THE HISTORICAL DEVELOPMENT OF BIOLOGY 537 



demonstrated some of its properties. Even then scientists be- 

 lieved that when a substance burned it gave off something in- 

 stead of combining with something (oxygen) as we now know to 

 be the case. 



Vaccination. All of us are vaccinated and think nothing of it, 

 but before 1796, smallpox raged unchecked and was so common 

 that about 95 per cent of all people had it. We little realize the 

 struggle of Dr. Edward Jenner, an English physician, who was 

 the first to suggest vaccination as its cure. 



He observed that the dairy maids who had had cow pox (a 

 mild form of smallpox) did not fall prey to the latter disease. 

 Reasoning from this he proposed to inoculate people with cow- 

 pox as a protective measure, and suffered ridicule, opposition, 

 and persecution before he could convince the public. Even now 

 there are a few misguided individuals who oppose vaccination, 

 even though its practice has made smallpox one of the rarest of 

 diseases. 



DEVELOPMENT OF BIOLOGY 



It would be impossible to enumerate here all the famous names 

 in biology or to sketch their contributions to our knowledge. 

 Only a few can be mentioned, but there are books, like " Bi- 

 ology and its Makers " by Locy, which deal with the subject in 

 fascinating style and treat of all the important discoverers. 



A few of these are listed in the tabulation at the end of this 

 chapter, and a glance at it will show two things, how old some 

 of our biologic ideas are, and how young is our definite knowledge 

 sufficient to apply them. The Greeks theorized vaguely about 

 evolution and development, but it was over two thousand years 

 before Darwin and others proved it. Galen was the foremost 

 physician of his time, but modern medicine scarcely had its be- 

 ginnings till fifteen hundred years later. 



Cells and Protoplasm. Hooke saw cell walls in cork bark in 

 1671, but it was nearly two hundred years before the importance 

 of the cell as a unit of tissue structure was proven by Schleiden 

 and Schwann in 1838-39. Both Schleiden and Schwanri noticed 



