COMPARATIVE ANATOMY TJ 



supply part of the lateral line system, gill region, oesophagus, 

 stomach, and other viscera. It is both motor and sensory in 

 function. 



Brain of the Shark — Ventral Surface 



After demonstrating your dissection to the instructor, cut 

 the cranial nerves and remove the brain from the cranium. 

 Work carefully so as not to injure the ventral surface. 



Identify as many as possible of the structures mentioned 

 for the dorsal surface. 



The optic chiasma is the place where the optic nerves cross 

 on the ventral side of the diencephalon. The optic tracts extend 

 posteriorly and dorsally from the optic chiasma and lead to 

 the optic lobes. 



The infundihulum is the large ventral bulge of the dien- 

 cephalon posterior to the optic chiasma. It consists largely 

 of two lobes, the lobi inferiores. 



The pituitary body may be partly destroyed in the dissection, 

 as It fits into a depression in the floor of the skull. It extends 

 caudally from between the lobi inferiores. 



Ventricles of the Shark Brain 

 With a sharp knife or a razor blade remove the dorsal side 

 of the brain so as to expose the cavities within. The cavities 

 of the telencephalon are the first and second, or lateral ventricles. 

 They extend forward into the olfactory bulbs. Posteriorly they 

 connect by a passage, the foramen of Monro, with the third 

 ventricle, which is the cavity of the diencephalon. The roof 

 of the third ventricle is the choroid plexus. The large triangular 

 cavity in the medulla is the fourth ventricle, previously men- 

 tioned. It is also covered by a choroid plexus. A narrow 

 passage, the iter, joins the third and fourth ventricles. The 

 iter connects with the optic ventricles of the optic lobes and the 

 cerebellar ventricle of the cereb-ellum. 



Brain of the Cat 



Remove the eyes and lower jaw and clean the skull down to 

 the bone. Detach the head, together with a few neck vertebrae, 

 from the rest of the body. With the bone forceps make a 



