HOW TO PREVENT DISEASE. 171 



directly from the one affected to another by inhaling the 

 breath or the exhalations from the body, or they may be 

 carried by a third person from the first to the second, or by 

 means of a book or other inanimate object. Again, the germs 

 may lie dormant for an indefinite period, perhaps in clothing 

 or on the walls of a room, like wheat in a granary stored 

 away, ready to grow when sown on a suitable soil. Instances 

 are not uncommon where a contagious disease appeared, when 

 it was impossible to ascertain its source. It is known that 

 these diseases do not arise spontaneously. As well expect to 

 have a crop of corn without planting corn, as to have scarlet 

 fever, for instance, without having had the germs of that 

 disease planted in the system. Doubtless, in the instances 

 referred to the germs had been lying undisturbed upon some 

 object. or in some article of clothing for a time past recollec- 

 tion ; or, as has often Happened, a family has moved into a 

 dwelling where a case had existed, and proper disinfection 

 had not been made. 



Certain contagious diseases are only contracted once in 

 life, as measles and scarlet fever, with some few exceptions. 

 Sometimes a person may be exposed to a contagious disease 

 without catching it, and when again exposed is not so fortu- 

 nate. This is due either to the existence of a more powerful 

 poison at the last exposure, or to what is called a predisposition 

 on the part of the individual. He may be at this time in less 

 robust health, and the vital powers are unable to cope with 

 the germs successfully. It is to be remembered that no one 

 in poor health should expose himself as attendant upon the 

 patient. The more contagious the disease, as in scarlet fever- 

 or small-pox, the greater the care to be observed. While 

 the' welfare of the patient is duly attended to, the welfare of 

 others should not be neglected. There need be no conflict 

 between the two necessities. 



The first thing to be done when a case of contagious disease 



