EFFECTS OF SECTION OF THE CORD. 



649 



the muscles 

 the muscles 



tone, owing to the subsidiary vaso-motor centres in the cord. The remote effects 

 come on much later, and are secondary descending degeneration in the crossed and 

 direct pyramidal tracts and ascending degeneration in the postero-internal columns 

 (fig. 455). According to the seat of the lesion, the functions of the bladder and 

 rectum may be interfered with. Injury to the upper cervical region sometimes 

 causes hyperpyrexia.] 



[Unilateral section results in paralysis of voluntary motion in 

 supplied by nerves given off below the seat of the injury, although 

 do not atrophy, but when secondary descending degeneration 

 occurs they become rigid, and exhibit the ordinary signs of 

 contracture. There is vaso-motor paralysis on the same side, 

 although this passes off below the injury, while the ordinary and 

 muscular sensibility are diminished on both sides (fig. 459). 

 There is bilateral anaesthesia. On the opposite side there is 

 total anaesthesia and analgesia below the lesion, but on the same 

 side in the dorsal region there is a narrow circular anaesthetic 

 zone (fig. 459, b), corresponding to the sensory nerve-fibres 

 destroyed at the level of the section. The sensory nerves 

 decussate shortly after they enter the cord, hence the anaes- 

 thesia on the opposite side, but they do not cross at once, but 

 run obliquely upwards before they enter the grey matter of the 

 opposite side, so that a unilateral section will involve some 

 fibres coming from the same side, and hence the slightly dimin- 

 ished sensibility in a circular area on the same side. There is 

 a narrow hyperaesthetic area on the same side as the lesion, at 

 the upper limit of the paralysed cutaneous area (fig. 459, c), due 

 perhaps to stimulation of the cut ends of the sensory fibres on 

 that side. In man there is hyperaesthesia (to touch, tickling, 

 pain, heat, and cold) on the parts below the lesion on the same 

 side, but the cause of this is not known. The remote effects 

 are due to the usual descending and ascending degeneration 

 which set in.] 



[In monkeys, after hemi-section of the cord in the dorsal region, 

 there is paralysis of voluntary motion and retention of sensibility with 

 vaso-motor paralysis of the same side, and retention of voluntary motion 

 with anaesthesia and analgesia on the opposite side. The existence of 

 hyperaesthesia on the side of the lesion is not certain in these animals, 

 but there is no doubt of it in man. Ferrier also finds (in opposition to 

 Brown-Sequard) that the muscular sense is paralysed as well as all other forms of sensibility, on 

 the side opposite to the lesion, but unimpaired on the side of the lesion. The muscular sense, 

 in fact, is entirely separable from the motor innervation of muscle (Ferrier). The power of 

 emptying the bladder and rectum was not affected.] 



Fig. 459. 

 Diagrammatic repre- 

 sentation of a lesion 

 of the left half of the 

 spinal cord in the 

 dorsal region. (a) 

 oblique lines, motor 

 and vaso-motor para- 

 lysis ; (b, d), com- 

 plete anaesthesia ; (a, 

 c), hyperaesthesia of 

 the skin. 



The Brain. 



365. GENERAL SCHEMA OF THE BRAIN. In an organ so complicated in its structure 

 as the brain, it is necessary to have a general view of the chief arrangements of its individual 

 parts. Meynert gave a plan of the general arrangement of this organ, and although this plan 

 may not be quite correct, still it is useful in the study of brain function. The weight of the 

 brain is in man about 1358 grammes, and in woman 1220 grammes (Bischqff). 



[A special layer of grey matter of the cerebrum is placed externally and spread as a thin 

 coating over the white matter or centrum ovale which lies'internally, and consists of nerve- 

 fibres or the white matter. That part lying in each hemisphere is the centrum semi-ovale. The 

 grey matter is folded into gyri or convolutions separated from each other by fissures or sulci. 

 Some of the latter are very marked, and serve to separate adjacent lobes, while the lobes 

 themselves are further subdivided by sulci into convolutions. For a description of the lobes 

 see 375. Some masses of grey matter are disposed at the base of the brain, forming the 



