554 THE RABBIT CHAP. 



cartilaginous nasal septum. Also cut away all the remaining bone on 

 the same side of the middle line, slit up the naso-pharynx, and reduce 

 your dissection to a neat longitudinal section, noting 



2. The cranial cavity r , the roof of which will have been cut away if 

 the brain has been removed. 



3. The aper tit-re of the Eustachian tube : pass a probe from it into 

 the tympanic cavity. 



4. The position of Jacobsotfs organ, on the ventral side of the nasal 

 septum ; and after cutting away the latter, the ethmo-turbinals, maxillo- 

 turbinals, and naso-turbinals of the other side (p. 493, Fig. 135). 



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, cricoid, and arytenoid cartilages, the 

 epiglottis, and the vocal cords (p. 517). Sketch. 



G. The Brain. 



I. External characters. Note (Fig. 141): 



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

 the pons Varolii ; the convoluted cerebellum, consisting of a central lobe 

 and two lateral lobes &x\&flocculi. 



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

 cerebellum ; the crura cerebri. 



3. The oljactory lobes and cerebral hemispheres (frontal, 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 pittiitary 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 hypogiossaL 



Sketch the brain from above and from below. 



II. Carefully remove successive slices from one of the hemispheres 



