370 CORNUA OF THE LATERAL VENTRICLES. 



and terminating by a point in the anterior lobe of the brain, at a 

 short distance only from its surface. 



The Posterior cornu or digital cavity curves inwards, as it extends 

 into the posterior lobe of the brain, and likewise terminates near to 

 the surface. An elevation corresponding with a deep sulcus between 

 two convolutions projects into the area of this cornu, and is called 

 the hippocampus minor. 



The Middle or descending cornu, in descending into the middle 

 lobe of the brain, forms a very considerable curve, and alters its 

 direction several times as it proceeds. Hence it is described as 

 passing backwards and outwards and downwards, and then turning 

 forwards and inwards. This complex expression of a very simple 

 curve has given birth to a symbol formed by the primary letters of 

 these various terms ; and by means of this the student recollects 

 with ease the course of the cornu, BODFI. It is the largest of the 

 three cornua. 



The middle cornu should now be laid open, by inserting the little 

 finger into its cavity, and making it serve as a director for the 

 scalpel in cutting away the side of the hemisphere, so as to expose 

 it completely. 



Its Superior boundary is formed by the under surface of the thala- 

 mus opticus, upon which are the two projections called corpus 

 geniculatum internum and externum ; and the inferior wall by the 

 various parts which are often spoken of as the contents of the middle 

 eornu : these are the 



Hippocampus major, 



Pes hippocampi, 



Pes accessorius, 



Corpus fimbriatum, 



Choroid plexus, 



Fascia dentata, 



Transverse fissure. 



The Hippocampus major or cornu dmmonis, so called from its re- 

 semblance to a ram's horn, the famous crest of Jupiter Ammon, is a 

 considerable projection from the inferior wall, and extends the whole 

 length of the middle cornu. Its extremity is likened to the club-foot 

 of some animal, from its presenting a number of knuckle-like eleva- 

 tions upon the surface : hence it is named pes hippocampi. The 

 hippocampus major is the termination of the lateral edge of the 

 hemisphere, which in this situation is very much attenuated and 

 rolled upon itself. If it be cut across, the section will be seen to re- 

 semble the extremity of a convoluted scroll, consisting of alternate 

 layers of white arid gray substance. The hippocampus major is 

 continuous superiorly with the fornix and corpus callosum. 



The Pes accessorius is a swelling somewhat resembling the hippo- 

 campus major, but smaller in size ; it is situated on the outer wall 

 of the cornu, and is frequently absent. 



The Corpus jimbriatum is the narrow white band which is pro- 



