MIND AND THE NERVOUS SYSTEM. 13 



In such instances as these — and many others might be adduced — 

 the brain has been so occupied with a train of thought that it has 

 taken no cognizance or superintendence of the actions of the body. 

 The spinal cord has received the several sensorial impressions and has 

 furnished the nervous force necessary to the performance of the vari- 

 ous physical acts concerned in turning over the leaves, avoiding obsta- 

 cles, taking the right route, and stopping in front of the right door. 



All cases of what are called " absence of mind " belong to the same 

 category. Here the brain is completely preoccupied with a subject of 

 absorbing interest, and does not take cognizance of the events which 

 are taking place around. An individual, for instance, is engaged in 

 solving an abstruse mathematical problem. The whole power of the 

 brain is taken up in this labor, and is not diverted by circumstances of 

 minor importance. Whatever actions these circumstances may require 

 are performed through the force originating in the spinal cord. 



The phenomena of reverie are similar in some respects to those of 

 somnambulism, to which attention will presently be directed. In this 

 condition the mind pursues a train of reasoning often of the most fan- 

 ciful character, but yet so abstract and intense that, though actions 

 may be performed by the body, they have no relation with the current 

 of thought, but are essentially automatic, and made in obedience to 

 sensorial impressions which are not perceived by the brain. Thus, a 

 person in a state of reverie will answer questions, obey commands in- 

 volving a good deal of muscular action, and perform other complex 

 acts, without disturbing the connection of his ideas. "When the state 

 of mental occupation has disappeared, there is no recollection of the 

 acts which may have been performed. Memory resides in the brain, 

 and can only take cognizance of those mental acts which spring from 

 the brain, or of impressions which are made directly on the encephalon. 



In the case of a person performing on the piano and at the same 

 time carrying on a conversation, we have a most striking instance of 

 the divei'se though harmonious action of the brain and spinal cord. 

 Here the mind is engaged with ideas, and the spinal cord directs the 

 manipulations necessary to the proper rendering of the musical com- 

 position. A person who is not proficient in the use of this instrument 

 can not at the same time play and converse with ease, because the 

 spinal cord has not yet acquired a sufficient degree of automatism. 

 Darwin gives a very striking example of the independent action of the 

 brain and spinal cord. A young lady was playing on the piano a very 

 difficult musical composition, which she performed with great skill and 

 care, though she was observed to be agitated and preoccupied. When 

 she had finished, she burst into tears. She had been intently watching 

 the death-struggles of a favorite bird. Though the brain was thus 

 absorbed, the spinal cord had not been diverted from the office of car- 

 rying on the muscular and automatic actions required by her musical 

 performance. 



