270 ELEMENTARY PHYSIOLOGY. [XXVI 



a. The hyaline capsule of the lens. 



b. The columnar epithelium of the anterior 

 surface of the lens ; at the sides these rapidly 

 but gradually elongate into fibres. 



c. At the sides, the nuclei of the fibres forming 

 an irregular band. 



5. Take a lens as in § 4, and cut transverse sec- 

 tions through its centre. Observe the cross sec- 

 tions of the fibres, and their junctional lines. 



6. Place the lens of a rabbit or rat in osmic acid 

 •25 p.c. for about three hours ; it will swell up 

 somewhat, and the outer coat becomes jelly-like 

 and easily torn ; to obviate this, place it in gold 

 chloride "25 p.c. for a minute or less ; then tear 

 off as long a strip as possible of the outer coat, 

 and tease out in water. Observe the long band- 

 like fibres with serrated edges usually adhering 

 together in layers but in some cases isolated. 



In some of the fibres a nucleus will be seen; 

 when the fibres form a layer, the nuclei appear 

 as an irregular band running across it. 



Iris. 



7. Cut out a piece of an iris from an eye which 

 has been preserved in potassium bichromate, 

 stain and cut radial vertical sections. Observe 



a. On the posterior surface, the uvea or thick 

 layer of pigment epithelium-cells (cp. § l,d). 

 The pigment will probably be too abundant 

 to allow the outlines of the individual cells 

 to be seen. 



