413 



Croonian Lecture : — On Globulins. 



By W. B. Hardy, M.A., F.R.S. 



(Being the Croonian Lecture delivered May 25, 1905. — MS. Received 



April 9, 1907.) 



Globulins are a class of proteids which occur in both animal and vegetable 

 tissues. They are peculiar in the complexity of their relations to electrolytes. 

 Insoluble in water, they are soluble in low concentrations of acids, alkalies, 

 or neutral salts. In presence of acids the globulin is electro-positive, in 

 presence of alkalies it is electro-negative, in presence of neutral salts it is 

 •electrically neutral. Electrically active globulin (i.e., dissolved by acids or 

 alkalies) is precipitated by minute amounts of neutral salts ; also, no matter 

 what its electrical state may be, or how dissolved, globulins are precipitated 

 by neutral salts near the saturation point of the latter. The problem I 

 propose to consider is their diversified relation to electrolytes. 



Connected with this problem is another, namely, the relation of solutions 

 of globulins to colloidal solution. Do they form hydrosols at all, and, if so, 

 to what extent ? Krafft urged the colloidal nature of soap solutions, because, 

 within certain limits of temperature and concentration, they gelatinise, and 

 have the vapour pressure of pure water. Kahlenberg and Schreiner, 

 however, regard soap solutions as being crystalloid in character, because 

 over the whole range of concentration the soap is a good electrolyte — it 

 ionises and undergoes hydrolytic splitting, like other salts of a weak acid and 

 strong base. Smits, again, by measurement of the vapour pressure over a 

 wide range of concentration, is convinced that above a critical concentration 

 the soap passes wholly into the colloidal state. 



Exactly the same points arise in connection with proteid. Waymouth 

 Eeid has shown that the proteids in a solution exert no measurable influence 

 upon the vapour pressure. On the other hand, solutions of globulins are 

 relatively good conductors over the whole range of concentration through 

 which it is possible to follow them. The dilution curve shows no break 

 indicating a general change of state, eveu when concentration is pushed to 

 the point where fluidity almost vanishes. 



Again, colloids, as a class, are chemically inert. But globulins react 

 actively with acids or alkalies to neutralise them. Globulin solutions, even 

 at extreme concentration, form syrups and not true gels, except, perhaps, 

 under special circumstances. Clearly, therefore, it is pertinent to ask 

 whether globulins form colloidal solutions. 



vol. lxxix. — b. 2 H 



