GENERAL OBSERVATIONS: ON REST AND RECREATION 661 



getic good work, Juvenal's 7nens sana in corpore sario is the 

 ideal! Especially be very careful of your eyes since they are 

 your most precious instrument of research and avenue of infor- 

 mation. Very often, unknown to the student and the man of 

 science, bad headaches result from slight eye-strain. For this 

 reason consult good oculists frequently and, in general, avoid 

 reading in bed, on a moving train, in fading daylight, or by a 

 dim or flickering artificial light. Use your eyes interchangeably 

 at the microscope and rest them frequently if the instrument 

 tires. Properly used, the microscope ought to strengthen the 

 eyesight, or at least ought not to harm it. 



Finally, remember that much use dulls a delicate instrument, 

 especially the brain, while frequent rest and recreation tone up 

 the mind to keener insight. Years ago a well-known man of 

 science told me that two of his most interesting discoveries were 

 made on days when he had decided to do nothing and had gone 

 out to lie under the trees. The late Sir William Osier said to me : 

 "I work tremendously hard nine months in the year, but the 

 other three I play." Change of scene often means renewed life 

 and energy and even change of subject helps somewhat. Many 

 scientific men are rather narrow in their outlook on life and would 

 be greatly improved not only socially but in every other way, 

 by getting at frequent intervals entirely away from their narrowing 

 specialty, through the cultivation of literature, music, art, nature 

 in her more general aspects, and the amenities of social life. 



