352 AGRICULTURAL BACTERIOLOGY 



The control of infectious diseases rests on the prevention 

 of the passage of the causal organism from diseased to 

 healthy animals. This is accomplished in part by the iso- 

 lation of diseased animals, thus preventing contact with 

 non-infected animals. The federal and State quarantines, 

 and those established by other agencies, seek to prevent the 

 spread of disease in this way. Another phase in the pre- 

 vention of disease is the destruction of the organisms in 

 the material discharged from the body of the affected ani- 

 mal by the use of some physical or chemical agent before 

 any healthy animal has opportunity to come in contact 

 with the infectious material. This method is being used 

 with the greatest success in the prevention of human dis- 

 eases. It is evident that, before it can be applied, definite 

 knowledge must be obtained of the nature and resistant 

 powers of the organism, and the ways in which it is elimi- 

 nated from the body; otherwise all efforts are likely to be 

 unsuccessful, for, to secure effective results, every organism 

 must be destroyed. 



In the case of typhoid fever it is easy to treat all of the 

 infectious discharges of the patient so as to prevent the 

 spread of the disease. Indeed, the concurrent disinfection 

 or the immediate treatment of all infectious material as 

 soon as it leaves the body of the patient is so successful that 

 practically all of the transmissible diseases of man are now 

 treated in the same wards in some of the great hospitals of 

 the world, without the various diseases spreading from one 

 patient to another. The former plan was to pay little at- 

 tention to the treatment of the discharges, but to attempt to 

 destroy the organisms in the room and on the objects with 

 which the patient had been in contact after death or recov- 

 ery had taken place. This is called terminal disinfection, 

 and represents that which must be employed in the control 

 of animal diseases, together with isolation of the affected 



