152 CHEMICAL STATICS 



"The concentrated hard rubber-like mass of protein obtained 

 in this way cannot be discriminated from serum protein. It 

 is easily soluble in distilled water and in dilute salt solutions. 

 From the solution in water a globulin fraction can be precipitated 

 by acid, or by saturation with magnesium sulphate. From the 

 solution in dilute salt solution a globulin fraction can be pre- 

 cipitated by saturation with salt (NaCl, or MgSO^. The ni- 

 trate, after removal of the globulin by saturation, contains a 

 protein which is precipitated by acetic acid." 



"The position is that in serum one has protein which can be 

 thrown into the ionic state and which then moves in a field as a 

 single substance. From it an electrically active fraction, namely 

 globulin, can be split off, and the protein thereby becomes elec- 

 trically heterogeneous." 



"Now the globulin fraction has an abiding characteristic. In 

 all its solutions its molecular state is so gross as to cause the 

 molecules to be arrested by a porous pot. They will not pass 

 such a filter even under pressure. In this it is sharply distinct 

 from the parent serum protein, which is readily filterable. If 

 globulin be present as such in serum it is not only non-ionic, but 

 the agent which dissolves it must be something more than alkali 

 and salt since either alone or together they will not produce so 

 high a grade of solution (78)." 



"The difference in the molecular grade of globulin when once 

 separated, and the electrical homogeneity of serum protein and 

 of the fraction (still capable of further subdivision by salting 

 out) which remains after the alkaline globulin fraction which 

 most readily appears has been removed suggests that serum 

 protein is a complex unit. If such a unit exists it is not satu- 

 rated with globulin. Fresh ox-serum has an extraordinary power 

 of dissolving globulin, it will take up almost its own volume of 

 the thick cake at the bottom of a centrifuge tube; and in ox- 

 serum so saturated there is not a trace of alkali globulin nor of 

 any ionic protein." 



The phenomena observed by Hardy appear to admit of in- 

 terpretation on the view (102) that the protein-complex in serum 

 is formed by the union of a number of alkali protein compounds, 

 the union taking place in a manner strictly analogous to the 

 combination of neutral salts with protein (Cf. Chap. VI), alkali 

 protein molecules behaving like inorganic salt molecules thus: 



