v SPINAL COED AND NEEVES 333 



and disappears after a few days, even before the complete healing 

 of the spinal wound. 



As soon as the wound is healed, and the animal begins to 

 move about, an abnormal erosion of the nails is noticed, followed 

 shortly after by loss of hair on the dorsum of the foot and by 

 some excoriation. If the animal is left to itself an ulcer soon 

 forms that involves the derma and subjacent tissues, the capsules 

 of the joints open, and the phalanges and even the metatarsal 

 bones fall off. To prevent this, or to heal the lesions, it is 

 necessary to keep the insensitive limb constantly in bandages. In 

 dogs with bilateral transection of the sensory roots of the lumbo- 

 sacral region the cutaneous alterations set in more rapidly. After 

 this operation the animal cannot retain either faeces or urine, so 

 that precautions must be taken to prevent irritation from these 

 sources. Immediately after the operation the rectal mucosa and 

 the penis are slightly relaxed and markedly hyperaemic ; but in 

 time the hyperaemia disappears and the parts are apparently normal. 

 Before long, however, erythema, ulcerations, t and other lesions of 

 the tissues of the limbs set in, and become incurable unless treated 

 with the greatest care. 



The effects of dividing the motor roots to a hind-limb differ 

 little from the above. Essentially different, however, are the 

 effects of simple transection of the cord between the last dorsal 

 and the first lumbar vertebrae, as repeatedly carried out by Goltz. 

 After the shock effects have disappeared and the wound has 

 healed, these animals exhibit no dystrophic changes in the tissues 

 of the limbs, although in progression they drag either the perineum 

 or one or the other hip on the ground, and pull the posterior parts 

 of the trunk along, since it receives no voluntary impulses. 



If in dogs in which the dorsal roots or ventral roots of one 

 hind-limb are cut the hair of both hind-legs is shaved off in two 

 corresponding areas, the hair in the limb operated on takes more 

 than twice as long to regain its original length, and the new coat 

 is thinner and poorer than that of the normal limb. The nails, 

 too, grow more slowly in the limb operated on than in the normal 

 limb. If croton oil is smeared upon symmetrical areas of both 

 limbs, the blister appears twenty-four hours later in the operated 

 leg, and the new epidermis forms a fortnight later than in the 

 healthy limb. 



Under the microscope the skin of the insensitive limb is 

 seen to be much atrophied and the Malpighian layer sometimes 

 disappears. 



Various hypotheses have been put forward to account for these 

 trophic disturbances consequent on nerve lesions. The following 

 are among the more general and widely accepted : 



(a) The dystrophic effects are produced by the neuro-paralytic 

 hyperaemia which sets up disorders of nutrition in the tissues ; 



