POLYSACCHARIDES OF MICR0-0RGANIS3IS 361 



(a) 69 per cent, of a soluble specific polysaccharide, 



[b] 16 per cent, of insoluble conjugated protein, (c) 3 to 4 

 per cent, of a benzene soluble lipin fraction and {d) 8 per 

 cent, of an alcohol soluble acetyl polysaccharide. The 

 conjugated protein is toxic but is neither antigenic nor 

 a hapten. The lipin fraction, insoluble in acetone, 

 appears to be a phosphatide. The main fraction, which 

 can be precipitated by alcohol, is a hapten, reacting with 

 antisera, but is neither antigenic nor toxic. It has 

 [«]d+103°, contains no nitrogen and on hydrolysis 

 yields 93 per cent, of reducing sugar, of which 31 per cent, 

 is glucose, 21-5 per cent, mannose and 19 per cent, 

 galactose. It contains no ketose, pentose or uronic acid. 

 The antigenic complex can be dissociated by precipitation 

 from weakly alkaline solution to give a small amount of an 

 amphoteric protein and a non-antigenic " undegraded " 

 polysaccharide which reacts specifically with Sal. typhi- 

 murkirn antisera. The complete antigen, possibly a 

 calcium salt of a phosphatide-polj^saccharide-protein 

 complex, occurs only in the smooth organisms ; the 

 rough variants contain the " residual antigen," which is 

 the complete antigen deprived of the phosphatide fraction. 

 The rough variants apparently contain an enzyme which 

 breaks down the complete antigen. 



The second method of isolation depends on removal of 

 the protein of the organism by digestion with trypsin 

 and precipitation of the polysaccharide in the solution 

 with alcohol. The complete antigen so obtained behaves 

 in the same way as that extracted by trichloracetic acid. 

 These are the so-called " F 68 " polysaccharides since 

 they are precipitated by 68 per cent, of alcohol. The 

 third process is extraction of the dried organisms with 

 diethylene glycol, which gives products which may not 

 be degraded to such an extent as those obtained by the 

 more drastic methods, although their properties are 

 essentially the same. 



The trichloracetic acid method has been applied to a 



