THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM 53 



by which the organs of the body are coordinated is the complex and 

 nearly all-pervasive system of bloodvessels and of lymphatics. The 

 other chief means is the nervous system, and this is still more complex. 

 (See the experiments and the theoretical notes on them in the Appendix.) 

 The nervous system, then, is that fabric of linear structures which 

 serves to connect in a functional manner the various parts of the body, 

 coordinating them into an individual, just as the connective-tissue 



FIG. 22 



A leaf of Venus' fly-trap (Dionea), much enlarged. Conductivity, the basal function of the 

 nervous system, and a process common to all protoplasm, is seen well-developed even in 

 certain plants. A stimulus (from an insect, for example) applied to the hair-like projections on 

 the edge of the leaf is promptly conveyed to the (motor) hinge and occasions there a quick 

 approximation of the two halves. There are present here, then, all the essentials of a reflex 

 action (see below) and of a useful neuro-muscular mechanism the immediate agent of all the 

 world's advancement. 



anatomically binds the organs and parts together. The nervous tissue 

 comprises physiologically a vastly complex " protoplasmic bridge" (Loeb) 

 between cells and between organs, and transmits (more or less changed 

 perhaps) the myriad influences which originate in these organic units. 

 The nerve-fabric only takes up and perfects in the biological division of 

 labor one of the functions of all protoplasm, conductivity. If we omit 

 for the present the relations of the nervous system to the mental process, 

 we may say in advance that the function of the nervous system is almost 

 wholly conduction, using this term in a broad way to include coordination. 



THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM. 



The general functions of the nervous system may be classified as 

 follows: (1) To represent consciousness, at least as a connector or 

 coordinator; (2) to receive and to transmit impulses " inward," affer- 

 ently; (3) to direct muscular function: (a) actuating it, (b) inhibiting 



