150 CHEMICAL STATICS 



(110) (111)). The precipitate produced by admixture of an 

 excess of globin with sodium caseinate in solution contains about 

 34.5 per cent of casein. A compound of globin with deutero- 

 albumose has been prepared by Schmidt (HI). 



Thymus histone combines with haemoglobin, according to 

 af Ugglas (117), in the proportion of one part of thymus histone 

 to two of haemoglobin, and with casein to form a compound 

 containing about 30 per cent of the histone. 



A particularly interesting compound protein is the haemo- 

 globin caseinate which has been prepared by af Ugglas. To a 

 solution of casein in alkali an excess of hydrochloric acid is added 

 until the precipitate of free casein which is at first formed is 

 redissolved. The casein hydrochloride is precipitated from this 

 solution by the addition of sodium chloride and the precipitate 

 redissolved and reprecipitated until the washings from the pre- 

 cipitate are perfectly neutral. A solution of this substance 

 added to an excess of a solution of haemoglobin, produces a pre- 

 cipitate containing 33 per cent of casein and 66 per cent of 

 haemoglobin. The commonly accepted molecular weight of haemo- 

 globin, which has now been confirmed by a variety of measure- 

 ments (Cf. section 11), is about 16,700. We have seen that the 

 minimal molecular weight of casein is about 8800 (Chap. V). 

 It would, therefore, appear that casein and haemoglobin combine 

 with one another in molecular proportions. 



From important observations of Hardy's it appears extremely 

 probable that many of the protein constituents which may be 

 isolated from the various tissues and tissue fluids do not pre- 

 exist there but are bound up in complex compounds of proteins 

 with proteins. I quote from the appendix to Hardy's article 

 on globulin (35). 



''The facts of the case are these. The proteins of serum are 

 electrically inactive. Neither the whole nor any fraction moves 

 in a field. It is not possible to detect a trace of 'ionic' protein. 

 Dialysis or dilution disturbs the equilibrium and 'ionic' globulin 

 appears, and can be swept out of the general mass of proteins as 

 an opalescent cloud before dialysis has been pushed to the point 

 where precipitation occurs. The development of even minute 

 quantities of 'ionic' globulin can be detected in this way. The 

 direction of the movement is towards the anode, therefore the 

 globulin which appears is the anion of alkali-globulin." 



