542 



THE NERVOUS SYSTEM. 



with the lateral ventricles by two small apertures, called the foramina inter 

 ventricularia. 



The cerebrum is connected with the parts in the posterior cranial fossa (pons 

 cerebellum, and medulla oblongata) by a narrow stalk called the mesencephalon o: 

 mid-brain. The mid-brain is built up of (1) the pedunculi cerebri, passing from th< 

 pons to the cerebrum ; (2) the corpora quadrigemina, forming its dorsal part ; am 

 (3) the brachia conjunctiva (O.T. superior cerebellar peduncles), proceeding from th< 

 cerebellum to the cerebrum. It is tunnelled by a narrow passage, the aquseductu 

 cerebri, which extends between the fourth and third ventricles. 



In a view of the intact brain the greater part of the mesencephalon am 

 diencephalon is hidden by the cerebral hemispheres ; but a precise idea will b 

 obtained of the inter-relationships of the various parts of the brain, if we stud; 



Epithelial roof of third ventricle 

 Lamina co mm is s u re I^SS&SJSS"* ^ "* ">> 



merit nf the enithfilial rnof nf thirrl ventricle > Ttpnia thalami 



men 



ia commissurte hippocampi at the attach- 

 nt of the epithelial roof of third ventricle 



Corpus callosum 

 Columna fornicis 

 Septum pellucidum 

 AnterioFcommissuie^- 

 Rostrum corporis callosi^^^""'^ \ \ 

 Germ corporis callosi 



! Tsenia thalami 

 i \ Vena cerebri interna 

 | i \ Plexus chorioideus ventriculi tertii 

 \ Commissura habenularum 

 1 { Recessus suprapinealis 

 J__ ; ; Pineal body 



~""|>^Splenium corporis callos 

 ! / 7^ Lamina quadrigemina 

 ! ; ?-^A Anuaeductus cerebri 



Vena magna cerebri 



Velum medullare anterius 

 / Lobulus centralis cerebelli 

 Culmen cerebelli 



Fissura prima 



Fourth ventricle 

 Attachment 

 epithelial ro 



Paraterminal body 

 Lamina terminalis 



Infundibulum 



Hypophysis-- 



intermedia . . 

 Sulcus hypothalamicus / 



Corpus mamillare / j / 



Oculomotor nerve / ,' 



Posterior commissure / 



Tegmentum (mesencephali) /' 



Pons 



Pyramid -'' 

 Fourth ventricle'' 



Central 

 Decussation of pyramid' 



Pyram. 



Uvula 

 Tonsilla 



Edge of apertura medialit 

 Chorioid plexus of fourth v< ide 

 (the pointing line passes th .'b 

 the apertura medialis) 



FIG. 477. THE PARTS OF THE BRAIN CUT THROUGH IN A MEDIAN SAGITTAL SECTION. 

 The side walls of the ventricular cavities are also shown . 



the relationship of these structures to the series of cavities in the interior of t 

 brain as they are displayed in a median sagittal section (Fig. 477). 



The central canal which tunnels the spinal medulla is seen to extend into t 

 medulla oblongata for a short distance ; then it expands into the irregular cavity 

 the fourth ventricle, the floor (anterior wall) of which is formed partly by t 

 medulla oblongata and partly by its continuation upwards, the pars dorsalis pont 

 Behind the fourth ventricle lies the cerebellum, but it forms only a small part of t 

 roof (tegmen). The roof consists mainly of the velum medullare anterius abo 

 and the thin epithelial lamina (lamina chorioidea epithelialis) below. 



The fourth ventricle is continued upwards into the aquseductus cerebri, whi 

 tunnels the mesencephalon, of which the thick mass of the tegmentum is placed 

 front of it and the lamina quadrigemina behind. 



The aqueduct opens in front into the third ventricle, the major portion 

 each side wall of which is formed by the thalamus. Near the antero-super ' 



