56 D. A. L. DAVIES 



activity in the residue but only about one-third of the total lipid 

 is removed in ether. Extraction in the same way with chloroform/ 

 methanol (2:1) takes out two-thirds of the lipid and leaves an 

 inactive residue. Refluxing with ether until no more lipid is 

 extracted gives nearly half the total lipid and most of the remainder 

 can be removed by refluxing repeatedly with chloroform/ 

 methanol. The relatively low nitrogen content of the residue 

 suggested that lipid might not have been totally removed by this 

 treatment; when the material was hydrolysed with strong HCl 

 at 100° overnight, fatty acids could be extracted with ether and 

 they accounted for 10 per cent of the weight of the residue in 

 terms of phospholipid. There is, therefore, some closely bound 

 lipid which cannot be removed by solvent extraction and this is 

 not included in the lipid figures given in Table III. The main 

 ether-soluble lipid fraction has o* 8 per cent nitrogen and i • 6 per 

 cent phosphorus but no reducing sugars. The chloroform/ 

 methanol-soluble fraction contains 2*5 per cent nitrogen, 2-9 

 per cent phosphorus and 5 per cent carbohydrate. On hydrolysis 

 of this fraction with N-H2SO4 for eight hours, followed by 

 neutralization with Ba(OH)2 and removal of charged hydrolysis 

 products by passing through ion-exchange columns, chromato- 

 grams revealed the presence of glucose and galactose. The 

 proportions of these sugars have differed in the products of 

 different mouse strains but it is not yet clear how reproducible 

 these differences are. Hydrolysis for only 20 minutes and subse- 

 quent treatment in the same way reveals a third sugar on chro- 

 matograms which has not been identified. Attempts to test the 

 lipid fractions for serological activity by suspension as emulsions 

 have not been successful although SP active fractions show full 

 activity when emulsified in cholesterol and lecithin. 



The protein remaining after solvent extraction by refluxing is 

 very insoluble. It has 14-5 per cent nitrogen, o-6 per cent phos- 

 phorus and less than 2 per cent carbohydrate and after strong 

 hydrolysis chromatograms show at least 15 amino acids (Asp, 



