THE DOGFISH 13 



the capsule from the body. Note its large size and its connection 

 with the olfactory nerves. Cut it open and note the folds in its 

 mucous membrane, and their arrangement. 



Exercise 12. Draw the nasal capsule. 



The Eyes. Cut away the eyelids of the right eye and the carti- 

 laginous ridge of the skull which surrounds it, so as to expose 

 thoroughly the orbit. Study the eyeball as it lies in the orbit. The 

 white pupil, which is an opening admitting light into the inner 

 part of the eye, will be seen ; surrounding the pupil is the black 

 iris, and covering both and forming the outer coating of the 

 front of the eye is the transparent cornea. At the back and sides 

 of the eyeball the outer coating is called the sclera. A transparent 

 membrane called the conjunctiva, which is continuous with the 

 inner lining of the eyelid, passes over the front of the eye. 



Exercise 13. Draw the front aspect of the eyeball. 



The eyeball is hemispherical in shape, the front surface, the 

 cornea, being flattened. Press the eyeball medially and note the 

 broad, bandlike nerve which lies across the inner part of the orbit, 

 dividing into two branches near its outer edge. 



The muscles of the eyeball, by means of which its position in 

 the socket can be changed, are six in number. Press the eyeball 

 downward and note on its medial side two muscles which are in- 

 serted close together. The anterior one is the superior oblique 

 muscle, which goes to the inner anterior wall of the orbit; the 

 posterior one is the superior rectus muscle, which goes to the 

 inner posterior wall of the orbit. Note the white nerve strands ; 

 they may be distinguished from the muscles by their whiteness. 



Press the eyeball backward and medially and note the infe- 

 rior oblique muscle, which has its, insertion on the anteroventral 

 side of it and goes to the inner anterior wall of the orbit. On 

 the posterior side of the eyeball is the external (posterior) rectus 

 muscle, which goes to the hinder wall of the orbit. Cut the su- 

 perior oblique muscle at its insertion in the eyeball ; beneath and 

 in front of it will be seen the internal (anterior) rectus muscle, 

 which runs back to the hinder wall of the orbit. Cut all these 



