THE GENERAL PROBLEM OF KEEPING WELL 401 



over, it has to be evaporated with care. It should be boiled in a tall 

 vessel (a tin or copper vessel which holds about four times the quantity 

 to be evaporated) over a quick fire, the room being tightly closed 

 (openings around windows and doors plugged with cotton or cloth). 

 After three or four hours the room may be opened and thoroughly 

 aired. Since formaldehyde is most disagreeable to breathe, one should 

 not attempt to occupy the room until it is free from the gas. This will 

 require a day or more of thorough ventilation. 



Facts Relating to the Spread of Certain Diseases. The 

 problem of preventing disease in general often resolves 

 itself into the problem of preventing the spread of some 

 particular disease. It is then of vital importance to know 

 the special method by which the germs of this disease leave 

 the body of the patient and are conveyed to the bodies of 

 others. Some of these methods are novel in the extreme, 

 and are not at all in accord with prevailing notions. Par- 

 ticularly is this true of that disease known as 



Malaria, or Malarial Fever. This disease, so common 

 in warm climates and also prevalent to a large extent in 

 the temperate zones, is due to animal germs (protozoa), 

 which attack and destroy the red corpuscles of the blood. 

 These germs, it is found, pass from malarial patients to 

 others through the agency of a variety of mosquitoes 

 known as Anopheles. In sucking the blood of a malarial 

 patient, the mosquito first infects her own body. 1 In the 

 body of the mosquito the germs undergo an essential 

 stage of their development, after which they are injected 

 beneath the skin of whomsoever the mosquito feeds 

 upon. For the spreading of malaria, then, two conditions 

 are necessary : first, there must be people who have the 

 disease; and second, there must be in the neighborhood 

 the special variety of mosquito that spreads the disease. 



i An interesting biological fact is that the female Anopheles, and not the male, 

 sucks the blood of animals and is the cause of the spreading of malaria. 



