16 THE ELEMENTARY NERVOUS SYSTEM 



dered in the brain by virtue of the powers of the proper 

 material and form of that organ. And, although Stahl 

 attempted, a century and a half later, to revive the belief 

 that the soul and the sensorium commune were diffused 

 over the whole body, that is, were resident as well in the 

 tip of the finger as in the brain, the idea of the localization 

 of these active properties in the nervous system became 

 so well grounded through the investigations of the physi- 

 cians of that time, particularly Haller, as to assume the 

 form of permanency. This growth of knowledge led di- 

 rectly to the modern view that personality is, strictly 

 speaking, a property of the nervous system and is in no 

 true sense the direct result of any other system of organs. 

 (Foster, 1901.) 



The nervous system, to be sure, is embedded among 

 the other organs of the body, and the environment thus 

 provided influences profoundly its condition and action; 

 but what is meant by individual personality, acuteness or 

 dulness of sense, quickness or slowness of action, tem- 

 peramental traits, such as a gloomy or bright disposition, 

 incapacity, shiftlessness, honesty, thriftiness, or sweet- 

 ness, are all in the strictest sense functions of the nervous 

 system. Hence, it is a matter of no small biological inter- 

 est to ascertain from the conditions presented in the sim- 

 pler animals which of these various states are elemental 

 and what has been the probable line of evolution of that 

 system of organs with which our personality is so indis- 

 solubly connected (Parker, 1914 a}. 



The nervous system of the higher animals, though 

 enormously complex in its organization, is composed of 

 relatively simple cellular elements, the neurones, arranged 

 upon a comparatively uniform plan. This plan is well 

 exemplified in the spinal nerves and spinal cord of the 



