LYSINS 161 
physiological salt solution containing 0.5 per cent phenol as a preserva- 
tive. After several days' violent agitation in the dark it is strained 
through several layers of cheesecloth to remove coarser particles and 
stored in amber bottles in the refrigerator. Sedimentation takes 
place until a brownish, slightly opalescent fluid remains, which is the 
luetic antigen. 
Later work^ showed that alcoholic extracts of luetic liver were 
more stable than watery extracts. The specific reacting component, 
according to Forges and Meier, is lipoidal in nature, and in this sense 
it is not biologically specific. The fixation of complement appears to 
depend upon a substance in the antigen, lipoidal in nature, which 
effects a union of antigen, immune body and complement.- Citron 
has proposed the term "lues-reagine" for this substance. Alcoholic 
extracts of syphilitic liver are prepared by shaking finely comminuted 
liver with ten times the weight of absolute alcohol for a few days, 
then digesting the mixture at 87° 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 antigens as alcoholic 
extracts of syphilitic livers for the diagnosis of syphilis. In practice 
heart-muscle of normal guinea-pigs or cattle, freed from all fat, is used. 
Nognchi's Acetone-insoluble Lipoidal . intig en. ^—^o^uchi and others 
have shown that alcoholic extracts or organs may, and frequently 
do, contain sufficient amounts of neutral fats, or their hydrolytic 
cleavage products, to make the antigen hemolytic or anticomple- 
mentary. These substances are for the most part soluble in acetone, 
while the antigenic fraction is insoluble in acetone. He, therefore, 
suggested an acetone-insoluble antigen prepared as follows: One part 
of fat-free heart muscle or liver from a guinea-pig is cut into very fine 
pieces, mixed with 10 parts of absolute alcohol, and extracted in the 
incubator 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 rapidl}- evapo- 
rated to dryness.'* 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 10) 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 
discarded. The antigen thus prepared apparently consists largely of 
■ Especially by Forges and Meier (Berlin, klin. Wchnschr., 1908, 45, 731) and Weil 
•and Braun (Wien. klin. Wchnschr., 1908, 21, 151). 
- For discussion see Epstein and Paul: Arch. f. Hyg., 1921, 90, 98. 
■^ Noguchi: Serum Diagnosis of Syphilis. 
< Best by exposing the filtrate in a broad shallow dish to an air current from an electric 
fan. 
u 
