7 o8 HEMIPLEGIA. 



but slightly affected, or not at all, as their centre is elsewhere. There may be 

 alterations of sensibility and of the reflexes.] 



[Couduction through the whole of the pyramidal fibres coming from one hemisphere may be 

 interrupted, and yet all the muscles on the opposite side of the body are not paralysed. The 

 muscles wfiich are comparatively unaffected are those associated in their action with the muscles 

 of the opposite side, aj., the respiratory muscles. Broadbent assumes that such muscles have 

 a bilateral representation in the motor areas. Suppose in rig. 491, B, B', to represent the cerebral 

 cortex ; M, M, motor centres in it ; N, N', nerve nuclei in the spinal cord or medulla oblongata ; 

 P, P', the pyramidal tracts passing to spinal nuclei N, K'; m, m', nerves proceeding from the last. 

 .4,5, represent different lesions. In the case of muscles on opposite sides of the body, 

 which act independently, e.g., those of the hand, this is all the mechanism, but in bilaterally 

 associated muscles there is another mechanism, viz., commissural fibres between the nerve 

 nuclei, the one c conducting from right to left, and c' from left to right. When there is an 

 injury at 1 or 3, impulses can still pass from the uninjured side M to W and through c' to the 

 muscles m, m'. In this way, both muscles receive motor impulses from one hemisphere (Iioss).] 



Conjugate deviation of the eyes, with rotation of the head, is frequently present in the early 

 period of hemiplegia, although it usually disappears. When a person turns his head to one side, 

 there is an associated movement of certain of the ocular muscles with those of the neck. The 

 head and eyes are usually turned to the side of the lesion ; this is termed " conjugate deviation," 

 so that the power of voluntarily moving the eyes and head to the paralysed side is temporarily 

 lost The unopposed muscles rotate the head and eyes to the sound side. If the lesion be in 

 the posterior part of the pons, the deviation is to the paralysed side (Pre'rost). 



[Subsequent Effects. If there be a hemorrhage, say into these motor regions, or from the 

 lenticulo-striate artery, so as to compress the pyramidal fibres in the knee and anterior two- 

 thirds of the posterior segment of the internal capsule, then there is usually tonic or persistent 

 contraction of the muscles affected. These tonic spasms may accompany the haemorrhage, or 

 come on a few days after it, ami set up the condition of early rigidity. The contraction or 

 spasm if any accompanying the haemorrhage, is due to direct irritation of the pyramidal 

 fibres, while that which comes on a few days later, and usually lasts a few weeks, is also due 

 to irritation of these fibres, probably produced by inflammatory action in and around the seat 

 of the lesion. The affected limb is stiff and resists passive movement. After a few weeks, late 

 rigidity sets in and is persistent, and it is characterised by structural changes in the pyramidal 

 paths which lead to other results. There is secondary descending degeneration in the pyramidal 

 tracts, which causes "contracture" in the paralysed limbs, while at the same time, the deep 

 or tendinous and periosteal reflexes (ankle-clonus, rectus-clonus, and the deep reflexes of the 

 arm-tendons, are exaggerated). The spastic rigidity is usually more marked in the arm than in 

 the leg, and it generally affects the flexors more than the extensors, so that the upper arm is 

 drawn close to the trunk, the elbow, arm, and fingers flexed; in the leg, the extensors of the 

 leg overcome the peronei. Hitzig has pointed out that the contracture is less during sleep, and 

 after rest. The muscles at first can be stretched by sustained pressure, but after months or 

 years, structural changes occur in the muscles, ligaments, and tendons, and the limbs assume a 

 permanent and characteristic attitude.] 



In hemiplegic persons, the power of the uuparalysed side is sometimes diminished, which is 

 not sufficiently explained by the fact that some bundles of the pyramidal tracts remain on the 

 tanu side Brown SSquard, Charcot). 



Acquired Movements. Some movements performed by man are learned only after much 

 practice, and are only completely brought under the influence of the will after a time, such as 

 the movements of the hand in learning a trade. Such movements are reacquired only very 

 slowly, or not at all, after injury to the motor areas in which they are represented. Those 

 movements, however, which the body performs without previous training, such as the associated 

 movements of the eyeballs, the face, and some of those of the legs, are rapidly recovered after 

 such an injury, or they suffer but little, if at all. Thus, the facial muscles seem never to be so 

 completely paralysed after a lesion of the facial cortical centre, as in affections of the trunk of 

 the facial nerve; the eye especially can be closed. Sucking movements have been observed in 

 heinicephalous fatuses. 



Degeneration of the Pyramidal Tracts. After destruction of the cortical 

 motor areas, descending degeneration of the cortico-motor paths, or "pyramidal 

 tracts," takes place ( 365). Degenerative changes have been found to occur within 

 the white matter under the cortex in the anterior two-thirds of the posterior segment 

 of the internal capsule, [in the middle third of the crusta (figs. 492, * 493, L], pons, 

 in the anterior pyramids of the medulla oblongata (fig. 492), and thence they have 

 been traced into the pyramidal paths (direct and crossed) of the spinal cord (Charcot, 

 Singer). It is evident that lesions of these tracts at any part of their course must 



