A Text Book of Physiology V3 1892 Author:Michael Foster Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: to which the nerve is distributed lose the sensibility which they previously possessed. During the section of the root, and when the proximal stump is stimulated... more », sensory effects are produced. When the distal stump is stimulated no movements are called forth. /These facts demonstrate that sensory impulses pass exclusively by the posterior root from the peripheral to the central organs, and that motor impulses pass exclusively by the anterior root from the central to the peripheral organs; and as far as our knowledge goes the same holds good not only for sensory and motor but also for afferent and efferent impulses. ) An exception must be made to the above general statement, on account of the so-called " recurrent sensibility " which is witnessed in conscious mammals, under certain circumstances. It sometimes happens that when the distal stump of the divided anterior root is stimulated, signs of pain are witnessed. These are not caused by the concurrent muscular contractions or cramp which the stimulation occasions, for they persist after the whole trunk of the nerve has been divided some little way below the union of the roots above the origins of the muscular branches, so that no contractions take place. They disappear when the posterior root is subsequently divided, and they are not seen if the mixed nerve trunk be divided close to the union of the roots. The phenomena are probably due to the fact, that bundles of sensory fibres of the posterior root after running a short distance down the mixed trunk turn back and run upwards in the anterior root, (being distributed probably to the pia mater) and by this recurrent course give rise to the recurrent sensibility. § 561. Concerning the ganglion on the posterior root, we may say definitely that we have no evidence that it can...« less