172 VERTEBRATES 



brain (X2). Turn the brain to one side, cut the nerves 

 that become visible on the under side, and sever the cord 

 below the medulla. The nerves that go out from the lower 

 surface are cranial nerves. The olfactory and optic nerves 

 have been noted, the others supply sensory nerves to the 

 organs of hearing, taste and touch; and motion to the 

 different movable parts of the head, and to the heart, lungs, 

 etc. Draw ventral view (X 2). 



(4) Examine the eye. Find the cornea, the iris, the 

 pupil, and the optic nerve. Do you find a crystalline lens? 

 Do you find the different coats, the sclerotic and the choroid f 

 Compare with the eye of the fish. Make a diagram showing 

 the structure of the eye. 



(5) Study the ear. Examine the membrane, the tym- 

 panum, and remove it. Look carefully beneath it for the 

 labyrinth. Trace the membranes back, find the shape and 

 arrangement of the tube and if possible find the auditory 

 nerve at the end. Draw a diagram of the section of the- ear. 



VII. The Skeleton. — (i) For this study it is prefer- 

 able to take a fresh specimen or one kept in weak alcohol 

 or formalin. The flesh should be carefully removed with 

 the scalpel and the bones allowed to remain at for least 

 forty-eight hours in weak potassium hydrate. This will 

 enable one to remove the flesh and leave the bones attached 

 by the ligaments. 



(2) Note the general framework of the skeleton; the 

 head, the spinal column, the shoulder girdle and fore limbs, 

 the pelvic girdle and hind limbs. 



(3) The Head. — Note the general shape and size com- 

 pared with the framework. Note the size and position of 

 the upper and lower jaws, the maxillaries. Study the mode 



