The Nervous System 



221 



disorganized by disease, the result may be a complete loss 

 of sensation and voluntary movement below the point of 

 inj ury . 



If by accident 

 the spinal cord is 

 injured at some 

 point, all sensa- 

 tion and power 

 of motion may 

 be lost below 

 that spot. The 

 impulse to move- 

 ment started in 

 the brain by the 

 will does not 

 reach the mus- 

 cles, because 

 traveling down 

 the spinal cord, 

 it cannot pass the 

 seat of injury. FlG . I2I The Base of the Brain . 



So the impres- A, anterior lobe of the cerebrum; B, olfactory nerve; 

 sion produced bv *^' s P nen id portion of the posterior lobe; D, optic 



pricking the leg 

 with a pin, which, 

 before pain can be 

 felt, must travel 

 up the spinal cord 

 to the brain, cannot reach the brain because the injury 

 obstructs the path. The telegraph wire has been cut, and 

 the message can no longer be sent. 



/ 338. The Spinal Cord as a Reflex Center. Besides serv- 

 ing as a great nerve conductor to carry sensations to the 



chiasm ; , optic tract ; F, abducens ; H, M, hemispheres 

 of the cerebellum ; A', occipital portion of the occipital 

 lobe ; L, fissure separating the hemispheres; N, medulla 

 oblongata ; O, olivary body ; />, anterior pyramids ; ft, 

 pons Valorii; S, section of olfactory nerve, with the 

 trunk removed to show sulcus in which it is lodged ; 

 T, anterior extremity of median fissure. 



