200 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



tion known as hemiplegia. The facts given above regarding the 

 origin and course of the pyramidal system of fibers explain the 

 crossed character of the paralysis quite satisfactorily. The 

 schema thus presented to us is, however, not entirely without ex- 

 ception. In cases of hemiplegia in which the whole motor area of 

 one side is included it is known that the paralysis on the other side 

 does not involve all the muscles, and, in the second place, it is 

 said that there is some muscular weakness on the same side. The 

 paralysis in hemiplegia affects but little, if at all, those muscles 

 of the trunk which are accustomed to act in unison, the muscles 

 of inspiration, for instance, the diaphragm, abdominal and inter- 

 costal muscles, and the muscles of the larynx. It would appear 

 that these muscles are bilaterally represented in the cortex; so 

 that if one side of the brain is intact the muscles of both sides are 

 still under voluntary control; or, possibly, these more or less auto- 

 matic movements may be under the control of subcortical motor 

 mechanisms such as are referred to in the preceding paragraph. 



Are the Motor Areas Only Motor in Function? The great 

 number of nerve cells in the cortex in addition to the large 

 pyramidal cells that give origin to the fibers of the pyramidal 

 system makes it possible histologically that other functions may 

 be mediated in the same region. This possibility has been kept 

 in view since the early experiments of Munk, in which he showed 

 that lesions in the Rolandic region are followed by disturbances 

 in what are designated as the body sensations, that is, in 

 muscular and cutaneous sensibility, but especially the former. 

 It was suggested, therefore, at one time that one and the same 

 spot in the cortex might serve as the origin of the motor impulses 

 to a given muscle and as the cortical termination of the sensory 

 impulses coming from the same muscle, the reaction in con- 

 sciousness, the muscular sensations, being mediated perhaps 

 through cells other than those giving rise to the pyramidal fibers. 

 Recent physiological and clinical work has, however, not tended 

 to support this view. The motor areas appear to be confined 

 to the region in front of the central sulcus of Rolando, while the 

 cortical area, in which the afferent fibers mediating body sensibility 

 (muscular-cutaneous) make their final termination extends back of 

 this sulcus in the posterior central convolution. Whether, 

 on the other hand, the sense areas for the body (cutaneous and 

 muscular) extend forward into the cortex of the frontal lobe is 

 not clearly shown by experimental or clinical evidence. Flechsig, 

 from his studies upon the time of myelinization of the afferent 

 fibers in the embryo brain, concludes that this is the case, and 

 that, therefore, the motor and sensory areas overlap for a part 

 at least of their extent (see p. 226 and Fig. 98). On the con- 



