xi PRACTICAL DIRECTIONS 555 



parietal, and temporal lobes) by gently separating them, 

 the corpus callosum will be seen, and just behind them the 

 pineal body; the diencephalon is covered above by the 

 hemispheres, below it is visible and is continued into the 

 infundibulum; the pituitary body is nearly always left 

 behind in the brain-case when the brain is removed, and a 

 small aperture is seen in the centre of the infundibulum 

 where it was attached ; the optic chiasma. 



4. The origins of the nerves from the brain ; these cannot, 

 of course, be plainly made out unless the nerves have been 

 carefully cut through when removing the brain. Compare 

 pp. 163-166, and note in addition the spinal accessory and 

 hypoglossal. 



Sketch the brain from above and from below. 



II. Carefully remove successive slices from one of the 

 hemispheres nearly parallel to its upper surface, down to 

 the level of the corpus callosum, noting the fibres of the 

 latter and the relations of the grey and white matter in the 

 hemispheres. Cut through the corpus callosum longitudin- 

 ally, near the middle line, and remove sufficient of the 

 hemisphere already dissected to expose the lateral ventricle 

 and its extensions into the frontal, parietal, and temporal 

 lobes. Note : 



1. The hippocampus, the corpus striatum, the choroid 

 plexus, and the septum lucidum (p. 531). Then cut away 

 the rest of the same hemisphere so as to expose 



2. a, The diencephalon and its two lateral halves (optic 

 thalami) between which the third ventricle is enclosed ; from 

 its roof the stalk of the pineal body arises ; b, the two pairs 

 of optic lobes. Cut away the lateral half of the cerebellum 

 of the same side, and note 



3. The valve of Vieussens, the fourth ventricle, and the 

 tree-like appearance (arbor vitce] of the cerebellum in section. 



III. Now reduce the whole brain to a longitudinal vertical 

 section (Fig. 142), cutting it through with a sharp knife very 

 slightly to that side of the median line which you have 

 already dissected, so as to expose the median ventricles in 

 section. Make out, on the uninjured half, the relations of 

 the third ventricle, iter, fourth ventricle, foramen of Monro, 

 infundibulum, optic chiasma, corpus callosum and fornix, 

 lamina terminalis, anterior, middle, and posterior commissure, 

 crura cerebri, valve of Vieussens, pons Varolii, &c. Sketch. 



IV. A series of thick transverse sections should be made 

 through another thoroughly hardened brain, and the rela- 

 tions of the Darts already seen by dissection examined. 



M M 2 



