306 BIOLOGY OF PNEUMOCOCCUS 



of the experiments, 0.1 cubic centimeter of the enzyme afforded 

 mice protection against one million times the fatal dose of virulent 

 Type III Pneumococcus. Avery and Dubos also showed that again 

 the action of the enzyme was specific for Type III; that the 

 greater the activity of the enzyme in vitro the greater was its pro- 

 tective action in mice ; and that the enzyme exerted a curative ac- 

 tion since the mice receiving the enzyme eighteen hours after the 

 onset of infection recovered. The extraordinary enzymatic princi- 

 ple, therefore, not only strips the capsule from Type III Pneumo- 

 coccus, but renders innocuous a large multiple of the infecting dose 

 of the organism and, what is more, under certain conditions it ac- 

 tually cures mice of an already active infection. 



PHILOSOPHICAL ASPECT OF THE ACTION OF THE ENZYME 



The possibilities presented by this and other similar enzymes in 

 the prevention and cure of pneumococcal infection in man were 

 strikingly promising, but before going on to experiments leading in 

 that direction, it may be interesting and more profitable to con- 

 sider first the important philosophical aspects of the action of an 

 enzyme of this particular type on bacterial polysaccharides. It 

 would be impossible to improve on Avery and Dubos' discussion of 

 this phase of the subject, so it is quoted in full. 



The present study emphasizes the importance of the capsule in the 

 biological reactions of the pneumococcus. It is, indeed, a significant 

 fact, that no matter whether one regards this organism from the view- 

 point of type-specificity, antigenicity, or its capacity to undergo varia- 

 tion, or whether, as in the present instance, one considers the pneumo- 

 coccus with reference to its virulence and fate in the animal body, the 

 one dominant factor influencing all these phenomena is the function of 

 the cell to elaborate the specific capsular polysaccharide. These rela- 

 tionships, however, are not to be interpreted as meaning that virulence 

 is dependent merely upon differences in the structural morphology of 

 the bacterial cell. For it is a common observation that an encapsulated 

 strain of Pneumococcus may be virulent for one species and not for an- 

 other. However, it is equally true that the function of elaborating the 



