PRACTICAL APPLICATIONS OF METHOD 201 



incubator at 37.5 C., for from 5 to 7 days. At the end of this time 

 it is filtered through cheesecloth and then through coarse paper, and 

 the filtrate placed in a large crystallizing dish in which it is evapo- 

 rated at room temperature with the aid of an electric fan. A gummy 

 yellow residue is left, which is then taken up in as small a quantity 

 of ether as possible. This ether solution is then precipitated with 

 4 times its volume of acetone, in consequence of which there is a pro- 

 fuse precipitation of coarse white flakes. This acetone-insoluble 

 substance, which is at first white, later yellowish, in color, is the 

 stock antigen. A little of this is taken up in a very small quantity 

 of ether, and this ethereal solution is shaken up in salt solution until 

 the ether has evaporated or the material has gone into very fine col- 

 loidal suspension in the salt solution. This is the antigen ready to 

 be used. 



It is immediately evident that these antigenic substances must 

 consist very largely of lipoidal extractives of the organ substances, 

 and it has been found that such antigen contains sodium oleate, leci- 

 thin and cholesterin. Indeed, Forges and Meier have claimed that a 

 1 per cent, solution of commercial lecithin may be used with success. 

 Browning and Cruikshank 14 have found further that the addition 

 of small amounts of cholesterin to syphilitic antigen very largely 

 increases its specifically diagnostic value, and this idea has since 

 been utilized more especially by Sachs, 15 Walker and Swift, 16 and 

 others. Sachs, especially, has obtained excellent antigens in the 

 following way: 1 gram of moist guinea pig heart substance was 

 extracted with 5 c. c. of alcohol and left at room temperature for 

 twelve hours or in the ice box for two days ; it was then filtered and 

 0.5 to 1 per cent, of cholesterin was added; frequently the alcohol 

 extract had to be diluted two or three times before use. Sachs and 

 Rondoni 17 have also recommended artificial mixtures of lipoids con- 

 taining sodium oleate, lecithin, and oleic acid. 



The fact that cholesterin added to alcoholic organ extracts in- 

 creases the antigenic value of these for the Wassermann reaction is 

 all the more curious inasmuch as cholesterin alone has practically no 

 antigenic action. Walker and Swift have recommended an antigen 

 in which alcoholic extracts of human or guinea pig hearts were made 

 up to 0.4 per cent, of cholesterin, 0.4 per cent, having been found by 

 comparative test to be the most favorable concentration. Cholesterin- 

 liver extracts or even alcoholic extracts of syphilitic livers without 

 cholesterin were found to be inferior in specific antigenic value to 

 0.4 per cent, cholesterin-heart antigens. From the experience of 

 many investigators it now seems unquestionable that additions of 



14 Browning and Cruikshank. Journ. of Path, and Bact., Vol. 16, 1911. 



15 Sachs. Berl kl Woch., No. 46, 1911. 



16 Walker and Swift. Journ. of Exp. Med,, Vol. 18, 1913. 



17 Sachs and Rondoni. Zeitschr. f. Imm., Vol. 1, 1909. 



