350 ANATOMY or THE CBNTHAL NBEVOUS STSTEM. 



still lacks its medullary sheath, the direct cerebellar tract forms a delicate- 

 white border along the periphery of a large part of the lateral column 

 (Fig. 223). 



Later iuYestigations (Loewenthal, Mott) have shown that the ventral 

 portion of the lateral cerebellar tract, which Growers, from pathological find- 

 ings, had already distinguished as the antero-lateral tract, does not arise 

 from Clarke's cells, but from other cells in the gray matter. This tradus 

 cerebello-spinalis ventralis courses along with the corresponding dorsal tract 

 up to the bulb, but is separated from it there, and, extending farther for- 

 ward, enters the vermis superior of the cerebellum with the peduncles {vide 

 page 328). 



Up to this point then, from the study of secondary degenerations and 

 embryology we have learned to recognize in the white matter the following 

 divisions (systems of fibers, so-called): In the anterior columns the direct 

 pyramidal tract; in the lateral columns, the crossed pyramidal and direct 

 cerebellar tracts; in the posterior columns, the tracts of Burdach and GoU. 



In Figs. 225 and 226 are represented all of the white tracts mentioned. 

 The tract, marked 2, reaching from the anterior column around to the lateral 

 column, has not been described. This area, pierced by the ventral roots, is 

 known as the anterior radicular zone. That portion of it lying within the 

 anterior column is also called the anterior ground-iundle. The portion lying 

 within the lateral column is correspondingly further known as the antero- 

 lateral mixed zone. 



Further divisions in this region should doubtless be made; hut as yet 

 the recorded cases of secondary degeneration do not enable one to define them 

 exactly. They would be very desirable, since it is to the anterior column 

 that one can trace the fasciculus longiiudinalis posterior, and it was into 

 the antero-lateral mixed zone in the cat that Boyce followed that tract from 

 the "deep gray" of the optic lobes (ant. corp. quad.), which corresponds to 

 the lateral longitudinal bundle in the lower vertebrates. In this region also 

 are to be found the prolongations of the large fibers from Deiter's nucleus 

 in the cerebellum, shown in the diagram. Fig. 211, after Ferrier and Turner. 



Most of the fibers in the antero-lateral column, which do not belong 

 to the ventral roots, arise in the gray matter; here are found, besides, in all 

 probability, the central continuations of the sensory paths. The region 5 

 {lateral marginal zone) contains fibers coming direct from the posterior roots, 

 which, after crossing through the dorsal horn, ascend in this region {Gf. 

 Fig. 223, right). 



