172 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



been described, such as Helweg's bundle or the olivospinal tract, 

 lying on the margin of the cord at the junction of the anterior and 

 the lateral columns and supposed to arise in the olivary bodies; 

 the anterior and the lateral reticulospinal tracts arising from cells 

 in the reticular formation of medulla, pons, and midbrain; and 

 the continuation into the cord of the important posterior longitu- 

 dinal bundle which extends from the midbrain through to the cord 

 and connects the motor nuclei of the cranial nerves with the 

 motor centers of the cord. Concerning these and similar tracts 

 our physiological knowledge is scanty, and it is not possible at 

 present to employ them with certainty in explaining the activity 

 of the neuromuscular apparatus. 



