W. p. LARSON 183 



cells. It will perhaps not be considered too theoretical to assume that the rate of 

 growth is influenced by the effect the most immediate surface tension depressants 

 have upon the organism. If it happens to be an idealfood for the particular bacterium, 

 it constitutes an ideal culture medium. If, on the other hand, the surface-tension 

 depressants are toxic, there will be little or no growth. The use of bile in culture 

 media may illustrate the point in question. It has been known for many years that 

 bile salts, when added to culture media, stimulate the growth of the colon-typhoid 

 bacteria, whose normal habitat is the intestinal tract. The pneumococci and strepto- 

 cocci, on the other hand, are very sensitive to bile salts and soluble soaps. 



Studies published from this laboratory have shown that relatively low concentra- 

 tions of sodium ricinoleate deprive pneumococci,' streptococci, and tubercle bacilli^ of 

 their power to infect. Netter and his collaborators^ have recently confirmed and some- 

 what extended this observation. Ayers et al.,^ studying the effect of the surface ten- 

 sion of the culture medium on the growth of streptococci, suggested that the surface 

 tension of the medium may be used as a basis for classification. Frobisher^ has empha- 

 sized the importance of using high-tension medium in growing pneumococci. Albus 

 and Holm* have further shown that B. biilgaricus is more sensitive to surface-tension 

 depressants than B. acidophilus. They believe the difficulty of successful implantation 

 of B. biilgaricus in the intestinal tract i? due to its inability to grow at the low-surface 

 tension created by the bile salts. Hansen,^ Frobisher,* and others have shown that the 

 action of some disinfectants is enhanced by surface-tension depressants. 



It is an interesting observation that the micro-organisms which thrive well upon — 

 even prefer — a low-tension medium are splendid antigens, and as a rule produce 

 infections which are followed by an immunity which is reasonably permanent, as is 

 the case with typhoid, paratyphoid, and cholera vibrio infections. 



Infections by the pneumococci, streptococci, and tubercle bacilli, on the other 

 hand, confer no such degree of immunity. It is not possible at the present time to 

 show a definite relationship between the optimal surface tension for an organism and 

 its antigenic properties. The apparent relationship may be purely incidental, but 

 nevertheless interesting. 



The nature of the interfacial zones mentioned above undoubtedly plays an im- 

 portant role in antibody reactions. Where bacterial surfaces are of such a nature as to 

 resist being wet by water it might be expected it would have an influence upon the 

 union between antibody and bacterium. Studies in this connection were made by 

 Larson and Greenfield.' A staphylococcus was grown for several generations on 

 glycerol broth until it grew in a pellicle which resembled the growth of the tubercle 



' Larson, W. P., and Nelson, E. N.: Proc. Soc. Exp. Biol, and Med., 22, 357. 1925. 



^Larson, W. P., and Montank, I. A.: ibid., 20, 229. 1923. 



•5 Netter, A., Andre, E., Cesari and Contoni: Compl. rend. Soc. de bioL, 96, 184. 1927. 



* Ayers, S. W., Rupp, P., and Johnson, W. T., Jr.: Jour. Infect. Dis., 33, 202. 1923. 

 5 Frobisher, M.: ibid., 38, 66. 1926. 



'' Albus, W. R., and Holm, M. L.: Proc. Soc. E.xp. Biol, and Med., 22, 337. 1925. 

 7 Hansen, T.: Comp. rendu, soc. biol., 86, 215. 1922. 



* Frobisher, M.: Jour. Bad., 13, 163. 1927. 



' Larson, W. P., and Greenfield, R.: Proc. Soc. Exp. Biol, and Med., 20, 348. 1923. 



