250 INFECTION AND RESISTANCE 



Jacoby. 6 7 Jacoby, working with a vegetable antigen, ricin, found 

 that by trypsin digestion he could obtain a substance which still 

 retained antigenic properties, but no longer gave any of the pro- 

 tein reactions. Obermeyer and Pick, by the same method, claim 

 that they have produced a non-protein precipitinogen from egg al- 

 bumen. On the other hand, others have had negative results, and 

 Kraus 8 himself, after reviewing the evidence on both sides, comes 

 to the conclusion that available data do not justify us in separating 

 the antigenic properties from the protein molecule. In unpublished 

 experiments which the writer carried on in the laboratory of Profes- 

 sor Friedemann in Berlin also attempts to produce a non-protein 

 precipitinogen from horse serum by bacterial putrefaction were en- 

 tirely negative. The putrefaction of the serum, though carried out 

 in dialyzing bags for the removal of diffusible products, was ex- 

 tremely slow, and when finally the Biuret reaction disappeared the 

 serum was no longer precipitable by potent antisera. However, the 

 flaw in these experiments is that the true test of the presence of 

 precipitinogen is not the precipitable character of the solution, in 

 question, since actual precipitation is dependent, as we shall see, 

 upon many modifying secondary factors, but rather the ability of 

 the substance to induce precipitins in treated animals. 



The fact that Nicolle, 9 and later Pick, 10 were unable to obtain 

 alcohol-soluble substances from bacteria and bacterial extracts which 

 were still precipitable might also be taken to point toward the non- 

 protein character of the precipitinogens, suggesting that these sub- 

 stances may be of a lipoidal nature. However, as Landsteiner 11 

 points out, mere solubility in organic solvents can no longer be taken 

 as a proof of lipoidal character, since it is more than probable that 

 non-lipoidal substances may go into alcoholic and other organic solu- 

 tion when lipoids, such as lecithin, are present. Thus Miiller 12 

 found that the antigen of typhoid bacilli was soluble in chloroform 

 in the presence of old preparations of lecithin. Pick and Schwartz, 1 3 

 who had previously studied similar antigen solubilities in the pres- 

 ence both of lecithin and of other organ lipoids, suggest that possibly 

 such solutions represent lipoid-protein combinations colloidal "so- 

 lutions" which permit the presence of protein mechanically or 

 chemically united to the lipoid in the organic solvents alcohol, 

 chloroform, etc. Here, too, then there is no. evidence for the ex- 

 istence of non-protein precipitinogen. 



6 Jacoby. "Hofmeister's Beitrage," Vol. 1, 1901. 



7 Oppenheimer. "Hofmeister's Beitra^e," Vol. 4, 1904, p. 259. 



8 Kraus in "Kolle u. Wassermann Handbuch," Vol. 4, p. 605. 



9 Nicolle. Ann. de I'lnst. Past., 12, 1898. 



10 Pick. "Hofmeister's Beitrage," Vol. 1, 1901. 



11 Landsteiner. "Weichhardt's Jahresbericht," Vol. 6, 1910, p. 214. 

 12 Muller. Zeitschr. f. I mm., Vol. 5, 1910. 



13 Pick and Schwartz. Biochem. Zeitschr., Vol. 15, 1909. 



