202 



Zupnik," 1897, states that Joseph, of the Agricultural Institute of 

 Breslau, in 1882 originated the use of favus fungus for the destruc- 

 tion of mice. Zupnik tested B. typhi murium and Danysz virus upon 

 mice. No experiments with rats. 



Issatschenko,'' in 1898, described briefly a bacillus obtained by him 

 from gray rats. Recent investigation showed this baciUus to be very 

 virulent for rats and mice, but harmless for the different species of 

 domestic animals. Four hundred and forty-three experiments were 

 made upon rats with pure cultures of the bacillus combined with 

 dough and fed to the rats. He gives a table showing that the mor- 

 tality occurred in 431 rats at an average of ten and one-half days. 

 The greatest mortality occurred during the first fifteen days (84.2 per 

 cent), with the greatest number on the seventh day (20.1 per cent). 



Danysz," 1900, isolated a cocco-bacillus during an outbreak of 

 spontaneous disease amongst field mice which presented the general 

 characteristics of the colon bacillus and to this extent resembled 

 Loeffler's bacillus {B. typhi murium), and which from the begiiming 

 exhibited some pathogenicity for gray rats {M. decumanus). Of ten 

 such rats fed upon a culture of this orgaiiism, two or three died, while 

 others that had fallen sick recovered and the same remained well. 

 This small mortality offered some hope that it would be possible to 

 increase the virulence of the bacillus by ordinary methods; that is, 

 passing it from rat to rat. It was found, however, that the opposite 

 was true; the virulence was always weakened by this process regard- 

 less of the method of administration. Thus in every series the first 

 culture killed the animals in seven to twelve days; occasionally after 

 one or two passages five to seven days; but subsequent passages 

 decreased the virulence so that none died. 



The general result is that it is difficult to maintain the virulence of 

 the cocco-bacillus of the rat or to increase it when it is found to be 

 small. It can only be effected by constantly making a large number 

 of experiments and frequently testing the virulence of the culture. 

 Danysz succeeded in keeping up a supply of cultures of sufficient 

 strength for eight years. In 60 per cent of the operations where this 

 culture has been used it has been successful in causing the absolute 

 disappearance of the rats. In 15 per cent the result was entirely 

 negative, and in the remaining 25 per cent there was a large dimi- 

 nution. 



o Zupnik, Leo: Ueber die pratische Verwendbarkeit der Mause bacillen inbeson- 

 dere dee Loeffler'schen Bacillus typhi murium. Centblt. f . Bakt., Orig., vol. 21, 1897, 

 p. 446. 



6 Issatschenko, B.: Untersuchungen mit dem fiir Ratten pathogenen Bacillus. 

 Centblt. f. Bakt., Orig., vol. 31, 1902, p. 26. 



" Danysz, J.: TJn microbe pathogfene pour lea rats {Mus decumanus et Mus rattus) 

 et Bon application ^ la destruction de ces animaux. Ann. Inst. Pasteur, 1900, vol. 14, 

 p. 193. 



