'////; S1>I.\AL CORD 7fi( 



Some of the axones of the dorsal fasciculus proprius cross the mid-line to distribute 

 impulses to the neurones of I lie opposite side. These commissural axones. together 

 with certain collaterals of the dorsal root axones. which cross the mid-line outside 

 the dorsal white commissure, compose the so-called cornu-commissural tract at 

 the base of the posterior septum. 



The lateral funiculus or column. .Not all the axones of the posterior or dorsal 

 nerve-roots extend to the encephalon. Kstimation shows that the sum of all the 

 dorsal roots is greatly in excess of the sum contained in the fasciculi cuneatus and 

 gracilis just before these enter their nuclei of termination. Therefore many of the 

 ascending dorsal root axones are concerned with spinal-cord connections wholly. 

 The marginal zone of Lissauer, situated along the lateral margin of the postero- 

 lateral sulcus, is composed largely of dorsal root axones. Many of these finally work 

 across the line of the sulcus into the posterior column. .Many of the dorsal root -fibres 

 which do not reach the brain occur in Lissauer' s zone. Many others, of course, occur 

 throughout the posterior column. Lissauer's /.one also contains some fibres arising 

 from the small cells of the dorsal horn, and to this extent corresponds to a 

 fasciculus proprius. 



The lateral fasciculus proprius (lateral ground bundle, lateral limiting layer) 



FIG. 571. SCHEMATIC REPRESENTATION OF THE SHAPE AND POSITION OF THE VARIOUS FASCIC- 

 OK CONDUCTION PATHS OF THE SPINAL COHD AND THE (iuorriM; AND SIGNIFICANCE OF 

 THE CELI,-H<. mils OF THE GREY SUBSTANCE. (Compiled from the schemes of von Lenbos- 

 sok and Held.) 



FAScicri.rs GRACILIS (Coircotuimo 

 FAScn-ri.ru rr\K.i rr.i f rnxTKitinit .VKIII.I i, HUH r /.OXK \ 



(Burdock' column-, j MIDDLE HOOT ZOXK , \ 



DORSAL ROOT 



5/V.V.l/, <MV<,V./OV ~~ 

 HSLLS 



FA.irrrn.r.i <-Ki;i:nF.l.j.n- 



.s'/'/V.i/./N -.' ,r 



t-Axi-n-ri.r.t i-t:itKiu;ii.ftrr.\ ti 



, l/./N (croutd ifyramid'il (I-...M 



IXTKH.VK1HA rt: in: VKHTIHI'I.II- 



-S7'/ \ I/. / 1X7, 



Hticltu* and red nucfew) 



fill: fi>l;\ (jr i/'/.'/'.'f w.\ i 



run 



FASCICULI N \-t:xrit<i-i..\Tl i: \i rs 

 ''-' ' 



iiKi.H-fn ft >'A.<i-riTtr.i<oi.rrAKrS) 



' :ia,lfrom) FOK.VA TIU II KTIITI.AK1S / 

 ^'' N(; Ml/./N VKSTKAl.lS (from niH-ltui 



Jaitigti uf cerebellum) 



OVAL Bl'XDLE '.tcpto-marginal root-tone) 

 I COJUIA-SHAPBD TRACT (SckulUe) 



F4.scicrt.rs PROPRITS DORSAL'S (anterior 



root-Man*) 

 STRATCSI KIXAI.K 



MARGINAL ZOXR OF LISSAUKR 

 ' (lateral root nine, 



rr.i I:KLATIXOSA (Roiar.ni 



-\ I I'l.KfS OF POSTERIOR HOSX 



til-CLBVS DORSALIS (Clark,-, 

 column) 



I FASCICl'Ll'S PROPRIUS 



LATERAL1S 



- DORSO-LATBRAL 

 IXTERtlBDIATR 



\ DORSO-MElil I ;. 



aRorptr 



or \-KX- 



TRAl, 



Bonn 



. VENTRALIS 



(direct pyramidal tiin'1) 



FILA RAliirVLARIA OF VRXTRAL ROOT 

 \ \ FASI-1 IHl-S VEXTXALIU 



\' COMMISSVRAl. trXULK 



nscmvLvt 



is situated in the lateral concavity of the grey column and is continuous with the 

 other fasciculi proprii both dorsal and ventral. Beyond that it probably does not 

 rmtain commissural axones, it is of the same general significance as the others. 

 is frequently divided into small bundles by the reticular formation. 

 The lateral cerebro-spinal fasciculus '(crossed pyramidal tract). In contrast 

 to the sensory fibres passing through the spinal cord to the cerebral cortex, av 

 are -nen off from the pyrami lal cells of the cortex, which descend to terminate 

 about the cells of tlu> grey subst uice of the spinal cord, chiefly the cells which -ive 

 .gin to the ventral root-fibres. Kpon readmit: the medulla oblomrata in their 

 escent, these axones are accumulated into two well-defined, ventrally placed bun- 

 dles, the pyramids, one from each cerebral hemisphere. In passing through the 

 brain stem the pyramids contribute many fibres to the motor nuclei of the cranial 

 n >i->'es. and thus decrease appreciably in bulk. According to the estimate of 

 1 hornpson, about 160,000 of the pyramidal fibres are destined to enter the spinal 

 cord. 



I pon reaching the lower part of the medulla, the greater mass of the fibres of 

 each pyramid, which are destined to enter the cord, suddenly cross the mid-line in 

 the decussation of the pyramids.' The remainder retain their ventral position in 

 49 



