H. DUCREYI 807 



smooth and relatively rough strains ; a high proportion of the former, including 

 both Pittman's smooth strains and the more " typical " strains isolated from the 

 normal nasopharynx, produce indole, but only a small proportion of the latter. All 

 strains reduce nitrates. 



H. influenzce, as that species is here defined, does not as a rule produce haemolysis, 

 which has been recorded only in a very few strains. 



Antigenic Structure. — The majority of smooth strains, as defined by Pittman (1931), fall 

 into 6 well-differentiated antigenic types which appear to be characterized by 

 specific polysaccharide surface antigens, sometimes occurring in a capsular form. 

 The more common rough, or partially rough, strains are antigenically heterogeneous. 



Pathogenicity. — Pathogenic for man, particularly in association with virus infections, or with 

 other bacterial diseases. Produces toxic death when injected in large doses into 

 laboratory animals, and infective death when injected in smaU doses together with 

 mucin. 



The Koch-Weeks Bacillus 

 There is no known way in which this organism can be distinguished from H. 

 influenzce. The fact that strains so labelled have been isolated from the conjunctiva 

 does not seem to warrant the allotment of a separate specific name. 



H. influenzse-suis 



Isolated from cases of swine influenza in which it is associated with a filtrable 

 virus. The characters of this species as recorded by Lewis and Shope (1931) differ 

 from the human strains oi H. influenzce only in that no carbohydrates are fermented, 

 and no indole is produced. The number of strains as yet examined does not, 

 however, justif}^ any definite generalized statement on this point. (See also 

 Kirchenbauer 1934.) 



H. para-influenzae 



Strains of this organism differ from //. influenzce in requiring the V factor but 

 not the X factor for their growth, and in fermenting maltose, saccharose and 

 often dextrin. In this last respect they resemble the rougher strains of H. influenzce, 

 except that their action on maltose is far more consistent. Their individual and 

 colonial morphology often resembles that of " atypical " H. infltienzce strains. 

 Some are hsemolytic, others are not, and a few strains produce indole. In man 

 hsemolytic strains tend to be associated with acute pharyngitis and both the hsemo- 

 lytic and non-haemolytic strains with ulcerative endocarditis (Russell and Fildes 

 1928, Fox 1935, Stuart-Harris et al. 1935, Miles and Gray 1938). The organism 

 survives only 2-4 days on soUd culture media. 



H. canis 



Isolated by Friedberger (1903) from the prepuce of dogs. It is apparently 

 parasitic, but not pathogenic. It differs from H. influenzce in the following ways : 

 It requires the X factor, but not the V factor, for its growth. On solid media it 

 forms colonies that are at first indistinguishable from those of H. influeyizce, but 

 later become larger and more opaque. As regards its fermentation reactions it 

 ferments dextrose, saccharose and mannitol, produces indole and reduces nitrates. 

 In its fermentation of mannitol it differs from both typical and atypical strains of 

 E. influenzce. 



H. ducreyi 



Morphologically in the piu'ulent discharge from the ulcerated surface of the 

 lesion the organisms appear as small ovoid rods, arranged in pairs, in groups, or 

 in chains lying parallel to one another. Several forms may, however, be assumed. 

 Thus, it may appear as a short rod with parallel sides and rounded ends, staining 

 evenly ; or it may be ovoid or navicular in shape with marked bipolar staining ; 



