Archive image from page 335 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana0401todd Year: 1847 a, lachrymal gland of a tortoise; b, eye-ball of a tortoise ; r, circle of osseous sclerotic plates. {After Bojanus.) in its composition to the sclerotic of a bird ; and in like manner, in many reptiles, contains in its anterior portion a circle of horny plates, which are enclosed between its laminae with- out being continuous with the substance of the membrane, from which they are conse- quently easily detached. These plates are generally ten or twelve in
Archive image from page 335 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana0401todd Year: 1847 a, lachrymal gland of a tortoise; b, eye-ball of a tortoise ; r, circle of osseous sclerotic plates. {After Bojanus.) in its composition to the sclerotic of a bird ; and in like manner, in many reptiles, contains in its anterior portion a circle of horny plates, which are enclosed between its laminae with- out being continuous with the substance of the membrane, from which they are conse- quently easily detached. These plates are generally ten or twelve in number, and are constantly met with in tortoises, and also in the crocodiles, chameleons, and many other lizards. In many genera the sclerotic is di- vided into two layers, the external being fibrous and of equal thickness throughout its whole extent; whilst the internal layer is of a cartilaginous texture, and is thicker at the posterior part of the eye than it is in front. This layer in the vicinity of the entrance of the optic nerve is perforated by numerous foramina for the passage of bloodvessels. The structure of the cornea presents no- thing remarkable, but its convexity varies considerably in different genera. The choroid coat of the eye exhibits the usual structure. In lizards and serpents the ciliary processes are scarcely distinguishable; and in the Chelonians their existence would be doubtful were it not for the elegant im- pression left by them upon the vitreous hu- mour. In the crocodile, however, these processes are well developed, and very beauti- ful. The iris, to some extent, resembles that of fishes, having frequently the same metallic splendour. The shape of the pupil varies: in the crocodile it is a vertical slit, like that of the cat; in the tortoise it is round, as likewise in the chameleon and the generality of lizards. The optic nerve enters the eye externally Fig. 228. Section of the Eye-ball of a Tortoise. Sojanus.') to the axis of vision, pierci
Size: 1355px × 1476px
Photo credit: © Bookive / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: 1840, 1847, anatomy, archive, book, bookauthor, bookdecade, bookpublisher, booksubject, bookyear, drawing, historical, history, illustration, image, london_sherwood_gilbert_and_piper, page, physiology, picture, print, reference, todd_robert_bentley_1809_1860, vintage, zoology
