THE HIGHER ORGANISMS 179 



Thus, a consideration of the functions of the nervous 

 system inevitably brings us to psychology, and we are 

 tempted to inquire whether there is any essential differ- 

 ence between such motor automatism with its coordi- 

 nated movements and the psychic movements we know 

 as thoughts. The answer should be no. There are no 

 differences other than may be accounted for by the 

 materials and the mechanism. Thought seems to be a 

 succession 'of nerve transmissions following one another 

 in endless number and in orderly sequence, having their 

 source in an external impression. Once set in motion, 

 the stimulus passes on and on, the memory of each cell 

 reviving some other related memory in another cell. 

 Experience shows that these memories arise simulta- 

 neously in many cells, though the more lively are usually 

 developed to the exclusion of the others. Each thought 

 has its beginning in some external impression. Those 

 who doubt this may amuse themselves by endeavoring 

 to create something in thought. 



But the higher animals not only live in adjustment 

 to the external world; they have internal organs whose 

 functions are indispensable, and upon whose coordi- 

 nated activities the life of the whole body depends. For 

 these there must be governing mechanisms, and chief 

 among them we again find the nervous system. Here, 

 however, automaticity of operation and properly cor- 

 related action are the chief requirements. These func- 

 tions progress without intellection. The nervous ar- 

 rangements by which this work is done, therefore, form 

 an almost independent system, the sympathetic system, by 

 which the organs are automatically innervated. Thus, 

 the heart beats continually automatically though it 

 communicates with the central nervous system through 

 the vagus nerves and with the sympathetic system through 

 its cardiac branches, and is, therefore, impressed by general 

 psychic conditions. It is difficult to trace the inception 

 of this part of the nervous system, as automatic action, 

 such as it supplies to the organs of the higher animals, 



