580 T. M. RIVERS 



Morphology, staining, motility. It is a small pleomorphic, 

 Gram-negative, non-motile rod which looks very much like 

 H. influenzae. 



Type of growth. On 2 per cent rabbit-blood meat-infusion 

 agar young colonies are non-hem oly tic, round, mth a small 

 granular area on top. At this time they are indistinguishable 

 from colonies of H. influenzae but as they grow older the former 

 become distinctly more opaque than the latter. Old cultures 

 on blood agar slants show a luxuriant opaque growth that 

 resembles H. pertussis more than H. influenzae. A diffuse 

 growth occurs in the proper Uquid medium. 



Grou'th requirements. H. canis grows well on 5 per cent human 

 blood agar. This is a distinct difference between H. canis and 

 H. influenzae as the latter does not grow well on media contain- 

 ing fresh unheated human blood (Rivers, 1919). H. influenzae 

 (Rivers and Poole, 1921) requires two food accessory factors, 

 one autoclave labile, the other autoclave stable. H. canis, how- 

 ever, requires the addition of only the autoclave stable sub- 

 stance as an accessory factor. It will not hve more than one or 

 two generations on meat infusion agar, meat infusion agar plus 

 ascitic fluid or 2 per cent peptone agar plus yeast extract. Suc- 

 cessful transplants can be made indefinitely on meat infusion 

 agar plus hematin or 2 per cent peptone agar plus hematin. 

 It is aerobic. 



Indole production. All the strains produced indole. 



Nitrate reduction. All the strains reduced nitrates to nitrites. 



Reaction in milk. Very Uttle change was noticed in blood 

 milk mixtures when inoculated with H. canis. 



Sugar fermentations. The medium used for fermentation 

 tests was the same as described in a previous paper. (Rivers 

 and Kohn, 1921). All the strains formed acid without gas from 

 glucose, fructose, galactose, mannitol, sucrose, and xj'lose. 

 Neither acid nor gas was formed from maltose, lactose, dextrin, 

 arabinose and glycerol. 



Hemolysis. Red blood cells were not hemolyzed in solid 

 or in liquid media by any of the strains. 



