756 MICROBIOLOGY OF DISEASES OF 'MAN AND DOMESTIC ANIMALS 



into the body is but the first of three essentials, the other two being 

 poison-production by the germ and poison-action on the tissues. 

 Many persons are insusceptible to the poisons of one or more disease 

 germs. In whatever way this insusceptibility originate, (natural, 

 acquired by a previous attack, or acquired by artificial treatment) 

 the existence of insusceptibilty tends to prevent 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 infectees 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, paratyphoid 

 and cholera. 



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 is known and therapeusis along this line 

 contents itself largely as yet in so controlling the patient's condition as 

 to permit and encourage to the highest the natural forces of the body 

 to attack 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 resistant or 

 immune. 



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 



