540 THE BACTERIOPHAGE 



cannot be considered as proof of a "spontaneous" appearance of the active agent. 

 All these substances may conceivably be contaminated with phage/ On the other 

 hand, it is known that many strains of bacteria (particularly those of recent isolation) 

 frequently carry phage^ which cannot always be demonstrated, probably because only 

 a few individuals in the culture may be susceptible to its action. Thus, the phage may 

 be carried by a given culture, unnoticed for a time, and may become manifest if the 

 susceptibility of the culture is suddenly changed, or if the filtrates of such "lysogenic" 

 cultures are allowed to act upon more susceptible strains of homologous and occasion- 

 ally even of heterologous bacteria. This "lysogenic" power of some cultures, mani- 

 festing itself against other homologous and heterologous bacteria, has been given as an 

 instance of "spontaneously" arising phage action as the result of bacterial antibiosis.^ 

 However, the writer has been able to imitate this phenomenon in every detail by con- 

 taminating cultures with phage artificially. Subjecting a phage-free culture of colon 

 bacilli to the action of a polyvalent phage and isolating the overgrowth of resistants, 

 we found it to carry the phage for months without showing any signs of its pres- 

 ence.'' When, however, this resistant culture was grown in symbiosis with stock cul- 

 tures of B. coli or of B. dysenteriae (Shiga), the presence of phage could be readily 

 demonstrated.^ 



In view of the fact that cultures of bacteria may thus carry phage without reveal- 

 ing any signs of its presence, one must be very cautious in interpreting the 

 sudden appearance of phage in cultures subjected to various influences of physical 

 or chemical nature, or even in cultures merely kept in the laboratory for a long period 

 of time.^ Quite apart from the possibility of occasional direct contamination of these 

 cultures with phage present in the laboratory, such manipulations as, for example, 

 filtration through Berkefeld filters (which is a usual step in the preparation of bac- 

 teriophage) have been known to result in contamination of filtrates with phage- re- 



' The only promising experiments of this nature have been reported by Doerr {loc. cit.) who ob- 

 tained bacteriophage by feeding susceptible bacteria to sterilely hatched chickens. These experi- 

 ments have not been repeated, however, and it is impossible to say at present whether or not the 

 result was merely an accidental occurrence. Somewhat similar experiments were performed by Ebel- 

 ing in collaboration with the writer, but without obtaining the same result in the preliminary trials. 

 In these experiments bacteria were introduced into the pure cultures of cells of intestinal mucosa of 

 a chick embryo. 



^Button, L. O.: /. Infect. Dis., 39, 48. 1926; Manninger, R.: Ccntralbl. f. Bakleriol., 99, 203. 

 1926. 



3 Gildemeister, E., and Herzberg, K.: Centralbl.f. Bakteriol., Ref., 77, 188. 1924; ibid., 93,402. 

 1924; Lisbonne, M.,and Carrere, L.: Compt. rend. Soc. de bioL, 86, 569. 1922; ibid., 87, loii. 1922; 

 Bordet, J.: ibid., 93, 1054. 1925. 



^ A few susceptible bacteria present among the bulk of resistants apparently permitted very slight 

 regeneration of phage to take place at each transfer, thus securing conditions perpetuating the re- 

 sistance of the majority of bacteria in the culture. 



s Unpublished experiments in collaboration with Muckenfuss, 1927. 



« Jotten, K. W.: loc. cit.; Otto, R., and Winkler, W. F.: loc. cit.; Blair, J. E.: loc. cit.; Gate, J., 

 and Gardere, H.: Compt. rend. Soc. dc bioL, 96, 545. 1927; Gildemeister, E., and Herzberg, K.: 

 Centralbl.f. Bakteriol., 91, 12. 1923; Ogata, N.: ibid., Orig., 93, 329. 1924. 



'Otto, R., and Winkler, W. F.: loc. cit.; Putter, E., and Vallen, S.: loc. cit.; Weinberg, M., and 

 Aznar, P.: Compt. rend. Soc. de bioL, 86, 833. 1922; ibid., 87, 136. 1922; Seififert, W.: Med. Klin., 

 19, 833. 1923; Otto, R., and Munter, H.: Deutsche mcd. Wchnschr., 48, 382. 1922. 



