582 William Patten 



of Krohn (3), who considered it bìconvex, he cannot see sufficient rea- 

 son to combat the definite description and drawings of Keferstein. The 

 flatteued appearance of the lens, drawn by Hensen, is caused, as he 

 rightly supposed, by the chromic acid, since I bave niyself observed 

 that an exactly similar shape is produced by treatment with this re- 

 agent. A similar result also appears to bave misled Carrière (19), 

 whose drawiug represents exactly the effect certain reagents produce 

 upon the shape of the lens. Hickson (15), who was surprised at the 

 failure of bis predecessors to determine such a simple point, has 

 himself been equally unfortuuate, for he considers the lens to be ellip- 

 tical, a cross section being circular, or equally biconvex, according as it 

 passes through the major, or minor axis. Sharp was led to believe, from 

 the researches of Hensen and bis own observations, that the lens fiUed 

 the entire space between the retina and cornea. 



The soft nature of the lens renders it almost impossible to isolate 

 uninjured, before it is hardened; the majority of reagents destroy its 

 originai shape, by causing violent contractions of the muscular walls of 

 the eye. Treatment in weak sulphuric acid for twenty-four hours will 

 enable one to isolate the lens in its perfect and normal condition. By 

 examining many specimens, some eyes will be found with large, cho- 

 roid fissures, through which the real shape of the lens may be studied 

 and compared with those treated in sulphuric acid. 



Neither Hensen nor Hickson could find any membrane covering 

 the lens, or any fibres connected with it, although the latter described 

 a ligamentary support for it, ignorant of its having been already more 

 correctly described by Krohn, as the se p tum, or septal mem- 

 brane. 



The lens is suspended in a large, blood sinus, which has been 

 regarded as a »vitreous humor.« Carrière first saw the isolated cells in 

 this space, and correctly interpreted them as blood corpuscles. I am at 

 a loss to account for their presence there, since the retina seems to shut 

 out ali communication with the blood cavities of the eye stalk. They 

 probably enter through the narro w Spaces between the lateral branch of 

 the optic nerve and the surrounding connective tissue. At times, a great 

 many blood corpuscles are found in these Spaces, while, again, they 

 may be entirely absent. It is possible that they are forced into the cavi- 

 ty artificially by the violent and unnatural contractions of the connective 

 tissue, caused by reagents. 



The lens and the two Corneas form the anterior, dioptric part of 

 the eye. The posterior portion consists of a thick, concave disc, com- 



