520 THE RELATION OF COLLOIDS AND LIPOIDS TO IMMUNITY 



which tend to aggregate in masses (although these may be so small as 

 to be invisible) and reduce their surface tension in just the same manner 

 as agglutination and precipitation are brought about after the colloidal 

 theories. When corpuscles and hemolytic antibody are subsequently 

 added, hemolysis does not occur because free complement is absent. 



A process similar to complement absorption by a specific antigen 

 and its antibody is the Wassermann reaction. According to the col- 

 loidal theories, this reaction may be explained as due to the formation 

 of an invisible precipitate by interaction between some substance in 

 the serum of a luetic person (probably in the nature of an altered globu- 

 lin), complement, and lipoidal substances contained in an alcoholic or 

 watery extract of a normal or a diseased organ. This view is supported 

 by the fact that euglobulin is known to be generally increased in the 

 body fluids of syphilitics, and by analogy with the various precipitin tests 

 that have been devised for the diagnosis of syphilis, as, for example, the 

 reaction of Forges and Meier, which is dependent upon the appearance 

 of a precipitate when luetic serum is mixed with an emulsion of lecithin 

 or sodium glycocholate, etc. The exact nature of the antibody in 

 syphilitic serums that forms these new compounds with lipoids and 

 complement, resulting probably in the absorption of complement, is 

 unknown. It is most likely in the nature of a globulin, its main char- 

 acteristic being the power it possesses of reacting with lipoids. Schmidt 1 

 ascribes the reaction to the physicochemical properties of the globulins 

 of the syphilitic serum, which he believes possess a greater affinity for 

 the colloids of the antigen than do normal globulins. This view is 

 supported by the common observation that the turbidity of the antigen 

 emulsion is closely related to its efficiency, since clear solutions are less 

 active. Since various lipoidal substances may be employed, the Was- 

 sermann reaction can not be regarded as specific in the immunologic 

 sense, although practically it is highly specific, as similar conditions are 

 to be found in only two other diseases with any degree of regularity, 

 namely, frambesia and tuberous leprosy. 



THE RELATION OF LIPOIDS TO IMMUNITY 

 It is becoming more and more evident that lipoids bear an important 



relation to various immunologic processes, especially to certain cytolytic 



phenomena. 



As stated in Chapter VIII, the results of some researches that go to 



1 Zeit. f. Hygiene, 1911, 69, 513. 



