DISINFECTION FOB CONTAGIOUS DISEASES. 361 



in any locality so that eradication is impossible. It should not be 

 practiced in territories where a given disease may still be extirpated 

 by ordinary precautions. Preventive inoculation is applicable to 

 only a few maladies, and therefore its aid in the control of diseases 

 is limited. 



AVhen an infectious disease has gained foothold in a herd the course 

 to be pursued will depend upon the nature of the malady. A good 

 rule is to kill diseased animals, especially when the disease is liable 

 to run a chronic course, as in tuberculosis. The next important step 

 is to separate the well from the sick by placing the former on fresh 

 ground. This is rarely possible; hence the destruction or removal 

 of the sick, wdth thorough disinfection of the infected locality, is the 

 next thing to be done. As to the disinfectants to be used, special 

 directions are given under the various diseases, to which the reader 

 is referred. Here we will simply call attention briefly to the gen- 

 eral subject. 



DISINFECTION AND DISINFECTANTS. 



Disinfection consists in the use of certain substances which possess 

 the power to destroy bacteria or their spores, or both. Those which 

 are cheapest and most available for animal diseases are ordinary 

 freshly slaked lime or unslaked in powder, chlorid of lime, crude car- 

 bolic acid, corrosive sublimate, formaldehj^de gas, formalin, and 

 compound cresol solution. 



(1) Slaked lime is perhaps the most easily procured, but its disin- 

 fecting power is limited. While it is capable of destroying all bac- 

 teria in their vegetative state, it is unable to destroy such spores as 

 those of anthrax and blackleg. It is probable, however, that in 

 incrusting spores it may destroy their vitality sooner or later. It is 

 regarded as safe practice to use only spore-destrojdng substances for 

 the virus of those diseases of which we have no definite knowledge. 

 Nevertheless, in the absence of other disinfectants, lime is very useful. 

 It may be employed as a whitewash on wood and stone and sprinkled 

 as a dilute wash or in powder over yards, manure heaps, and over 

 carcasses before they are buried, and over the ground on which they 

 have lain to prevent other animals from carrying the infection away. 



(2) Chlorid of lime is more efficient than simple slaked or unslaked 

 lime, as it destroys spores. It is the ordinary bleaching powder 

 of commerce and is quite unstable, hence old preparations, unless 

 sealed, are of little value. A 5 per cent solution is sufficiently strong 

 for all spore-bearing bacteria (3 ounces in 2 quarts of water) . It may 

 be efficiently applied to the walls and floor of an infected stable by 

 mixing with limewash in the proportion of 6 ounces of the lime to 

 each gallon of limewash. The ceilings and those portions of the 

 walls which can not be reached should be disinfected by means of 



