104 



HUMAN PHYSIOLOGY 



nearly or quite intermit activity. Glands of the latter 

 type are often found to be as distinctly subject to 

 nervous government as are the skeletal muscles. The 

 nerves which stretch out to them from the central 

 organs are spoken of as secretory nerves. They are 

 efferent but not motor according to our definitions. 



One of the most familiar examples of the reflex ex- 

 citation of secretion is afforded by the flow of tears when 

 this results from a cinder in the eye. As there are 

 winking movements at the same time we have here a 



FIG. 27. This differs from the second diagram in Fig. 26 in the fol- 

 lowing respect. The afferent fiber does not connect directly with the 

 motor cells but with intermediate or association neurons which extend 

 the effect of the original impulse to groups of efferent elements. 



particularly good demonstration of two kinds of reflex 

 action. When the tears start from emotional causes the 

 reflex character of the act is not so plain. A hot or an 

 acid fluid taken into the mouth produces a reflex secre- 

 tion of saliva. Warming the skin will call forth a reflex 

 discharge of perspiration. 



Psycho -reflexes. In characterizing the standard 

 reflex we insisted that consciousness does not enter into 

 it as an essential feature. We may notice our own re- 

 flexes but to observe is not to control them. Often 

 they run counter to our desires; we may be compelled 



