BIOLOGY IN HUMAN AFFAIRS 



of internal secretion. By this path medicine proceeds to 

 conquer one field after another, so that to-day the scope 

 of medical knowledge is far beyond the conception of any 

 one man. 



Optimists assert that eventually disease will be obliter- 

 ated. They paint a glorious picture of long life with 

 freedom from disease. Scientists know that this is a vain 

 hope, for the human body changes, the environment 

 changes, and diseases meet these altered conditions. 

 Many diseases are caused by living organisms which un- 

 dergo evolution exactly as man has undergone evolution. 

 The changing habits of man affect the condition of his 

 tissues and his health. The invention of new devices for 

 transportation, for light, for heat, and for amusement, 

 unquestionably affect the human body. The introduction 

 of powerful rays may introduce new diseases due to the 

 effects of those rays. Moreover, down through the centu- 

 ries intermarriage and uncontrolled breeding have served 

 gradually to modify the nature of the human being, so that 

 one of the most serious phases of medical study to-day 

 is that applied to constitution and heredity. 



Specialisation. Until the middle of the nineteenth cen- 

 tury the practice of medicine was carried on by an individ- 

 ual who was presumed to be competent in every medical 

 field. He could take care of a pain in the abdomen, a cough 

 or a cold, pneumonia, tuberculosis, an eruption on the 

 skin, infantile diarrhea, or typhoid fever. He advised for 

 the baby, for the mother, and for the grandfather. In an 

 emergency he would take off a limb, open the abdomen, 

 and even the skull. Not infrequently, however, he over- 

 looked serious conditions for the simple reason that the 

 methods and machinery for diagnosing and treating such 

 conditions had not been perfected. 



Around 1880, the discoveries made by Pasteur definitely 

 changed the trend of medicine. The establishment of the 



[198] 



