Neural Integration 163 



non's recent book, Bodily Changes in Pain, Hunger, Fear 

 and Rage, has been especially drawn upon. 



The Fundament a1ity of Cellular Integration in the Reflex 



Arc 



In no department of physiology do cells keep themselves 

 more persistently in the attention of the student than in the 

 physiology of the nervous system. But likewise nowhere 

 is the fundamental dependence of cells on other cells more 

 clearly seen ; for while, speaking from the standpoint of 

 general functions, cells may be looked upon as individual 

 units, when it comes to the study of nerve cells as such, 

 that is, as constituents of the functioning nervous system, 

 the individual cell is found to be no longer the basal unit. 

 Viewed thus the reflex-arc and not the individual cell is the 

 unit. 



The distinction thus indicated is important from the or- 

 ganismal standpoint and must be considered a little more 

 fully. The general functions of cells to which reference is 

 made above are those common to all cells, even those of the 

 tissues of fully differentiated multicellular animals. No 

 matter what tissue be under consideration, muscle, gland, 

 epithelial or what not, so long as it is truly living, each and 

 every cell assimilates, breathes, excretes, and carries on all 

 the metabolic processes. Thus far each cell is an indepen- 

 dent unit in a high degree. Now while all tissue cells, using 

 the term tissue in its common histological sense, have a rela- 

 tional or integrational function in addition to these indi- 

 vidual functions, it is in the nervous system that this inte- 

 grative aspect of cell life is most positive and definable. 

 The reflex-arc, as the unit of the nervous system, is itself a 

 combination of three indispensable parts or elements : the 

 receptor, the conductor and the effector. Typically these 

 structures contain at least four cells, one for the receptor, 



