xi PRACTICAL DIRECTIONS 555 



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 longitudinally, 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 thalamt) 

 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, tier, fourth ventricle, foramen 

 of Monro, infundibulum, optic chiasma, corpus callosum and fornix, 

 lamina terminalis, anterior, middle, and posterior commissure, crtira 

 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 relations of the parts 

 already seen by dissection examined. 



H. The Eye, 



On account of its larger size, it is better to substitute the eye of an ox 

 or sheep which can be- obtained fresh from a butcher for that of the 

 rabbit. Two specimens should be obtained, and the fat, muscles, 

 and any portions of the eyelids remaining attached cleared away. 

 Dissect under water. 



I. After noting the conjunctiva, cornea, sclerotic, optic nerve, iris, and 

 piipil, insert the scissors into the margin of the cornea and cut round 

 and remove it, so as to expose the aqueous chamber, noting the aqueous 

 humour, as well as the iris, lens, and ptipil (compare Fig. 57). 

 Sketch. 



