48 VETEEINAEY HYGIENE 



in the digestive or respiratory tract of healthy animals, 

 their presence there in moderate numbers being unattended 

 by any untoward consequences, although in special circum- 

 stances they may be capable of inducing serious and even 

 fatal disease. 



Bearing these facts in mind, an attempt may be made to 

 explain the beneficial effects of proper ventilation and a 

 pure atmosphere in the prevention of bacterial diseases or 

 in the amelioration of their effects. 



It is obvious that none of the diseases caused by bacteria 

 that are obligatory in their habit can be produced merely 

 by causing an animal to inhale an impure atmosphere, and 

 Coleman was therefore wrong when he held that glanders 

 could be so produced in healthy horses. That is sufficiently 

 attested by the distribution of glanders at the present day. 

 In Great Britain glanders is now mainly confined to 

 London and a few other large towns, and experience shows 

 that in provincial towns and country places horses may 

 remain permanently free from the disease although kept in 

 badly ventilated and otherwise insanitary stables. The 

 indispensable condition for an outbreak of glanders is the 

 introduction of the agent of infection — the glanders bacillus, 

 and that is nearly always effected by the agency of a horse 

 that is already the subject of the disease. 



But while it is thus certain that even the long-continued 

 inhalation of impure air cannot produce glanders, it does 

 not follow that the stable conditions which are necessary 

 to insure a reasonably pure atmosphere are without effect 

 in preventing glanders, or that an impure atmosphere 

 is not favourable to the spread of the disease. On 

 the contrary, it is evident that, given the existence 

 of a glandered horse in a stable, an overcrowded con- 

 dition of the inmates and a stagnant vitiated atmosphere 

 may in two different ways facilitate the spread of the 

 infection. 



In the first place, these conditions will tend to make it 

 more certain that the germs of the disease escaping from 

 the already infected horse will be inhaled or otherwise 



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