NERVOUS SYSTEM. VERTEBBATA. 133 



specimen the large size of the cerebellum, its small cavity 

 continuous with the fourth ventricle, and its composition of 

 layers of white and grey matter are also clearly visible. 



D. 167. The brain of a Goose (Anser ferus). The hemispheres 

 have been pressed to either side to show the lamina terminalis 

 and the anterior commissure. This method of treatment 

 has also uncovered the dorsal surface of the thalamen- 

 cephalon, the tectal commissure, and anterior lobe of the 

 cerebellum. The origin of the tractus hippocampo-mesen- 

 cephalicus can be clearly seen upon the surface of the median 

 walls of the hemispheres. 0. C. 1321 A. 



D. 168. The brain of a Goose (Anser ferus) partially divided from 

 above by a median sagittal incision and with the two halves 

 turned aside to show the diverticulum of the fourth ventricle 

 within the cerebellum and the arrangement of the layers 

 of white and grey matter that form the arbor vitse. The 

 outer surface of the left optic lobe has been removed to 

 expose its ventricle, and a bristle has been passed from it 

 into the aqueduct of Sylvius to demonstrate the continuity 

 of the two cavities. The right lateral ventricle has been 

 opened by section of its thin mesial wall. Its extent and 

 continuation into the olfactory bulb are thus shown, as well 

 as the great disproportion in bulk between the corpus 

 striatum and pallium. 0. C. 1321. Hunterian. 



D. 169. The brain of a Duck (Anas boscas) from which the greater 

 part of the left side has been removed. The superficial 

 appearance of the brain is very similar to that of the Goose. 

 In taking away the left hemisphere the anterior commissure 

 has been isolated and kept intact from its termination in the 

 left corpus striatum to its entry into the right hemisphere. 

 The optic tracts and chiasma have also been dissected, 

 showing in the latter the interlacing of six large independent 

 bundles of fibres (three belonging to each optic nerve) as 

 they pass from one side to the other. All the fibres of the 

 optic nerves cross to the opposite side of the brain in the 

 chiasma. The course of the ascending root of the tri- 

 geminal nerve has also been dissected out, and a bristle 



