Chap. 27/f Plexus Choroides. zjt 



cerebrum. To this fubftance the feptum lucidum is 

 connected. At the pofterior part of the fornix are two 

 other crura, which unite with two medullary protu- 

 berances called pedes hippocampi. Under the fornix, 

 and immediately behind its anterior crura, there is a 

 hole by which the two anterior ventricles communicate. 

 In examining the fubftance of the cerebrum, the deeper 

 we go towards the bafis of the cranium, we find that the 

 medullary part becomes the broader. 



The plexus choroides is a very fine vafcular texture, 

 confiding of a great number of arterial and venal ra- 

 mifications, fpread over the lateral or anterior ventri- 

 cles. When we have removed this plexus, we difcover 

 feveral protuberances included in thefe cavities. Thefe 

 are the corpora flriata, the thalami nervorum optico- 

 xum, and the nates and tefles. 



The corpora ftriata are two curved oblong eminences, 

 which extend along the anterior part of the lateral ven- 

 tricles. They are called ftriata or ilriped, becauie in. 

 cutting them we meet with a number of white and ' 

 afh coloured lines alternately difpofed. Thefe two 

 eminences are of a greyifh colour on the furface, and 

 larger before than behind, where they are narrow and 

 bent. They may be confidered as forming the convex 

 bafes of the ventricles. 



The thalami nervorum opticorum are externally 

 white, but alfo contain both cortical and medullary 

 fubftance, and derive their name from being the chief 

 fource of the optic nerves. They are two eminences 

 placed near each other, between the pofterior portions 

 or extremities of the corpora ftriata. They are clofely 

 united, and at their convex part form one body. Im- 

 mediately under the union of the thalami nervorum, 

 opticorum lies a cavity^ called the third ventricle of tke 

 cerebrum. This cavity communicates at its upper and 



fore 



