310 BACTERIOLOGY OF THE EYE 



evident, and the base of the ulcer was covered with the necrotic 

 debris of the corneal lamellae. The process can take on the form of a 

 ring abscess (vide infra). The toxins from the cornea so act on the 

 tissues around that the conjunctiva bulbi may swell and give the 

 impression of a panophthalmitis before the deeper parts of the vitreous 

 are suppurating. This is due to the free formation of toxins. Slight 

 cases may also occur ; according to Herbert (Bombay), a Pyocyaneiis 

 obtained from a slight case of keratitis, when inoculated on to the 

 conjunctiva, produced small abscesses and a superficial keratitis 

 without any deep destruction. These experiments, with those of 

 A. Ewing, show that many strains of Pyocyancus can have a patho- 

 genic action on the unwounded conjunctiva, and from there can 

 attack the cornea, first through a digestive action, then by infection ; 

 a Pyocyaneiis conjunctivitis has been described by G. S. Derby. In 

 the cases of severe keratitis quoted above an injury could not be 

 proved to have occurred in every instance. 



According to Ewing, a single inoculation with this organism pro- 

 duces an immunity against renewed infection in the cornea lasting for 

 six to eight weeks. 



The Bacillus Pyocyaneus (bacillus of green or blue pus) (Plate III., Fig. IV.). 

 A small slender rod, approximately of the same length and thickness as the Koch- 

 Weeks bacillus, 1 either single or in pairs, and in culture forming long filaments; 

 Gram -negative. Freely motile, with a terminal cilium. Grows as a facultative 

 aerobe on the ordinary media even at room temperature. Rapidly liquefies 

 gelatine, causing green fluorescence in the neighbourhood of the growth. Bouillon 

 becomes cloudy and stains a yellowish-green. On agar a whitish-grey scum forms, 

 the medium becoming green to a variable extent and shade ; glycerine agar becomes 

 dark blue. On potatoes the growth takes the form of a thick scum, yellowish-green 

 to brown in colour. Blood-serum is rapidly liquefied. 



The pigments formed are : (1) pyocyanin blue, soluble in chloroform, and thus 

 easily extracted from the medium ; (2) a pigment insoluble in chloroform, and of 

 a greenish fluorescence. The formation of these pigments is influenced by the 

 nature of the medium. 



The differentiation of the two varieties (B. pyocyanem, a. and ) is now generally 

 given up, as a definite separation is often impossible. 



Many strains of the Pyocyaneus freely form toxins, which pass out into the media. 

 Eabbits and guinea-pigs are very susceptible. Wassermann states that both an 

 antitoxic and a bactericidal immunity can be produced. The latter is so intense 

 that the Pfeiffer reaction (as in the case of the cholera vibrio) can be obtained in 

 the abdominal cavity of the immunized animal in a very short time. 



Virulent strains have a powerful necrotic and suppurative action (Sattler) in the 

 eye, especially in the vitreous, but also in the anterior chamber or the cornea so 



1 Seeing that the Koch- Weeks bacillus can only infect the cornea in the course of a 

 typical conjunctivitis, and even then almost never causes a purulent keratitis, such a 

 finding in the cornea as is shown in Plate III., Fig. IV.. with a hypopyon-keratitis at 

 once raises the suspicion of Pyocyaneus. It can easily be differentiated from the other 

 organisms which produce this condition (cf. the plate). 



