NERVOUS DISCHARGES 21 



The working of nervous systems has been viewed by science 

 mainly in two aspects. First, the physiologists have studied 

 their structure, growth and functions by dissection and experi- 

 ment. Secondly, experimenters in the laws of animal behavior 

 have gathered data of value from scientific observation. Under 

 the same head might be put facts generally known about the 

 training of animals and the teaching of young children. Our 

 knowledge of the effect of time and of repetition in modifying 

 nervous action is derived mainly from the sources under the 

 second head. 



It is thought that the engineering profession has not con- 

 tributed greatly to the study of nervous systems, at least since 

 Herbert Spencer, an engineer, wrote his book on psychology. 

 As the co-operation of workers in different fields of knowledge 

 is necessary in these days of specialists it may be argued that 

 engineers can consistently join in the consideration of a subject 

 of such importance to man. As a member of the engineering 

 profession then, the writer is not without excuse for advancing 

 ideas on the working of nervous systems for the consideration 

 of physiologists and others who have knowledge of the matter. 



In discussing the subject of this article diagrams are neces- 

 sary and demand no apology. To many minds the explanation 

 here given of the modification through sensory experience of 

 nervous channels may be clear enough and even sufficiently 

 convincing. It is thought, however, that the hypotheses ad- 

 vanced could be made more convincing to others if they were 

 embodied in a practical mechanical device such as could be 

 built and operated. This device would simulate the working 

 of nervous discharges by purely mechanical means. With it, 

 one could demonstrate the modification of action or behavior 

 by experience. 



OPERATION 



Figures i, 2, and 3 show the construction to be used with 

 compressed air or hydraulic pressure. In this description it 

 will be assumed that hydraulic pressure is used. 



In figure 1 the slide valve 6 is shown at the extreme end of 

 its inward stroke as in receiving a signal. This valve, known 

 as the spur valve, when in this position, opens ports 4 and 5 

 on the pressure side. The spur valve spring 7 is now com- 

 pressed. The pawl 8 which is attached to the spur valve, is 



