96 HAND-BOOK OF PHYSIOLOGY. 



of the medulla, and consists of fibres which decussate in the anterior fis- 

 sure arid pass downward in the lateral columns near the posterior cornu 

 of the grey matter to the lower end of the cord;. (3) Direct cerebellar 

 tract (Fig. 319), which corresponds to the peripheral portion of the pos- 

 terior lateral column between the crossed pyramidal tract and the edge 

 of the cord, can be traced up directly to the cerebellum and down to 

 the mid-lumbar region; (4). Posterior medium column, or Fasciculus 

 of Golly is found on either side of the posterior commissure, and is trace- 

 able upward as the fasciculus gracilis of the medulla, the fibres are con- 

 nected with the cells of the posterior vesicular column. It is traceable 

 downward to the mid-dorsal region. As regards the remaining part of 

 the cord unoccupied by the above tracts little can be said. The portion 

 of the posterior column between the posterior median column and the 

 posterior roots of the spinal nerves, known as fasciculus cuneatus or Bur- 

 dach's column, is composed of fibres of the posterior roots on their way to 

 enter the grey substance at different heights. The antero-lateral column 

 contains fibres from the anterior cornua of the same as well as of the op- 

 posite side. 



Functions of the Spinal Nerves. The anterior spinal nerve-roots 

 are efferent or motor: the posterior are afferent or sensory (Sir. C. Bell). 

 The fact is proved in various ways. Division of the anterior roots of 

 one or more nerves is followed by complete loss of motion in the parts 

 supplied by the fibres of such roots; but the sensation of the same parts 

 remains perfect. Division of the posterior roots destroys the sensibility 

 of the parts supplied by their fibres, while the power of motion continues 

 unimpaired. Moreover, irritation of the ends of the distal portions of the 

 divided anterior roots of a nerve excites muscular movements; irritation of 

 the ends of the proximal portions, which are still in connection of the 

 cord, is followed by no appreciable effect. Irritation of the distal portions 

 of the divided posterior roots, on the other hand, produces no muscular 

 movements and no manifestations of pain; for, as already stated, sensory 

 nerves convey impressions only toward the nervous centres: but irritation 

 of the proximal portions of these roots elicits signs of intense suffering. 

 Occasionally, under this last irritation, muscular movements also ensue; 

 but these are either voluntary, or the result of the irritation being reflected 

 from the sensory to the motor fibres. Occasionally, too, irritation of the 

 distal ends of divided anterior roots elicits signs of pain, as well as produ- 

 cing muscular movements: the pain thus excited is probably the result 

 either of cramp or of so-called recurrent sensibility (Brown-Sequard). 



Recurrent Sensibility. If the anterior root of a spinal nerve be di- 

 vided and the peripheral end be irritated, not only movements of the 

 muscles supplied by the nerve take place, but also of other muscles, in- 

 dicative of pain. If the main trunk of the nerve (after the coalescence of 

 the roots beyond the ganglion) be divided, and the anterior root be irri- 



