CONJUNCTIVITIS 121 



the Gram-negative Diplococci, the chain-forming cocci (Ketten-bildner), 

 the Hsemophiles (Koch-Weeks and influenza) all present this difficulty, 

 and I feel that I must explain what facts are available and what 

 questions are still open regarding these particular points. 



When in healthy persons we find organisms otherwise con- 

 sidered as pathogenic, we must have either a defective patho- 

 genic power in the bacteria or a refractory condition of the 

 nidus, or a combination of both in varying proportions. 



To what degree these factors are of importance in the various forms 

 of conjunctivitis will be shown in the chapters dealing with them 

 in particular. I will, however, give here a general review of the 

 question. 



The presence of any bacterium in a healthy tissue does not render 

 doubtful its pathogenic significance under favourable circumstances, 

 provided that there is otherwise certain evidence of such pathogenicity. 

 Just as in a cholera epidemic every one who is attacked by the virus 

 does not necessarily become ill, so in the case of conjunctival infec- 

 tions. There are refractory individuals and those who only react 

 slightly. And as there are infectious diseases which are at one time 

 very infectious and at another less so, as there are abortive and 

 severe cases, and persons who are immune after a single attack, we 

 must not lay down any hard-and-fast rules when dealing with the 

 conjunctiva. 



Gonococci and Koch-Weeks bacilli evidently lose their power of 

 causing a conjunctivitis, very slowly indeed, and are very independent 

 of any disposition. The same is true for the Morax-Axenfeld 

 Diplobacillus, but not to the same high degree. 



These organisms, which previously were with exaggeration called 

 ' unconditionally infectious,' are, as a rule, so pathogenic for the con- 

 junctiva, that even when only a few individuals are found in the secre- 

 tion, the probability is very great that they are causal ; for, on account 

 of their great virulence and the marked susceptibility to them, a very 

 small number suffices. 



Occasionally, however, scattered individuals certainly not large 

 numbers of these organisms may be found on the conjunctiva without 

 producing any effect. That every infection with these organisms does 

 not produce the disease is obvious in the case of gonorrhoea, from its 

 not infrequent one-sided character. 1 It is well to note that the secre- 

 tion very often does not come into actual contact with the other con- 

 junctiva because of the flushing action of the tears; and, further, that 



1 Cf. section on ' Blennorrhcea. ' 



