OOTOBEB 2, 1908] 



SCIENCE 



421 



to consider the relations of the proteins to 

 this acid. 



The behavior of seed globulins toward 

 acid is shown by studies made in my 

 laboratory on edestin. Crystallized prep- 

 arations of edestin, obtained by dialyzing 

 or cooling sodium chloride extracts of 

 hemp-seed, frequently contain protein in 

 three forms ; one, soluble in pure water and 

 also in strong saline solutions, another, in- 

 soluble in water but soluble in strong 

 saline solutions, and still another, insoluble 

 either in water or in saline solutions. The 

 proportion of these products varies with 

 slight differences in the conditions under 

 which the edestin is isolated, and plainly 

 depends upon changes in the protein which 

 take place during its preparation. 



The explanation of these changes has 

 been found in the presence of a small 

 amount of acid extracted from the seed to- 

 gether with the protein. The part of the 

 edestin preparation just referred to, which 

 is insoluble in neutral saline solutions, has 

 been found to be a product of the hydro- 

 lytic action of the acids of the extracts. 

 This product is not the result of a pro- 

 found splitting of the edestin molecule, for 

 the changes leading to its formation are so 

 slight that they can be detected only by 

 the altered solubility. For such primary 

 products of protein hydrolysis, which were 

 designated * ' albuminates ' ' by Weyl, I have 

 proposed the name "protean" and for the 

 products derived from the individual pro- 

 teins, a corresponding name ending with 

 the affix an. Thus the product derived 

 from edestin may be called edestan. The 

 part of the edestin above referred to which 

 is soluble in water contains more combined 

 acid than the part insoluble therein. The 

 preparation, therefore, contains a mixture 

 of salts of edestin. These edestin salts 

 contain some of all the anions present in 

 the solution at the time of precipitation, 

 that salt being predominant whose free 



anion was most abundant in the solution 

 from which the edestin was last precipi- 

 tated. When freed from this combined 

 acid by making the preparation neutral to 

 phenolphthalein, the edestin is wholly in- 

 soluble in water, but soluble in neutral 

 saline solutions. Edestin has, consequent- 

 ly, the properties of a true globulin. Other 

 seed proteins behave towards acids in a 

 similar way, except that some- of them, 

 when neutral to phenolphthalein, are sol- 

 uble in water. Many of these latter be- 

 have as globulins when in the form of 

 salts, and as they are obtained as salts by 

 the methods employed in preparing them, I 

 have for convenience, placed them among 

 the globulins. 



The fact that our protein preparations, 

 as usually obtained, are protein salts is 

 fundamental for a correct conception of 

 their behavior under the conditions of 

 isolation and purification, and for an ex- 

 planation of many of their physiological 

 relations. 



The seed proteins which are described as 

 globulins, differ in some of their properties 

 from some of those that are commonly as- 

 sumed to characterize the globulins of ani- 

 mal origin. In this connection, however, 

 the fact should not be overlooked that 

 our knowledge of animal globulins is rela- 

 tively small, and it is probable that further 

 study will modify our present conception 

 of them. It has become customary for 

 physiologists to consider that all glohulms 

 are precipitated by adding to their solu- 

 tions an equal volume of a saturated solu- 

 tion of ammonium sulphate, and of recent 

 years it appears to have become an almost 

 universal practise to designate as globulin 

 all the protein that can be thus precipi- 

 tated. This practise is unfortunate and 

 leads to confusion, for it wholly ignores 

 the original conception of a globulin, 

 namely, a protein soluble in neutral saline 

 solutions but insoluble in water. 



