EXAMINATION OF THE NERVOUS SYSTEM 229 



pecially carbolic), also alcohol and certain narcotics (especially cocaine). 

 Peripheric aniPsthesia may be caused by some traumatism, compression, 

 malformation, or inflammatory exudates; also through inflammations, 

 such as degenerating process, etc., of the peripheric nerves. Spinal 

 anaesthesia is seen and, as a rule, is double-sided; due to compression of 

 the nerve or the spinal cord. Cases of cerebral ansesthcsia are caused by 

 hemorrhages, tumors, inflammations, etc., in the zone of the sensitive 

 nerves. It may also be caused by the effects of various poisons — chloro- 

 form, ether, alcohol, morphia, or bromine. 



Hyperaesthesia. — This is an increased sensitiveness of the cutaneous 

 nerves, and is, as a rule, found in the early stages of certain diseases of the 

 spinal cord. It is very rarely seen in the later stages of such diseases. In 

 rabies it is indicated by gnawing of certain portions of the body, and in 

 neuritis and secondary paralysis. 



3. Disturbances of motility appear in paralysis and convulsions of 

 the affected muscular system. 



Paralysis. — We generally make a distinction between paralysis 

 and lameness, that is to say, an entire loss of movement, and paresis or 

 weakness, which is simply due to debility. In the first ease there is not 

 the slightest movement performed in a muscle or a whole group of muscles. 

 In some cases, there are slight muscular movements, but they are weak, 

 wit hout strength, and do not last very long. In order to determine the origin 

 of paralysis, it is necessary to have some knowledge of the psychomotor 

 centres. These centres are located in the cerebrum, and are called the 

 cortico-muscular leading tracts. Up to the present time they have 

 definitely located the following motor centres in the external surface of 

 the cerebrum, the position of which is indicated in figure 92: 1 is the centre 

 for the movements of the muscles of the neck; 2 is that of the extensors 

 and adductors of the anterior limb; 3 is for extending and turning the 

 anterior limbs; 4 controls the movement of the posterior limbs; 5, the 

 facial muscles; and 6, the lateral movement of the tail; 7, for the re- 

 traction and adduction of the anterior limbs; 8, for elevating the shoulders 

 and stretching the front legs (walking) ; 9, for dilating and contracting the 

 orbicularis palpebrarum and zygomaticus muscles. In the front of 9 we 

 also find the centre for the movements of the tongue. Between the 

 anterior and middle portion of 9 is for closing the jaw. On irritating 

 9 we have a retraction and elevation of the corners of the mouth. By 

 irritating 6 the mouth is opened and the tongue is moved. c,c causes a 

 retraction of the corners of the mouth; c lifts the corners of the mouth 

 and half of the facial muscles as far as the closing point of the eyelids. 

 The middle e (on irritation) opens the eye and dilates the pupil. 



Any disease which becomes located in any portion of this cortico- 

 muscular brain centre and inflames or stops the power of these centres 



