31 



Martha Wollstein,* starting with the fact that the appropriate 

 "bacteriophage" for dysentery bacilli causes these organisms, 

 when plated out, to divide up into " regular " and " irregular " 

 colonies, compared the action of the lytic principle on cultures of 

 each of these types. It was found that the " regular " strains 

 were more resistant than the " irregular." Tests with the filtrates 

 from these strains showed that the lytic principle was carried by 

 the latter but not by the former. Both the regular and the 

 irregular colonies were subcultured on plates for more than 

 40 generations. The former retained their characters without 

 any alteration; the latter approximated to the former type, 

 until more regular than irregular colonies were present. " The 

 explanation seems to be that the sensitive bacilli die off more 

 rapidly than the resistant ones, which form the regular colonies 

 in later generations. It is a matter of selection." She then 

 endeavoured to ascertain whether the acquired lysogenic property 

 was retained permanently. " Working with the original, normal 

 culture as a whole, it was found that after the seventh generation 

 on agar or in broth the bacilli which had survived contact with a 

 lytic fluid were no longer able to transmit the lysogenic property 

 to other cultures or to dissolve the normal Shiga bacilli." As 

 regards the two main properties of the regular colonies, resistance 

 to lysis and loss of lysogenic power, it was found in some experi- 

 ments that a certain amount of lysis was produced on bacilli 

 cultured from regular colonies. The explanation was that these 

 cultures were not absolutely " pure," i.e., some less resistant 

 bacilli were still present. This was shown by re-plating, when both 

 regular and irregular colonies developed from a broth culture of 

 the strain in question, which had been in contact with lytic fluid 

 over night. The regular colonies picked from this plate were com- 

 pletely resistant to lytic action. Put briefly, the results of the 

 action of a lytic principle were : — (1) production of strains which 

 resisted lytic action, were not lysogenic, and were not agglutin- 

 able ; (2) production of strains which were lysogenic, agglutinable, 

 and sensitive to lytic action; (3) gradual conversion of these 

 latter strains into the resistant and non-lysogenic type. 



If a lytic principle (a) derived from bacillus A is found to act 

 on a different bacillus B, it is not surprising that the lytic prin- 

 ciple (b) derived from filtrates of B may differ from a in its range 

 of action. But it is a curious fact (mentioned on p. 22) that b, 

 even after many transmissions through cultures of B, may retain 

 a certain impress of the individuality derived from A. This 

 individuality may be demonstrated by immunising animals with 

 a lytic substance and obtaining in their serum the corresponding 

 specific antibody. Two examples are worth quoting. Bruynoghe 

 and Appelmans| prepared antisera with two typhoid " bacterio- 

 phages," the one obtained from Strasburg and the other from 

 Louvain. The latter was originally a coli " bacteriophage " but 



* Journ. Exper. Med., XXXIV., p. 467, 1921. 



f C.R. Soe. Biol., LXXXVIL, p. 96, 27th May, 1921. 



