76 GENERAL SCIENCE 



come more or less automatic after a time. The control of 

 them as exercised by a person in early life may be almost or 

 wholly lost. 



Where any certain sensation is received over and over again 

 at any nerve centre, and the reaction to it results in nerve 

 impulses that bring about the same kind of an act, there 

 comes a time when the mind gives these sensations no further 

 special attention. The reaction (motor impulse) occurs 

 when the sensation is received without any considerable 

 thought being given to it. A "nerve-track" of sensory and 

 motor impulses has been established through the nerve centre 

 that may not at all involve conscious effort of will. Only by 

 exercise of long-sustained and powerful self-restraint can 

 these motor impulses be brought again under control of the 

 will, and the physical condition within the nervous system 

 changed. Physiologists thus explain "habit" as a state of 

 the body. 



Long continued use of alcohol even in small portions so 

 affects the nerve centres as to destroy more or less com- 

 pletely the power to control acts prompted by certain 

 sensations known as "cravings," or an abnormal appetite. 

 Even the sight or smell of liquor may arouse desires that are 

 not controllable by the victim of alcoholism. These cravings 

 constitute the misery and unspeakable torture endured by 

 those who have become slaves of "habit-forming" drugs and 

 preparations when they are denied the ever-increasing 

 amounts demanded by the shattered nervous system, or 

 when they are struggling to be free of these habits. The 

 knowledge that the craving is relieved by a further supply 

 of the drug becomes sufficient incentive for any act that will 

 furnish relief for the craving. 



The users of patent medicines are always in danger from 

 these evils. Most of such medicines depend upon narcotics 

 in them to afford relief from pain or to bring about sleep, 



