528 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



tions of the nervous system, even in those which are most 

 complicated, only certain manifestations of energy. Moreover, 

 he believes that in neurons, as in all other cells of the body 

 and as in the world generally, the law of the conservation of 

 energy during transformation holds, and consequently regards 

 the phenomena of irritability, as exhibited by a neuron or by 

 groups of neurons, as the kinetic representative of the poten- 

 tial forces of the cells and their foodstuffs. The metabolic 

 activities and the vital manifestations of the cell are concomi- 

 tant processes another example of the inseparable connection 

 which exists between what we term matter and energy. There 

 has been in many quarters a certain amount of hesitancy in 

 accepting the view that the capacities of the nervous system, 

 particularly those of the brain, are dependent directly upon 

 the chemical and physical alterations which are continually 

 going on within its constituents: a hesitancy which, though 

 it has in the past proved a serious obstacle to progress, is 

 happily now fast disappearing. For the plant, all the evi- 

 dence goes to prove that under the influence of sunlight and 

 heat marked chemical and physical changes take place within 

 it which we recognize in its vital processes. In the animal 

 be it granivorous, carnivorous, or, like man, omnivorous it is 

 the chemical energy introduced as food which represents, in 

 the main, the source of the energy of the organism. . . . 

 The physiologists have been struggling for fifty years or more 

 to gain an insight into the nature of what they call nerve- 

 impulses, by which is to be understood the occurrences inside 

 axons: for example, at the time when we have good reason 

 to believe that they are functionally extraordinarily active. 

 Their efforts have supplied us with a multitude of data, phys- 

 ical and chemical, interesting enough, no doubt, but which can 

 serve as only the barest prolegomena to an explanation of the 

 essence of the occurrences. If we are so badly informed con- 

 cerning these elementary and fundamental phenomena we may 

 very well be content to be modest for some time to come in our 

 claims as regards a physiological psychology. It is by no means 

 impossible that in the nervous system forms of energy are 

 concerned which do not exist outside the animal body and 

 which yet remain to be recognized and studied. 



