32 THE SPINAL CORD. 



Destruction of the gyms fornicatus of one hemisphere is also followed by degeneration 

 extending down the pyramidal tract, although the gyrus fornicatus cannot be reckoned in 

 with the <; motor " region of the cortex cerebri, but rather appears to be connected with the 

 appreciation of sensory impressions. Since, however, it is not possible to cut away the gyrus 

 fornicatus without pushing aside and thus somewhat injuring the motor cortex, it may 

 be alleged that the degeneration in question is really the result of such injury to that cortex. 

 Nevertheless there is no serious improbability in supposing that afferent as well as efferent 

 fibres are conveyed along the course of the pyramidal tract. Indeed, so far as experimental 

 evidence upon animals is of value in determining the course of afferent impressions along the 

 cord, it is rather in favour of some kinds at least of those impressions passing up this part of 

 the lateral column. 



Marchi and Algieri found extensive degeneration in the tracts of Burdach after removal of 

 a part of the cortex a little behind the motor zone in the dog, and also after removal of the 

 occipital lobe ; in the latter case combined with some degeneration in Goll's column. Singer 

 and Munzer were unable to confirm these results. 



Sherrington finds, after removal of parts of the cortex cerebri, a few scattered degenerated 

 fibres in the anterior and lateral cornua of the spinal cord (and also in the grey matter of the 

 pons and in the substantia nigra of the crus cerebri). The same observer has noticed that 

 even when the cortical lesion is entirely confined to the so-called " arm-area " of the cortex, a 

 certain number of fibres are found to degenerate right down the pyramidal tract of the oppo- 

 site side, even as far as the lumbo-sacral region. 



3. Degenerations in the spinal cord resulting from lesions of the cere- 

 bellum. These have been described by Marchi, who has found, as above mentioned 



Fig. 26. SECTION OF SPINAL CORD OF DOG (LUMBAR RKGION) KILLED 



THREE MONTHS AFTER REMOVAL OF THE RIGHT HALF OF THE 



CEREBELLUM (Marchi). THE DEGENERATED PART is SHADED 



WITH DOTS. 



(p. 25), that removal of one lateral half of the cerebellum 

 in the dog is followed by degeneration extending down the 

 circumferential part of the antero-lateral column. The 

 degeneration is most extensive in the upper regions, and 

 gradually lessens in the lower parts of the cord, but can 

 be traced almost to its termination. It also extends 



along some of the fibres of the anterior roots, thus indicating a direct connection 

 between these and the cerebellar cortex (fig. 26, , d). 



4. Degenerations resulting from lesions of the cord itself. a. Sec- 

 tion of the spinal cord in any part is followed by certain degenerations above 

 and certain below the section. These may be classed as 1, Short degenera- 

 tions which extend only a limited distance above or below the plane of section ; 

 and 2, long degenerations which extend an unlimited distance upwards or downwards 

 in the cord. Of the short degenerations, the most marked are in the anterior 

 column and the anterior part of the lateral column near the grey matter (antero- 

 lateral ground-bundle), where there are seen numerous scattered degenerated fibres 

 both ascending and descending ; they probably are due to the section of fibres 

 which serve to connect cells of one segment of the cord to the grey matter of 

 other segments above or below. Of the long degenerations, the " descending " 

 ones are those of the pyramidal tracts, crossed and direct ; the descending 

 cerebellar tract of the antero-lateral column, and, for a few centimeters, the small 

 descending tract (comma tract) of the posterior column ; the "ascending" are in 

 the posterior column, where they are the same as would have resulted from section 

 of all the posterior roots below the point of section, and in the lateral column in 

 the situation of the direct (dorso-lateral ) cerebellar tract and of the antero-lateral 

 ascending tract. The continuation of these towards the brain has already been 

 mentioned (p. 25) and will again be referred to in connection with the medulla 

 oblongata and pons Varolii. 



