408 



THE NERVOUS SYSTEM. 



FIG. 108. 



tions in the posterior columns are always ascending; that is, they 

 extend from the primary lesion upward toward the brain, and never 

 in a downward direction. But all parts of the posterior columns are 

 not affected alike. The inner portion of these columns consists of a 

 narrow band, next the median line, which throughout the cervical 

 region is distinctly divided from the remainder by a narrow superficial 

 furrow. This portion is known as the funiculus 

 gracilis, or the " column of Goll." At the medulla 

 oblongata it diverges from the median line, occupy- 

 ing on each side the inner border of the restiform 

 bodies, and forming the so-called "posterior pyra- 

 mids." These columns, in ascending degeneration 

 of the spinal cord, are affected throughout their 

 length, above the starting-point of the alteration, 

 often quite to the level of the medulla oblongata 

 i<r 108) ; and from this it is inferred that they 



FIG. 109. 



TRANSVERSE SECTION OF 



THE SPINAL CORD ; show- ... 



ing ascending degenera- consist mainly of fibres running continuously 



tion of the columns of thrrmrrhrmt 

 Gdl. <?,<?. (Charcot.) Ut ' 



On the other hand, in the external portion of 



the posterior column, or that situated nearest the posterior horn of 

 gray substance (Fig. 109), ascending degenerations extend only for 

 two or three centimetres above their origin. It is therefore inferred 

 that the longitudinal fibres in this part of the column have no great 

 length, and that they originate successively from the gray substance, 

 to terminate in it again soon afterward at a higher level. 



III. Among the most important facts bearing on this question are 

 those connected with the disease known as locomotor ataxia. In this 

 affection there is a remarkable difficulty in walk- 

 ing, of such a character that the patient's natural 

 gait is altered, and he is no longer sure of his 

 movements. He loses the power of equilibrium, 

 and cannot guide his foot to a particular point 

 \^Jjjjj I ljj\ / without a direct effort of the will. Consequently 

 H^/ locomotion, as usually performed, becomes imp6s- 

 sible; and yet the patient has not lost in any 

 TRANSVERSE SECTION OF degree the power of voluntarv movement, since 



THE SPINAL CORD; * ,. 



showing sclerosis of he can often exert his full muscular force m 

 lateral portion of Poste- grasping an object or in pushing or pulling with 



rior Columns. Locomo- f. , J 



tor Ataxia. (Charcot.) "is legs or arms. But he has lost the power of 

 involuntary muscular combination, which is es- 

 sential for ordinary locomotion. For this reason the affection is called 

 "ataxia," and not paralysis. 



In this disease the only parts of the nervous system invariably 

 affected are the posterior columns of the spinal cord. They are the 

 seat of a structural degeneration termed " sclerosis," in which the con- 

 nective tissue is increased in quantity and density, while the nerve 

 fibres are altered and atrophied. According to Brown-Sequard, if 



