322 



Dr. E. K. Martin. 



[Feb. 5, 



also made on the media 1 hour, 5 hours, and 8 hours after the death of 

 the animal, the results obtained being identical with those from fresh 

 specimens. 



The photographs were taken at the Imperial College of Science and 

 Technology, South Kensington, those of the visible spectrum in Sir Wm. 

 Abney's laboratory, the ultra-violet series in the Astrophysical Laboratory, 

 by kind permission of Prof. Fowler, F.E.S., to whom I am indebted for 

 valuable suggestions. 



II. Histology. 



Normal Capsule. 



Method of Handling the Anterior Lens Capsule. — The most satisfactory 

 fixative solution for uniformity of results is Zenker's fluid. Formalin, in 

 solution or vapour, gives excellent fixation of the cells, but renders the 

 homogeneous layer of the capsule too elastic to allow of its being fixed flat 

 on a slide. In addition, the epithelium shows a tendency to adhere to the 

 lens substance rather than to the capsule. 



The following method has given the most uniform results : — 



The globe is bisected at the equator, and the anterior half fixed in 

 Zenker's fluid for two hours, washed, and adherent vitreous removed. The 

 capsule is then cut through round the equator, and the lens shelled out 

 entire, leaving the anterior capsule attached to the ciliary processes by the 

 suspensory ligament. The latter is then divided, and radial incisions made 

 into the capsule, allowing it to be floated, epithelium uppermost, on to a 

 slide, and blotted flat. 



As a stain, Ehrlich's acid haematoxylin has been used exclusively, as it 

 gives by far the most constant results. The iron-haematoxylin methods give 

 clear pictures, but are somewhat irregular, while the aniline stains have the 

 drawback that they colour the homogeneous layer of the capsule, and so 

 spoil the contrast. 



Occurrence of Mitoses. — From the systematic examination of the anterior 

 capsule cells of the rabbit's lens mounted as described, it appears that at 

 birth, and for the first six to eight weeks of life, numerous mitoses occur, 

 scattered uniformly round the equator over a zone equal in breadth to a 

 quarter of the radius of the capsule. Cell division in this zone becomes 

 progressively less active till the third or fourth month, and, in animals 

 over six months, 10 to 15 mitoses only are found at the extreme periphery. 



Cell division in the pupillary area is extremely rare at any age, and has 

 been found only once in 10 capsules examined systematically for that 

 purpose. The age of the animal and the topography of the normal capsule 



