IN the previous lecture we discussed, as far as tinme would permit, certain synmptomi3s produced by injuries of the -spinal cord, selecting those whiich were the most imnportant and interesting; in the present lecture the disturbances of sensation, especially those that result from inicom11plete or unilateral lesions, will be described, and observationis that may contribute to our knowledge of tlhe course and grouping of tlhe sensory afferent imnpulses within thle coid will be particularly emphasizcd.If you permit me it will be advisable, lhowever, before passing to miiy owin observations, to give a slhort slietch of the conduction of sensation within thle cord as far as it is at presentlknown.Nearly sxty years ago tlhe first valuable contribution to this subject was muade by Brown-S6quard,7 wlho from botlh clinical and experimental observations concluded that a one-sided lesion of the spinal cord produces m-otor paralysis, with hyperaesthesia and loss of muscle sense on the same side, and in addition anaesthesia of all other forms of sensibility oni the oppositelhalf of the body. These conclusionslhave been,hlowever,violentlyattacked by botlh physiologists and clinicians, and even Brown-S36quard himself later modified hiis views, but they lhave formed tlle basis of all subsequent contributions, and it lias been, in fact, only within recent years that any important additions or modifications have been made to ,them.The exact intraspinal course of the various forms of sensation soon began to excite interest. Maniy workers, following Brown-S6quard and Selliff, held that pain and teinperature at least pass upwards thlrouglh the grey matter, while tactile imnpressions and those that underlie the sense of position, ascend, according to Scliff, through the dorsal columns. Beeibterew's and Bikel's experiments, however, made it probable that impressions of pain are conducted, after decussation, tlhrouglh the white matter of the ventral part of the lateral columns. But it is obvious