44 Physiology. 



Importance of Reflex Action. It is important that we 

 understand the nature of reflex action, for very many of 

 the processes of the body are regulated by it. Not only 

 such motions as winking when anything comes quickly 



Nerve Cells Connected by Interlacing Nerve Network. 



Afferent Nerve Fiber " Efferent Nerve Flber 



_ Muscle 



Sensory 



Epitheliur 



(Skin) 



Fig. 28. Parts used in Reflex Action. 



toward the eye, dodging, jumping when suddenly touched 

 by anything hot or when pricked by a pin, but also the 

 regulation of circulation, respiration, and digestion, are 

 brought about through reflex action. 



Destination of Nerve Fibers. The sciatic nerve (the 

 large nerve of the thigh, see Fig. 23) is composed of many 

 fibers. If this nerve is traced outward, it is found to be 

 continually subdividing and sending smaller branches to 

 the muscles, and finally in the muscles one fine nerve fiber 

 goes to each muscle fiber. (See Fig. 13.) Many fibers go 

 on past the muscles to the skin. We can feel in any part 

 of the skin, and we can tell just where we are touched. 



