INTEGUMENT 



23 



Reptiles. 



In adaptation from the first to a terrestrial in place of an 

 aquatic existence, the skin of Reptiles is dry and more or less 

 pneumatic. Integumentary glands are practically wanting. The 

 " femoral pores " of Lizards, which were formerly looked upon as 

 glands, are now known to be merely subcutaneous, branched, 

 tube-like cavities lined by cornified cells which project from the 

 pores in the form of solid cones, and possibly serve as clasping 

 organs during copulation : it is doubtful whether these structures 

 originated from glands in the first instance. In the Crocodilia a 

 row of about twenty small, gland-like sacs are present under the 

 skin along the back from the neck to the base of the tail, at the 

 boundary between the first and the second rows of scutes. 

 Nothing is known as to the function of these, or of the evaginable 



FIG. 17. DIAGRAMMATIC SECTIONS THROUGH VARIOUS KINDS OF EPIDERMIC 

 SCALES OF REPTILES. (From Boas's Zoology.) 



A, rounded scales ; B, shields; C, imbricating scales; D, the same, with bony 

 scutes in the underlying derm ; h. horny layer, and s, Malpighian layer of 

 the epiderm ; /, derm ; o, bony scutes. 



and odoriferous " musk-gland" on the lower jaw of Crocodiles and 

 the imaginations of the integument on the margins of the carapace 

 in Chelonians. 



A further characteristic difference between the skin of 

 Reptiles and that of most Amphibians is seen in the presence of 

 scales (Fig. 17). Horny epidermic scales and dermal bony 

 structures, both of which may be present in the same animal, 

 must be distinguished from one another (D). In all cases, the first 

 traces of the scales are due to the formation of dermal papilla?, 

 which may or may not become calcified or ossified. In the former 

 case, the resulting bony scale or scute still remains covered by the 

 more or less horny epiderm (e.g. Anguis, Scincidse). As a general 

 rule, the epidermal cornification is much more marked than the 

 ossification. 



