BREATHING 267 



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 unmediate 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. 



Summary 



It is plain, then, that there are various facts the house- 

 wife should know in order to help prevent the distribution 

 of contagious diseases. It is especially important to remem- 

 ber that no contagion can take place unless three conditions 

 are fulfilled : (i) the disease germs must be eliminated from 

 the patient's body ; (2) they must be carried to a healthy 

 individual ; and (3) they must have some means of invad- 

 ing the second individual. If this chain of events is broken 

 at any point, the spread of the disease can be prevented. 



Realizing this, it is well to remember the important means 

 of elimination, of carriage, and of invasion. Elimination 

 may take place through saliva or body discharges (especially 

 from nose and throat), through forcible breathing (such as 

 coughing), and through skin eruptions. With disease germs 

 that cannot infect a new human being directly, exit may be 



