THE NERVOUS SYSTEM. 635 



in the rabbit and rat, a result very similar to those observed in the case of 

 the frog and pigeon has been obtained. The animal is able to maintain its 

 equilibrium, to run or jump, and in fact carry out all the most compli- 

 cated co-ordinated movements, but it is unable to originate them without 

 stimulation. In the case of the dog, however, it has been found impos- 

 sible to remove the whole brain, but when it has been removed piece- 

 meal the animal may be kept alive for some time, and can carry out co- 

 ordinated movements well, and even manifest intelligence. 



It is quite evident, therefore, that the apparatus for carrying out co- 

 ordinated movements is in these animals not localized either in the cere- 

 brum or in the spinal cord, and must therefore be connected in some 

 way with the parts of the brain below the cerebrum and above the 

 cord. There i$ no reason why such an arrangement may not be supposed 

 to exist in the in man brain. 



We must look upon the cerebrum,. however, for the originator of vol- 

 untary movements. 



As regards the theory of the localization of different movements in 

 different parts of the cerebral cortex which as we have seen has received 

 so much support from observation on animals such as the dog and the 

 monkey, at any rate, we may say that certain parts of the cerebral cortex 

 appear to be highly sensitive to electrical stimuli, particularly the 

 Rolandic area and the frontal lobe in front of it. Stimulation of cer- 

 tain other regions, viz. , of the occipital region, of the parietal and tem- 

 poral region, and of the gyms fornicatus and the frontal region in front 

 of the motor area, does not give rise to such movements. Such observa- 

 tions as it has been possible to make on man show that the localization 

 of movement on the human cerebral cortex is, if anything, superior 

 to that observed in monkeys. We have, of course, but few data upon 

 which to base our conclusion, except such as have been obtained from 

 the observation of the symptoms of disease, but with the help of these 

 we may assume that in the cerebral cortex the co-ordinated movements 

 of the body in some way are represented. The cases which have given 

 us most of our knowledge upon the subject are those in which hemorrhages 

 have occurred in different parts of the brain, followed by paralysis of 

 the opposite side of the body. These haemorrhages chiefly occur in 

 the neighborhood of the corpus striatum. The paralysis of the extremities 

 is practically permanent, although, as a rule, the muscles connected with 

 the trunk are not paralyzed. This means that some interruption has 

 taken place between the cerebral cortex and the paralyzed muscles, and if 

 the lesion is a destroying one, the connection is never re-established . In the 

 case of the animals, such as the dog, this is not the case, as the paralysis 

 is temporary. It is supposed that in man not only the more highly 

 skilled movements but all voluntary movements of the muscles are 



