OCTOBEK 2, 1908] 



SCIENCE 



419 



Although Eitthausen afterwards showed 

 that a large part of many of his previously 

 described preparations, which had been 

 obtained by extraction with dilute alka- 

 lies, was soluble in solutions of neutral 

 salts, and that the composition of many of 

 the proteins which he had previously 

 analyzed was the same as that of prepara- 

 tions obtained by extraction with solutions 

 of sodium chloride, nevertheless physiolo- 

 gists continued to repeat the criticisms of 

 Hoppe-Seyler, and the work of Eitthausen 

 failed to receive the recognition which it 

 deserved. 



REVIEW OF THE WRITER'S WORK 



Since Eitthausen ceased his work with 

 vegetable proteins little has been done in 

 this field outside of my own laboratory. 

 It is true that from time to time papers 

 have appeared dealing with special ques- 

 tions in the chemistry of these substances, 

 but no other connected and extensive in- 

 vestigation has been described, and as the 

 work which I have been doing during the 

 past twenty years has now reached a point 

 where it can be profitably reviewed, I pro- 

 pose to take up some of its more important 

 features and briefly discuss them. 



As Eitthausen 's researches were far 

 from exhaustive and left the subject in 

 such a state of confusion that it was im- 

 possible to form definite conclusions re- 

 specting much that he had described, it 

 seemed best to me to direct attention 

 chiefly to those seeds which had been 

 previously studied by him and by others, 

 and to try to clear up the existing uncer- 

 tainties, rather than to add to them by 

 describing new proteins. As a result, we 

 now have about twenty-five different pro- 

 teins of vegetable origin, the important 

 characters of most of which have been 

 studied by all the means at present avail- 

 able. These proteins appear to represent 

 the different types to be found in seeds and 



are, I think, sufBeient in number to form a 

 suitable foundation for the future study of 

 their chemistry. All of these are con- 

 stituents of seeds. A few of them repre- 

 sent constituents of the physiologically ac- 

 tive embryo, but the majority represent the 

 reserve food protein of the endosperm, and 

 serve not only for the nutrition of the 

 growing seedling, but also for the nutri- 

 tion of men and animals. Of the protein 

 constituents of other parts of plants very 

 little indeed is known. 



CHEMICAL INDIVIDUALITY OP PROTEINS 



In considering the position of our pres- 

 ent knowledge of the seed proteins, the 

 question of chemical individuality should 

 first be considered. We are now well past 

 the time when agreement in solubility, 

 ultimate composition and color reactions, 

 are to be accepted as evidence of the iden- 

 tity of two preparations of protein. It is 

 not necessary to explain why it is at 

 present not possible to demonstrate the 

 chemical individuality of any single pro- 

 tein, for the reasons are evident to all who 

 will give this question the slightest con- 

 sideration from the standpoint of the 

 organic chemist. While it is not possible 

 to establish the individuality of any pro- 

 tein, it is possible to show differences be- 

 tween the various forms which can be 

 isolated, and to establish a constancy of 

 properties and ultimate composition be- 

 tween successive fractional precipitations 

 which give no reason for believing the 

 substance to be a mixture of two or more 

 individuals. 



On the basis that agreement in ultimate 

 composition affords no evidence of identity 

 of two similar proteins, but that distinct 

 and constant differences in composition are 

 conclusive evidence that they are not alike, 

 I have endeavored to differentiate the 

 several seed proteins that I have studied, 

 and have since subjected them to careful 



