256 THE ANATOMY OF THE HOESE. 



Striatum ; behind, another body of about the same size, but white on its 

 surface — the hippocampus ; between the corpus striatum and the 

 hippocampus, a groove, in which there lies a red granular cord — the 

 choroid plexus. Where the hippocampus bounds this groove it is 

 margined by a wliite band — the tcenia hippocamjn ; and if the choroid 

 plexus be pulled gently backwards another white band will be seen to 

 margin the corpus striatum where it bounds tlie groove — this is the 

 tcenia semicircidaris. ^ 



The anterior cornu is occupied by the base of the corpus striatum. 

 It curves downwards and forwards into the anterior part of the 

 hemisphere, where it communicates with the cavity of the olfactory bulb. 



The descending cornu contains the prolongations of the hippocampus 

 and its tfenia. It passes at first backwards and outwards, and then 

 curves downwards, forwards, and inwards, terminating at the base of the 

 hemisphere in the uncinate convolution. The ventricles are lined by a 

 ciliated epithelium, which is continuous through the foramen of Monro 

 with the lining of the .3rd ventricle. 



The Septum Ldoidum is a thin, translucent partition between the two 

 lateral ventricles. It is broadest in front, where it is attached to the 

 rostrum, or reflected part of the corpus callosum. Its upper edge 

 is attached to the corpus callosum, and its lower edge to the fornix ; 

 and posteriorly these edges meet at an acute angle. The septum 

 consists of white matter in its centre, with a layer of grey matter 

 on eaoii side. In man it contains a small isolated cavity — the 5th 

 ventricle. 



The Fornix, or arch, is a mesially placed white band consisting of a 

 central part, or body, and two pairs of processes or pillars. The body 

 is flattened above and below, and broadest behind. Its upper face is 

 adherent posteriorly to the corpus callosum, but in front it dips down 

 and leaves beneath the forepart of the corpus callosum a space occupied 

 by the septum lucidum. The under surface of the body rests on the 

 velum interpositum, and at its anterior extremity arches over the 

 foramen of Monro. ( The anterior pillars of the fornix are two white 

 cords which descend in front of the foramen of Monro, being separated 

 by a slight interval. Eeaching the base of the brain, they turn on 

 themselves, forming thus the corpus albicans, and they then enter the 

 optic thalamus. The posterim^ pillars are broader and flatter, and not 

 so well defined. Each in part bestows its substance on the surface of 

 the hippocampus, and in part it descends along the anterior edge of 

 that body as the tcenia hippocampi, or corpus fimhriatum. 



1 The optic thalamus and taenia semiciroularis are generally enumerated among the objects 

 visible in the body of the lateral ventricle. In the brain of the horse, however, the choroid 

 lilexus completely conceals from view the optic thalamus, and in most cases also the ta;nia 

 semiciroularis. 



