INOCULATION OF LISTERELLA INTO ANIMALS 399 



renals is common. Occasionally abscesses in the myocardium and inflammation of the 

 meninges may be met with (sec Burn 1935). After intraperitoneal inoculation, much 

 the same lesions are found, l>ut in addition there is a sero-til)rinous peritonitis, with abscesses 

 containing thick white pus in the roUed-up omentum. The organisms can rarely be 

 recovered from the blood stream. Instillation of a pure culture into the conjunctiva, 

 or swabbing of the everted lid, gives rise to a severe conjunctivitis within 24 hours followed 

 by keratitis ; the animal itself rarely dies. 



Guinea-pigs. — These animals die after inoculation with large doses. The lesions at 

 necropsy are similar to those in mice. The organisms may be recovered from the spleen 

 and sometimes from the heart blood. 



Chick embryos. — Paterson (19406) has shown that ListereUa gives rise to focal lesions 

 on the chorio-allantoic membrane of chick embryos. 



Classification. — In the Erysipelothrix group three species were differentiated 

 by Eosenbach (1909) — muriseptica, porci, and erysipeloides. Rickmann (1909), 

 however, pointed out that the morphological and cultural distinctions on which 

 Rosenbach relied for differentiation were insufficient to serve as a means of classifi- 

 cation ; and since he found that all three organisms agglutinated to the same 

 titre with immune sera, and exhibited the same pathogenicity to animals, he 

 concluded that they should be regarded as belonging to a single species. To 

 this the name Erysipelothrix rhusiopathice is now commonly applied. 



For the organism isolated by Murray, Webb, and Swann (1926) and called 

 non-committally by them Bacterium monocytogenes, Pirie (1927) suggested the 

 generic name ListereUa in honour of Lord Lister. Apart from the inappositeness 

 of this name — Lord Lister having neither discovered nor worked with this organism 

 — it was too premature, since at that time no thorough comparison had been 

 made between Bact. monocytogenes and Erysipelothrix, which it resembles in many 

 respects (Topley and Wilson 1936). 



Barber (1939) and Julianelle (1941) have now carried out a comparative study 

 of these two organisms, and their observations seem to show that the relationship 

 between them is even closer than was at first suspected. Thus, both organisms 

 are small, Gram-positive rods, showing an extraordinary similarity in the morpho- 

 logical and cultural appearances of their smooth and rough forms. Both have 

 much the same growth requirements and much the same degree of resistance. 

 Both have a wide range of pathogenicity for animals, and both occasionally give 

 rise to disease in man. In rabbits, experimental inoculation of either organism 

 results in the development of a generalized infection accompanied by the appear- 

 ance of conjunctivitis and, if the disease is not acutely fatal, of a considerable mono- 

 cytosis ; at post mortem focal necroses are found in the liver. Against these 

 similarities, it may be said that ListereUa is fatter and is motile, attacks rather 

 more sugars, is antigenically distinct, and is fatal experimentally to guinea-pigs 

 but not to pigeons, in contrast to Erysipelothrix which is fatal to pigeons but 

 not to guinea-pigs. 



No one who is familiar with systematic bacteriology and who has observed 

 several strains of each of these organisms side by side can deny that the differences 

 between them are less than those existing between different species of many other 

 organisms classified in the same genus, as, for example, between members of the 

 Corynebacterium, Pasteurella, Bacillus, or Clostridium groups. The differences 

 between Erysipelothrix and ListereUa are those characteristic of specific, not of 

 generic, differences ; and it seems to us to be doing violence to the principles 



