HEAD AND NECK OF THE HORSE 



191 



and left bauds, and is connected with the corpus callosum and the 

 septum pellucidum. It is triangular in outline, and is related ventrally 

 to the third ventricle and thalami, the choroid tela intervening. At 

 each end of the body the right and left constituent parts of the fornix 

 separate. At the anterior end the amount of divergence is not very 

 great and results in the production of the columnce fornicis, two 

 rounded cords that curve ventralwards, in front of the interventricular 

 foramen and behind the anterior commissure, to end at the base of the 

 brain in the prominent mammillary body. A few fibres of the columns 

 pass in front of the anterior commissure to end in the medial strise of 

 the olfactory lobe ; and some run backwards as the strise medullares 

 attached to the thalami. 



From the posterior end of the body of the fornix arise the two 

 widely-diverging crura fornicis. These are at first connected with the 



Fig. 89 — Key-outline of the brain to indicate the -plane of the sections 

 illustrated in subsequent figures. 



corpus callosum ; but each soon forms the white hem — Jimhrict ^ hipijo- 

 camiyi — that is adherent to the hippocampus of its own side, and, as 

 such, is continued down the inferior cornu of the lateral ventricle. Some 

 fibres of each crus are spread out as the white layer (alveus) on the 

 surface of the hippocampus. 



Dissection. — Cut across the fornix about the point where the crura 

 are leaving the body. Then, with the utmost care, remove the isolated 

 posterior part of the cerebral hemisphere, that is, the hippocampus and 

 the adjacent part of the wall of the inferior cornu of the ventricle. 



This is a convenient time to revise the examination of the hippo- 

 campal fissure and determine its associations. Between the fissure and 

 the fimbria hippocampi there is a narrow and somewhat corrugated strip, 

 i\iQ fascia dentata Jiippocampi. 



The removal of the posterior part of the hemisphere has revealed the 

 choroid tela of the third ventricle. 



The choroid tela of the third ventricle (tela chorioidea ventriculi 

 ^ Fimbne [L.], the extremity of anything, a border, edge, fringe. 



