330 ADVANCED PHYSIOLOGY 



horse; the animal soon ceases to mind the whip, or refuses to 

 go without its constant application. The only substances in 

 common use which act in this way are coffee and tea (caffein 

 and thein). Persons who have become accustomed to these 

 stimulants are no longer normal individuals, they cannot 

 readily work without them and really suffer if deprived of 

 them. Sometimes the effect of tea and coffee is so great as 

 to cause positive ill health. 



Strychnin, which is a deadly poison when taken in con- 

 siderable quantity, will, when given in small amounts, quicken 

 the heart beat. For this reason it has been prescribed by 

 physicians in cases of critical illness where it is necessary to 

 accelerate the action of the heart, and it has therefore been 

 called a heart stimulant. The habit of using even mild stimu- 

 lants like tea and coffee is, however, a useless and very un- 

 wise one for young people to acquire. 



Narcotics. Narcotics have an effect the reverse of that of 

 stimulants. Instead of producing an increase of activity, 

 they lessen it; instead of making the organs work more vigor- 

 ously, they dull and render them less efficient. In particular 

 they have the effect of causing the brain to become sluggish 

 and finally of putting it to sleep. Just as fast as the brain 

 comes under their influence, it loses its unique powers. The 

 use of a narcotic thus deprives the individual of his most 

 valuable possession. 



The commonest narcotics are opiates; e.g. laudanum, pare- 

 goric, morphine, soothing syrup. Cocaine, chloral, chloroform, 

 ether and the like also produce a deadening effect, though 

 their action is different from the opium products. When 

 one of these drugs has an action on the brain strong enough 

 to cause unconsciousness, it is said to act as a general anes- 

 thetic, and if it produces insensibility to pain in only one 

 particular part of the body without causing unconsciousness, 

 it is called a local anesthetic. 



Narcotics have their uses,, and as a means of relieving pain 



