THE RELATION OF GENETICS TO PHYSIOLOGY 

 AND MEDICINE^ 



By Thomas Hunt Morgan 

 Director of the Wm. O. Kerckhoff Laboratories, California Institute of 



Technology 



[With 2 plates] 



The study of heredity, now called genetics, has undergone such an 

 extraordinary development in the present century, both in theory and 

 in practice, that it is not possible in a short address to review even 

 briefly all its outstanding achievements. At most I can do no more 

 than take up a few topics for discussion. 



Since the group of men with whom I have worked for 20 years has 

 been interested for the most part in the chromosome mechanism of 

 heredity, I shall first briefly describe the relation between the facts 

 of heredity and the theory of the gene. Then I should like to dis- 

 cuss one of the physiological problems implied in the theory of the 

 gene, and, finally, I hope to say a few words about the applications 

 of genetics to medicine. 



The modern theory of genetics dates from the opening years of the 

 present century with the discovery of Mendel's long-lost paper that 

 had been overlooked for 35 yeai^s. The data obtained by de Vries 

 in Holland, Correns in Germany, and Tschermak in Austria showed 

 that Mendel's laws are not confined to garden peas, but apply to other 

 plants. A year or tAvo later the work of Bateson and Punnett in 

 England and Cuenot in France made it evident that the same laws 

 apply to animals. 



In 1902 a young student, William Sutton, working in the labora- 

 tory of E. B. Wilson, pointed out clearly and completely that the 

 known behavior of the chromosomes at the time of maturation of the 

 germ-cell furnishes us with a mechanism that accounts for the kind 

 of separation of the hereditary units postulated in Mendel's theory. 



The discovery of a mechanism that suffices to explain both the first 

 and the second law of Mendel has had far-reaching consquences for 



^ Nobel lecture, presented in Stockholm on June 4, 1934. Reprinted by permission from 

 the Scientific Monthly, July 1935. 



345 



