144 The Alligator and Its Allies 

 Special Sense Organs 



It Is not possible in a work of this size to give 

 much space to the discussion of the anatomy of 

 the special sense organs. A few of the main fea- 

 tures will be given here, taken mainly from Bronn's 

 Thierreich, but for details of structure the reader is 

 referred to that larger work. 



The Eye. As might be expected, the Crocodilia 

 have the usual upper and lower eyelids and the 

 nictitating membrane. Except along their thick- 

 ened rims the lids are usually rather faintly pig- 

 mented, and near the thickened border numerous 

 goblet cells are found. 



The structure of the upper and lower lids is 

 similar except that in the former a bony formation 

 is present, as a support to that lid, even in very 

 young animals. The arrangement of the muscles, 

 which are of both smooth and striped fibers, and 

 the histological structiu-e cannot be described here. 



The nictitating membrane is strongly developed 

 in the Crocodilia. Its outer surface is marked by 

 two fairly high folds that are conspicuousl}'' pig- 

 mented. The cartilage described in the nicti- 

 tating membrane of Lacerta is wanting, according 

 to Bronn, in the Crocodilia. 



The glands of the eye are of three types: the 

 lachrymal glands proper, the Harderian glands, 

 and the conjunctival glands. The lachrymal gland 

 is small in proportion to the size of the eye. It 



