ST&UCTU&E OF THE ENCEPHALON. 



203 



In the developed brain, the fissures into the lateral ven- 

 tricles, converted by the adhesion of the lateral halves of 

 the fornix into one trans- 

 verse fissure as pointed out, 

 extend round the crura 

 cerebri to the extremity of 

 the middle lobe of the 

 brain at the inner end 

 of the fissure of Sylvius; 

 and the extensions of the 

 lateral ventricles, into 

 which they open, are called | 

 the descending cornua; the 

 margin of the fissure in 

 each descending cornu is 

 bounded by a slender pro- 

 longation of the fornix, 

 called tcenia hippocampi, 

 because it lies beside a 

 convexity of the floor of Fig. 107. THE LATERAL VENTRICLES. 

 the cornu, the hippocampus a, Posterior border of corpus callo- 



sum; 0, front of corpus callosum, 

 and below it fifth ventricle, bounded 

 by the layers of the septum lucidum; 

 c, fornix, and, beyond it, the cho- 

 roid plexus ; d, corpus striatuin, 

 and, between it and the fornix, a 

 portion of the optic thalamus ; e, 

 section of corpus striatum; /, de- 

 scending cornu of lateral ventricle, 

 with hippocampus major in its 

 floor, and taenia hippocampi in 

 front; g, hippocampus minor in the 

 floor of the posterior cornu. 



major: the posterior and 

 anterior cornua being blind 

 pouches in the correspond- 

 ing lobes. In front, the 

 fornix dips down in the 

 form of a couple of pillars 

 in front of the optic 

 thalami; and these pillars, 

 after dipping to the base 

 of the brain, and forming 



the corpora albicantia, twist 



upwards, and enter, each one, the optic thalamus of its own 



side. The fornix is thus a band of junction between the 



back parts of each hemisphere and the corresponding optic 



thalamus. 



In leaving this difficult subject, it is necessary to point the 

 student's attention to one point which appears to have escaped the 

 attention of anatomists, but which, to me at least, is pretty obvious 

 from considerations alluded to in the preceding description, namely, 



