SPINAL CORD AS A PATH OF CONDUCTION. 169 



Evidently, therefore, the importance of the pyramidal system 

 varies in different animals, and it is necessary to bear this fact 

 in mind in applying the results of experiments on the lower animals 

 to man. In the lowest vertebrates there are undoubtedly motor 

 paths between the brain and cord through which so-called voluntary 

 movements are effected, but these are probably short paths in- 

 volving a number of neurons. The higher the position of the 

 animal in the phylflgenetic scale, the more complete is the develop- 

 ment of the long pyramidal system; but even in the higher mam- 

 mals it is probable that the more primitive mode of motor con- 

 nection between brain and cord is not entirely displaced by the 

 evolution of the pyramidal system. 



Less Well-Known Tracts in the Cord, In addition to the 

 tracts just described there are a number of others mainly, descend- 

 ing tracts concerning which our anatomical knowledge is less com- 

 plete, and the physiological value of which is entirely unknown or 

 at best is a matter of inference from the anatomical relations.* 



Descending Tracts in the Posterior Column Comma Tract; 

 Oval Field. In the posterior columns several tracts of descending 

 fibers have been described. The comma tract of Schultze, s. } Fig. 

 75, is found in the cervical and the upper thoracic cord. The 

 bundle lies at the border-line between the columns of Goll and 

 Burdach. In the lower regions of the cord, lumbar and sacral, 

 similar small areas of descending fibers are found oval field 

 (Flechsig), median triangle (Gombault and Philippe) which repre- 

 sent possibly different systems. It is probable that these fibers 

 belong to the group of long association fibers connecting distant 

 portions of the cord. Nothing is known regarding their physiology. 



Descending Tracts in the Anterolateral Column. The prepyram- 

 idal tract, known also as Monakow's bundle, the fasciculus inter- 

 mediolateralis, or the rubrospinal tract, is a conspicuous bundle 

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

 (pp., Fig. 75) between the crossed pyramidal tract and the tract 

 of Gowers. 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 

 columns, in which they may be detected as far as the sacral region. 

 Its fibers terminate around cells lying in the posterior part of the 

 anterior horn 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 connected with the cerebrum, it may 



* Collier and Buzzard, "Brain/' 1901, 177; and Fraser, "Journal of 

 Physiology," 28, 366, 1902. 



