THE SPINAL NERVES 587 



funiculus by the sides of the anterior fissure, figure 360, 10. It is smaller 

 than the lateral tract and is not present in all animals, though conspicuous 

 in the human cord and in that of the monkey. It can be traced upward to 

 the cerebral cortex, and downward as far as the mid or lower thoracic region, 

 where it ends. 



Antero-lateral Descending Tract. This is an extensive tract, elon- 

 gated but narrow, and reaching from the lateral pyramidal to the anterior 

 pyramidal tract. It is a mixed tract, since not all of its fibers degenerate 

 below the lesions. 



Comma Tract. This is a small tract of fibers in the posterior funiculus 

 which degenerates below the point of section of the cord. It consists of the 

 descending collaterals of the posterior nerve roots as they pass into the 

 cord. 



Tracts of Ascending Degeneration. The fasciculus gracilis, tract of 

 Goll, and the fasciculus cuneatus, tract of Burdach. These tracts degenerate 

 upward on section of the cord, also on section of the posterior nerve roots, 

 figure 362, i. They exist throughout the whole of the cord and can be traced 

 into the bulb. They are sensory tracts, see page 586. 



The Fasciculus Cerebello-spinalis, or Direct Cerebellar Tract. This 

 tract is situated on the outer part of the cord between the lateral pyramidal 

 tract and the margin. It is found in the cervical, thoracic, and uppjf 

 lumbar regions of the cord, and increases in size from below upward. It 

 degenerates on injury or section of the cord itself, but not on section of the 

 posterior nerve roots, since its fibers arise from the cells of the dorsal nucleus. 

 As the name implies, it is believed to pass up into the cerebellum, see 

 Page 597. 



The Fasciculus Antero-lateralis, Tract of Gowers. This tract lies 

 at the margin of the lateral funiculus of the cord and extends the full length, 

 see figure 364. 



It will thus be seen that the three general divisions of the white matter 

 of the spinal cord the anterior, the lateral, and posterior funiculi are 

 subdivided into tracts in which the fibers degenerate upward, those in which 

 the fibers degenerate downward, and still others in which the fibers degener- 

 ate either way for only short distances when the cord is cut across. These 

 latter parts of the cord are composed of association fibers which connect 

 different levels of the cord. The association tracts form the antero-lateral 

 columns and the lateral limiting layer. The arrangement of these tracts is 

 shown well in figures 362 and 364. 



The Spinal Nerves. The spinal nerves consist of thirty-one pairs, 

 from the sides of the whole length of the cord, their number corresponding 

 with the intervertebral foramina through which they pass. Each nerve 

 arises by two roots, an anterior and a posterior, the latter being the larger. 

 The roots emerge through separate apertures of the sheath of dura mater 



