138 SUTHERLAND SIMPSON 



running along the margin of the ventral longitudinal fissure, 

 forming the direct ventral pyramid tract otherwise known 

 as the bundle of Tiirck. This last can be followed to about the 

 middle of the thoracic region. It is said to be wanting in all 

 mammals below the anthropoid apes; such, however, is not the 

 case, since it is present as a well-marked tract in the porcupine 

 (Erethizon dorsatus, Linn.) and to some extent in the raccoon 

 (Procyon lotor, Linn.), as shown by Simpson ('12). 



In the monkey, cat, dog and rabbit the same subdivision takes 

 place at the decussation as in man, except that the direct ven- 

 tral pyramid tract is absent. 



The few species of ungulates that have been examined show 

 that the cortico-spinal fibers of the tract are practically absent 

 and those that do reach the cord cannot be followed beyond the 

 upper cervical segments. Ziehen ('00), in the sheep, says that 

 they decussate, some passing into the dorsal and some into the 

 lateral columns. Dexler and Margulies ('06), in the sheep and 

 goat found that the decussation is not complete; most of the 

 fibers cross and pass into the lateral column of the opposite side; 

 some, however, remain in the ventral column of the same side. 

 King ('11), in the sheep, found also an incomplete decussation; 

 the crossed fibers passed into the lateral column of the opposite 

 side, the direct fibers into the corresponding column of the same 

 side. None could be traced beyond the first cervical segment. 

 Bischoff ('00), in the pig and deer, was unable to say whether 

 the crossed fibers pass into the lateral or the dorsal column. 



All are agreed, at any rate, with regard to the ungulates, that 

 the fibers entering the cord are extremely scanty and termi- 

 nate early. 



The insectivora and chiroptera — hedgehog, mole, bat — show 

 similarly an almost complete absence of cortico-spinal fibers, and 

 the very few that do enter the cord end in the first cervical seg- 

 ment. Whether the decussation is complete, partial or entirely 

 absent is still an open question: Bischoff ('00), Ziehen ('99), 

 Kotzenberg ('99), Obersteiner ('03), Edinger ('H), Van der Vloet 

 ('06), Draseke ('03), Merzbacher and Spielmeyer ('03), and Hat- 

 schek ('03). 



