128 



PRACTICAL HISTOLOGY. 



[IV. 



paraffin, and mount the former in Warrant's solution and the latter 

 in' balsam. 



(ti.) Observe the prickle-cells in situ, i.e., polygonal cells in the 

 deeper layers of the rete mucosum, with fine processes connecting 

 adjoining cells, leaving thus a system of fine spaces between the cells 

 (fig. 87). The fine fibres which pass from cell to cell form "inter- 

 cellular bridges," and when these bridges arc broken across they 

 give the appearance as if the cells were beset with fine prickles. 



8. Isolated Cells from th9 Different Layers of the Epidermis 

 (H). It is usual to macerate very small pieces of any membrane 

 covered with stratified epithelium in g- or $ per cent, of potassic 

 bichromate, which usually takes more than a week to dissociate the 

 cells. 



Fm. 87. Prickle-Cells from the 

 Deeper Layers of the Epi- 

 dermis of the Palm, showing 

 intercellular bridges and 

 channels. Osmic acid. 



FIG. 88. Prickle Cells Isolated from 

 the Human Epidermis by means of 

 Iodised Serum. n. Prickles ; d. 

 Space between nucleus and cell- 

 body, x 800. 



A much speedier method is that of Schiefferdecker. Make a 

 watery extract of " pancreaticum siccum " of Dr. Witte of Rostock. 

 Filter, and in the filtrate place a small fragment of fresh skin or 

 the pad from the upper jaw of a sheep. Place the fluid near the 

 fire or in an oven at 40 C. Within four hours, the epidermis can 

 be detached, and its cells fall readily apart. Preserve it in a test- 

 tube in a mixture of equal parts of water, alcohol, and glycerine. 

 It forms a deposit at the bottom of the tube. A little of the deposit 

 is mounted in glycerine or Farrant's solution, covered and examined. 

 It may be stained with picro-carmine or methylene-blue. 



(a.) Observe numerous cslis of different shapes, some flattened, 

 others cubical, and many "prickle-cells" (fig. 88). Many of the 

 cells exhibit facets where they have been pressed against each 

 other. 



9. Isolated Prickles and other Cells from the Pad of a Sheep's 

 Mouth (H). Isolated by means of "pancreaticum siccum" (v. 

 supra). Many of the somewhat cubical-shaped cells show tho 

 " prickles " beautifully. These cells may be stained with an aniline 

 dye or picro-carmine, and some of them show two nuclei. 



