PHOCA VITULINA. 99 



of course no sac nor ductus ad nasum ; so that the tears must pass over 

 the cheek or be washed away in the water. The membrana nictitans 

 is pretty broad, but not transparent, having a cartilage in its middle 

 passing from its edge towards the inner canthus of the eye : and upon 

 the common surface of this membrane, near its root or inner canthus of 

 the eye, is placed a gland 1 longer than the lacrymal, the ducts of which 

 penetrate through the membrane, and open upon the concave surface of 

 the membrane. The number of the eyelids is properly only one, for it 

 surrounds the whole eyeball, with its muscles arising from the bottom 

 of the orbit, passing forwards and diverging to be inserted equally 

 everywhere into the upper and lower eyelids. The uses of this muscle 

 must be various, and as if there were many [muscles] ; for, according to 

 the different part of it that acts, it will have different uses ; e. g., if the 

 whole acts it will dilate the whole eyelids, both upwards or downwards ; 

 to the nose or from it : but, if the superior acts, it will raise the upper 

 eyelid only ; if the inferior, it will depress the under eyelid : if the 

 outer portion acts, it will draw the angle outward ; the reverse if the 

 inner portion acts. 



This muscle arises in conjunction with the straight muscles of the 

 eye, and seems to be only an expansion of the external part. There 

 are two oblique muscles, as in the human subject. The eye is very 

 large ; as large as that of a calf six months old : it is pretty globular, 

 being only a little depressed behind, having a little circular depression 

 round the termination of the sclerotic coat. The cornea is broad, and 

 seems to be nearly a segment of the same circle with the sclerotic. 

 There are six large veins passing into the posterior part of the sclerotic ; 

 their direction through that coat is very oblique. The sclerotic coat is 

 much thicker at its- beginning and termination than what it is in the 

 middle : the cornea is of an equal thickness throughout. The nigrum 

 pigmentum is everywhere upon the external surface of the tunica 

 choroides and iris : it is only upon the anterior part of the inner surface 

 of the choroides, being at the posterior part of that surface white ; but 

 it Hues the iris wholly on its posterior surface. The posterior part of the 

 inner surface of the choroid [tapetum lucidum], round the entrance of 

 the optic nerve, is equally and pretty broad on all sides. This is a little 

 uncommon, its being white [the tapetum extending] equally all round 

 the optic nerve ; but it is perhaps owing to the eyelids being opened 

 equally on all sides ; for in other animals it is generally broadest above, 

 and in them they only open the upper eyelid. The processus ciliares 

 are pretty deep, and the iris is pretty broad, so that the dilatation and 



1 [' Grlandula lacrymalis Harderi.' Hunt. Prep. No. 1778.] 



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