l8o MANUAL OF BACTERIOLOGY. 



bullet-proof." Nevertheless, as was clearly shown in the 

 cholera epidemic in Hamburg, Germany, in 1892, many per- 

 s )ns were found who harbored the comma bacillus in their in- 

 testines without exhibiting any symptoms of the disease. 

 Many healthy persons have been found to harbor the diph- 

 theria bacillus in their throats. Pneumococci are present in the 

 mouths of many healthy individuals. From these and other 

 examples which might be cited, it is apparent that individual 

 resistance and individual predisfusition, due to. causes as yet 

 obscure, are important factors in infectious diseases. 



It is probable that the importance of an hereditary 

 tendency to certain infections, notably tuberculosis, has been 

 overrated. 



Predisposition of Different Organs and Tissues. — Cer- 

 tain tissues of the body are liable to attack from one kind of or- 

 ganism, while another tissue maybe more susceptible to invasion 

 by a different species of bacterium. The mucous membrane 

 of the urethra is specially open to attack from the gonococcus; 

 that of the intestines from the dysentery bacillus, the cholera 

 spirillum and the typhoid bacillus; the lungs are more liable to 

 attack from the tubercle bacillus than other organs; the eye 

 may be attacked by a large number of different organisms* 

 beside being subject to attack of a special, possibly of two or 

 more special bacteria. Conjunctivitis has been found to 

 be caused by the pneumococcus, the diphtheria bacillus, 

 streptococcus, staphylococcus, gonococcus, B. coli communis, 

 meningococcus intercellularis, several of the group of organ- 

 isms to which the Friedlander's pneumococcus belongs, B. 

 influenzae. In addition to these organisms, a special bacterium, 

 the Koch-Weeks bacillus, has been found to cause epidemic 

 conjunctivitis in all lands. This is a fine bacillus much resem- 

 bling that of mouse septicemia. 



Race.— The influence of racial predisposition is undeniable. 



*Axenfeld in KoUe and Wassermann. Bd. III., 1903. pp. 489-575. 



