Chapter 1, The Reptilian Spectacle - UWSpace - University of ...

quote above, the relationship between that shed scale and the eye remained open to debate and
speculation on whether the scale was affixed to the cornea, to an eyelid, or if it simply floated over the
cornea (reviewed in Cloquet 1821).
Cloquet (1821) is credited with offering the first thorough and accurate account of the gross
spectacle anatomy and its relationship with the eye, an account from which most later researchers drew
inspiration. His illustration of the relationship of the snake spectacle with the eye is reproduced in
Figure 1-1. Making use of fine dissections, he recognized three main layers: 1- a hard corneous layer
(ie. the ocular or spectacle scale) at the exterior, 2- the dermis, and 3- the inner conjunctival layer.
Whereas the first two layers are homologous with the corneum stratum and dermis of the skin, the
inner conjunctival layer is homologous with the palpebral conjunctiva that lines the inner surface of
eyelids and is thus continuous with the scleral conjunctiva. Between the spectacle conjunctiva and the
cornea of the eye is a fluid-filled cavity called by various names such as subspectacle space or
conjunctival sac.
Fig. 1-1. The earliest accurate illustration of the
spectacleʼs relationship with the eye. The spectacle
(c) is separated from the eye (a) by the subspectacle
space (F). Also labeled are the optic nerve (b), upper
and lower periocular scales (d), and the fornix (e).
Reproduced from Cloquet 1821.
Not until more than 50 years later, when Ficalbi (1888a, 1888b) published his monumental
treatise of the reptile integument, was the histological structure of the spectacle well understood to
have a far more complex layering nearly identical to that of the rest of the skin. Ficalbi recognized 5
main layers (Figure 1-2, next page), listed here from external to internal: 1- an external stratum
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