THE CORNEA 309 



of subcutaneous injections of pneumococcal serum, an immunity 

 against the ulcus serpens ; he also attempted to show experimentally 

 whether a general immunity could occur from an ulcus serpens. Such 

 was not the case to any appreciable extent. 



Ulcus serpens, and, indeed, any severe corneal infiltration, is rare 

 in pneumococcal conjunctivitis. Cases have been described by Petit 

 and Hertel. Gasparrini reports that he has often seen slight (catarrhal) 

 marginal ulcers ; this has not been the experience of Axenfeld, Junius, 

 and Gifford. 



It is only in very exceptional cases that the object causing the 

 injury also carries in the infection ; affections of the lacrymal sac, 

 contaminations with sputum, 1 etc., are the most common infecting 

 agents. In many cases, perhaps, the cocci normally present on the 

 conjunctiva may have some action. A lesion of the epithelium is 

 necessary for the occurrence of the infection, as the Pneumococci 

 cannot, like the diphtheria bacilli, loosen the epithelium by the action 

 of their toxins (Coppez). So that we may see a cornea bathed for 

 years in lacrymal pus rich in Pneumococci without any damage, until 

 an epithelial lesion is produced by an injury, or in some other way 

 (e.g., by a herpes). 



That peculiar infection of old adherent corneal scars, which often 

 progresses rapidly into the interior of the eye, has been shown by the 

 researches of Wagenmann, confirmed by Terson, Dolganoff, and 

 Sokolow, 2 to be of ectogenous nature. The infection finds its way 

 into the scar through an epithelial defect. In sections of such cases 

 Wagenmann demonstrated Diplococci and chain cocci most frequently ; 

 by cultures I have most commonly found Streptococci and Pneumococci. 

 Terson records Pneumococci. 



In a few isolated cases of purulent keratitis, the Bacillus pyocyaneus 

 has been proved to be pathogenic for the human eye. The cases 

 recorded by Gallenga, Bietti, Macnab, De Berardinis, Szczbalski, 

 D. Smith, Callan, and A. Ewing, were obviously due to very virulent 

 bacteria ; in them an extensive necrosis of the cornea was very 



1 Hotta conducted experiments in Uhthoff's laboratory to determine the action of 

 sputum on superficial corneal injuries in rabbits. A hypopyon-keratitis only occurred 

 when a pocket had been made ; it never occurred in a perforating wound, and only once in 

 a superficial erosion. The infectiousness of the sputum varied, and the organisms present 

 in the corneal ulcers varied: in 36 per cent. Pneumococci, in 56 per cent. Streptococci, in 

 30 per cent. Staphylococci occurred. Mixed infection occurred with comparative frequency 

 in these experiments. Doetsch considers that infection from sputum is rare, especially 

 from the contamination of handkerchiefs, etc. , and in those cases where a corneal infection 

 occurs without any sac affection or conjunctivitis, he would consider the condition to be 

 due to the occasional occurrence of Pneumococci on the healthy conjunctiva. 



2 A.f. A., 1903, xlvii. 361. See the literature here. 



