554 APPLIED BIOLOGY 



causes ; and hence the narcotics give only temporary relief. 

 Obviously, it is wiser to consult a doctor, who may be able 

 to find the cause and prescribe treatment, 



The remarks made above concerning narcotic drugs might 

 well be applied to habitual taking of any kind of medicine 

 without a physician's advice. An immense amount of harm 

 is done by the thousands of patent medicines. 



IH. BACTERIOLOGY APPLIED TO HUMAN HEALTH 



482. Bacteriology and Health. The principles of bac- 

 teriology which have been discovered within the past thirty 

 years are not only of interest in connection with the cause 

 and cure of many diseases, as stated in 259, but are also of 

 much greater importance in that they are capable of being 

 applied so as to maintain health. The relation of bacteri- 

 ology to hygiene is already a vast subject, and we can take 

 time for only a few of the most important points. We shall 

 consider (1) how to avoid the disease germs which are wide- 

 spread, and (2) how to prevent the wide distribution of 

 disease germs. 



483. Avoiding Disease Germs. The methods of avoiding 

 the introduction of disease germs into one's body depend 

 upon the nature of the disease and the causative organism. 

 As a rule, the germs are introduced into the alimentary canal 

 with food and water, into the respiratory organs, into the 

 blood by insect bites, or into wounds. 



484. Infection through Alimentary Canal. Typhoid fever 

 and Asiatic cholera are good examples of intestinal diseases 

 caused by germs which are spread by excreta. Imperfect 

 sewerage and insects may lead to contamination of various 

 foods (milk, vegetables, fruits, raw oysters) and drinking 

 water. In places where these diseases are common the only 

 safety for the individual is in the use of cooked foods and 

 served hot or at least guarded from contamination by flies, 



