DISTURBANCES OF CONSCIOUSNESS. 501 



2. Paralysis. Loss of power, may be taken as an instructive 

 illustration of motor disturbance. Comparably with pain, 

 paralysis depends on injury or disease, of whatever nature, in 

 some part of the motor side of the nervous system the convo- 

 lutions, basal ganglia, medulla, lateral column and other 

 motor tracts, the anterior root of the spinal nerve, the nerve 

 trunk, or the terminal motor apparatus in the muscle ; occasion- 

 ally it is distinctly a reflex effect of sensory disturbance ; but 

 the paralysis is always seen in the muscle. No class of disease 

 teaches us more clearly the dependence of rational thera- 

 peutics upon an accurate knowledge of the anatomy, physio- 

 logy, and pathology of the parts affected. 



3. Side by side with pain and paralysis respectively, there are 

 to be ranged many allied conditions. Thus, allied to pain, and 

 depending like it on disturbance of some part of the sensory 

 tract, are the sensations of numbness, coldness, excessive 

 sensibility to touch (hyperaesthesia) , excessive sensibility to 

 painful impressions, such as pin-prick (hyperalgesia) , and the 

 various disturbances of the special senses ; loss of the sense of 

 touch (anaesthesia), loss of thesense of pain (analgesia), andaltera- 

 tion or loss of the organic sensations relating to the stomach, 

 bowels, heart, bladder, etc. In the same way we place beside 

 paralysis other motor disturbances, whether in the form of 

 increased muscular movements chorea (St. Vitus's dance), 

 tremors, spasms, convulsions, or disturbed movements of the 

 viscera, as of the heart, intestines, uterus, vessel walls, etc. ; and 

 we say that they may be due to disease of any part of the motor 

 tract from one extremity to the other, or of some part of the 

 sensory area of the nervous system by reflection through the 

 centres. Reflex spasms, convulsions, and visceral disorders, are 

 especially common. 



4. Disturbances of consciottsness, and of the other higher 

 faculties of the nervous system, include unconsciousness or 

 insensibility, delirium or excitement, and the great class of 

 "diseases of the mind" constituting insanity. Unconscious- 

 ness may be the result of injuries to the head ; of interference 

 with the blood-supply to the brain, familiarly seen in fainting ; 

 of interference with the supply of air to the brain, as in as- 

 phyxia ; or of poisons, such as alcohol and opium. To these 

 causes we may add organic diseases of the brain, and indeed 

 most diseases just before death. Delirium and other forms of 

 excitement are phenomena of many diseases, and of the action 

 of a variety of poisons, and must be regarded as associated, both 

 as effects and causes, with excessive nervous metabolism, lead- 

 ing rapidly to exhaustion. 



5. Sleep is most commonly deficient or absent when it calls for 



