310 



ANATOMY OF VERTEBRATES. 



nerves progressively increase in length in the Turtle, Iguana, and 

 Crocodile. The distrilnition of their tihres u])on the vascular 

 pituitary membrane, supported by the turbinal cartilage, is well 

 displayed in a Hunterian preparation of the Turtle.' 



The optic nerves, corresponding in size with that of the eyes, 



200 



are smallest in the fish-like Batrachians. They arise from the 

 optic Idbcs, fig. 192, (), tlialami, and o]itic tracts, ib. d, and blend, 

 by a few decussating lamina\ into a chiasma, ib. /*, before diverg- 

 ing to the visual organ : their course is shown, in the Python, at 

 2, fig. 188. Tlie position of the 'third' or oculo-motor nerve is 



' XX. vol. iii. p. 89. iios. 1.532, l.lIiS. 



