THE INFLUENCE OF SYMBIOSIS. 83 



Conradi and Kurpjuweit 12 showed that the growth of B. typhosus 

 and B. paratyphosus was definitely inhibited by B. coli. The inhibiting 

 and antagonistic action of B. coli toward some other organisms has been 

 shown by a number of authors. 



Gabricewski and Maljatai 13 found that S. cholerw inhibited the growth 

 of B. coli. 



Heineman 14 found that streptococci isolated from milk interfered 

 with the development of B. lactis aerogenes. 



Herter 15 has demonstrated repeatedly that streptococci grown from 

 the human intestine may repress cultures of B. coli from the same source. 



Walker showed that the typhoid bacillus when grown in the presence 

 of its antiserum acquires a greater virulence for animals and that a larger 

 dose of protective serum is necessary to save guinea pigs from infection 

 with the immunized culture than is needed to protect from the same 

 strain which had not been immunized. Wechsberg demonstrated that 

 diphtheria bacilli could be made to produce a larger amount of toxin 

 by adding diphtheria antitoxin to the culture media in which they are 

 grown. 



Many more examples of the above conditions might be mentioned, but 

 these suffice to show the influence which surroundings, even in the test 

 tube, may have upon cultures of bacteria. This influence might properly 

 be considered under the headings of nutrition, metabolism and produc- 

 tion, and the relation between these three conditions is surely more close 

 and significant than we are accustomed to consider it to be in laboratory 

 technique. If such influences as these may modify our artificial cultures 

 of bacteria, how much greater may be the effect upon the three factors 

 mentioned above of the more complex conditions surrounding mixed cul- 

 tures in unknown symbiosis. Furthermore, what a mass of additional 

 factors are -brought forward when we attempt to study the results of the 

 three we have considered, acting and reacting between such a complex 

 of organisms and the animal tissues. 



Vaughan, in studying the chemistry of bacterial cells, found that so 

 many definite bodies could be split off along fixed lines of cleavage that 

 he concluded the bacterial cell to be made up of a compound of various 

 chemical groups. If this hypothesis be true it seems reasonable to believe 

 that the character of the various chemical groups would depend partially, 

 at least, upon the character of the substances which may be brought 

 together in the environment. 



Eieketts, in discussing the hypothesis of AVelch, says : "Certain con- 

 stituents of our body fluids may, by combining with suitable bacterial 



"Munchen. med. Wchnsch. (1905), 52, 2164, 2228. 



™ Central, f. Bakteriol. (1893), 13, 780. 



14 J. Infect. Dis. (1906), 3, 173. 



ls Bacterial Infections of the Digestive Tract. Macmillan, 1907. 



