44 BACTERIOLOGY OF THE EYE 



symbiotic. The same is true for the allied influenza bacillus, which, 

 according to M. Neisser and Eymovicz (' Postemp. okul.,' 1901), can be 

 propagated in symbiosis with xerosis, but alone dies out even on 

 haemoglobin media. L. Miiller has also recorded the benign influence 

 of what he calls ' air germs ' i.e., the Staphylococei on his bacillus 

 (B. Miiller), i.e., the Bacillus influenza. The conjunctival Staphylococei 

 also have the same action. Usher and Fraser have corroborated this 

 by numerous experiments (R.L.O.H. Reps., 1906, xvi., p. 434). Bacillus 

 xerosis, Staphylococei and Diplococci, favour the growth of Koch- 

 Weeks bacilli, which flourish in their vicinity, when cultures are made 

 from these united organisms. The Koch-Weeks organism can subse- 

 quently be cultivated alone, though at first it would not grow without 

 their presence. 



Rymowicz has reported a similar fostering action of xerosis on the 

 Diplobacillus. In conjunction with Macnab I have, after many trials, 

 failed to convince myself that such is the case. Both organisms 

 grow well together on blood-serum, but the Diplobacillus does so alone. 

 We failed to induce strains of these Diplobacilli, which would not grow 

 by themselves on simple agar, to do so in symbiosis. Similar 

 attempts with Gonococci have so far failed. 



The fact that Koch -Weeks bacilli are pathogenic exclusively in the 

 eye only finds a partial explanation in its symbiosis and furtherance 

 by the xerosis, for pseudo-diphtheria bacilli occur also in the nose, in 

 the throat, and elsewhere ; but the Koch-Weeks is not pathogenic in 

 these sites; although carried by the tears, it comes freely in contact with 

 their mucous membranes. A complete explanation of this exclusive action 

 on the eye is for the present not available, as in the similar phenomenon 

 in the case of trachoma. Some affinity, or some peculiar type of 

 ' receptor,' must be present to determine the infection in this locality. 



The support which the Koch- Weeks and influenza bacilli receive 

 from the presence of these organisms is repaid by the improved 

 nutritive conditions for the saprophytes due to the inflammatory 

 reaction produced by the presence of the pathogenic organisms. 

 Xerose bacilli from an inflamed conjunctiva grow more easily, more 

 profusely, and are not so dried up. In the case of Staphylococei this, 

 however, is less marked. In some cases certainly the catarrhal 

 secretion seems sufficient to cause the saprophytes to disappear, and 

 that to a varying degree in various infections. Thus, for example, at 

 the height of a pneumococcal conjunctivitis the Pneumococci may be 

 found in pure culture, but as it decreases the saprophytes again 

 become evident. 



