i io PRACTICAL HISTOLOGY. 



markings on the outer segment of the cone ; sometimes it may be found split transversely. 

 A view of the cones imbedded amongst a great number of the narrow rods may be obtained 

 from above (PI. XXVI., Fig. 3). Many non-medullated fibres of the optic nerve will be found. 



DOUBLE-STAINING OF THE RETINA. 



Rosein and Iodine-green. Stain a section of the retina of a cat or ox in a solution of 

 rosein (p. xlv), and then in iodine-green. Mount it in dammar. The two nuclear or granular 

 layers become of a greenish colour, and all the other parts are red. 



HEXAGONAL PIGMENT-CELLS OF THE RETINA. 



From an eye hardened in chromic acid and spirit scrape off a little of the black pigment 

 lining the choroid. A sheet of flattened hexagonal pigment-cells is easily obtained. The 

 nucleus is not pigmented (PI. XXV., Fig. 7). 



THE EYELIDS. 



The eyelids are prepared in exactly the same way as recommended for the lips (p. 60). 



THE LACHRYMAL GLANDS. 



Prepare them in the same way as the salivary glands, which they closely resemble in 

 structure. 



