FUNCTIONAL ANALYSIS, CENTRAL AND PERIPHERAL 67 



ent sort of adjusting apparatus which insures general integration of 

 these systems, with provision for conditioning of reflexes and other 

 forms of individually acquired behavior and for release of accumu- 

 lated reserves of nervous potential as needed. These four groups 

 intergrade but, in general, are recognizable. 



The peripheral fibers are grouped in functional systems, each of 

 which is defined as comprising all nerve fibers and related end- 

 organs, which are so arranged as to respond to excitation in a com- 

 mon mode, either sensory or motor. These functional systems are 

 convenient anatomical units also, for all fibers of each sensory sys- 

 tem, regardless of variations in the peripheral distribution of their 

 end-organs and regardless of the particular nerve trunks or roots 

 through which they connect with the brain, are segregated internally 

 and converge into local areas or zones. In higher vertebrates (but less 

 so in lower) the secondary connections of these terminal stations tend 

 to retain their physiological specificity. From this it follows that the 

 peripheral systems of sensory analyzers are extended into the brain 

 as far as related central pathways are separately localized — in the 

 human brain it may be even up to the projection areas of the cerebral 

 cortex. Accordingly, we include in the sensory zone as here defined 

 not only the terminal nuclei of peripheral sensory nerves but also 

 their related nervous connections, so far as these are with other parts 

 of the sensory zone and not directly with the motor zone. The neu- 

 romotor apparatus can be similarly analyzed into functional sys- 

 tems, each of which is concerned with the synergic activation of some 

 particular group of muscles. 



This anatomical segregation of the functional systems is not car- 

 ried to perfection, even in the human nervous system. The various 

 modalities of cutaneous and deep sensibility, for instance, are not 

 completely segregated and localized either peripherally or centrally. 

 Yet this differentiation has gone so far that it provides our most use- 

 ful guide in the analysis of the structure of the brain. 



The activities of the body may be divided into two major groups; 

 (1) those concerned with adjustment to environment, the somatic 

 functions, and (2) those concerned with the maintenance and repro- 

 duction of the body itself, visceral functions. These, of course, are not 

 independent of each other; nutrition, for instance, involves somatic 

 activity in the search and capture of food and visceral activity in its 

 digestion and assimilation. Nonetheless, these types of function are 

 so different, especially in the responses evoked, that this strictly 



