. Cunningham's Text-book of anatomy. Anatomy. THE WHITE MATTEE OF THE SPINAL MEDULLA. 535 posterior nerve-root have three main modes of distribution : (1) the majority take part in the formation of the fasciculus cuneatus, and pass upwards or downwards to end in the gray matter at some other level in the central nervous system; (2) some fibres, and many collaterals of fibres in the fasciculus cuneatus, lie close to the posterior column and describe a series of graceful' curves as they pass forwards, prior to turning laterally into all regions of the gray matter to end at the same level as they
. Cunningham's Text-book of anatomy. Anatomy. THE WHITE MATTEE OF THE SPINAL MEDULLA. 535 posterior nerve-root have three main modes of distribution : (1) the majority take part in the formation of the fasciculus cuneatus, and pass upwards or downwards to end in the gray matter at some other level in the central nervous system; (2) some fibres, and many collaterals of fibres in the fasciculus cuneatus, lie close to the posterior column and describe a series of graceful' curves as they pass forwards, prior to turning laterally into all regions of the gray matter to end at the same level as they enter the medulla spinalis ; (3) a third series form the postero-lateral fasciculus and end in connexion with the cells of the substantia gelatinosa and other cells in the posterior and anterior columns of gray matter (Fig. 473). The fibres derived from the posterior nerve-roots which ascend in the posterior funiculi of the medulla spinalis to the medulla oblongata of the brain constitute a direct sensory tract; other fibres are described which give rise to a crossed sensory tract termed the fasciculus spino- thalamicus. These latter fibres arise as the axons of certain of the cells in the posterior column in con- nexion with which fibres from the posterior nerve- roots have ended, and crossing to the opposite side of the medulla spinalis through the anterior commis- sure they ascend in the antero-lateral funiculus to the brain, where they ultimately reach the thalamus. As the spino-thalamic tract ascends in the spinal medulla its fibres are not gathered into a compact strand, but are more or less loosely scattered in the lateral funiculus (Fig. 473). Association Fibres in the Posterior Funiculus.—But the whole of the fibres of the posterior funiculus are not derived from the posterior nerve-roots. A few fibres exist in this funiculus which have a different origin. They are derived from certain of the cells of the gray matter, and, entering the posterior funiculus, they divi
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
