QUANTITY AND COMPOSITION OF BLOOD 867 



globulin in alkaline solution. Moreover serum can be readily filtered 

 through a porous cell, and this method is adopted for obtaining it free 

 from contamination by micro-organisms. Globulin in any of its solutions 

 will not pass through a porous cell. If globulin be present as such in the 

 serum it is therefore not ionised, but the agent which dissolves it must be 

 something more than alkali or salt, since either alone or together they will 

 not produce a solution which will pass through a porous cell. Serum has 

 still the power of taking up globulin and will dissolve almost its own volume 

 of precipitated globulin, though in oxalate serum there is not a trace of 

 alkali globulin nor of any ionised protein. We are justified therefore in 

 concluding that serum protein may be regarded as a complex unit. By 

 simple means, such as dialysis, dilution, or addition of salt, this unit can 

 be broken up with the separation of the various proteins which we have 

 designated as serum albumen and serum globulin, &c. The question 

 naturally suggests itself whether in plasma we have not a similar com- 

 bination of all its varied colloidal constituents to form one labile mass of 

 fluid protoplasm. 



