33 



its identity. Under all conditions this organism retains its char- 

 acteristics, and in all cases gives rise to the same disease. 



For example, the oi'ganism of tnbercnlosis always produces this 

 particular disease, and by no means whatever can it be so altered 

 that it may produce another, such as glanders. When liberated 

 from the body of a diseased animal, the germs may under certain 

 natural conditions retain their vitality for a very long time, in some 

 instances even months and years. Then, if after this long time 

 they are again brought under favorable conditions inside the body 

 of a susceptible animal, they may develop and produce disease. 



The object of disinfection is the destruction of these disease- » 

 producing organisms and parasites, as well as the cleansing of the 

 stable of other objectionable impurities existing in the form of 

 living matter which may gain access to the milk, impairing its 

 keeping qualities, imparting to it an objectionable odor, color or 

 flavor. 



The fact that it is impossible for one of the contagious diseases 

 to develop independently of the particular organism which can 

 produce it, and that the organism can only originate in an animal 

 suffering from the disease, shows the necessity of destroying or 

 rendering it inactive before it can gain access into the healthy in- 

 dividual. * 



Disinfection and thorough cleaning, as viewed from the bacte- 

 riologist's point of view, are essentially the same. Nature has pro- 

 vided us with one of the most powerful disinfectants we possess, 

 namely, sunlight. In order to avail ourselves of it, we must so 

 construct our barns that it may act to the best advantage. Active, 

 virulent cultures of the germs of tuberculosis, glanders, typhoid 

 fever or diphtheria are rendered perfectly harmless if exposed to 

 the action of direct sunlight for a few hours. The same is true 

 where the germs are given off from the body of a diseased indi- 

 vidual, provided they are not protected from the direct action of 

 the light by being enclosed in other matter, such as mucus, pus, 

 faeces, etc. Diffuse daylight has a disinfecting action but is much 

 less powerful than direct sunlight. Where one or two hours' ex- 

 posure to the action of direct sunlight would suffice to destroy 

 disease-producing organisms, several days or weeks might be re- 

 quired to accomplish the same thing hy diffuse light. 



Sunlight not only acts beneficially in the stable by destroying 

 objectionable micro-organisms that may be present, but it has a 

 beneficial effect upon the animals kept in such a stable. Occa- 

 sionally we see stables arranged in such a manner that the animals 

 are placed upon the shady north side, while the sunny south side 



