308 THE ZOOLOGIST. 



tried on suitable ground with satisfactory result. All the holes were 

 stopped up, and poisonous coal and sulphur-smoke (bisulphide of carbon) 

 was allowed to pour into the burrows which the voles reopened ; but this 

 efficacious mode of destroying them could not be employed, everywhere, and 

 was very expensive. People knew not what to do, because they had 

 neglected to destroy the mice at the proper time." 



Thus far Brehm. I believe it would be possible to destroy 

 the Voles effectually by means of the bacillus which I have 

 discovered, even if they did not devour their dead and dying 

 comrades, as they do in captivity. It would be easy to produce 

 any quantity of cultivated fluid, to drop it on bread or corn, and 

 to scatter this infected food over the fields infested. 



But, before attempting this experiment on a large scale, it 

 would be necessary to make extensive trials to discover whether 

 other animals besides Voles could be infected with the bacilli 

 per os f or not. I have made a series of experiments in this 

 direction, and have obtained the following results. The natural 

 destroyers of the voles, namely, cats, are proof against the bacillus. 

 I have fed five cats with many dead or dying house- and field- 

 mice, and not one of them contracted the disease. I have also 

 fed a large number of rats on the bacillus without their becoming 

 affected. 



Among the field-mice which were brought me I found several 

 specimens of the "Brandmaus" (Mus agrarius), which is dis- 

 tinguished by a black stripe along the middle line of the back, 

 over a reddish yellow fur; this species, too, did not become 

 diseased. Nor did small singing birds of different kinds, whose 

 food was damped with the solution, sicken. No result followed 

 in the case of fowls, pigeons, guinea-pigs, and rabbits, though they 

 were fed with infected food for a long time. 



In the case of two four-weeks' old pigs, which were fed with 

 large quantities of cultivated bacilli, one remained quite healthy 

 after several months' observation, and the other died, eight days 

 after the comrriencement of the experiment, of abdominal catarrh, 

 which was probably not produced by the bacilli. No trace of the 

 bacilli could be obtained from the organs of the animal by means 

 of cultivation. 



Amongst all the animals on which experiments were tried by 

 infection through the digestive system, only the house-mouse and 

 the field-vole have hitherto shown themselves susceptible. Con- 



