122 BACTERIOLOGY OF THE EYE 



it is to some extent due to variation in susceptibility and immunity 1 

 that the contagion does not always result. 



In the case of the Koch-Weeks bacillus and the DiplobacUlus, though 

 there is less secretion, still the catarrh almost always affects the other 

 side. There may, perhaps, be a difference in the disposition of the 

 two eyes in the same individual. 



Groenouw and Meyerhof state that after a gonorrhoea has subsided the conjunctiva 

 is immune to the Gonococcus for some time. (This requires further confirmation, 

 the other Gram-negative Diplococci being also considered.) 



Plaut and Zelewski have found the Diplobacillus a few times on the healthy 

 conjunctiva after the sac has been excised. Erdmann and Rymowicz found it, too, 

 in normal people. 



Only in very rare cases has the Koch-Weeks bacillus been found in normal cases 

 (Plaut and v. Zelewski). Meyerhof reports that it can remain dormant in tracho- 

 matous cases without causing a catarrh. This and the fact that cases of very mild, 

 hardly recognizable Koch-Weeks conjunctivitis do occur, and may produce a virulent 

 infection in others, make it not unlikely that this organism may occasionally be 

 benign. The actual pathogenic nature of this bacillus is, however, definitely 

 established by many positive inoculations, and is naturally not controverted by 

 these facts. 



In the case of the Gonococcus, Koch-Weeks bacillus, and 

 bacillus, we must assume that they have been introduced by infection 

 from without shortly before the affection shows itself, and that only 

 exceptionally an organism, though present, may be latent, and then, 

 becoming virulent, cause the disease. In dealing with the other 

 facultative producers of conjunctivitis, however, this last possibility 

 occurs to a far greater extent. In the case of Pneumococci there is 

 certainly the possibility of contagion ; we have the evidence of definite 

 inoculations, and the occurrence of epidemics to prove this. But, as 

 the author first showed, along with this we must also bear in mind 

 that, as the result of increased susceptibility or raised virulence, a 

 form of self-infection may occur, due to saprophytic Pneumococci 

 previously present, and these are common on the normal conjunc- 

 tiva. This is probably the explanation of sporadic cases. 



The same may occur with influenza bacilli and Streptococci. It is 

 still disputed whether a self-infection can occur in the case of the diph- 

 theria bacillus, in the sense that the Bacillus xerosis, that constant 

 saprophyte, can change into virulent Loffler's bacilli. When Staphylo- 

 cocci are the cause of a conjunctivitis, it is not the method of infection 

 from without, but that of self-infection, which is of importance. 



1 Panas and Randolph insist that one-sided gonorrhoea in adults is more often right-sided, 

 and is due to the eye being rubbed with the right hand. The disposition here consists 

 in the mechanical injury. Von Michel and Bach emphasize the importance of this rubbing 

 of the eyes. 



