THE NERVOUS SYSTEM AND CONSCIOUSHESS. 739 



ditioned by nerve-matter, and by the special adjustments of this mat- 

 ter found in the spinal cord. It is interesting to remember, in this 

 connection, that the motions which may be the occasion of sensation 

 are carried to the posterior roots of the cord, while those motions 

 which result in movements are carried to the anterior roots of this 

 organ. 



These roots are the crescentic-shaped arrangements of cell-substance 

 before described. The functions of the cord are not limited to trans- 

 mission. The cord is the source of in- 

 dependent or reflex activities. The pe- 

 culiarity of these activities is that no 

 consciousness and no volition accompany 

 or occasion them ; they are strictly mo- 

 tions. In swallowing food we have an 

 illustration of these reflex activities, and 

 of their close succession to activities that 

 were both conscious and voluntary. Con- 

 sciously and voluntarily the food is car- 

 ried to the fauces ; at once, the excitation 

 made by the food upon the afferent nerves 

 is carried to the cord and the medulla 

 oblongata ; here force is liberated and 

 sent along efferent nerves to the mus- 

 cular walls of the (Esophagus. These 

 walls contract, and the food is passed 

 on into the stomach. 



When the cord is broken, those parts 

 of the body which lie below the break 

 will move violently upon irritation, 

 though they can not be moved by any 

 effort of will or be known by any sen- 

 sation. Many actions, not at first reflex, 

 become so by repetition. Walking is 

 a good example : the movements are 

 learned slowly, and upon numerous ef- 

 forts ; afterward, the work is performed by the centers of the spinal 

 cord, so that walking is really hindered by conscious volition. Dr. 

 Carpenter mentions the case of a shoemaker who was subject to sud- 

 den loss of consciousness ; at such times he always continued the work 

 he was engaged in when consciousness left him ; if walking, he would 

 walk into water or fire ; if using his awl, he would continue doing so, 

 frequently to his serious injury. 



While this reflex action of the cord may thus take place apart from 

 the brain, the brain exercises a strong inhibitory influence over the 

 action. Some persons, by sheer force of will, can hold their feet still 

 under constant tickling of the soles. The following experiment seems 



Fig. 7.— Under Sttrfacte or Cerebbal 

 Peduncle, Pons and Meduli.a, show- 

 ing Connections of the Cranial 

 Nerves. (Sappey, after Hirschfeld.) 



I, infundibulum of pituitary body; 2, 

 part of floor of third ventricle ; 3, cor- 

 I)ora mamillaria; 4, cerebral pedun- 

 cles ; 5, pons ; 6, optic nerves, crossing 

 ill the middle line so as to form the 

 chiasma; 7, common motor nerves of 

 eyeball ; 8, nervus patheticus ; H, tri- 

 geminus ; 10, external ocular nerve ; 



II. facial nerve; 12, auditory nerve; 13 

 nerve of Wrisberg; 14, glosso-pharyn- 

 geal nerve; 15, vagus or pneuinogaa- 

 tric ; 16, spinal accessory ; 17, hypo- 

 glossal nerve (cut away on one side). 



