v SPINAL COED AND NEEVES 349 



obtained from the dorsal columns, and next from the lateral 

 columns of the same side. 



The difficulty of examining and interpreting the phenomena 

 due to partial transaction of the spinal cord, particularly the 

 different disturbances of sensibility, becomes much less when the 

 observations are made upon man in cases of spinal disease, or local 

 traumatic lesions of the cord. On the other hand such disease or 

 injury is rarely sharply circumscribed to one part or one entire 

 half of the cord, so that the symptoms necessarily vary and their 

 value is impaired. 



In lesions confined to one half of the cord, Kocher (189G) 

 found that the motor disturbances do not differ from those 

 observed after hemisection in the higher animals. There is total 

 homolateral paralysis which diminishes in time and is eventually 

 reduced to a slight paresis. The sensory disturbances consist in 

 homolateral hyperaesthesia to contact and to pain, and in many 

 cases to heat and cold, which also involves the deeper tissues, as 

 movement of the limbs is very painful. On the side opposite to 

 the lesion there is as a rule diminished sensibility, which is marked 

 or slight, according to the extent and severity of the spinal lesion. 

 Sometimes every form of sensibility is abolished ; more frequently 

 tactile sensation remains and pain sensation is reduced, with or 

 without diminished sensibility to heat and cold. But these dis- 

 turbances of sensibility, whether direct or crossed, are not 

 permanent, as the homolateral hyperaesthesia and the contra- 

 lateral anaesthesia or different dissociated hypoaesthesias disappear. 



It is thus obvious that Brown-Sequard's syndrome is seen in 

 the majority of cases of unilateral lesions of the cord. 



None of the interpretations so far put forward to explain the 

 clinical homolateral hyperaesthesia and controlateral anaesthesia 

 have, however, reconciled these with the experimental observations 

 on the higher mammals. Serious objections can be brought 

 against the old doctrine of the spinal decussation of sensory paths, 

 the chief of which are as follows : (a) simple puncture of the 

 dorsal cord induces homolateral hyperaesthesia, with motor and 

 vasoniotor paralysis ; (&) hemisection of the thoracic cord along 

 with transection of the opposite side of the cervical cord does not 

 affect the sensibility of the two lower extremities ; (c) the homo- 

 lateral hyperaesthesia is more marked than the coiitralateral anaes- 

 thesia, which varies greatly both in man and animals, and 

 frequently bears no relation to the seat of the lesion ; (rf) 

 Galen's experiment of dividing the decussating fibres only by 

 median longitudinal section of the lumbar enlargement does not 

 abolish but only diminishes sensibility. 



Owing to these objections Brown-Sequard gave up his view 

 that the anaesthesia results from interruption of the crossed 

 sensory paths, and regarded it as an inhibitory phenomenon, and 



