ZINSSER AND MUELLER 723 



II 



Elementary analysis, or even extraction and fractionation of the bacterial cell 

 body by methods in which immunological properties are "denatured" or destroyed, 

 can be of little service. Insufficient attention to proper correlation of chemical proper- 

 ties with biological activity, therefore, has considerably delayed progress in this field. 

 It is useless, then, to detail the many earlier studies which are of purely biochemical 

 interest, but make no direct contributions to immunology. 



In varying proportions, all pathogenic bacteria contain considerable amounts of 

 lipoidal, nitrogenous, protein or protein-like, and carbohydrate material. 



THE LIPOIDS 



Concerning the immunological significance of the lipoids, little can be said with 

 certainty. Much has been written about the antigenic properties of the lipoids — es- 

 pecially in connection with alexin fixation reactions, but the issue has here been cloud- 

 ed by the non-specific elements which are involved in tuberculosis and syphilis fixa- 

 tions and, in cases where these considerations can be eliminated, by the probability 

 that the lipoids in question may have been impure, containing traces of protein. Both 

 Landsteiner" and, more recently, Wells- have subjected the evidence to critical 

 analysis, and neither of them is willing to accept without reservation any of the 

 claims of antigenic activity for the bacterial lipoids. 



THE BACTERIAL NUCLEOPROTEIN 



The substances which it has lately been the custom to speak of as the "bacterial 

 nucleoproteins" are probably not nucleoproteins in the structural chemical sense. 

 They constitute the bulk of the bacterial cell as judged by quantitative yields of 

 material, and from the method of obtaining them and their gross physical attributes — 

 solubility, etc. — they probably consist of a mixture of different things in which, as 

 Wells suggests, there are probably present not only nucleoproteins, but nucleins, 

 nucleo-albumins, mucin, and proteinates formed by the action of the alkali used in 

 their isolation upon proteins. It is important to bear in mind a fact that Wells has 

 repeatedly emphasized, that in most of the methods necessary for the preparation 

 of cell extracts of any kind, relatively severe treatment is necessary, which may de- 

 nature and alter normal cell constituents; and that it is next to impossible to obtain 

 pure, unaltered proteins. A discussion of the chemical problems involved may be 

 found in the chapter on the nucleoproteins of Wells's book. For our own purposes we 

 may limit ourselves to those phases of the chemical problem which have immunological 

 bearing. 



Whether or not the bacterial nucleoproteins have been obtained from cen- 

 trifugated broth cultures, as in the work of Avery and Heidelberger,'' Lanceiield,'' and 

 others, or from ground, dried bacteria grown on agar, as in our own work, 5 the prin- 



' Landsteiner, K.: JahresherichI ither die Ergehn. d. Immunitatsforschnng, 6, 209. 1910. 

 -Wells, H. G.: op. cil. 47-51. 1925. 



^ Avery, O. T., and Heidelberger, M.: J. Exper. Med., 38, 81. 1923; Avery, O. T., and Morgan, 

 H.: ibid., 42, 347. 1925. 



•> Lancefield, R. C: ibid., p. 377. 1925. 



s Zinsser, H.: ibid., 34, 495. 1921; Zinsser, H., and Parker, J. T.: ibid., 37, 275. 1923. 



