IVAN C. HALL 207 



These he believed to be reducing agents as shown by their decoloration of methylene 

 blue in broth, but he also emphasized the necessity of heating just prior to inoculation, 



Liefmann,' Guillemot and Szczawinska/ and Rosenthal all recognized clearly that 

 the growth of obligate anaerobes in the presence of such substances is truly anaerobic, 

 not aerobic, and agreed with Wrzosek in attributing such growth to the reducing ac- 

 tion supposedly possessed by them. 



Hata,'' on the other hand, emphasized the importance of the particulate nature 

 of reducing agents and suggested that the best results are to be expected when these 

 agents are in a finely divided condition, as finely minced animal and plant tissues, 

 or iron filings. Douglass, Fleming, and Colebrook^ objected that organic substances 

 can scarcely be expected to retain their chemical reducing action after heating. This 

 seems valid. But while a surprisingly large list of organic and inorganic solids may 

 be used in broth cultures to provide anaerobic conditions, including ashes, sand, card- 

 board, wool, cotton, lint, sponge, charcoal, chalk, cork, cloth, and iron nails, all have 

 a more or less porous or particulate consistency, and the degree of success achieved 

 with them depends upon this and upon the amount of substance used. Finally, the 

 use of small pieces of capillary tubing in broth affords a striking proof of the fact that 

 anaerobic growth begins in the interstices of such substances as afford occluded spaces 

 into which oxygen diffuses with difficulty after once being driven out by heat. At 

 least motile anaerobes find their way into such interstices by reason of a negative 

 chemotactic response to oxygen, and once growth starts, the generation of gas im- 

 proves the conditions of anaerobiosis through its action in sweeping out oxygen. This 

 has been clearly recognized by Novy,^ Wright,^ Wolf, McGill, and Harris^ and others. 



We thus come to the conclusion that physico-chemical factors play an important 

 role in the so-called "aerobic cultures" of anaerobes in the presence of plant and ani- 

 mal tissues. The action of such tissues is physical to that degree in which they in- 

 terfere with the reabsorption of oxygen ; it is chemical to that degree in which actual 

 reduction of free oxygen by unheated tissues occurs. It is probable also that certain 

 tissues contribute valuable nutrients to the media and that they serve as important 

 buffers against unfavorable H-ion concentrations. The Italian work started with the 

 biological hypothesis of a reducing ferment, but it ended without proof. And while 

 many were able to demonstrate the growth of obligate anaerobes in broth containing 

 animal and plant tissues and other particulate substances, no one was ever able to 

 secure surface growth of obligate anaerobes in pure culture in contact with air. 



Yet the idea that unheated plant and animal tissues may accelerate anaerobic 



' Liefmann, H.: Munchen. med. Wchnsckr., 54, 823. 1907; Centralbl. f. Bakleriol.. Abt. I.Orig., 

 46, 377. 1908. 



^ Guillemot, L., and Szczawinska, W.: Compt. rend. Soc. de biol., 64, 171. 1908. 



J Rosenthal, G.: ibid., 67, 702. 1909. 



iHata, S.: Centralbl. f. Bakteriol., Abt. I, Orig., 46, 539. 1908. 



s Douglass, S. R., Fleming, A., and Colebrook, L.: Lancet, 2, 530. 1917. 



*Novy, F. G.: Centralbl. f .Bakteriol., A.h\..l,Orig., 14, $go. iSgs; Ztschr.f. Ilyg., 17, 2og. 1894. 



7 Wright, A. E.: Lancet, i, i. 1917. 



» Wolf, C. G. L., McGill, C, M., and Harris, J. E. G.: ibid., 2, 787. 1917. 



