An American text-book of physiology . Fig. 174.—Schema showing pathway of the sen-sory impulses. On the left side 8, S representafferent spinal nerve-fibres; C, an afferent cranialnerve-fibre. This fibre in each case terminatesnear a central cell, the neuron of which crossesthe middle line and ends in the opposite hemi-sphere (van Gehuchten). CENTRAL NERVOUS SYSTEM. 669 number of fibres among those degenerating after section of the dorsal rootsmay run tlie longer course, the larger portion run a short or an intermediatecourse, and are therefore distributed at different points between tlie term
An American text-book of physiology . Fig. 174.—Schema showing pathway of the sen-sory impulses. On the left side 8, S representafferent spinal nerve-fibres; C, an afferent cranialnerve-fibre. This fibre in each case terminatesnear a central cell, the neuron of which crossesthe middle line and ends in the opposite hemi-sphere (van Gehuchten). CENTRAL NERVOUS SYSTEM. 669 number of fibres among those degenerating after section of the dorsal rootsmay run tlie longer course, the larger portion run a short or an intermediatecourse, and are therefore distributed at different points between tlie to the dorsal roots at different levels shows, moreover, that the fibres. Fig. 175.—Sections showing the degeneration in the dorsal columns of the dogs spinal cord when thedorsal roots from the sixth lumbar to the second sacral have been cut on the left side (Singer): A, levelof the sixth lumbar; B, level of the fourth lumbar; C, level of the sixth thoracic. Degenerated area inblack. from a given level which run the length of the dorsal columns do not mingleindiscriminately with those from other levels, but form a bundle, and thatthis bundle in the cephalic part of the cord tends to lie nearer the middle linethe more caudad the level from which it arises. From these relations it is evident that comparatively few of the dorsalroot-fibres run the entire length of the dorsal columns. If, then, it is remem-bered that in describing the arrangements of the cord emphasis is usuallyplaced on the very short pathways formed in part by collaterals and con-cerned in the simpler reflexes, and on the longest pathways concerned in thevoluntary reactions, as two extremes
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Keywords: ., bookautho, bookcentury1800, bookdecade1890, booksubjectphysiology
