74 ANATOMY OF A CHELONIAN. 



fully separate the outer surface of the posterior portion 

 of this muscle from the side of the skull against which 

 it lies, and note the sixth nerve entering it. Trace the 

 nerve back till it disappears in the bone (i8o, /). 



185. Clean the internal rectus muscle which passes from 

 the posterior part of the inter-orbital septum to the in- 

 ner side of the eyeball. On its course it crosses over 

 the Harderian gland. Detach the muscle from the eye- 

 ball, carefully turn it back, and note the branch of the 

 third nerve which enters its under surface. 



186. Note the lachrymal gland on the outer side of 

 the eyeball, and then, separating it and the Harde- 

 rian gland from the globe, expose the pyramidalis mus- 

 cle. Its fibres arise from the inner side of the eyeball, 

 arch over the optic nerve, and then turn down and 

 around the latter and the external rectus to be inserted 

 into the lower eyelid and the nictitating membrane. 



187. Remove the lachrymal gland ; raise the eyeball 

 and note the inferior oblique muscle^ placed transversely 

 near the front of the orbit ; it arises from the lower 

 part of the inner wall of the orbit, and is inserted upon 

 the outer side of the eyeball. As the eyeball is being 

 raised note more closely the nictitating lid, and the 

 fibrous prolongation from its lower margin to the py- 

 ramidalis muscle, which will now be better seen than 

 previously. 



188. Turn the eyeball back (dividing any fibrous 

 bands that interfere) so as to expose its under surface, 

 with the insertion of the inferior rectus muscle upon it. 



