14 



Second Skate. 



Examine the arteries and veins described under I., 1 and 2, p. 20, and after re- 

 moval of the alimentary canal and liver as described above, examine — 



E. The nervous system. 



Eemove the roof of the skuU and the upper part of the anterior vertebral plate, so 



as to expose the brain and a portion of the spinal cord, taking care to leave 



uninjured the eye and ear of the left side. 

 J. Note— 



(a) The gelatinous matter contained in the anterior portion of the cranial 



cavity. 



(b) The arachnoid fluid. 



(c) The dura mater lining the cartilaginous walls of the cavity. 



(d) The pia mater enveloping the brain and spinal cord. 



2. Make a sketch (2 nat. size) of the dorsal surface of the brain, etc., indicating — 

 (a) The elongated olfactory nerves. 



(6) The fused cerebral lobes. 



(c) The optic thalami. 



(d) The pineal gland (lying on the optic thalami). 



(e) The rounded optic lobes. 



(/) The elongated cerebellum, its anterior and posterior lobes marked by eleva- 

 tions (gyri) and depressions (sulci). 



(g) The medulla oblongata and the convoluted corpora restiformia which form 

 part of the medulla and lie on each side of the cerebellum. 



(h) The spinal cord which is divided by fissures into a pair of dorsal and a pair 

 of ventral columns. 



(i) The cranial and spinal nerves within the cavity of the skull and vertebral 

 column. 



3. CarefuUy make out the distribution of the cranial nerves : — 



T. The large olfactory nerve springing from the cerebral lobe and passing for- 

 wards to enter the nasal capsule, where it forms a cylindrical band, from 

 which small branches pass to the transverse folds of the nasal mucous 

 membrane. 



II. The optic nerves forming the optic chiasma and passing outwards through 



the optic foramina to enter the eye-balls. 



III. The oculo-motor arising from the crura cerebri and passing outwards and 

 forwards to supply the superior and internal recti muscles of the eye, 

 and then downwards to the inferior rectus and inferior oblique muscles. 



IV. The pathetic arising from the anterior region of the cerebellum and 

 supplying the superior oblique muscle of the eye. 



