DISSECTION OF THJU SHARK 27 



Draw the contents of the orbit as seen from above, including 

 the eye, its muscles, and all nerves which enter the orbit. 



13. The eyeball. Remove the eyeball from the orbit by cut- 

 ting all of its attachments, and dissect the eye. Open the eye- 

 ball by a cut around the equator between the cornea and the 

 optic nerve. In the inner half of the eyeball note the three 

 coats the tough sclerotic, the pigmented choroid, and the 

 grayish- white retina. The retina in preserved specimens is apt 

 to be partly disintegrated and pulled loose from the choroid 

 coat. In the outer half notice the lens and observe its attach- 

 ment by a delicate suspensory ligament attached to the margin 

 of the eyeball in front of the retina The space behind the lens 

 is filled with vitreous humor (corpus vitreum) ; the space in 



FIG. 5B. An analysis of the cranial ganglia of Squalus acanthias ("pup" 

 stage). The somatic motor roots are omitted; cf. Fig. 5 A. For the sig- 

 nificance of the conventional symbols see the accompanying legend. 



ABBREVIATIONS 



ac-lat., area acustico-lateralis of brain. 



buc. VII, ramus buccalis VII. 



cbl., cerebellum. 



dors.X, rarnus dorsalis X. 



g ac., ganglion acusticum. 



g buc., ganglion of ramus buccalis VII. 



gen., ganglion geniculi VII. 



gg., ganglion gasseri. 



g gl., visceral ganglion of IX. 



g II. X, ganglion of rarnus lateralis X. 



g mde., lateralis ganglion on hyornandibular trunk. 



g op., ganglion of ramus ophthalmicus profundus. 



g os. VII, ganglion of ramus ophthalmicus superficialis VII. 



g spt.IX, ganglion of ramus supratemporalis IX. 



g spt.X, ganglion of ramus supratemporalis X. 



g X.I to g XA, visceral sensory ganglia on the vagus. 



hy.VII, ramus hyoideus VII. 



IX, nervus glossopharyngeus. 



IX r., roots of nervus glossopharyngeus. 

 lat.X, ramus lateralis X. 



max. V, ramus maxillaris V. 



md. V, ramus mandibularis V. 



mde.VlI, ramus mandibularis externus VII. 



mdi.VII, ramus mandibularis internus VII. 



mes., midbrain. 



op. V, ramus ophthalmicus profundus V. 



os.V, ramus ophthalmicus superficialis V. 



os. VII, ramus ophthalmicus superficialis VII. 



pal.VII, ramus palatinus VII. 



rest b., "corpus restiforme" (anterior end of acustico-lateral area). 



spt.IX, ramus supratemporalis IX. 



spt.X, ramus supratemporalis X. 



VII r., roots of facialis proper. 



VII r II., lateral line roots of facialis. 



X r., roots of vagus proper. 



X r II., lateral line root of vagus. 



X.I to XA, first to fourth branchial rami of vagus. 



