456 HUMAN BIOLOGY 



and it is therefore unnecessary to repeat them. But attention 

 should be drawn to the way in which surgery acts in a 

 similar way; the removal of local centers of bacterial infection 

 or septic foci, such as an inflamed vermiform appendix or a 

 small abscess on the finger, may prevent a severe peritonitis 

 or a general infection which would otherwise prove fatal. 

 Complete removal of a cancerous growth is another obvious 

 example. 



Dentistry, which until the end of the last century was 

 mainly mechanical in its conceptions, is now recognized as 

 a most eff"ective means of preventing general ill-health and 

 disease in other parts of the body, such as rheumatism. 



INDUSTRIAL MEDICINE 



In preventing disease among those employed in various 

 occupations, which were formerly known as dangerous trades, 

 medicine has done much and is progressively doing more for 

 the well-being of the race. In Great Britain as long ago as 

 1832 Dr. Turner Thackrah and in 1857 Dr. E. H. Grecnhow 

 enquired into the influence of industrial occupations on 

 health, and since then these problems have been widely and 

 intensively investigated; since 19 17 a special section of 

 the physiological department at Harvard University, Boston, 

 Massachusetts, has been devoted to scientific research into the 

 causation of industrial diseases under the direction of 

 Dr. C. K. Drinker. The poisonous eff'ects of lead which 

 attend a number of industries, such as white lead workers, 

 printers, potters, have long been known, and as the result of 

 carefully planned protective measures, including periodical 

 examination of the employees, based on investigations of the 

 circumstances of the industry, the evil effects have been 

 largely obviated. But other metals, such as nickel, zinc, 

 manganese, copper, and mercury (in hatters, thermometer 

 and mirror makers) may be responsible for industrial 

 poisoning. A number of occupational diseases are due to the 

 inhalation of dust, especiaUy among miners, as in the 

 "gold-miners phthisis" in which particles of sihca are 

 particularly harmful. 



As examples of the value of arresting the incidence of 

 toxic effects from dangerous occupations, reference may be 



