THE NERVOUS SYSTEM. 575 



Division of the anterior pyramids of the medulla at the point of 

 decussation is followed by paralysis of motion, never quite absolute, in 

 all parts below. Disease or division of any part of the cerebro-spinal 

 axis above the seat of decussation is followed by impaired or lost power 

 of motion on the opposite side of the body ; while a like injury inflicted 

 below this part induces similar, never quite absolute no doubt, on the 

 corresponding side. 



When one half of the spinal cord is cut through in monkeys, the 

 following results follow (Mott) : Motor paralysis of the muscles of the 

 same side (never complete of muscles used in bilateral associated action), 

 followed by gradual recovery of muscular movement, except of the finer 

 movements of the hand and foot ; wasting and flabbiness of the muscles ; 

 sensory paralysis of the same side (temperature, touch, pain and pres- 

 sure) ; temporary vaso-motor paralysis on came side. The temperature of 

 the affected side was depressed 1 to 3 (F.). 



Reflex Action. In man the spinal cord is so much under the control 

 of the higher nerve-centres, that its own individual functions in rela- 

 tion to reflex action are apt to be overlooked; so that the result of 

 injury, by which the cord is cut off completely from the influence of the 

 encephalon, is apt to lessen rather than increase our estimate of its 

 importance and individual endowments. Thus, when the human 

 spinal cord is divided, the lower extremities fall into any position that 

 their weight and the resistance of surrounding objects combine to give 

 them; and if the body is irritated, they do not move toward the irrita- 

 tion; and if they are touched, the consequent reflex movements are 

 disorderly and purposeless ; all power of voluntary movement is absolutely 

 abolished. In other mammals, however, e.g., in the rabbit or dog, after 

 recovery from the shock of the operation, which takes some time, reflex 

 action will occur in the parts below after the spinal cord has been divided, 

 a very feeble irritation being followed by extensive and co-ordinate 

 movements. In the case of the frog, and many other cold-blooded 

 animals, in which experimental and other injuries of the nerve-tissues 

 are better borne, and in which the lower nerve-centres are less subor- 

 dinate in their action to the higher, the reflex functions of the cord are 

 still more clearly shown. When, for example, a frog's head is cut off, 

 its limbs remain in, or assume a natural position ; they resume it when 

 disturbed; and when the abdomen or back is irritated, the feet are 

 moved with the manifest purpose of pushing away the irritation. The 

 main difference in the cold-blooded animals being that the reflex move- 

 ments are more definite, complicated, and effective, although less ener- 

 getic than in the case of mammals. It might indeed be thought, on 

 superficial examination, that the mind of the animal was engaged in 

 the acts; and yet all analogy would lead us to the belief that the spinal 

 cord of the frog has no different endowment, in kind, from those which 



