LEEUWENHOEK, THE FIRST GREAT 



MICROSCOPIST 



To know the history of our present control of dis- 

 ( else tlirough the destruction of its microbes, we have 

 to go back to Holland and the middle of the seven- 

 teenth century, when Antony van Leeuwenhoek was 

 making what the world thought useless discoveries of 

 bacteria and protozoans. The microscope, then just 

 invented in a simple form, was little more than a toy, 

 but it so fascinated Leeuwenlioek that it is said he 

 gave a great part of his life to study with it and 

 examined almost everything he could lay his hands on. 

 It is recorded that he had more than two hundred in- 

 struments with an incredible number of lenses which 

 he ground himself. It was his discovery of the flow 

 of blood in the capillaries connecting the arteries and 

 veins that was the iinal proof of Harvey's theory of 

 the circulation. This man's work is only one instance 

 of the ultimate practical value of theoretical research : 

 most of the biological discoveries of greatest value in 

 industrial and medical science have been made in the 

 course of studies in pure science. Can we not make 

 it possible that more of the young men of America 

 have a chance to do scientific research? The Leeuwen- 

 MENDEL, THE WORLD'S MOST FAMOUS hoeks of the future are among them 



STUDENT OF HEREDITY 



Gregor Mendel (1822-1884), abbot of a monastery at Briinn, Austria, through experiments made in 

 his garden, chiefly with peas, demonstrated a law of inheritance which was one of the great biological dis- 

 coveries of the nineteenth century. This law is based upon his discovery that, in cross breeding, the jiaren- 

 tal characters are not blended but retain their individuality to such an extent that in subsequent genera- 

 tions they may be separated and recombined like the cards in a pack. Mendel's interests were along 

 theoretical lines and not in any way utilitarian, yet so important was his discovery that today Mendelism is 

 becoming a household word. The most successful breeder of animals of the future will be biologically 

 trained and will know every twist and turn of the latest Mendelian formula (See page 562) 



556 • 



