786 THE NERVOUS SYSTEM 



(1) Fibres belonging to the lateral fasciculus proprius which are oflonger extent gradually 

 course farther away from the grey substance of the cord and such mix into the intermediate 

 fasciculus. . . 



(2) It is said to contain fibres descending from the cerebellum to associate with the neurones 

 of spinal cord, probably directly with the ventral root or motor neurones. 



(3) The rubro-spinal fasciculus.— This arises from cell-bodies in the red nucleus of the 

 tegmentum (in the mesencephalon) and is a crossed fasciculus. Axones arising from the red 

 nucleus of one side cross the mid-line while yet in the mesencephalon and descend in the lateral 

 funiculus of the cord to terminate gradually about cell-bodies of the ventral horn, both those 

 which give rise of ventral root fibres and those which contribute to the fasciculi proprii. Its 

 fibres are more thickly bundled in a crescentic area fitting onto the ventral side of the lateral 

 cerebro-spinal fasciculus, and some are said to mix into the area of this latter. 



(4) The vestibulo-spinal fasciculus. — This is sometimes called the lateral vestibulo-spinal 

 fasciculus from the fact that there is a tract of similar significance in the ventral funiculus of 

 the cord. It arises from some of the cell-bodies comprising Deiter's nucleus, the lateral nucleus 

 of termination of the vestibular nerve, and from some of those of the spinal nucleus (nucleus 

 of the descending root) of this nerve, all of which is in the medulla. It descends the cord, un- 

 crossed, to terminate gradually about ventral horn cells, thus comprising a part of the apparatus 

 for the equilibration of the body. Its fibres are thought to be more closely collected in the area 

 immediately ventral to the rubro-spinal fasciculus, but of course commingle with the latter. 



(5) The corpora-quadrigemina-thalamus path. The most lateral portion of the intermediate 

 fasciculus, a small area once included in Gower's tract, contains fibres both ascending and de- 

 scending, connecting the spinal cord with the thalamus (diencephalon) and the quadrigeminate 

 bodies of the mesencephalon. These are crossed paths. The ascending fibres arise from cell- 

 bodies in the ventral horn of one side, cross in the ventral white conimissure (commissural 

 neurones) and course upward in the intermediate fasciculus to their termination in the opposite 

 side. Those terminating about cell-bodies in the thalamus form what is known as the spino- 

 thalamic tract, while those terminating in the nuclei of the quadrigeminate bodies are called 

 the spino-mesencephalic or spino-tectal tract (iractus spino-tectalis) . It is not known in which 

 region of the cord most of these fibres arise but it is quite probably the cervical region. The 

 fibres which arise from cell-bodies of the thalamus and nuclei of the quadrigeminate bodies cross 

 the mid-line in the mesencephalon and descend the cord to terminate gradually about cell- 

 bodies in the ventral horn of the opposite side. Those from the thalamus are known as the 

 thalamo -spinal tract and those from the quadrigemina, as the mesencephalo- or tecto-spinal 

 tract. The latter is thought to be the larger. 



By the fibres of the above tracts general sensory impulses from the body (skin, etc.) are 

 carried to the central portion of the optic apparatus, and the descending fibres give a simple 

 anatomical possibiUty for the movements of the body in response to visual and auditory im- 

 pulses. The descending fibres are thought to terminate chiefly in contact with association 

 neurones of the fasciculi proprii, these transferring the impulses to the neurones giving origin 

 to the ventral or motor root fibres, but some are thought to terminate directly about the cell- 

 bodies of ventral-root neurones. A portion of the intermediate fasciculus, most adjacent to 

 Gower's tract, has been designated as Loewenthal's tract. 



The anterior funiculus or column [funiculus anterior]. — The intermediate 

 fasciculus is continued ventrally and mesially across the Une of exit of the ventral 

 root axones, and thus into the anterior funiculus. This portion is also mixed, but 

 its axones of long course associate somewhat different portions of the nerve axis 

 from those connected by the more lateral portion. 



According to the studies of Flechsig, von Bechterew, and Held, this mesial portion contains 

 fibres, both ascending and descending, which associate the various levels of the grey substance 

 of the spinal cord with the neurones in the reticular formation of the medulla oblongata. 

 The levels to which they have been traced comprise the olivary nuclei, which are largely 

 concerned in cerebellar connections, and the nuclei of the vagus, glosso-pharyngeal, auditory, 

 facial and the spinal tract of the trigeminus. Also some of the ascending fibres are probably 

 associated with the nuclei of the eye-moving nerves. This portion of the intermediate 

 fasciculus also grades into and is mixed with the axones of the ventral fasciculus proprius, as is 

 its lateral portion with the lateral fasciculus proprius. In other words, the fasciculi proprii 

 proper, the axones nearest the grey substance, serve for the intersegmental association of the 

 different levels oi the grey substance of the cord, while the intermediate fasciculus contains 

 axones of longer course which serve to associate more distant levels of the grey substance 

 (if the nerve axis — ^that of the spinal cord with its upward continuation into the medulla 

 oblongata, pons and mesencephalon. 



The anterior marginal fasciculus, ventral vestibulo-spinal tract (Loewenthal's 

 tract) forms the superficial boundary of the mesial portion of the intermediate- 

 fasciculus. It is a narrow band, parallel with the surface of the cord, and extends 

 mesially from the mesial extremity of Gowers' tract (from Helweg's bundle) to 

 the beginning of the anterior median fissure. , 



The axones belonging to it proper are descending from the recijjicnt nuclei of the vestibular 

 nerve. Of tliese nuclei it lias l)cc-n held by sonic investigators that only Dciters' nucleus (the 

 lateral nucleus of termination in the uj)i)er extremity of the medulla oblongata) gives origin 

 to the axones of the anterior marginal fasciculus. Ot liers agree with Tschermak that the superior 

 and more laterally situated Becliterew's nucleus of the vestibular nerve also contributes axones 



