HABITAT 703 



suggest such changes in definition as would necessitate the degradation of the 

 generic term Salmonella to specific rank, and the numbering as varieties of all 

 the present named species. Convenience and expediency must be our justification 

 for adopting the recommendations of the Salmonella sub-committee in face of the 

 obvious illogicality of using a different system of nomenclature for members of 

 the Streptococcus group. 



If, however, we decide to employ Salmonella as a generic term, we must take 

 care to define it as far as possible on the same general principles as have guided 

 us in defining other genera. The lines of demarcation in biology can rarely be 

 sharp. It is dangerous to rely, therefore, on any single character in the identifi- 

 cation of a bacterium. Here we find ourselves in conflict with Kauffmann (1941), 

 who lays down the following definition : " Salmonella bacteria are Gram-negative 

 bacteria which, on the ground of their antigenic structure, can be included in the 

 Kauffmann- White scheme." If we rely solely on antigenic constitution, as Kauff- 

 mann does, we shall be logically compelled to include in the Salmonella genus 

 every organism, no matter how different it may be in other characters, that con- 

 tains a single antigen hitherto recognized in the scheme of classification drawn 

 up by Kauffmann and White. Already numerous strains of coliform and para- 

 colon bacilli have been found to contain one or more of the H or antigens of 

 Salmonella (Habs and Arjona 1935, Gard 1937, Gard and Eriksson 1939, Schiff, 

 Bornstein, and Saphra 1941, Saphra and Silberberg 1942, Peluffo, Edwards, and 

 Bruner 1942, Leon 1942, Wheeler et. al. 1943, Edwards, Cherry and Bruner 1943) ; 

 and some of the Salmonella antigens have been recognized in strains of Flexner 

 dysentery bacili (Bornstein, Saphra, and Daniels 1941), and even in members, 

 of the Paste^irella group (Schiitze 1928, Pirosky 1938). To transfer these organisms, 

 which differ in fermentation and pathogenic characters, to the Salmonella genus, 

 merely because their constituent antigens happen to share some of the necessarily 

 limited groupings with those common among the salmonellae, is not only to lose 

 all sense of proportion, but to sanction a principle in bacterial nomenclature that 

 cannot but lead to progressively increasing confusion. 



We have felt it important to define the Salmonella genus in terms of fermenta- 

 tive activity, antigenic constitution, and pathogenicity, so as to exclude the 

 dysentery, the coliform, and the paracolon bacilli. Our definition is necessarily 

 tentative. Apart from their consistently negative reaction to Gram's stain, there 

 is practically no criterion to which all strains conform. As with so many other 

 groups of bacteria, the decision whether a given organism should or should not 

 be classified as a Salmonella must be determined by a careful consideration of all 

 its properties ; unless the majority of these are in agreement with those laid down 

 in the definition, it would be better for the present to treat it as a member of the 

 wide Bacterium group. (For reviews of the Salmonella group see Tesdal 1938, 

 Kauffmann 1941, Bornstein 1943.) 



Habitat. — There is no reason to doubt that members of the Salmonella group 

 are primarily intestinal parasites. It is true that they may be found in the blood, 

 the lymphatic nodes, the ovary, the eggs of fowls, and other situations such as 

 water and sewage (see Ferramola, Monteverde, and Leiguarda 1943) ; but their 

 commonest location appears undoubtedly to be the intestine of man, mammals, 

 and birds. The chief reservoirs of infection are fowls and pigs. From fowls 

 over 40 different species have now been isolated in the United States and Panama 

 alone, and from pigs nearly 30 (Edwards and Bruner 1943). Rodents, ruminants. 



