CH. L.] HEMIPLEGIA AND MONOPLEGIA 729 



The rougher experiments performed by nature in the shape of 

 diseases of the brain produce corresponding results. 



Some diseases are of the nature of extirpation. 



An instance of this is cerebral haemorrhage. If the haemorrhage 

 is in the region of the internal capsule, it cuts through fibres to the 

 muscles of the whole of the opposite side of the body, as they are 

 all collected together in a narrow compass, and the condition 

 obtained is called Tiemiplegia. The varieties of hemiplegia are 



FIG. 448. Brain of dog, viewed from above. F, frontal fissure, sometimes termed crucial sulcus, 

 corresponding to the fissure of Rolando in man. 6', fissure of Sylvius, around which the four 

 longitudinal convolutions are concentrically arranged; 1, flexion of head on the neck, in the 

 median line ; 2, flexion of head on the neck, with rotation towards the side of the stimulus ; 3, 

 4, flexion and extension of anterior limb; 5, 6, flexion and extension of posterior limb; 7, 8, 9, 

 contraction of orbicularis oculi, and the facial muscles in general. The unshaded part is that 

 exposed by opening the skull. (Dalton.) 



numerous, according as motor or sensory fibres are most affected, 

 and in one variety of hemiplegia, called crossed hemiplegia, the face 

 is paralysed on one side of the body, the limbs on the other ; this 

 is due to injury of the tracts in the bulb, above the crossing of the 

 pyramids. 



If now the haemorrhage occurs on the surface of the brain, a much 

 more limited paralysis, called monoplegia, is the result ; if the arm area 

 is affected, there will be paralysis of the opposite arm ; if the leg 

 area, of the opposite leg ; if a sensory area, there will be loss of the 

 corresponding sense. 



