ANATOMY AND PHYSIOLOGY OF THE SPINAL CORD. 407 



on the integrity of the cord, since, in broken-backed 

 animals, the parts supplied by nerves given off below the 

 lesion are usually cold, but always vary in temperature. 



The spinal cord is a conductor of sensitive impressions 

 to the brain, and it has been held that the transmission is 

 effected through the posterior columns, while the anterior 

 columns conduct motor power only. This, however, seems 

 incorrect. The transverse section of one-half of the cord, 

 and the posterior column of the other half, does not prevent 

 the transmission of impressions of sensation to the brain. 

 Bernard, who found such impressions conveyed even after 

 cutting the anterior and lateral columns, rightly concludes 

 that sensative impressions are largely conveyed through 

 the gray substance ; but Dr ISTonat, Brown-Sequard, and 

 others, have arrived at the conclusion, founded on numerous 

 carefully conducted experiments, that not only do the grey 

 matter and posterior columns convey such impressions, but 

 that the anterior columns as well are to a limited extent 

 possessed of a similar property. Dr Nonat, moreover, insists 

 that not only do the anterior columns convey sensory, but 

 that the posterior, in their turn, are capable of transmitting 

 motor force. In either case, however, this substitution 

 takes place only to a limited extent. 



The fibres of sensation cross each other in the whole 

 length of the spinal cord, those of motion only in the 

 medulla oblongata. Brown-Sequard cut transversely through 

 one lateral half of the spinal cord, and then divided the 

 motor roots of the lumbar nerves on the other side, that the 

 opposite hind limb might not be contracted by reflex move- 

 ment ; and on pinching the limb on the same side as the 

 cord was divided, the most marked symptoms of suffering 

 were elicited. The opposite limb had at the same time 

 become insensible. The decussation of the fibres would 



