. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. REPTILIA. In all reptiles there is but one ossiculum auditus (the columncllu}, which is generally of a trumpet shape. Its external extremity is in the Saurians connected to the membrana tym- pani by means of a cartilaginous process; but in tortoises it is implanted directly into the mnmbrana tympani, which has a cartilaginous texture. The inner extremity of the auditory ossicle enlarges into an oval or triangular disc {Patina), which is applied to the fenestra rotunda, in the same way as the disc of the stapes is in the
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. REPTILIA. In all reptiles there is but one ossiculum auditus (the columncllu}, which is generally of a trumpet shape. Its external extremity is in the Saurians connected to the membrana tym- pani by means of a cartilaginous process; but in tortoises it is implanted directly into the mnmbrana tympani, which has a cartilaginous texture. The inner extremity of the auditory ossicle enlarges into an oval or triangular disc {Patina), which is applied to the fenestra rotunda, in the same way as the disc of the stapes is in the ears of mammalia. It does not appear that there are any mus- cles implanted into the auditory ossicle of the reptilia. In most reptiles that possess a membrana tympani, it is situated on a level with the general integument. In the crocodile, however, something like an external meatus exists. Organ of Vision. — In all the reptilia the eye resembles, in its general structure, that of birds and quadrupeds : there are, however, certain modifications rendered necessary by the habits of these animals, many of which are semi-aquatic in their habits, which it will be important to notice. The sclerotic coat of the eye is very similar Fig. 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 cartil
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