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REVIEWS. 



found good anatomical reasons and pathological facts to support the be- 

 lief, that the voluntary motor fibres of the trunk and limbs make their 

 decussation at the lower part of the medulla oblongata, and that the 

 anterior pyramids are, for the most part, formed by these conductors 

 after their decussation. He could not have given his assent to the 

 view of Foville and Valentin, that there are, in the medulla oblongata, 

 two sets of motor columns, one the anterior pyramids, the other the 

 olivary columns, the fibres of which last they conceived to decussate 

 all along the pons varolii. Sir Charles wished to balance the notion of 

 the decussation of the motor fibres in the crossing of the anterior 

 pyramids (for which idea he had good foundation) by the idea of a 

 similar decussation of the sensitive fibres at a somewhat correspond- 

 ing point posteriorly (for which he had no foundation at all.) Many 

 physiologists, feeling dissatisfied with a baseless, purely speculative 

 theory, made this important question of the precise place of decussa- 

 tion for sensitive impressions, the subject of careful experiment ; and 

 some of them came very near to making the discovery, whose accom- 

 plishment was, however, reserved for Dr. Brown- Sequard, and which 

 is not only one of the most conclusive, of his demonstrations, but is 

 an addition to science of great practical importance. 



lstly. The spinal cord of a mammal is laid bare at the level of the 

 two or three last dorsal vertebra?, and a lateral half of this organ, 

 (including the posterior, the lateral, and the anterior columns, and 

 all the grey matter on one side,) is divided. (See diagramatic figure, 

 3.) The animal is left at rest a little while, and then it is ascer- 

 tained that sensibility seems to be much increased in the posterior 

 limb, on the side of the section, while it seems to be lost, or extremely 

 diminished, in the posterior limb on the opposite side. There seems 

 to be therefore hypercesthesia behind and on the same side as, a trans- 

 verse section of a complete lateral half of the spinal cord, while on the 

 contrary, there seems to be ancestliesia behind and on the opposite side 

 to the section. With reference to motion it is the reverse ; power of 

 movement is lost on the side of the section, but persists on the unin- 

 jured side: see the diagramatic view, in which suppose thelesion marked 

 number 3 to be made in the dorsal or lumbar region, and let a r. re- 

 present the anterior or motor nerve root, continued on by a dotted 

 line to its decussation in the anterior pyramid, while p r. represents 

 the posterior, sensitive, nerve root, also continued through its sup- 

 posed decussation by a dotted line. For the present let us disregard 

 the increase of sensibility, a phenomenon which we shall subsequently 

 consider, and we have the following results of a complete section of 

 one half of the spinal cord in the dorsal or lumbar region. 



On same the side as the injury. 

 Power of movement is lost, 

 sensibility continues. 



On the opposite side to the injury. 

 Power of movement continues, 

 sensibility is lost. 



