328 PRACTICAL HISTOLOGY. [XXIX. 



strated the passage of the fibrils of one epithelial cell into adjacent epithelial 

 cells, thus giving rise in the intercellular spaces to the appearances known as 

 "intercellular bridges " (p. 128). The fresh skin of the sole of the foot or 

 palm of the hand is hardened in absolute alcohol. Failing this, use part of an 

 epithelionia. It may be stained with alum-carmine or borax-carmine, and then 

 embedded and cut in paraffin. The sections must be very thin (at least 0.005 

 mm.), and in order to obtain these the knife must be placed obliquely and the 

 sections cut from the epithelial surface towards the cutis vera. 



The sections are placed in a watch-glass and xylol added to dissolve the 

 paraffin. Add fresh xylol, pour it off', and then slowly add absolute alcohol. 

 Gradually add water until the sections float flat on the surface. They are then 

 carefully transferred to a slide, and by the aid of a pad of filter-paper gently 

 fixed on the same. The sections so fixed are stained on the slide. 



The best staining reagent is methyl- violet-6B, prepared as follows : Mix 

 equal parts of aniline- water and a saturated watery solution of methyl -violet. 

 Pour a few drops of this fluid on the section fixed on the slide, and in five 

 minutes lave the section in water. 



Decolorise (few seconds) in iodine solution (p. 93). Wash in water. Remove 

 the water by pressing blotting-paper on the section, and then flood it with 

 aniline-xylol (aniline oil, I : xylol, 2). This mixture extracts the surplus 

 dye very rapidly, so that the preparations must remain but a few seconds 

 therein. 



The march of events, supposing one wishes to stain the cell nuclei before 

 staining the protoplasm fibrils, is as follows the cells being previously 

 hardened : 



(i.) Alum-carmine. 



(2.) Wash in water (HCl-alcohol, 



absolute alcohol). 

 (3. ) Methyl-violet-aniline-water. 

 (4. ) Wash' in water. 



(5.) lodo-potassic-iodide fluid. 



(6.) Wash in water. 



(7.) Aniline-xylol. 



(8.) Xylol-balsam. 



LESSON XXX. 

 SPINAL CORD. 



THE spinal cord, like the brain, is invested by three membranes, 

 named, from without inwards, dura, arachnoid, and pia mater. 

 The pia mater closely invests the cord, and sends processes into its 

 substance as well as into its fissures. The cord itself is composed 

 of white matter externally and grey matter internally. Running 

 along the cord anteriorly and posteriorly are the anterior and 

 posterior median fissures; the former is the wider, the latter 

 rather a groove than a fissure. The two fissures do not meet in the 

 middle line, but they serve to divide the cord incompletely into two 

 lateral halves, which are united across the middle line by a com- 



