X PRACTICAL DIRECTIONS 537 



3. The aperture of the Eustachian tube : pass a probe from il into 

 the tympanic ca\ity. 



4. The position ol Jacobson's organ, on the \cntral side of the nasal 

 septum ; and after cutting away the latter,'^he ethmo-turbiuals, maxillo- 

 turbinals, and tiaso-turbinah of the other side. 



Sketch the entire longitudinal section. 



IV. Remove the larynx with the anterior part of the trachea. Make 

 a longitudinal vertical section of it, keep one half entire, and from the 

 other dissect away the muscles and mucous membrane so as to see the 

 cartilages clearly. Examine first the cartilages and then the soft parts, 

 noting the relations of the thyroid, •criioid, and arytenoid cartilages, the 

 epiglottis, and the vocal cords. Sketch. 



G. The Brain. 



I. — External characters. Note : — 



1. The medulla oblongata, with its dorsal and ventral fissures and 

 the/tf«y Varolii ; the convoluted cerebellum, consisting of a central lobe 

 and two lateral lobes sxiA flocculi, 



2. The optic lobes, seen on slightly separating the hemispheres and 

 cerebellum ; the crura cerebri. 



3. The olfactory lobes and cerebral hemispheres (frontal, parietal, and 

 temporal lobes) — by gently separating them, the corpus callosum will be 

 seen — and just behind them is the pineal body ; the diencepkalon is 

 covered above by the hemispheres, below it is visible and is continued 

 into the infimdibulum ; 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 longitudinally, near the middle line, and remove sufficient 

 of the hemisphere already dissected to expose the lateral ventricle 



