32 BACTERIOLOGY OF THE EYE 



Regarding this point, I would refer to the facts relating to the 

 diphtheria group on page 190, and especially to the drawings Plate I., 

 Fig. 1 and Fig. 6, a and b, and figures in the text (xerose and 

 diphtheria bacilli) and would merely state that, as a matter of fact, a 

 morphological and cultural differentiation of the organisms named 

 cannot always be carried out. 



A slender form, a clustered grouping, and a frequent peculiar varicosity, especially 

 when a secretion smear is being examined, are no doubt points in favour of virulent 

 diphtheria. After long experience and much practice in the examination of diph- 

 theria, considerable certainty in diagnosis is attained, especially when cultures are 

 available, so that it can be understood how Max Neisser, Morax, and others, rely 

 considerably on this method. For a certain diagnosis, of course, it cannot be relied 

 upon. In the same way a certain culture diagnosis sometimes cannot be carried 

 out, although, as a rule, the Bacillus dipJitherice grows more freely on blood-serum 

 than does the Bacillus xerosis, forma acid in bouillon more strongly and rapidly, 1 

 and actually grows in the bouillon more diffusely and freely. But here again there 

 is no absolutely constant distinction. 



The method of polar staining given by Max Neisser cannot be considered as a 

 radical distinction, for, as Schanz has stated, it only shows a difference in the 

 rapidity with which the same phenomenon occurs. 



In various xerose bacilli obtained from sixty normal conjunctivas, Heinersdorff 

 never obtained a characteristic staining reaction in a culture of more than nine to 

 sixteen hours old, similarly Naito and Bietti. Gelpke, whose Bacillus septatus is 

 identical with the Bacillus xerosis, never obtained a positive staining. Individual 

 cases, however, are quoted in the literature where non-virulent bacilli have shown 

 polar-staining (Doetsch, Bach and Neumann, Tertsch, Schwoner). If the claim 

 be made that these were diphtheria bacilli which have become non- virulent, then 

 the question arises as to how we can distinguish such from xerose bacilli. A posi- 

 tive result ivith Neisser' s stain in the case of the xerose bacillus must be considered 

 as an extreme rarity, I consider it necessary that the identical method of Neisser or 

 Heinersdorff must be followed. It is not enough that a few granules should stain, 

 but that a general polar staining should take place in the slender bacteria. For the 

 future, too, it is very desirable, in exceptional cases, that the observations should be 

 exactly described, and not merely the statement ' positive staining ' given. Con- 

 sidering that, in the general bacteriological literature, cases of true diphtheria 

 have been quoted with typical virulence for animals, in which polar stain- 

 ing failed (Lehmann-Neumann), a radical distinction cannot be based upon this 

 point. 



Attempts to differentiate the two by means of diphtheria serum (Schwoner, 

 Tertsch) of high agglutinating valency show that the majority of xerose bacilli do 

 not react. The latest experiments of Tertsch, however, show that not a few (about 

 20 per cent.) of the non-virulent inhabitants of the normal conjunctiva were agglu- 

 tinated. If, with Tertsch, we deny the existence of true, but non-virulent, 

 diphtheria bacilli, then we must conclude that the agglutination test is not an 

 absolute differentiation. The practical application of this test in the case of 

 organisms of the diphtheria group presents quite exceptional difficulties. It would 

 be very interesting if attempts were made to exalt the virulence of these non- 

 virulent agglutinating organisms. 



1 Further research is necessary before the difference in the acid formation with different 

 kinds of sugar described by His, and later by Knapp, can be accepted as invariable. 



