110 HUMAN PHYSIOLOGY. 



(1) On the same side, paralysis of voluntary motion and a relative or 

 absolute elevation of temperature and an increased flow of blood in the 

 paralyzed parts ; hyperaesthesia for the sense of contact, tickling, pain and 

 temperature. 



(2) On the opposite side, complete anaesthesia as regards contact, and 

 tickling and temperature, in the parts corresponding to those which are 

 paralyzed in the opposite side. Complete preservation of voluntary power 

 and of the muscular sense. 



A vertical section through the middle of the gray matter results in the 

 loss of sensation on both sides of the body below the section, but no loss of 

 voluntary power. 



FUNCTIONS OF THE SPINAL CORD. 



i. Asa Conductor. The Lateral columns, particularly the posterior 

 portions, the " pyramidal tracts," and the columns of Tiirck, are the chan- 

 nels through which pass the voluntary motor impulses from the brain to the 

 large multipolar nerve cells in the anterior cornuae of gray matter, and 

 through them become connected with the anterior roots which transmit the 

 motor stimuli to the muscles. 



The Anterior columns, especially the portion surrounding the anterior 

 cornuae, the " anterior radicular zones," are composed of short longitudinal 

 commissural fibres, which serve to connect together different segments of 

 the spinal cord, a condition required for the coordination of muscular 

 movements. 



The Posterior columns are composed of short and long commissural 

 fibres which connect together different segments of the cord. They are 

 insensible to direct irritation, but aid in the coordination of muscular 

 movements in walking, standing, running, etc. Degeneration of the pos- 

 terior columns give rise to the lack of muscular coordination observed in 

 locomotor ataxia. 



The Gray matter, and especially that portion immediately surrounding 

 the central canal, transmits the sensory nerve fibres from the posterior roots 

 up to the brain. Decussation of the sensory fibres takes place throughout 

 the whole length of the gray matter. 



The Multipolar cells of the anterior cornuce are connected with the 

 generation and transmission of motor impulses outward ; are centres for 

 reflex movements ; are the trophic centres for the motor nerves and mus- 

 cular fibres to which they are distributed. The anterior roots give passage 

 to the vaso- constrictor and vaso-dilator fibres which exert an influence 



