INFECTIOUS DISEASES OF CATTLE. 375 



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 a 

 limited one. 



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

 to be pursued in getting rid of it will depend upon the nature of the 

 malady. A good rule is to kill diseased animals, especially when the 

 disease is likely 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 destruc- 

 tion or removal of the sick, with 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 general subject. 



Disinfection consists in the use of certain substances ^vhich 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, fonnaldehyde gas, formalin, creolin, 

 and lysol. 



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

 fecting power is limited, ^^^lile it is capable of destroying all bac- 

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

 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-destroying 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, since it destroys spores. It is the ordinarT>^ bleaching powder 

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

 coaled, 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 chlorid of 

 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 chlorin gas liberated from the chlorid of lime by crude carbolic 

 acid. This is accomplished by making a cone of 5 or 6 pounds of 



