THE LATERAL VENTRICLES 23 



of the back have been noticed, but the opposite movements 

 have also been observed in similar cases. 



The blood-supply of the cerebellum is derived from the 

 basilar and the two vertebral arteries (p. 120). Cerebellar 

 haemorrhage, though not a common lesion, is of importance 

 owing to the proximity of the fourth ventricle and the im- 

 portant centres in its floor (Fig. 5). The veins of the 

 cerebellum terminate in the transverse (lateral) and other 

 cranial blood-sinuses (p. 114). Septic infection may spread 

 from the tympanic (mastoid) antrum, through the transverse 

 sinus and cerebellar veins, and so give rise to abscess 

 formation. 



THE INTERNAL STRUCTURE OF THE BRAIN 



The Lateral Ventricles of the brain are roofed in by the 

 corpus callosum, which is covered on its inferior surface 

 with ependyma. When the roof of the lateral ventricle is 

 removed, the free surface of the caudate nucleus is exposed 

 (Fig. 13). Its enlarged anterior extremity, or head, forms a 

 prominent elevation in the anterior part of the floor of the 

 ventricle, but, as it is traced backwards, it diminishes rapidly in 

 size ; at the same time, it arches upwards and laterally, so that, 

 in a horizontal transverse section of the brain, the head of the 

 caudate nucleus is cut through in frpnt and the tail behind, 

 but, owing to its upward bend, the body does not appear in 

 the section (Fig. 18). 



The superior surface of the thalamus lies in the floor of the 

 ventricle to the medial side of the body of the caudate 

 nucleus. It is overlapped by the free lateral margin of the 

 tela chorioidea (velum interpositum) (p. 26), which contains the 

 veins of the chorioid plexus. The serum which is transuded 

 from the veins of this plexus through the ependyma into the 

 lateral ventricle constitutes the cerebro-spinal fluid. This fluid 

 circulates through the ventricular system and ultimately drains 

 away into the subarachnoid space (p. 1 1 1). Excessive secretion 



