230 DISEASES OF THE NERVOUS SYSTEM 



must lead to paralysis of the centre which it controls. "VVe therefore can 

 locate any disturbance in the motor centres of the brain by the paralysis 

 which occurs in certain parts of the body. A diseased condition of the 

 covering of the brain, if not very extensive, generally causes the paralysis 

 of one part of the body, as the single motor centres are separated and 

 very distinct from one another. Diseases of the brain, when they occur 

 in the inner surface between the capsules and the pyramids, where all 

 the motor fibres are close together, cause a more or less complete paralysis 

 of one side of the body. That is to say, a hemiplegia (affecting one side 

 of the brain) causes the paralysis of the muscles of the other side of the 

 body. For instance, if the disease is located on the left side of the brain, 

 the muscles of the right side become paralyzed. In diseases of the spinal 

 cord the muscles affected are on the same side, except in the case of 

 diseases of the cervical portion of the spine, when, as a rule, paralysis is 

 seen in all the extremities, and in disease of the lumbar region paralysis 

 of the posterior extremities is seen. We therefore summarize in a general 

 way that hemiplegia is usually a form of cerebral paralysis (of the con- 

 trolling centres); paraplegia indicates a diseased condition of the spine; 

 and monoplegia is due to a paralysis of the brain as well as the spine. 

 This description gives only the fundamental theories on this subject. 

 Concerning more precise details we would direct our readers to some one 

 of the various physiological text-books. 



The most important peripheric paralyses which have been observed 

 in the dog (by traumatism, compression, or exudation, inflammatory or 

 degenerating processes of the affected nerves) are as follows: 



1. Motor Trigeminal Paralysis. (Paralysis of the lower jaw.) — 

 The lower jaw hangs down; mastication is impossible; saliva runs out 

 of the mouth. This condition occurs very frequently as a symptom of 

 rabies. In rare instances it has been observed as a result of some other 

 disease. 



2. Paralysis of the Anterior Limhs. — The front legs hang inert and 

 all the joints flex very easily. 



3. Paralysis of the Posterior Limbs. — The hind legs are dragged along 

 the ground, the paws being flexed and drawn backward. If the paws 

 are drawn forward and this flexion overcome, the animal is able to stand 

 on its legs if the body is held. 



4. Paralysis of the Cruralis. — In this condition the animal does not 

 use the posterior limb. All the joints become flexed abnormally, and 

 the thigh bends backward. This condition may also be due to some 

 disease of the spine. 



The electrical current is very useful to determine how much certain 

 muscles and nerves can be excited by the current and is particularly 

 useful in the diagnosis of paralysis of the nerves and muscles and nutritive 



