192 BACTERIOLOGY OF THE EYE 



more often with club-shaped ends. This thickening at the ends in the form of 

 a club is very characteristic, and is especially well seen in cultures. The rods are 

 often curved, especially the longer ones. The bacilli are generally arranged parallel 

 to each other, clustered in a radial manner so as to form irregular rosettes, or else 

 crossed. Their form and size varies, and a differentiation of the organisms according 

 to their length (' bacilles longs,' ' bacilles courts '), and thus an estimation of their 

 virulence cannot always be carried out. 



The same strain can vary in form, according to the medium and the length of time 

 it has been cultivated. In culture long threads may form, often with club-shaped 

 ends ; these may stain segmentally, and so resemble chains of cocci. Many strains, 

 especially when grown on egg media, show definite branching (Fninkel). These 

 branching bacilli may resemble Actinomyces. (It was the occurrence of this branch- 

 ing which suggested the name of ' corynebacterium.' Lehmann and Neumann 

 bring the glanders bacillus and the bacilli of the diphtheria group together under 

 this name). Del Monte considered that the bacilli of this group belonged to the 

 group of the Streptothrix. 



In a preparation from the secretion of a diphtheritic conjunctivitis variations in 

 the form of the bacilli are of some diagnostic value. Cases do occur in which the 

 slender forms, with swollen ends arranged parallel or in V-form, so predominate 

 that the experienced observer, when polar staining occurs, can give a probable diag- 

 nosis of ' true diphtheria ' from the smear alone, as the non-virulent Bacillus xerosis 

 does not occur in this form. In this connexion it may be of interest to compare 

 Fig. IV. on Plate I., which is drawn from a true diphtheria of the conjunctiva (proved 

 by inoculation), with the five drawings of the Bacillus xerosis in secretion, which 

 are to be found on Plate I., Fig. I. ; Plate II., Figs, III. and V. b ; also pp. 7 and 14. 



In other cases, as shown by the figures in the text, the form may so vary in one 

 and the same preparation that from a mere examination of a slide it is impossible to 

 make even a probable diagnosis between Bac. diphtheria and Bac. xerosis. In the 

 former, according to my opinion, the slender forms are never entirely absent, though 

 the larger irregular ones may preponderate. Fig. VI. a on Plate I. is drawn from 

 a case of true diphtheria of the conjunctiva, though it could equally well represent 

 a secretion with the xerose bacilli. Inoculation alone can decide the question. 

 Morax definitely claims that it is possible to diagnose the Bacillus diphtheria from 

 the smear preparation. It is certainly true that the expert is often right in the cases 

 mentioned, but in other cases the actual form of the bacilli is not diagnostic, and 

 is never an absolutely certain criterion. 



Cultures. The diphtheria bacilli grow best aerobically. Growth occurs between 

 the temperatures of 20 C. and 40 C. ; best from 33 C. to 37 C. 



Loffler's blood-serum and ascites agar are the best media. 



On gelatine growth is scanty and not characteristic. 



White or yellow glistening colonies grow on glycerine agar; they vary in size, 

 are transparent, circular with ragged edges, and coarsely granular ; they are 

 brownish and darker in their centres. Old colonies become crumbly, opaque, and 

 show darker patches in their interior. Other colonies from the first appear denser 

 and more finely granulated, especially when they are grown on ascites agar. In 

 exceptional instances they may develop other colours. 



On Loffler's blood-serum development is more vigorous than on agar. 



In bouillon a fine dusty deposit occurs at the bottom and sides of the tube, or else 

 a fine flocculent mass at the bottom. On the surface a fine skin of variable thick- 

 ness forms. The bouillon becomes acid and after a few days again alkaline. 



In milk growth is free, usually without coagulation, and with an amphoteric 

 reaction. 



On alkaline potatoes a thin shining film develops ; it is rarely thick. 



