CONDITION OF THE SPIXAL CORD. 499 



anterior columns, and the contiguous grey matter of the 

 cord. 



/. Decussation of motor impulses occurs, not in the 

 spinal cord, as is the case with sensitive impressions, but, 

 as hitherto admitted, at the interior part of the medulla 

 oblongata. This decussation, however, does not take place, 

 as generally supposed, all along the median line, at the 

 base of the encephalon, but only at that portion of the 

 . anterior pyramids, which is continuous with the lateral 

 columns of the cord. Hence, the mandates of the will, 

 having made their decussation, first enter the cord by the 

 lateral tracts and adjoining grey matter, and then pass to 

 the anterior columns and to the grey matter associated 

 with them. Accordingly, division of the anterior pyramids, 

 at the point of decussation, is followed by paralysis of 

 motion in all parts below; while division of the olivary 

 bodies, which constitute the true continuations of the 

 anterior columns of the cord, appears to produce very 

 little paralysis. Disease or division of any part of the 

 cerebro-spinal axis above the seat of decussation is followed, 

 as well-known, by impaired or lost power of motion on 

 the opposite side of the body; while a like injury inflicted 

 below this part, induces similar paralysis on the corre- 

 sponding side. 



2. In the second place, the spinal cord as a nerve- 

 centre, or rather as an aggregate of many nervous centres, 

 has the power of communicating impressions in the several 

 ways already mentioned (p. 485)- 



Examples of the transference and radiation of impressions 

 in the cord have been given ; and that the transference at 

 least takes place in the cord, and not in the brain, is nearly 

 proved by the case of pain felt in the knee and not in the 

 hip, in diseases of the hip ; of pain felt in the urethra or 

 glans penis, and not in the bladder, in calculus ; for, if 

 both the primary and the secondary or transferred impres- 

 sions were in the brain, both should be always felt. Of 



K K 2 



