240 BACTERIA, YEASTS, AND MOLDS 



that pass into the air fill the space in the immediate vicinity 

 of the patient, but do not disseminate themselves to a very 

 great distance. Hence persons near the patient are exposed 

 to the disease by breathing the air, while those at some dis- 

 tance are but slightly exposed, and those at a greater dis- 

 tance, not at all. The danger is mostly confined to the room 

 in which the patient is kept, and hardly extends to the rest 

 of the household. The only protection against this method 

 of invasion, then, is to avoid the immediate vicinity of the 

 patient, and to keep the air of the room and the rest of the 

 house as fresh as possible. If one who is obliged to breathe 

 such air will take the opportunity frequently to breathe fresh 

 air out of doors, his danger will be reduced. 



Bacillus carriers. It frequently happens that persons who 

 have had germ diseases continue for some time after recovery 

 to carry around in their bodies the bacteria of the disease. 

 Although the germs no longer do any harm to the recovered 

 patient, they are still as dangerous as ever, if, by any chance, • 

 they should reach another individual. Such persons are 

 called "bacillus carriers," and as long as they continue to 

 harbor these disease germs they are a source of danger to 

 their associates. Such bacillus carriers are particularly com- 

 mon after cases of typhoid fever and diphtheria. Recovered 

 typhoid patients have been known to carry active typhoid 

 bacilli for many years. In one famous case such a person 

 was employed as a cook, and for a period of twelve years 

 cases of typhoid fever appeared in all families shortly after 

 she was first employed by them as cook. Such bacillus car- 

 riers in a dairy have also been known to infect the milk and 

 produce a typhoid epidemic, distributed by the milk supply. 

 Even more common is the distribution of diphtheria by 



