220 University of California Publications in Anatomy l^oh. 2 



position of every individual in its relationship to surrounding nature 

 is, therefore, usually that of an object and at the same time, that of 

 a subject. External agents act incessantly upon individuals which in 

 turn are provoked to a reaction or to a response. In such a way the 

 action of the environment upon an individual and the reaction of the 

 latter seem to be the essence of life 's function. And again, the appro- 

 priate reaction of the individual is indispensable for its welfare and 

 even for its very existence. Only by reacting in a suitable way to the 

 external factors can the individual satisfy its inherent urge to main- 

 tain its own existence and to continue it by new individuals. 



In the higher forms of animals, in ]\Ietazoa, the supreme arbiter of 

 the individual in its adjustment to environment is the nerv'ous system. 

 In higher stages of the animal scale, that role is chiefly performed by 

 the central nervous system. Yet not only the actual environment out- 

 side the individual but the somatic part of its own body appears in 

 some respect as the "external world." Thus the actual surrounding 

 of the individual and in addition the somatic part of its own body both 

 stand in opposition to the central nervous system. 



The central nervous system, accordingly, occupies the position of 

 an "Ego" to surrounding objects and also to the somatic part of the 

 individual. That "Ego," or the central nervous system, in the first 

 place the cerebral cortex, is the real subject which must be brought in 

 relationship to the "environment" and to decide upon the reactions 

 to be taken in each of the major changes of situation. 



When considering the relation of the individual to outside objects, 

 this is achieved by the external impulses through which the central 

 nervous system gets knowledge about the changes in external condi- 

 tions. In this phase the individual or the central nervous system plays 

 the role of a passive object. The second subsequent act of the central 

 nervous system is its reaction or response, wherein it is an active 

 subject. 



From this speculation it appears evident that the task of all afferent 

 systems of neurons is to receive stimuli arising in the environment 

 (without separately considering here those impulses ha\ang their origin 

 in various somatic organs) and to convey these stimuli to the central 

 nerv'ous system. Here the decision is made on the mode of reaction. 

 In general terms the task of aiferent systems is to bring the indi^adual 

 into various special relationships to the environment and thus to enable 

 its proper orientation. 



