Locomotor Ataxy 223 



which are supplied by the cross fibres, and those on the right which 

 are supplied by the fibres of the direct tract, Tiirck's column. Thus 

 it is that a lesion on one side of the brain may be followed by paralysis 

 and contracture of muscles on both sides of the body. The degeneration 

 descending in the pyramidal tracts (as after hemorrhage in the motor 

 area of the brain), the muscles associated with them are not only 

 paralysed but also contractured, and if the disease extends into the 

 anterior horn of the grey crescent they also begin to atrophy. 



The postero-external or BurdacKs column consists to a large extent 

 of fibres of the posterior roots of the nerves and of fibres that convey 

 tactile impressions to the brain. Under the guidance of the brain, 

 these fibres co-ordinate muscular movements. Thus, when the postero- 

 external columns are diseased the muscles are not paralysed, but they 

 act tumultuously, without co-ordination. There are also the peripheral 

 pains, impaired sensation, and the other characteristics of locomotor 

 ataxy. Later, as the sclerosis extends to the anterior cornua, mus- 

 cular weakness appears, with atrophy (p. 218). But when the anterior 

 cornua remain sound, whilst the posterior and lateral columns are 

 diseased, the nutrition of the muscles continues, though they become 

 weak because of the implication of the crossed pyramidal tract. 

 Thus locomotor ataxy (a, without ; ra^iy, order) is a want of harmony 

 in the working of muscles of locomotion, and is due to fibroid degene- 

 ration (sclerosis : oK\r)pos, hard) beginning in the columns of Burdach 

 and spreading into those of Goll. As the fibrosis is followed by atrophy 

 in the spinal or dorsal cord, the disease also bears the name tabes 

 dorsalis (tabeo, waste away}. Burdach's column being very closely 

 associated with the posterior roots of the spinal nerves conveying 

 sensory impulses and co-ordinating movements the sclerosing irrita- 

 tion of the sensory nerve roots accounts for the characteristic peri- 

 pheral ' lightning-pains ' of locomotor ataxy ; and as the strands are 

 pressed upon by the inflammatory thickening their power of co-ordi- 

 nating diminishes. Normal sensation is gradually lost, and the patient 

 cannot tell when his feet touch the ground. As the disease advances 

 the ataxic man can keep his muscles under nominal control only by 

 watching every step ; he stumbles and falls unless his path is light, and 

 with his eyes shut he cannot keep his balance. As he walks his feet 

 fly out in a meaningless manner, and in time the muscles of his hands 

 and arms become affected. The patella reflex is entirely lost because 

 the sensory impulse fails to reach or to traverse the grey crescent, and 

 erection of the penis, another reflex act, becomes in due course im- 

 possible. (For the state of the pupil, v. p. 59.) 



THE SYMPATHETIC SYSTEM 



The sympathetic system consists of two knotted cords along 

 the front of the vertebral column, which are joined together on the 

 anterior communicating artery (p. 42), and, at the tip of the coccyx, in 



