TWELFTH ANNUAL YEAR BOOK— PART X 499 



before operating renders his instruments free from the possible presence 

 .of bacteiia by boiling, and it is heat which renders a jet of live steam 

 destructive to bacteria. Sunlight, 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 suflBcient to know that they possess the power of destroying 

 bacterial life with the same certainty that poisonous drugs destroy ani- 

 mal 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, possessing certain advantages as 

 well as disadvantages, it may be w'ell to describe briefly a few of the 

 commoner forms. 



BICHLORIDE OF MERCUBT. 



Bichloride of mercury, also known as corrosive sublimate and mercuric 

 chloride, is used in solution in water, commonly in a strength of 1 to 

 1 000, though solutions of double such strength may be employed. Al- 

 though possessing great germicidal pow-er, it has the disadvantages of 

 being a violent poison, of corroding metals, and of uniting with albu- 

 minous substances, such as excreta, blood, etc., and thus forming inert 

 compounds. Unlike the coal-tar products, it leaves no odor in the stable, 

 which is an advantage in connection with the production of milk. On 

 the other hand, care must be used in the handling of a solution of this 

 drug, and feed boxes to which it has been applied should be washed 

 with clear water before animals are again permitted access to them. 



CHLORIDE OF LIME. 



Chloride of lime (sometimes termed chlorinated lime) is a wellknown 

 disirtfectant, although its value is doubtless greatly overrated. This may 

 be due in part to the fact that it is a powerful deodorant — such drugs 

 en account of their pungent odor being popularly believed to have great 

 disinfecting power. Being of uncertain strength and somewhat destruc- 

 tive to metals, and having a permeating odor especially objectionable in 

 a stable where milk is produced, chlorid of lime can not be classed as 

 the most desirable of disinfectants. For general disinfecting purposes it 

 may be mixed with water in the proportion of 6 ounces to the gallon. 



FORMALDEHYDE. 



An aqueous solution containing approximately 40 per cent of formal- 

 dehyde and known as farmalin has of recent years become a more or less 

 popular disinfectant. 



Formaldehyde gas is in most cases impracticable for stable disinfection, 

 case formalin is mixed with water and in the proportion of 6 ounces to 



