THE AQUEDUCT OF SYLVIUS. 773 



side, along which it sends forwards the thin band already described 

 as the pineal stria. 



This body is of a red colour and very vascular. It is not com- structure, 

 posed of nervous substance, but consists of small follicles lined by 

 epithelium, and containing minute granular masses of calcareous 

 matter (brain-sand) : similar concretions are often found on its 

 surface, and adhering to its stalk. 



The AQUEDUCT OF SYLVIUS (iter a tertio ad quartum ventriculum ; Aqueduct of 

 fig. 274) is a narrow passage, about five-eighths of an inch yhius< 

 long, uniting the third and fourth ventricles and passing beneath 



FIG. 282. POSTERIOR VIEW OF THE CONNECTIONS BETWEEN THE CEREBRUM, 

 MEDULLA OBLOXGATA AND CEREBELLUM. 



1. Superior : 2, Middle ; and 3, 

 Inferior peduncle of the cerebellum. 



4. Fillet. 



5. Funiculus gracilis. 



6. Tegmentum passing into the 



optic tbalamus. 



7. Lamina quadrigemiua. 



8. Optic tbalamus. 



9. Caudate nucleus. 

 10. Corpus callosum. 



the quadrigeminal bodies and over the united tegmenta of the 

 crura cerebri. It is lined by ependyma, external to which is a 

 layer of grey matter continuous with that of the floor of the two 

 cavities. 



FIBRES OF THE CEREBRUM. In the cerebral hemispneres three Three sets 



,., ,...,,. ,. - of fibres in 



systems of fibres are distinguished, viz., ascending, transverse, and cerebral 

 longitudinal. The ascending are derived in large part from the hemis P nere - 

 spinal cord and the lower portions of the encephalon ; the transverse 

 and longitudinal connect together parts of the cerebrum. 



Ascending or peduncular fibres (fig. 282). The longitudinal fibres Ascending 

 entering the midbrain from the pons are collected into two sets, fi 



