THE NERVOUS SYSTEM 249 



61. The Reflex Action of the Brain. The reflex function of 

 the organs within the skull is very active and important. Like 

 that of the cord, it protects the body by involuntary move- 

 ments, it regulates the so-called vegetative acts, and it takes 

 the place of the will in controlling the voluntary muscles, 

 when the attention is turned in other directions. The reflex 

 power of the medulla governs the acts of respiration, which 

 are absolutely and continuously essential to life. Kespiration 

 is, as we have seen, partly under the influence of the will ; but 

 this is due in part to the fact that respiration is indirectly con- 

 cerned in one of the animal functions that of speech. 



62. Reflex action also occasions coughing and sneezing, 

 whenever improper substances enter the air-passages. Wink- 

 ing is an act of the same sort, and serves both to shield the 

 eyes from too great glare of light, and to preserve them by 

 keeping the cornea moist. Looking at the sun or other strong 

 light, causes sneezing by reflex action. Laughing, whether 

 caused by tickling the feet or by some happy thought, and 

 also sobbing, are reflex acts, taking place by means of the 

 respiratory muscles. 



63. Certain of the protective reflex movements call into 

 play a large number of muscles, as in the balancing of the 

 body when walking along a narrow ledge, or on a slippery 

 pavement. The dodging motion of the recruit, when the first 

 cannon ball passes over his head, is reflex and involuntary. 



substance takes place, little blood and little nervous energy are required 

 for its support, and, therefore, little is sent ; nutrition in consequence 

 soon becomes languid, and strength impaired. To all these laws the 

 brain is subject equally as the rest of the body. Freque'nt and regular 

 exercise gives it increased susceptibility of action, with power to sustain 

 it, the nervous energy acquiring strength as well as the vascular. Dis- 

 use of its functions, or, in other words, inactivity of intellect and of feel- 

 ing, impairs its structure and weakens the several powers which it serves 

 to manifest. The brain, therefore, in order to maintain its healthy state, 

 requires to be duly exercised." Barlow on Physical Education. 



61. The reflex function of the organs within the skull ? The reflex power of the 

 medulla? Respiration? 



62. What else does reflex action occasion ? Winking ? Other examples ? 



63. Muscles called into play by certain reflex movements ? The somnambulist ? 



