THE RELATION OF LIPOIDS TO IMMUNITY 555 



While saponins, solanins, phallin, and other vegetable poisons are of 

 relatively simple chemical composition and quite unlike proteins, 

 enzymes, or toxins, it is possible that bacterial and vegetable hemo- 

 toxins, such as tetanolysin, abrin, ricin, crotin, and robin, may produce 

 their effects by a similar action on the lipoids of the erythrocytes. 

 Noguchi has shown that cholesterin inhibits the action of tetanolysin. 

 Landsteiner and Bottori have found that protagon, a brain lipoid, 

 possesses the property of binding tetanus toxin, which indicates that 

 this toxin may produce its effects by some action upon the lipoids of 

 nerve-cells. 



(c) The important relation of lipoids to the Wassermann reaction and 

 certain precipitin or floccule-forming reactions (Klausner, Porges-Meier, 

 Hermann-Perutz) has been mentioned repeatedly. Just what role the 

 lipoids play in these phenomena is not known. While the globulins of 

 syphilitic serums are strongly suspected of being concerned in these 

 processes, their relation is not clear. Klausner 1 now believes that the 

 precipitate that forms when distilled water is added to syphilitic serum 

 is due to the high lipoid content. 



LANGE'S COLLOIDAL GOLD REACTION 



Principles. According to the exhaustive studies of Zsigmondy 2 on 

 metallic colloids a solution of a protein will precipitate colloidal gold 

 in the absence of an electrolyte. An electrolyte, as sodium chlorid, 

 will in certain concentrations precipitate the colloidal gold itself; if 

 proteins are present this precipitation is inhibited. The degree of 

 protection afforded has been found specific for each protein, and is ex- 

 pressed in terms of milligrams of the protein capable of protecting 5 c.c. 

 of colloidal gold against 0.5 c.c. of a 10 per cent, solution of sodium 

 chlorid. 



Lange 3 endeavored to distinguish between normal and luetic sera 

 by this means on the basis of disturbances in syphilis, but failed; he 

 then sought to measure the protein content of cerebrospinal fluid by 

 the degree of precipitation of gold, but failed again, because he used 

 distilled water as a diluent, thereby throwing the protein, particularly 

 the globulins, out of solution, and rendering them inert. When, how- 

 ever, he used a 0.4 per cent, solution of sodium chlorid as a diluent it 

 was found that the proteins were not precipitated and that this amount 

 of salt was too weak to precipitate the colloidal gold. 



1 Biochem. Zeit., 1912, 47, 36. 



2 Ztsch. f. Anal. Chem., 1901, xl, 697. 



3 Berl. klin. Wchnschr., 1912, xlix, 897; Ztschr. f. Chemotherap., 1913, 1, 44. 



