52 IMMUNOLOGY 



information concerning the virulence of the organisms isolated 

 from carriers. Hadfield and Garrod (1938) review the studies in 

 the distribution of pneumococcus types in normal individuals re- 

 ported by Webster and Hughes (1931), Gundel and Linden (1931). 

 They say that the evidence indicates that the less virulent types 

 attack the respiratory tract, set up mild infection, establish them- 

 selves and remain in intimate relationship with the host for long 

 periods of time. This is in contrast with the virulent types which 

 iinist either produce an acute infection or be destroyed. 



Theobald Smith taught long ago that lymph glands are filters. 

 1^'ailure to realize that liacteria thus filtered out may survive for 

 long periods of time within the lymph glands is probably tlie rea- 

 son so many different kinds of bacteria have been described as the 

 cause of Hodgkin's disease. The phenomenon of phagocytosis ob- 

 served in various diseases is regarded by Smith as an expression 

 of an affinity possessed by certain infectious agents and cell types 

 of the host for each other. This subject is discussed more fully 

 in Chapters IV, V, and XXVII. 



References 



Cinndel, M., and Linden, H. : Cited by Hadfield and Garrod, Pneumonia, 

 Recent Advances in Pathology, P. Blakiston's Son and Co., Phila- 

 delphia, 1938. 



Hadfield, G., and Garrod, L. P.: Pneumonia, Recent Advances in Pathology, 

 P. Blakiston's Son and Co., Philadelphia, 1938. 



Rivers, T. M. : Filterable Viruses, Newer Knowledge of Bacteriology and 

 Immunology, Jordan and Falk, 1928, Univ. of Chicago Press, p. 517. 



Rivers, T. M. : The Nature of Viruses, Physiol. Rev. 12: 423, 1932. 



-Rivers, T. M. : Further Observations on the Cultivation of Vaccine Virus in 

 Lifeless Media, .T. Exper. Med. 57: 741, 1933. 



Topley, W. W. C, and Wilson, G. S. : Principles of Bacteriology and Im- 

 munity, Ed. 2, Baltimore, William Wood and Co., 1936. 



Webster, L, T. : Microbic Virulence and Host Susceptibility in Mouse Typhoid 

 Infection, J. Exper. Med. 37: 231, 1923. 



Webster, L. T.: Microbic Virulence and Host Susceptibility in Paratyphoid- 

 Enteritidis Infection of White Mice. IV. The Effect of Selective Breed- 

 ing on Host Resistance, J. Ex-per. Med. 39: 879, 1924. 



Webster, L. T. : Microbic Virulence and Host Susceptibility in Paratyphoid- 

 Enteritidis Infection of White Mice. VIII. The Effect of Selective 

 Breeding on Host Resistance. Further Studies, J. Exper. Med. 42: 1, 

 1925. 



Webster, L. T. : Inherited and Acquired Factors in Resistance to Infection; 

 Development of Resistant and Susceptible Lines of Mice Through Selec- 

 tive Breeding, J. Exper. Med. 57: 793, 1933. 



— : Inherited and Acquired Factors in Resistance to Infection ; Comparison 

 of Mice Inlierently Resistant or Susceptible to Bacillus Enteritidis 

 Infection with Respect to Fertility, Weight, and Susceptibility to 

 Various Routes and Types of Infection, Ibid., p. 819. 



