978 PHYSIOLOGY 



which would readily precipitate salt 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 some- 

 thing 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 combination of all its varied colloidal 

 constituents to form one labile mass of fluid protoplasm. 



