BACILLUS CARRIERS 261 



produce a t3rphoid epidemic, distributed by the milk supply. 

 Even more common is the distribution of diphtheria by 

 carriers. While the diphtheria germs do not remain in the 

 patient's mouth for any such length of time as those of 

 t3T)hoid fever linger in the body, they do remain there from 

 three to six weeks, and sometimes for some months. As 

 long as they are present the person is a source of danger to 

 his associates. A person may become a carrier of diphtheria 

 germs who has not himself had the disease. It frequently 

 happens in a school that after one or two cases of diphtheria 

 have appeared, quite a number of the children will be found 

 to have diphtheria germs in their throats, having obtained 

 them, doubtless, from associating with the patients. To 

 these carriers the bacilli may not be doing injury, since some 

 children are immune ; but as long as the germs are present in 

 their mouths the carriers are a source of danger to others who 

 may not be immune. The most efl&cient method of prevent- 

 ing the distribution of this disease through a school, or any 

 institution, is to examine the throats of all children who 

 are associated with cases of true diphtheria, and then tem- 

 porarily to isolate those whom a microscopic examination 

 shows to be carriers. By such means it is practically always 

 possible to check the spread of diphtheria and to prevent 

 epidemics in schools, and the method is more effective than 

 that of closing the schools. 



Against some diseases we do not yet know how to 

 protect ourselves. The best known of these is infantile 

 paralysis, the method of its distribution not being positively 

 known. It is certainly distributed by people either directly 

 or indirectly, and the wise precaution is to keep away from 

 patients or from those who have been in contact with them. 



