208 A MANUAL OF ANATOMY. 



I 

 ally becomes thinner and is termed the rostrum, where it 



passes backward into the lamina cinerea. The part of the 

 corpus callosum between the genu and splenium is the body, 

 and is thinner than those parts. 



There is a small extension of the corpus callosum 

 folded beneath the splenium, called the reduplicated fold of 

 the corpus callosum. Fig. 39. 



The corpus callosum has a bow-shape on transverse 

 section. The concave extremities of the bow arch over 

 the lateral ventricles (whose roofs they form), and the 

 central depressed portion is the portion of the corpus cal- 

 losum which is seen on separating the hemispheres. 



To the under surface of the corpus callosum is found 

 attached (anteriorly) the septum lucidum and (posteriorly) 

 the fornix. Figs. 41 to 48 inclusive. 



Remember that these three structures are all de- 

 veloped from the foetal lamina terminalis. Page 173. 

 Diag. 1 6. 



The anterior part of the corpus callosum covers in the 

 anterior horn and body of the lateral ventricle, while the 

 posterior part (the tapetum) forms, in a like manner, the 

 covering for the descending and posterior horns of the 

 same ventricle. 



The bundles of fibres which radiate to the frontal lobe 

 from the genu are called the forceps minor, while the bun- 

 dles of fibres which pass from the splenium and the redu- 

 plicated fold of the corpus callosum radiate to the occipital 

 lobe and constitute the forceps major. 



As stated, the corpus callosum is made up of transverse 

 fibres, with the exception of a few thin bundles of fibres 

 which extend from the anterior part of the base of the brain 

 to the forceps major, and use the corpus callosum as a 

 bridge for their course. Fig. 30. 



