POLYSACCHARIDE-SPLITTING ENZYMES 307 



specific capsular polysaccharide is most highly developed in pneumo- 

 cocci that are best adapted to growth in the animal body. From this 

 point of view, virulence and capsule formation, although not causally 

 related, are at least intimately associated. When the function of forming 

 the capsular substance is suppressed or inhibited, as in the case of the 

 R. variants, or when, as in the present instance, although this function 

 is unimpaired the capsule itself is destroyed by an enzyme, the naked 

 bacteria are thereby exposed directly to attack by the phagocytes of the 

 host. 



In this sense, the action of the enzyme may be said to result in pre- 

 paring the encapsulated bacteria for phagocytosis ; not as in the case of 

 antibodies, by specific sensitization, but by the process of decapsulation. 

 In the former instance, the reaction is an immunological one, whereby 

 the capsular material is altered by union with the type-specific anti- 

 body ; in the latter case, the reaction is a chemical one in which the cap- 

 sular polysaccharide is actually decomposed by the enzyme. Although 

 the mode of action of both these specific agents is different in each in- 

 stance, the end result, so far as the fate of the microorganism is con- 

 cerned, is the same in both cases. 



It is of interest that although neither the enzyme nor the specific 

 antibody is by itself bactericidal or bacteriolytic, yet each by reacting 

 specifically with the capsular substance exposes the virulent organisms 

 to the phagocytic action of the body tissues. The enzyme, like the spe- 

 cific antibody, serves merely to initiate the protective reaction, the com- 

 pletion of which is ultimately dependent for its successful issue upon 

 the effective cellular response of the host. 



The present study also suggests that the capsule — long recognized as 

 a defense mechanism on the part of virulent bacteria — is a decisive fac- 

 tor in determining the fate of pneumococci in the animal body, and that 

 this structure is vulnerable to attack by specific agents other than anti- 

 bodies. 



METHODS OF PRODUCTION 



Dubos 335 " 6 then attempted the development of practical methods 

 of production, purification, and concentration of the enzyme, and 

 investigated the influence of certain factors on the potency and 

 primary toxicity of the preparations. He first studied the growth 

 and enzyme production of the SHI bacillus in more than fifty dif- 



