PARANUCLEIN FROM CASEIN. 395 



the phosphorus content of his various preparations to variations 

 in the extent of proteolysis. Similar results regarding the 

 presence of organic phosphorus in the paranuclein and the 

 effect upon its composition due to changed conditions of 

 digestion have since been made in this laboratory by Dr. J. H. 

 M. Knox.* His preparations with an ash content of 2.8 per 

 cent showed a content of phosphorus equal to 2.98 per cent 

 attributable to organic phosphorus. The paranuclein obtained 

 by gastric digestion of casein from goat's milk gave a content 

 of organic phosphorus (2.7 per cent) agreeing closely with 

 that from cow's milk. 



A review of the preceding details indicates that most authors 

 have found a considerable content of organic phosphorus in 

 this peculiar cleavage product of casein. The results of 

 Chittenden alone stand in contrast to the others. The data 

 of the various investigators are, however, by no means in 

 accord with one another. They vary very widely according 

 to the conditions under which the experiments have been car- 

 ried out, both with respect to the quantity of paranuclein 

 formed and the composition of the latter. Furthermore, the 

 large ash content revealed by the analyses of previous investi- 

 gators makes it clear that they were working with preparations 

 which could scarcely lay claim to any considerable degree of 

 purity. The discrepancies noted and the more recent advances 

 made in the field indicated, have rendered it desirable to repeat 

 some of the older experiments, and especially to ascertain the 

 possibility of the formation of paranuclein, entirely devoid of 

 organic phosphorus as it was assumed by Chittenden to have 

 been formed in his experiments. 



DIGESTION I. 



In this first experiment, an attempt was made to repeat 

 closely the preparation of paranuclein as outlined by Chitten- 

 den.f Casein prepared according to the method of Ham- 

 marsten, was thoroughly extracted with ether and dried at 



* These results have not yet been published. 

 t Chittenden, loc. cit. 



