content. 

 The solutions employed were rennet whey with a low calcium content and iron 

 whey in which the proteids were jirecipitated by colloidal iron hydrate and 

 in which the calcium was mostly in insoluble form. 



The results obtained showed that the calcium content of the rennet whey 

 increased in the dialysis while that of the iron whey decreased, so that the 

 final calcium content of both wheys differed very little. Dialysis of a small 

 amount of distilled water against a large amount of milk yielded in the former 

 about the same amount of calcium which the latter originally contained. The 

 insoluble calcium content therefore was between the final calcium content of 

 both wheys and in these investigations it fluctuated between 0.06 and 0.07 per 

 cent and was equivalent to 40 to 50 per cent of the total calcium. By pre- 

 cipitating the casein by rennet, the amount of diffusible or soluble calcium was 

 hardly changed. This was also true as to the electrical conductivity and the 

 lowering of the freezing point, and indicates that by coagulating with rennet 

 only such bodies are precipitated as were originally present in a colloidal state. 

 On the contrary, with the iron whey the dissolved calcium was decidedly in- 

 creased. 



It is difficult to say in which form the calcium is present in the milk and it 

 is peculiar that the phosphoric acid content of the iron whey was very low 

 whereas that in the corresponding rennet whey was ten times higher. There 

 was evidently a precipitation of the phosphoric acid by the iron and a rendition 

 of the nondiffusible calcium into a diffusible state. No appreciable amount of 

 colloidal phosphate of calcium can be present in milk, as if this were the case 

 it would be precipitated totally by the iron. It is more certain that the greater 

 portion of the calcium is present as a salt of casein in solution. With raw milk 

 it is often possible to dialize out the calcium quantitatively with running water. 

 Casein probably has the faculty of forming with calcium a soluble and not 

 easily disassociatiable salt. The binding of the calcium by casein was also 



