PAEALYSIS. 543 



The superior lialf of tlie white matter may be divided at one 

 point, and the inferior half at another a little anteriorly, so that 

 all the white fibres shall be divided transversely by the one cut 

 or the otlier, without any material continuity of the cord or 

 damage to the grey matter; and wdien this has been done, 

 irritation of the sensory nerves connected with the parts below 

 the section excites the sensation of pain as strongly as ever. 

 Hence it follows that the impulses which excite pain reacli 

 the brain through the grey matter, and so long as a small 

 portion of the grey matter remains intact, these sensations are 

 transmitted. 



If one-half of the cord be cut through transversely down to its 

 very middle, so as to interrupt all continuity of both white and 

 grey matter, irritation of the skin of the same side will give rise 

 to as much pain as if the cord were not cut, but all voluntary 

 power will be lost in the muscles of that side below the section. 

 It thus follows that the channels which convey sensory impulses 

 must cross over from the side of the cord which they enter to 

 the opposite side, and that the motor influences sent down from 

 the brain must travel along that side of the cord by which they 

 pass out. 



There is increased temperature and sensibility on the side in 

 which sensation is preserved, and diminished temperature on the 

 side in wdiich sensation is lost, especially if the section is made 

 near the medulla oblongata. 



It would seem that the injury acts upon the vasa-motor 

 nerves contained in the cord, as well as upon the motor and 

 sensory nerves (it may be here stated that the vasa-motor fibres 

 do not arise from the sympathetic ganglia, but simply pass 

 through them on their way from the spinal cord to the upper 

 dorsal region), causing paralysis of the vasa-motor nerves on the 

 side in which there is increased temperature and sensibility, and 

 irritation of the vasa-motor nerves on the side in wliicli there 

 is diminished temperature and anaesthesia ; for the experiments 

 of Dr. Brown Sequard, Claude Bernard, and others have proved 

 that when the cervical sympathetic is paralyzed by dividing it, 

 a state of congestion, of which the most conspicuous signs are a 

 blood-shot state of the conjunctiva and lining membrane of the 

 ear and nostril, with a contracted pupil, and increased tempera- 

 ture, is at once set up on the same side of the head, and also 



