28 



specifically, in other ways. They may produce non- viable variants 

 by direct action upon bacterial growth, not by the indirect method 

 of stimulating the animal body to produce antibodies which 

 interfere with that growth. Experimentally there are many ways 

 of producing such variants without the employment of antibodies. 

 One of these methods, the use of " lytic substance," is of particular 

 interest, because what is seen to take place in the test-tube may 

 have some counterpart in the reactions going on in the animal 

 body. 



The first fact of importance about " lytic substance " is that, 

 as already mentioned, it may be derived from the bacteria 

 ab initio. Further, it is not necessary to wait for the chance of 

 its spontaneous emergence in an old culture. Various experimental 

 methods may be employed. For example, Otto and Winkler* 

 stated that lysin formation could be promoted in many different 

 ways, by adding to the culture filtrates from old cultures, by the 

 treatment of the bacteria with immune serum, and by physical or 

 chemical means (shaking in distilled water or the addition of a 

 small quantity of sublimate). But filtration through a bacterial 

 filter was especially useful and was preferable to centrifugalisation 

 because fewer passages were necessary in order to obtain the lysin. 

 Their method was to heat a broth culture at 58° C, filter, add a 

 few drops of filtrate to new broth containing fresh, living culture , 

 and incubate for 24 hours at 37° C. These steps constituted the 

 first " passage." The process was repeated until the lysin was 

 obtained. Weinberg and Aznar j obtained similar results by the 

 filtration method with B. Shiga. They termed their products 

 " autobacteriolysins " because they were obtained directly and 

 primarily from the bacteria. They also showed, by the method of 

 autolysis in distilled water, that these lysins could be obtained 

 from young cultures as well as from old. They took two loopfuls 

 of a 24 hours' growth, emulsified it in 20 c.c. of sterile distilled 

 water, incubated at 37° C, and then demonstrated the presence 

 of lysin in the filtrate. 



Lytic substances are of the same general characters, whether 

 produced directly with culture material or by more complicated 

 methods involving animal inoculation or the use of animal pro- 

 ducts. They are of bacterial origin but must be regarded as a 

 modification of bacterial constituents since they may not be 

 demonstrable as components of normal bacterial protoplasm. This 

 last fact may be illustrated by serological methods. 



For example, Bordet and Ciuca J thoroughly immunised rabbits 

 with a normal strain of B. coli and found that the serum had no 

 antilytic properties. From the same strain, however, they obtained 

 a lytic principle and produced a lysogenic variant. The serum of 

 rabbits immunised with this variant was antilytic. Their inference 

 was that lytic power was u ndoubtedly a newly acquired character. 



* Deutsch. med. Wochenschr., p. 383. 24th March, 1922. 

 t C.R. Soc, Biol. LXXXVI. (p. 833), 29th Apr., 1922, and LXXXVII. 

 (p. 136), 17th June, 1922. 



% C.R. Soc. Biol, LXXXIV., p. 280, 29th Jan., 1921. 



