CKOCODILIA. 343 



bring that membrane forwards towards the anterior or inner can thus. 

 Along the inner surface of the under eyelid there seems to be a ridge 

 of glands. There are four straight and two oblique muscles, but there 

 is not a trochlea for the superior oblique : the inferior oblique is the 

 smallest, and arises from the inner or outer angle of the orbit. The 

 four straight muscles are not inserted at equal distances from one 

 another, and not at equal distance from the optic nerve ; for the abductor 

 is much the broadest at its insertion, is nearest the optic nerve, and is 

 bound as it were to the nerve by the muscle of the membrana nictitans. 

 The muscle of the membrana nictitans arises, broad and thin, from the 

 sclerotic coat, between the depressor and adductor muscles, from thence 

 it passes backwards and outwards, winding up the optic nerve and the 

 abductor muscle; thence, forwards and outwards, and is lost in the 

 lower part of the edge of the membrana nictitans: the last course 

 makes it draw the membrane over the eye, which I saw it do, when 

 the head of the animal was put into water. 



The lacrymal [Harderian] gland is twice as large as in the human ; 

 it is very soft, and is white like a bit of fat ; it lies at the inner or outer 

 part of the orbit contiguous to the adductor muscle, and between the 

 two origins of the oblique muscles. It is oblong, one end towards the 

 bottom of the orbit ; the other towards the inner angle of the eye, and 

 is contiguous to the tunica conjunctiva. There its duct opens immedi- 

 ately into the cavity of the eyelid behind the membrana nictitans, so 

 that the duct from the gland is of no length : its mucus was as thick 

 and white as cream. The puncta lacrymalia are two, both of which 

 are in the under eyelids, and these two unite into one common duct 

 which passes to the nose. In another crocodile I could find but one 

 punctum lacrymale \ 



The tunica sclerotica is very dense, but is transparent, so that the 

 pigmentum nigrum appears through it. The pigment is on the outside of 

 the choroid ; is of a dark brown, and is pretty full of floating membranes 

 mixed with the nigrum. The inner surface has no pigmentum nigrum, 

 but is marked with a dark colour and a light one. The pupil of the 

 crocodile is vertical, and when in a pretty strong light it is almost a 

 mere line : when put into the dark the pupil dilates, but not into an 

 oval form, but a rhomboidal. The retina is very thick and opake. The 

 pigmentum covers the posterior part of the iris. The optic nerve runs 

 serpentine, and enters with an obtuse angle towards the nose, which is 

 contrary to [its direction in] the human subject. 



1 [Physiological Catalogue, vol. iii. pi. 17. fig. 3. Hunt. Preps. Phys. Series, Nos. 

 1769—1771.] 



