538 GENERAL THERAPEUTIC MEASURES 



control of infectious disease prevention is the most important procedure. 

 The healthy must be segregated from the sick^ and this is best accom- 

 plished by removing the healthy animals from the infected ones rather 

 than vice versa. In some cases destruction of the infected animals is im- 

 perative. Examples — in tuberculosis of cattle^ contagious pleuro-pneumo- 

 nia of cattle, foot-and-mouth disease, and in countries vrhere diseases ap- 

 pear that have not hitherto gained a foothold, it may become necessary to 

 destroy not alone the infected but also the exposed animals. This is the 

 method heretofore adopted in this country in the control of foot-and- 

 mouth disease, and the results have amply justified the means. 



Disinfection is important. It consists in the use of certain substances 

 which destroy the bacteria or their spores, or both. Among these are 

 found fresh slacked or unslacked lime, chlorinated lime (bleaching pow- 

 der), carbolic acid, corrosive sublimate, formalin, formaldehyde gas, cre- 

 olin, cresol, etc., etc. 



The prevention of some infectious diseases is most successfully ac- 

 complished by vaccination and without doubt this method of prevention 

 when properly applied reduces the losses to a minimum. Vaccination is 

 effective against blackleg, anthrax, tetanus, influenza, rabies, hemorrhagic 

 septicemia, white scours, hog cholera and rinderpest. It is always essen- 

 tial that the products used for the vaccination should be pure and potent 

 and they should be employed with proper care. The biological products 

 prepared for the cure and prevention of infections are prepared under 

 license of the United States Department of Agriculture. 



Parallel with our broader knowledge of the subject of immunity the 

 development of biological therapy is progressing. Since the beginning of 

 progress in the exploitation of products through which infectious diseases 

 may be prevented and cured it has been found that one of the most desir- 

 able means of preventing the extension of various infectious diseases is to 

 furnish the susceptible and exposed animals with artificial immunity. 

 This is the case in blackleg, anthrax, rabies, hog cholera, tick fever, and 

 the like. Many animals prove to be naturally immune against some of 

 these diseases, while others must be made immune by treatment with 

 suitably prepared materials before they are able to successfully withstand 

 attacks from a specific organism. 



Investigators the world over have expended the greatest amount of 

 their study in attempts to discover and perfect effective and at the same 

 time practical means of immunizing animals against the more destructive 

 of the infectious diseases. Large sums have been appropriated for the use 

 of able investigators for the advancement of these researches, both from 

 governmental sources and from gifts of private wealth. The goal sought 

 by these searchers is the discovery of some means by which immunity 

 may be conveyed to a large number of animals* at the least expense. Suc- 

 cessful vaccination against some of these diseases consists in giving the 

 animals that are to be protected a mild attack of the disease ; to provide 

 the body tissues with such a degree of resistance that no disease germs 

 taken into the system can remain to find lodgment, develop and cause in- 

 jury. After such vaccination the animal is sufficiently protected and can 

 go with perfect safety into fields that would have proved deadly before 

 vaccination was performed. 



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