64 ANATOMY OF A CHELONIAN. 



the conspicuous gray matter in the centre in relatively 

 small amount, but with well-marked cornua and a dis- 

 tinct gray commissure. 



On the dorsal aspect of the cord, note the shallow 

 groove indicating the posterior fissure^ and the furrow 

 on each side of it along which the posterior roots are 

 attached. 



167. Now proceed to the Dissection of the Brain and 

 Cranial Nerves and the Sense Organs connected with them. 

 With a jeweller's saw cut through the soft parts and 

 cranium in a plane parallel to the m.edian antero-pos- 

 terior vertical plane of the head, and passing in front 

 through the outer margin of the right nostril ; carry 

 your incision from above down through the base of the 

 skull, but leave the mandible undivided. The skull 

 will thus be divided into a larger left and a smaller 

 right segment, the former containing the brain, which 

 is exposed on its right side by the section. 



163. On the cut surface of the left portion, beginning 

 in front, note: 



a. The nasal chamber ^ lined by brown mucous 

 membrane, which is folded near the opening 

 of the anterior nostril. 



b. Separated from the nasal cavity by a thin plate 

 of bone is a small part of the median portion 

 of the right orbito-temporal fossa, with a bit of 

 the Hardcriafi gland {which has been divided by 

 the saw) lying in it anteriorly. 



c. Above and internal to this will be found part 

 of the superior oblique 7Jiuscle. 



d. Close to the membranous upper and posterior 



