302 BACTEKIOLOGY OF THE EYE 



with zinc, even when there is no marked conjunctivitis present. They 

 are very difficult to treat in any other manner. 



In a simple keratitis much valuable information can also be ob- 

 tained. We will not go so far as to say that every corneal infiltration 

 must be examined bacteriologically ; that, indeed, would be hardly 

 possible. But in very chronic cases and those which precede sup- 

 puration, or show a very markedly infiltrated border, a bacteriological 

 examination can be thoroughly recommended. When such an 

 infiltrate is centrally placed, we should not be so free in taking 

 material from it as from peripherally situated lesions. The 

 pupillary area of the cornea should not be injured. If all precau- 

 tionary measures are taken, we should not have any great anxiety. 



Scrofulous keratitis should be mentioned amongst the cases which 

 are negative bacteriologically. This affection is considered by many 

 to be a staphylococcal infection (Bach, Straub, Zur Xedden). Further 

 research is necessary to settle this question. Keratitis fasciculosa, 

 with its creeping character, proves to be a progressive infection of 

 peculiar type (due to the tendency of scrofular patients to the forma- 

 tion of vessels) ; in such cases I have often found the Pneumococcus. 

 Addario occasionally found the Stapliylococcus, and Macnab the Dipl>- 

 lacillus. Xerose bacilli have been found in simple infiltrates and in 

 sluggish ulcers, but these were secondary, and with no etiological 

 significance. Even in a case like that of Besio (Annali di Ottal, 

 1900, xxix. 626) the significance of these bacilli is doubtful. 



Purulent Keratitis. Hypopyon-Keratitis. Ulcus Corneae 



Serpens. 



Purulent keratitis, on account of its clinical importance, very early 

 attracted the attention of the bacteriologist. At first experiments 

 were chiefly directed to the determination of the action of the best- 

 known pyogenic organism, .the Sta2)hylococcus, in the production of 

 inoculation keratitis in rabbits (Leber, Strohmeyer, Hoffmann, Hess, 

 Fortunati, Silvestri, etc.). These experimental investigations, of 

 which those by Leber were the most conclusive, have furnished much 

 information regarding the development of an infiltrate, and especially 

 of a hypopyon. 1 This information can be applied in general to 

 hypopyon-keratitis in man, although it has been established that the 



1 According to Leber, the hypopyon is caused by the toxic chemiotaxis of the organisms 

 in the cornea ; it is therefore sterile until the cornea is completely perforated, even though 

 an early perforation of Descemet's membrane has occurred. 



