20 HILDA HEMPJU HELLER 



killed in most anaerobic isolation procedures. Because of 

 their close resemblance to Welchillus and because of the ubiq- 

 uity of organisms of that genus their detection is rendered 

 still more difficult. 



It may be that later workers will prefer to include this organ- 

 ism in the genus Welchillus. The action on milk is dependent 

 on the fermentation of lactose, and sugar fermentations are 

 not to be regarded as of generic significance. I place it in a 

 genus by itself because spore formation has not been demonstrated 

 for this organism. 



Gentjs 12. Rivoltillus nov. gen. 



Clostridtoideae possessing moderately strong saccharoljrtic 

 powers. Liquef}'- gelatin but do not produce US demonstrable 

 by a lead-acetate-paper test in blood broth. Produce in meat 

 medium gas and a pink coloration which does not rapidly fade. 

 Clot milk. Do not liquefy serum or egg or disintegrate meat 

 particles. Gram-positive rods, usually short, with median, 

 sub-terminal, or terminal spores, which usually bulge the sides 

 of the bacillus. Sporangia not often much larger than vegeta- 

 tive rods. In tissue the sporangia may be une\'en in their stain- 

 ing reactions, "granulose" being present; orgonts are long, 

 frequently with parallel sides. Usually form chains on the 

 liver of animals. Colonies in deep agar, though they may start 

 as lenticular structures, consist later of a dense center and a 

 wide loose woolly periphery. They vary in size, etc., according 

 to species. Typically highly pathogenic tissue invaders that 

 produce haemolysis and gas in the animal body. Pathogenic 

 for a wide range of species. 



Type species R. vibrion (the vibrion septique of Pasteur), 

 as defined in a future paper. Robertson (1920) has divided 

 the group into four sub-groups on the basis of the agglutination 

 reaction. 



Probably the group of anaerobes whose nature is most fre- 

 quently discussed. The morphological resemblance of individ- 

 uals and of colonies to organisms of the sporogenes type led to 

 the frequent description of mixed cultures of the two tjrpes, 



