K. F. MEYER 625 



probability concerned: exposure and temperature fluctuations (Freund); seasonal 

 influences ([Webster]; clinical snuflles in summer 20 per cent, in September and 

 October 60 per cent, followed by a decline to 35 per cent and a second rise in April to 

 50 per cent); diet; racial, hereditary (Chinchilla Giants showed greater snuffles inci- 

 dence and mortality per cent than Blue Beverns),' and innate non-specific individu- 

 al differences. Variations in the virulence of different strains of Bad. lepisepticum are 

 well known, but it is interesting to note that, according to Webster, highly virulent 

 D strains (De Kruif classification)^ are incapable of vegetating indefinitely in the 

 nasal passages of the rabbits surviving an epidemic, while less virulent, mucoid, and 

 G variants are capable of persisting indefinitely in the nasal passages. The highly 

 virulent strains produce either rapidly fatal infections in susceptible rabbits, or a 

 "healthy" carrier condition with definite inflammatory processes of the nasal mucosa 

 develops in the relatively resistant animals, or they are replaced by variants (type G) 

 of very low pathogenicity and finally disappear from the respiratory tract. On ac- 

 count of the very low carrier incidence the highly virulent strains are only encountered 

 during very destructive epidemics (Glaue)^ or in isolated cases. Under the prevailing 

 conditions and those usually met in a rabbit population the moderately virulent 

 type D (Tanaka) or mucoid variants of moderate and uniform virulence constitute 

 the carrier strains (Webster, Smith). ■* 



The question naturally arises, How do cases of snuffles and pneumonia develop? 

 Webster presents convincing evidence that the individual rabbits exhibit a different 

 response to the presence of Bad. lepisepticum in a stockroom. Usually three groups 

 of animals can be distinguished: (i) non-infected, resistant animals; (2) chronic 

 "healthy" carriers; (3) cases with local infections, such as snuffles, parasinusitis 

 (McCartney and Olitsky,^ Tanaka''), otitis media (Smith and Webster), ^ meningitis 

 (Meyer), ^ subcutaneous abscesses (Schimmelbusch and Miihsam,' Laven,'" Davis," 

 Tanaka,'^ Smith'^), pleuropneumonia, and septicemia cases (Davis, Webster, Baudet, 

 and others). Although the percentages of these groups may remain constant in a 

 rabbit population, it is again recalled that various accessory factors (seasonal changes, 

 injection of harmful substances) may lead to an increase in the percentage of snuffles 

 and pneumonia cases and a corresponding decrease in carriers and resistant animals. 

 Sporadic cases of rabbit septicemia are probably the sequelae of such a course of 

 events. When, on the other hand, a high incidence of snuffles and a corresponding 



■Webster, L. T. : ibid., 45, 529. 1927. 



^ de Kruif, P. H.: ibid., 33, 773. 1921. 



^Glaue: Centralbl. f. Bakieriol., 60, 176. 1910. 



■•Smith, D. T. : Jour. Exper. Med., 45, 553. 1927. 



5 McCartney, J. E., and Olitsky, P. K.: loc. cit. 



* Tanaka, A.: loc. cit. 



'Smith, D. T., and Webster, L. T.: J. Exper. Med., 41, 275. 1925. 



* Meyer, K. F.: unpublished observations. 



'Schimmelbusch, C, and Miihsam: Arch.f. klin. Chir., 52, 564. 1896. 



'"Laven, L.: Centralbl. f. Bakteriol., Orig. I, 54, 97. 1910. 



" Davis, J. D.: J . Infect. Dis., 12, 42. 1913. 



" Tanaka, A.: loc. cit. 'J Smith, D. T.: loc. cit. 



