CONDITION OF THE SPINAL CORD. 395 



posed, all along the median line, at the base of the enceph- 

 alon, 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 gray matter, 

 and then pass to the anterior columns and to the gray 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 corresponding 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 men- 

 tioned (p. 384). 



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 impressions were in 

 the brain, both should be always felt. Of radiations of im- 

 pressions, there are, perhaps, no means of deciding whether 

 they take place in the spinal cord or in the brain ; but the 

 analogy of the cases of transference makes it probable that 

 the communication is, in this also, effected in the cord. 



The power, as a nerve-centre, of comnmicating impressions 

 from sensitive to motor, or, more strictly, from centripetal to 

 centrifugal nerve-fibres, is what is usually discussed as the 

 reflex function of the spinal cord. Its general mode of action, 

 its general though incomplete independence of consciousness 

 and of the will, and the conditions necessary for its perfection, 

 have been already stated. These points, and the extent to 

 which the power operates in the production of the natural 

 reflex movements of the body, have now to be further illustra- 

 ted. They will be described in terms adapted to the general 

 rules of reflection of impressions in nervous centres, avoiding 

 all such terms as might seem to imply that the power of the 

 spinal cord in reflecting, is different in kind from that of all 

 other nervous centres. 



