180 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



bundle forming a wedge-shaped or triangular area in the lateral 

 columns between the lateral pyramidal fasciculus and the 

 superficial anterolateral fasciculus (Gowers'), or, perhaps, more 

 correctly speaking, forming the anterior portion of the lateral 

 pyramidal fasciculus; the two systems being more or less inter- 

 mingled. The fibers composing this bundle are descending 

 fibers that take their origin in the midbrain in the cells of the 

 red nucleus. Shortly after their origin they cross to the opposite 

 side and, passing through the pons and medulla, enter the spinal 

 cord in the lateral funiculi, in which they may be detected as far 

 as the sacral region. These fibers terminate around cells lying in 

 the posterior part of the anterior column of gray matter, whose 

 axons, in turn, probably emerge through the anterior roots. This 

 tract, therefore, constitutes a crossed motor path from midbrain 

 to the anterior roots, and, since the red nucleus, in turn, is con- 

 nected with the cerebrum, either directly or by way of the cere- 

 bellum, it represents a cerebrospinal motor path in addition 

 to that offered by the pyramidal system. 



The vestibulospinal fibers lie anterior to the preceding tract 

 in the anterolateral funiculus; they may extend into the anterior 

 funiculus as far as the anterior pyramidal fasciculus. It is stated 

 that they arise in cells of the nucleus of Deiters and the nucleus of 

 Bechterew, and similar cells lying in the region of the pons. In 

 the cord these fibers end around cells in the anterior column. 

 Since the Deiters nucleus forms a termination for the sensory 

 fibers of the vestibular branch of the eighth cranial nerve, and since 

 these fibers are believed to give us a sense of the position of the body 

 and to be concerned in the reflex adjustment of the muscles in the 

 movements used to maintain equilibrium, their connection in 

 Deiters' nucleus with a spinal motor path becomes very significant 

 as furnishing a reflex arc through which sensory impressions 

 from the vestibular apparatus in the ear may reflexly control 

 the musculature of the body. A number of other descending 

 paths in the anterior and lateral funiculi have 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 

 funiculi 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 medial longitudinal 

 fasciculus (post, long, 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. 



