BIOLOGY APPLIED TO HEALTHFUL LIVING 589 



in excusing dangerously excessive exercise because one or 

 more famous generals or other great men happened to play 

 football, or some other game, when they were boys. There 

 is no scientifically proved moral effect of physical strain 

 which in the slightest degree militates against the hygienic 

 rule that exercise for health should never be carried to extreme 

 exhaustion. The world would have far more healthy and 

 efficient men if this rule for muscular activity were more 

 often applied both in work and in play. 



H. PHYSIOLOGICAL EFFECTS OF STIMULANTS AND 

 NARCOTICS * 



463. Introduction. Man has long been more or less 

 accustomed to take into the body certain substances (alcohol, 

 tobacco, tea, coffee, certain drugs, etc.) which are not prop- 

 erly classed with the ordinary food materials, for their value 

 as sources of energy and materials for repair is so slight as to 

 be negligible. Ail these substances are conveniently grouped 

 under the heading " Stimulants and Narcotics," which 

 indicates that their action in the human body is either to 

 excite or stimulate greater activity of certain organs, or to 

 reduce their activity and tend to produce stupor or sleep 

 (narcosis). Both the exciting action of stimulants and the 

 quieting effect of narcotics are pleasurable to most people, 

 and it is solely for this peculiar pleasure that mankind has 

 adopted the habit of using the various substances which 

 afford stimulating and narcotic effects. 



464. Are Stimulants and Narcotics Needed ? It is 

 interesting to note that no animal naturally makes use of 

 any of the stimulants and narcotics ; and hence it is often 

 argued that the human species ought to be natural and 

 avoid them. However, this is a rather weak argument, for 



* To TEACHERS: See "Teachers' Manual" for notes concerning the use 

 of this section. 



