44 



THE NERVOUS SYSTEM 



muscle-sense are both entirely lost, and, on post-mortem 

 examination, the posterior funiculi are found to have under- 

 gone complete degeneration. 



The lateral funiculus (column) lies to the lateral side of 

 the columns of grey matter and contains, among others, the 

 lateral pyramidal and the spino-thalamic tracts. The former, 

 which undergoes decussation in the lower part of the medulla 

 oblongata (p. 37), is distributed ultimately to the muscles of 



FIG. 25. Transverse Section through Spinal Medulla (Schematic). 



I, II. Muscle and joint sense. 



III. Equilibration sense. 



IV. Motor tract (crossed). 



V. Painful, tactile and thermal 

 sensibility. 



VI. Motor tract (uncrossed). 

 VII. Anterior column of grey 



matter. 



VIII. Posterior column of grey 

 matter. 



the same side of the body. The spino-thalamic tract is 

 made up of the afferent fibres which convey painful^ thermal 

 and tactile sensations. These fibres enter the spinal medulla 

 in the posterior nerve-roots and at once cross the middle line 

 in the neighbourhood of the central canal (Fig. 26). They 

 then ascend in the lateral funiculus to reach the thalamus and 

 the posterior limb of the internal capsule, but little is known 

 with reference to the cortical areas with which they are 

 associated (p. 12). As the spino-thalamic tract passes up- 



