x BIOLOGY OF PNEUMOCOCCUS 



V. PNEUMOCOCCAL DISSOCIATION AND TRANSFORMATION 134 



Early observations of dissociation, 1891-1921. Later ob- 

 servations of dissociation: smooth and rough forms of 

 Pneumococcus ; modifications A, B, and C ; composite cul- 

 tures ; species-specificity of rough forms ; electrophoretic 

 potential of variants ; effect of charcoal, yeast, optochin ; 

 in vivo variation ; details of colony formation ; antigenicity 

 of rough forms ; respiratory capacity of variants ; in- 

 termediate forms ; reversal of dissociation ; reversion 

 by means of pneumococcal vaccine. Transformation of 

 type: transformation by vaccine and animal inoculation; 

 isolation of the transformative principle. Dawson classifi- 

 cation. Transmutation of species. Summary. 



VI. PATHOGENICITY OF PNEUMOCOCCUS: EXPERIMENTAL 

 ANIMALS 179 



Susceptibility of the animal host: the rabbit; the guinea 

 pig; the mouse; the rat; the monkey; the cat; the dog; 

 the horse; birds. Virulence of the organism: freshly iso- 

 lated strains; numbers of cocci required to infect; avenue 

 of inoculation ; determination of virulence ; substances 

 that enhance virulence ; cultural conditions and virulence ; 

 strain variations in virulence; virulence in respect to ani- 

 mal species; artificial exaltation of virulence; degradation 

 of virulence; dissociation and virulence. Summary. 



VII. PATHOGENICITY OF PNEUMOCOCCUS: MAN 214 



Etiology of pneumonia : pneumococcal types in lobar 

 pneumonia ; pneumococcal types in bronchopneumonia ; 

 pneumococcal types in pneumonia in infants and children. 

 Serological types and fatality-rates. Localized epidemics 

 of pneumococcal infection. Infectious processes other 

 than pneumonia. Pneumococcemia. Excretion of pneumo- 

 cocci. The carrier state. Summary. 



VIII. CHEMICAL CONSTITUENTS OF PNEUMOCOCCUS 238 



Work of earlier investigators. First description of the 

 pneumococcal carbohydrate. Isolation of carbohydrate 

 fractions. Isolation of C Fraction. Relation of the pneu- 

 mococcal carbohydrate to carbohydrates isolated from 

 other organisms. Function of sugars in determining anti- 

 genic specificity and conjugated proteins. Isolation of "A 

 substance." Comparison of various cellular carbohydrates. 

 Type VIII carbohydrate. Isolation of an unidentified con- 



