NUTRITION. 371 



water. It is possible that these, Hke the phosphatides, may be also 

 combined with protein. Similar fat-like products appear always to 

 accompany the lecithins of different origin, and these deserve more 

 attention than they have received in the past. We hope to have an 

 opportunity soon to investigate this long-neglected question. 



Much time has been devoted to extending our present quite incom- 

 plete knowledge of the proteins of milk, and manj'- data have been 

 collected. The lactoglobulin has been separated from the lactal- 

 bumin and the relative proportions and chief characteristics of these 

 two proteins have been more definitely established than in the past. 



We have demonstrated the presence, in perfectly fresh milk, of 

 not insignificant amounts of protein having the properties of proteose, 

 and have made preparations in sufficient amount for ultimate analyses 

 and studies of their properties. The alcohohc washings of our casein 

 preparations, as noted in our last report, contain a small amount of 

 protein which has approximately the same degree of solubility in 

 relatively strong alcohol as ghadin from wheat. Time-consuming 

 efforts have been made to determine whether this protein is an 

 original constituent of milk or an alteration product of casein, pro- 

 duced during the precipitation of the latter. ^Vhile conclusive evidence 

 on this point has not yet been obtained, little doubt remains that it is 

 originally present in perfectly fresh milk. 



In making our ''protein-free milk," the milk serum, from which 

 the casein was removed by precipitating with dilute acid and the 

 heat-coagulable proteins by boiling, gives a precipitate when neu- 

 tralized with alkaU, which consists of approximately two-thirds 

 calcium phosphate and one-third protein. A part of this protein, 

 probably consists of lecithalbumin, as we have already indicated, but 

 what relation the rest may have to the other proteins of the milk 

 remains to be determined. It is expected that the anaphylaxis reaction 

 will help to solve this question as it has already helped in determining 

 the individuality of the other milk proteins. In carrying out these 

 anaphylaxis tests we have had the hearty cooperation of Professor 

 H. G. Wells, of Chicago. The results which he has obtained illustrate 

 in a most striking way the value of this method for differentiating 

 the several proteins contained in a solution, or in an extract, as well 

 as for demonstrating the completeness of their separation from one 

 another. The results of this study of the milk proteins will be published 

 as soon as the relations of a few new preparations have been determined 

 by the anaphylaxis reaction. 



Several attempts have been made to fractionate the "protein-free 

 milk" by crystallization from alcohol of gradually increased strength, 

 in the hope of obtaining evidence of the existence of a growth- promoting 

 alcohol-soluble substance. Thus far no fractions have resulted which 

 showed any favorable influence on the growth of young rats. 



