338 LABORATORY MANUAL OF HUMAN ANATOMY 



Hypothalamus (O. T. Subthalamic Region). 

 Note that it is subdivisible into 



(a) Mammillary part of hypothalamus (pars mammillaris hypothalami). 



This belongs to the diencephalon and includes 

 (aa) Mammillary body (corpus mammillare) on each side. 



(b) Optic part of hypothalamus (pars optica hypothalami). This belongs 



to the telencephalon and includes 



(ba) Tuber cinereum (tuber cinereum) (" ash-like tuber" ). 



(bb) Infundibulum (infundibulum) ("funnel"). 



(be) Hypophysis (0. T. pituitary body). Cut through this in the 

 median sagittal plane and note 



(bca) Anterior lobe (lobus anterior), from the hypoblast. 



(bcb) Posterior lobe (lobus posterior), from the epiblast. 



(bd) Optic tract (tractus opticus). 



(bda) Medial root (radix medialis). 

 .(bdb) Lateral root (radix lateralis). 



(be) Optic chiasm (chiasma opticum). 



(bf) Terminal lamina (lamina terminalis). 



Corpus Callosum (Great Transverse Commissure of Cerebrum). 



With a sharp, thin, broad brain-knife, the upper part of the 

 right hemisphere should be sliced off at the level of the sulcus 

 cinguli. The cortical substance (substantia corticalis) and semi- 

 oval centre (centrum semiovale) of the hemisphere are thus 

 beautifully displayed. Cut transversely through the middle of 

 the gyrus cinguli; insinuate the fingers cautiously beneath it 

 and tear it away lateralward, observing how the fibres of the 

 corpus callosum enter the hemisphere. These fibres constitute 

 the radiation of the corpus callosum (radiatio corporis callosi). 

 This radiation is subdivisible into a frontal part (pars front alls] 

 (0. T. forceps minor), a parietal part (pars parietalis), a tem- 

 poral part (pars temporalis), an occipital part (pars occipi- 

 talis) (0. T. forceps major), and the " tapestry" (tapetum), the 

 layer of fibres coming from the truncus corporis callosi and 

 curving lateralward and downward over the inferior and poste- 

 rior horns of the lateral ventricle. In the gyrus cinguli, just 

 torn away, note on the deep surface a very definite bundle of 

 sagittally directed arcuate fibres, easily lifted out of the bed in 

 which it lies. This is the cingulum or "girdle," an association 

 bundle pertaining to the rhinencephalon. (See full description 

 in Barker's Nervous System, p. 1061.) Examine 



(a) Splenium ("bandage") of corpus callosum (splenium corporis cal- 



losi). 



(b) Trunk of corpus callosum (truncus corporis callosi) (0. T. body). 



(c) Knee of corpus callosum (genu corporis callosi). 



