36 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



THE NATURE OF DISINFECTION. 



The work of disinfection is based upon our recognition of the 

 presence of disease germs, and disinfection means the act of destroy- 

 ing the cause of the infection. In other words, disinfection is a re- 

 moval of the cause, and it will be clear to any practical man that in 

 dealing with disease any effort which stops short of a complete re- 

 moval of the cause is most unwise and unprofitable. To those unac- 

 customed to the work, disinfection may seem a most complicated 

 process. Any approved method, however, is comparatively simple 

 when carried out carefully, although like many another procedure it 

 is one in which attention to details counts for much. It is important 

 to bear in mind that the causative agents of many diseases are ex- 

 tremely small and may remain for an indefinite time in dust, cracks, 

 and crevices of buildings, so that efforts aiming at the eradication of 

 disease from contaminated premises must be thorough in order to 

 be effective. 



DISINFECTANTS. 



In the work of disinfection nature has provided man with a 

 most valuable ally sunlight. It is well known that the direct rays 

 of the sun are destructive to many forms of bacteria, in some cases 

 destroying them and in others lessening their influence. Thus the 

 importance of well-lighted stables is evident. The dark and sunless 

 building will be a favorable breeding place for bacteria, and the 

 structure which admits the greatest amount of sunlight will be the 

 least favorable for their development. Again, heat will destroy the 

 bacteria of disease. By this is not meant the ordinary heat of the 

 sun, but heat as developed in boiling water or in flame. It is upon 

 this principle that the surgeon before operating renders his instru- 

 ments free from the possible presence of bacteria by boiling, and it 

 is heat which renders a jet of live steam destructive to bacteria. Sun- 

 light, however, can not be considered more than an accessory in the 

 destruction of bacteria, while the application of heat in the form of 

 steam or flame is seldom possible. The result is that in the practical 

 work of disinfection we are dependent upon certain drugs, which 

 have power to destroy the organisms of disease. 



Such drugs are known as disinfectants, and, fortunately, we 

 have at hand a number that possess the power of destroying bacteria. 

 It is not the purpose here to consider further the relative values of 

 these drugs, neither will it be necessary to discuss the exact manner 

 in which they act. It is sufficient to know that they possess the power 

 of destroying bacterial life with the same certainty that poisonous 

 drugs destroy animal life. They have only to be brought in contact 

 with the bacteria in order to destroy them. As disinfecting drugs 

 vary more or less in potency and in adaptability to general use, pos- 

 sessing certain advantages as well as disadvantages, it may be well to 

 describe briefly a few of the commoner forms. 



FORMALDEHYDE. 



Formaldehyde formic aldehyde is available on the market 

 as paraform (a sort of condensed formaldehyde, which is sold as a 

 white powder or in the form of pastils) and also in aqueous solution 



