456 MAN CONTROLS HIS ENVIRONMENT FOR HEALTH 



and the flea, which transmits bubonic plague bacilli, are examples 

 of the second type. 



It is comparatively recently that we have discovered some of the 

 very definite ways in which these parasites do us harm. I am not 

 an old man. but I can well remember how my father used to keep 

 me in at dusk as he pointed to the mist rising from the lowlands 

 next the river and said. " See the malaria rising there. 7 ' We did 

 not know, little more than 30 years ago, that a certain kind of 

 mosquito carried the organism that causes malaria and that the 

 only connection between the mist and malaria was that those 

 low-lying marshlands were alive with the mosquitoes which carry 

 the disease organisms within their bodies. 



In the control of diseases, prevention is far more important than 

 attempts to cure. Experimentation and experience have taught 

 us that health is closely associated with conditions in man's 

 environment. TVe have learned to isolate the sick from the well, 

 so that diseases may not be communicated. Many diseases have 

 been partially or entirely controlled through scientific investiga- 

 tion and health education. Immunity or protection against dis- 

 ease may be both natural and acquired. The former is the immu- 

 nity that one has at birth and stays with one throughout his life. 

 The latter is acquired through the use of antitoxins, weakened 

 living germs, dead germs, or extracts containing poisons made by 

 germs, introduced into the body. 



Doubtless it seemed irksome and needless to some of you that 

 during an attack of measles the doctor insisted not only that you 

 should be isolated from the rest of the young people in the family 

 but also that you be kept in a darkened room for several days. Now, 

 measles is not an eye disease and you may have wondered why 

 he did this. If you had been older and wiser, you would have 

 realized that certain parasitic diseases are more feared for the 

 harm they may do the individual in later life than what they 

 do at the time. Doctors could tell you of many cases where 

 measles or scarlet fever have left a trail of weakened body 

 organs which have made people semi-invalids and sent some 

 to early graves. It pays to care for oneself at the time of an 

 illness. 



