EXAMINATION OF THE NERVOUS SYSTEM. 197 



body. la such a case, if aasesthesia corresponds with a region of 

 a special nerve or a mixed nerve, or if it is extended upon several 

 nervous regions, or if it is even double-sided, we can distinguish 

 peripheric anaesthesia. Peripheric anaesthesia indicates an injury 

 of the end organs of the sensitive nerves and originates through local 

 influences — intense cold, acids (especially carbolic), also alcohol 

 and certain narcotics (especially cocaine). Peripheric anaesthesia 

 may be caused by some traumatism, compression, malformation, 

 or inflammatory exudates; also through inflammations, such as 

 degenerating processes, etc., of the peripheric nerves. Special 

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

 sion of the nerve or the spinal cord. Cases of cerebral anaesthesia 

 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 — chloroform, ether, alcohol, morphia, and 

 bromine. 



Hypercesthesia. This is an increased sensitiveness of the cuta- 

 neous 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. Siedamgrotzky observed in one dog with 

 lameness in the hind-quarters such intense hypersesthesia in the 

 paralyzed centres that the animal gnawed his hindlegs to the bone, 

 notwithstanding all the precautions that were taken to prevent him. 



3. Disturbances of Motility appear in paralysis and convul- 

 sions of the affected muscular system. 



Paralysis. We generally make a distinction between paral- 

 ysis and lameness — that is to say, an entire loss of movement — and 

 paresis or weakness, which is simply due to debility. In the first 

 case 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, without 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 cor 

 tico-muscular leading tracks. Up to the present time they have 

 definitely located the following motor centres in the external sur- 

 face of the cerebrum, the position of which is indicated in Fig. 57 : 

 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 



