CONTROL OF INFECTIOUS DISEASES. 693 



way this insusceptibility originate (natural, acquired by a previous attack, 

 or acquired by artificial treatment) the existence of insusceptibility pre- 

 vents the acquiring of the disease. 



PRACTICE. 



Undoubtedly, the one wholly efficient method of preventing the spread 

 of infectious diseases would consist in immunizing all the possible in- 

 fectees against all the possible diseases. Unfortunately, we know of no 

 practical immunizing methods except in the case of a very few diseases, 

 notably smallpox and typhoid fever. 



Our methods of control of any disease therefore begin with the attempt 

 to destroy them at their origin in the body of the patient, but such methods 

 are merely incidental to the destruction of the germs for the good of the 

 patient himself, i. e. they belong rather to therapeusis than to public 

 health. Unfortunately, also, scarcely any efficient method of destroying 

 bacteria within the body of the patient without destroying the patient 

 also known and therapeusis along this line contents itself largely as yet 

 in so controlling the patent's condition as to permit and encourage to the 

 highest the natural forces of the body in their attacks upon the germs. 

 These natural forces, however, direct their chief energies and secure their 

 chief results, not in destroying the germ but in neutralizing the poisons the 

 germs throw off, and in practice, patients recover rather because they have 

 neutralized the poisons than because they have killed or ejected the germs. 

 For this reason a recovered patient often remains a breeding ground for 

 the germs which caused the attack, but to whose poisons he is now re- 

 sistant or immune to their poisons. 



Practically, then, the germs must leave the patient's body before they 

 can be destroyed. It is at this stage that the most efficient control can 

 be exercised, and that control consists in killing them before they become 

 scattered. In practice the efficient disinfection of all the discharges of 

 a patient will prevent the spread of any disease from him. But this is 

 not as easy to do as at first might appear. Ridding the body of its dis- 

 charges in health is a process dependent on the individual, carried out 

 by him consciously or unconsciously all his life by methods chiefly di- 

 rectly to conserve every convenience rather than to prevent their spread. 

 In health, the careless scattering of these discharges is not of great mo- 

 ment, but of course the habits of indifferent and careless discharge, ac- 

 quired in health persist after disease is contracted. The presence in the 



