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 structure 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 conspicuously 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 
