374 PHYSIOLOGY 



shock due to the severity of the lesion ; such an operative shock would 

 be effective in either direction, and we do not find that the method 

 of transection, whether by tearing across the cord or cutting it with 

 a minimum disturbance, alters appreciably the amount of shock 

 displayed by the segment of the cord situated below the lesion. 

 On the other hand, if in a dog, which has undergone transection 

 of the cord in the lower cervical region and has been allowed sufficient 

 time to recover from the shock, a second transection be carried 

 out two or three segments below the site of the first operation, the 

 influence of the second section is hardly noticeable on the lower 

 segment of the cord. Apparently then the chief factor in determining 

 shock in all those centres situated aborally of the lesion is the cutting 

 off of the impulses which are continually streaming down from the 

 higher centres and from the great sense-organs connected with the 

 anterior portions of the nervous system. With every rise in the 

 animal scale the impressions received by the special senses take an 

 increasing part in the determining of all the reactions of the body, 

 so that we might expect the effect of cutting off the impulses from 

 the higher centres to be greater, the higher in the scale of animal 

 life is the animal on which the experiment is carried out. 



The state of profound shock produced in the spinal cord by the 

 operation passes off gradually. The blood pressure, which may have 

 fallen to 40 or 50 mm. Hg., rises within two or three days to its normal 

 height, i.e. 90 to 110 mm. Hg. The sphincter muscles of the anus 

 gradually recover their tone, and within a short time the reflex evacua- 

 tion of the bladder and rectum may occur as in a normal animal. The 

 skeletal muscles recover their tone within a few days, and after a 

 short time co-ordinated movements can be brought about in the 

 trunk and limbs by appropriate stimulation of sensory surfaces. At 

 first the reactions thus produced are feeble and the reflex is rapidly 

 fatigued. Of these reflexes those excited by nocuous or painful 

 stimuli are the first to make their appearance ; a little later are 

 seen those due to stimuli affecting the tactile organs in the skin, or 

 the sense-organs of deep sensibility situated round the bones and 

 joints and excited by deep pressure or changes in posture of the 

 limbs. 



In a dog which has undergone complete cervical transection two 

 or three months previously, the tone of the muscles is somewhat 

 increased. Although the dog is unable to walk, if it be raised and 

 given a little push forward, so as to stretch the extensor muscles 

 of its hind limbs, it may take two or three steps forward before its legs 

 collapse. Although the locomotor apparatus is present, the nexus 

 is lacking which determines the regulation of these movements 

 through the organs of static sense, so that the spinal movements are 



