182 CLINICAL APPLIED ANATOMY. 



the exit of fluid from the third and lateral ventricles may be 

 obstructed by the pressure these tumours exert on the iter 

 or behind it. 



The sagittally directed falx cerebri, although firmly fixed at 

 its two extremities and above, has only a slight influence in 

 restricting pressure signs to one or other hemisphere of the 

 brain. 



Tumours are occasionally found to compress certain large 

 arterial trunks at the base of the brain, and then areas of 

 softening may occur in addition to the new growths. 



Tumours which interfere with the outlets of the ventricles 

 produce a peculiar train of symptoms, amongst which are 

 apathy, drowsiness, headache, and coma. Such symptoms may 

 accompany tumours of the corpus callosum or of the structures 

 forming the boundaries of the third ventricle or tumours 

 beneath the tentorium. 



Of the general symptoms of cerebral tumour, headache is of 

 some localising value if accompanied by local tenderness, and 

 this is most likely to occur if the tumour is on the convexity of 

 the brain. Speaking generally, frontal headache accompanies 

 tumours of the frontal lobes ; occipital headache tumours of the 

 occipital lobes ; and similar headache extending into the nape of 

 the neck, and often accompanied by^ retraction of the head, 

 tumours of the subtentorial region. With a cerebellar tumour 

 headache may occur in the opposite frontal region ; the crossed 

 connexion of each cerebellar hemisphere with the frontal lobe of 

 the opposite side is held by some to account for this anomaly. 



Vomiting, another general symptom, is most severe and most 

 common with tumours below the tentorium, presumably on 

 account of the proximity of the vagus centre. 



The fact that the motor tract traverses the brain from medulla 

 to cortex explains how tumours in widely different situations can 

 produce motor paralysis. The fan-like radiation *of the corona 

 radiata from the genu and anterior part of the posterior limb of 

 the internal capsule to the cortex of the Kolandic region allows 

 cortical and subcortical tumours to cause paralysis, which may 



