348 PHYSIOLOGY CHAP. 



perhaps of muscular sensibility as well, only pass along the same 

 side of the cord, while the paths for pain or thermal sensibility 

 pass along both sides. 



According to Mott's observations, the ascending degenerations ' 

 after hemisection of the cord are shaxply limited to the side of the 

 operation, as shown by the photograph reproduced in Fig. 194. 

 From this he concluded that the greater part of the crossed fibres 

 which conduct pain and thermal sensibility must undergo an 

 interruption in the grey matter of the cord before they pass to 

 the opposite side. 



The importance of Mott's observations lies essentially in their 

 contradiction of the theory of Brown-Sequard, which held its own 

 for so many years in physiology and medicine, and in their having 

 led Brown-Sequard in the last months of his working life (1894) 

 to renounce his old theory of the decussation of sensory paths in 

 the cord. 



Almost simultaneously with Mott, and while still ignorant of 

 his important publication (1893), we investigated on dogs the 

 immediate and remote effects of lateral hemisection of the cord, 

 which were published by Bottazzi in 1895, together with a critical 

 review of the subject, and some new experiments of his own. It 

 is interesting to note the almost complete accordance of our own 

 conclusions from dogs with those previously published by Mott 

 from experiments on the monkey. 



After transection of the right half of the lower thoracic cord, 

 we observed (a) immediate paralysis of the right hind-leg passing 

 into a state of persistent paresis, and temporary paresis of the left 

 hind-leg ; (b) obvious ataxy of the right hind-leg which became 

 more pronounced and definite as the motor paralysis diminished ; 

 (c) serious disturbance of tactile sensibility in both hind-legs im- 

 mediately after the operation, which disappeared in the left leg with 

 the period of irritation, but persisted though greatly diminished 

 in the right ; (d) diminution of pain and thermal sensibility in 

 both hind-limbs, but much more pronounced in the right leg. 



True hyperaesthesia was not observed in any of the dogs we 

 operated on, but the reflexes were increased in the right hind-leg 

 after the period of irritation. The ascending degenerations seen 

 in our dogs involved, as in Mott's experiments, the column of 

 Goll, the direct cerebellar tract of Flechsig, and the ventro-lateral 

 tract of Gowers. 



In 1891 Gotch and Horsley brought forward another clear 

 and quite original experimental proof of the theory that the 

 majority of centripetal impulses pass through the same half of the 

 spinal cord as that to which they were carried by the dorsal roots. 

 After hemisection of the lower thoracic region, they examined the 

 current of action in the various columns of the cord on stimulation 

 of the sciatic nerve. The maximal galvanometer deflection was 



