LYSINS 157 



then digesting the mixture at 37 C. for a week. The extract is 

 filtered through filter paper and placed in the refrigerator. 



Alcoholic extracts of normal organs, prepared in the same manner 

 as luetic livers, have been found to be quite as good as alcoholic 

 extracts of syphilitic livers for the diagnosis of syphilis. In practice 

 heart-muscle of normal guinea-pigs, freed from all fat, is used. 



Noguchi's Acetone-Insoluble Lipoidal Antigen. 1 Noguchi and others 

 have shown that .alcoholic extracts of organs may, and frequently 

 do, contain sufficient amounts of neutral fats, or their hydrolytic 

 cleavage products, to make the antigen hemolytic or anticomplemen- 

 tary. These substances are for the most part soluble in acetone, while 

 the antigenic fraction is insoluble in acetone. One part of fat-free 

 heart muscle or liver from a guinea-pig is cut into very fine pieces, 

 mixed with ten parts of absolute alcohol, and extracted in the incu- 

 bator at 37 C. for a week or ten days, being thoroughly shaken every 

 day. The soluble substances are freed from the fragments of tissue 

 by filtration through fat-free filter paper, and rapidly evaporated to 

 dry ness. 2 Sufficient ether is then added to take up the brownish 

 residue, and it is then allowed to stand until a clear, slightly colored, 

 ethereal solution is obtained, free from suspended material. The 

 ethereal solution is concentrated by evaporation to a point where 

 separation of a sediment begins, then it is poured into several volumes 

 (usually ten) of pure acetone. A voluminous precipitate forms at 

 once, and settles out as a tenacious gummy mass. This is retained, 

 under acetone, as the antigen. The acetone-soluble solution is dis- 

 carded. The antigen thus prepared consists largely of lecithins and 

 related substances. It keeps well and appears to be very sensitive 

 and reliable. From 0.2 to 0.3 gram are dissolved in a mixture of 1 

 c.c. of ether (free from alcohol and having a neutral reaction) and 

 10 c.c. of neutral absolute methyl alcohol. This solution is kept 

 in an amber bottle in the refrigerator as a stock antigen. One cubic 

 centimeter of this stock antigen is added to 19 c.c. of physiological 

 salt solution; this is the antigen used for the test. 



Before making a test it is necessary to standardize the antigen. 

 It is essential to know the anticomplementary titer, that is, that 

 maximum amount of antigen which will inhibit hemolysis in the 

 presence of syphilitic serum, but which will not inhibit hemolysis 



1 Noguchi, Serum Diagnosis of Syphilis. 



2 Best by exposing the nitrate in a broad shallow dish to an air current from an 

 electric fan. 



