THE RELATION OF LIPOIDS TO IMMUNITY 559 



Swalm and Mann, 1 Lee and Hiriton, 2 Weston, Darling and Newcomb, 3 

 Solomon and Welles, 4 Miller, Brush, Hammers and Felton 5 , and others, 

 show that under proper conditions the colloidal gold test is highly 

 specific and of value in the diagnosis of general paresis. 



A paretic colloidal gold reaction with the cerebrospinal fluid of a 

 luetic person may be the first sign of an incipient paresis. 



A paretic reaction with the cerebrospinal fluid of a luetic individual 

 should be regarded as of grave import; while positive symptoms of 

 paresis may not be present, intensive antiluetic treatment may serve 

 to arrest the disease. 



The colloidal gold reactions in tabes dorsalis and cerebrospinal 

 syphilis are not characteristic of these diseases, and at most may yield 

 the luetic zone type of reaction, and thereby prove of value in confirming 

 a doubtful diagnosis. 



THE EPIPHANIN REACTION 



Principle. This reaction is based upon the observation made by 

 Weichardt 6 in 1908; he found that diffusion is accelerated when dif- 

 ferently colored solutions of antigen and its specific antibody are brought 

 together. Changes in diffusion are associated with changes in the 

 surface tension, both of which depend on a change in the osmotic pres- 

 sure. This is the principle made use of by Ascoli in his miostagmin 

 reaction, which will be described further on. 



Later Weichardt made the reaction more accessible to practical use 

 by introducing into the solution of serums and antigen a system composed 

 of sulphuric acid and barium hydroxid, together with certain catalytic 

 agents. Using phenolphthalein as an indicator, he could show that 

 fresh serums in high dilutions alter the surface tension of the finely 

 divided barium sulphate particles by their colloidal action, so as to in- 

 crease the absorption of H-ions, thus rendering the solution more alkaline. 



This phenomenon has been utilized by Weichardt, under the name 

 of "epiphanin reaction," to determine the occurrence of such interac- 

 tion of antigen and antibody. The reaction probably depends upon 

 physicochemical principles of absorption, but the exact nature of the 



1 N. Y. Med. Jour., 1915, xi, 719. 



2 Amer. Jour. Med. Sci., 1914, cxlviii, 33. 



3 Amer. Jour. Insan., 1915, Ixxi, 773. 



4 Boston Med. and Surg. Jour., 1914, clxxi, 886; ibid., 1915, clxxii, 398. 

 6 Loc cit. 



Berl klin Wochenschr, 1908, No. 20; Centralbl. f. Bakteriol., xliii, 143- ibid 

 19U No 4 G1 154 r ' Immumt * tsforsch -> 1910 > > 651; Deutsch. med. Wochenschr.'; 



