180 PHYSIOLOGY OF CENTRAL NERVOUS 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 phylogenetic scale, the more complete is the develop- 

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

 mals it is probable that motor paths, other than the pyramidal 

 system, connect the cortex and subcortical centers with the motor 

 nuclei in the cord. In the dog, for example, section of the pyramids 

 is not followed by complete paralysis, and, indeed, after such sections 

 stimulation of the motor areas of the cortex still causes definite mus- 

 cular movements.* One such indirect motor path is referred to be- 

 low in connection with the rubrospinal tract (Monakow's bundle) . 



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 

 complete, and the physiological value of which is entirely un- 

 known or at best is a matter of inference from the anatomical 

 relations, f 



Descending Tracts in the Posterior Funiculus Comma Tract; 

 Oval Field. In the posterior funiculi several tracts of descending 

 fibers have been described. The comma tract of Schultze is 

 found in the cervical and the upper thoracic cord. The bundle 

 lies at the border-line between the fasciculus gracilis and the 

 fasciculus cuneatus. 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 represent possibly different systems. These fibers have been 

 explained as descending association tracts connecting distant parts 

 of the gray matter of the cord, but recent workj indicates that 

 they may represent simply the descending limb of entering poste- 

 rior root fibers. When the latter enter the cord they divide in T, 

 one branch passing upward, the other downward for a short dis- 

 tance. On this interpretation the fibers in question do not consti- 

 tute a descending tract, physiologically speaking, in spite of their 

 descending degeneration. 



Descending Tracts in the Anterolateral Funiculus. The pre- 

 pyramidal tract, known also as Monakow's bundle, the fasciculus 

 intermediolateralis, or the rubrospinal tract, is a conspicuous 



*Rothmann, "Zeitschrift f. klin. Med.," vol. xlviii., 1903; Schafer, 

 "Quarterly Journal of Exp. Physiology," 3, 355, 1910. 



t Collier and Buzzard, "Brain," 1901, 177; Fraser, "Journal of Physi- 

 ology," 28, 366, 1902. For summary and literature consult Van Gehuchten, 

 "Anatomic du systeme nerveux de rhomme." 



t "Brain," vol. xxxvi., 1913. 



