762 NEUROLOGY 





of the gray matter. The ventral spinocerebellar fasciculus begins about the level 

 of the third pair of lumbar nerves, and can be followed into the medulla oblongata 

 and pons almost to the level of the inferior colliculus where it crosses over the 

 superior peduncle and then passes backward along its medial border to reach the 

 vermis of the cerebellum. In the pons it lies along the lateral edge of the lateral 

 lemniscus. Some of its fibers join the dorsal spinocerebellar fasciculus at the level 

 of the inferior peduncle and pass with them into the cerebellum. Other fibers are 

 said to continue upward in the dorso-lateral part of the tegmentum of the mid-brain 

 probably as far as the thalamus. 



(c) The lateral spinothalamic fasciculus is supposed to come from cells in the dorsal 

 column and the intermediate gray matter whose axons cross in the anterior com- 

 missure to the opposite lateral funiculus where they pass upward on the medial 

 side of the ventral spinocerebellar fasciculus; on reaching the medulla oblongata 

 they continue in the formatio reticularis near the median fillet and probably ter- 

 minate in the ventro-lateral region of the thalamus. It is supposed to conduct 

 impulses of pain and temperature. The lateral and ventral spinothalamic fasciculi 

 are sometimes termed the secondary sensory fasciculus or spinal lemniscus. 



(d) The spinotectal fasciculus is supposed to arise in the dorsal column and 

 terminate in the (inferior ?) and superior colliculi. It is situated ventral to the 

 lateral spinothalamic fasciculus, but its fibers are more or less intermingled with it. 

 It is also known as the spino-quadrigeminal system of Mott. In the brain-stem the 

 fibers run lateral from the inferior olive, ventro-lateral from the superior olive, then 

 ventro-medial from the spinal tract of the trigeminal; the fibers come to lie in the 

 medial portion of the lateral lemniscus. 



(e) The fasciculus of Lissauer is a small strand situated in relation to the tip 

 of the posterior column close to the entrance of the posterior nerve roots. It 

 consists of fine fibers which do not receive their medullary sheaths until toward 

 the close of fetal life. It is usually regarded as being formed by some of the fibers 

 of the posterior nerve roots, which ascend for a short distance in the tract and then 

 enter the posterior column, but since its fibers are myelinated later than those of 

 the posterior nerve roots, and do not undergo degeneration in locomotor ataxia, 

 they are probably intersegmental in character. 



In addition the fasciculus or tract of Lissauer contains great numbers of fine 

 non-medullated fibers derived mostly from the dorsal roots but partly endogenous 

 in origin. These fibers are intimately related to the substantia gelatinosa which is 

 probably the terminal nucleus. The non-medullated fibers ascend or descend for 

 short distances not exceeding one or two segments, but most of them enter the 

 substantia gelatinosa at or near the level of their origin. Ransom 1 suggests that 

 these non-medullated fibers and the substantia gelatinosa are concerned with the 

 reflexes associated with pain impulses. 



(/) The lateral proper fasciculus (fasciculus lateralis proprius; lateral basis bundle) 

 constitutes the remainder of the lateral column, and is continuous in front with the 

 anterior proper fasciculus. It consists chiefly of intersegmental fibers which arise 

 from cells in the gray substance, and, after a longer or shorter course, reenter the 

 gray substance and ramify in it. Some of its fibers are, however, continued upward 

 into the brain under the name of the medial longitudinal fasciculus. 



Fasciculi in the Posterior Funiculus. This funiculus comprises two main fasciculi, 

 viz., the fasciculus gracilis, and the fasciculus cuneatus. These are separated from 

 each other in the cervical and upper thoracic regions by the postero-intermediate 

 septum, and consist mainly of ascending fibers derived from the posterior nerve roots. 



The fasciculus gracilis (tract of Goll) is wedge-shaped on transverse section, and 

 lies next the posterior median septum, its base being at the surface of the medulla 



1 Ransom, Am. Jour. Anat., 1914; Brain, 1915. 



