68 PRACTICAL HISTOLOGY. 



with intervening spaces. One may correctly imitate the arrangement by 

 expanding the fingers of both hands and apposing their tips. Possibly 

 the spaces constitute a system of lymph channels. 



870. The " prickle " cells may be isolated by teasing sections of the 

 skin after prolonged maceration in -^ per cent potassium bichromate, to 

 which one or two drops of carbolic acid have been added to prevent 

 putrefaction ( 289). They may also be readily obtained (Lister) by 

 placing one's foot in hot water for half-an-hour, and then scraping off 

 the epidermis, and macerating it in the above bichromate solution. 



870. Simple Squamous Epithelium. Omentum of 

 full-grown cat or guinea-pig, previously silvered by the 

 method described in 328. Excise a small piece of the 

 membrane with scissors, and extend it on a slide by the 

 method described in 87. Apply a drop of glycerine; 

 cover, and examine. 



(L.) The membrane is at some parts areolar, at others 

 continuous. In the non-areolar portions, chains of fat cells 

 may be recognised, and it will be just possible to see a fine 

 network of dark lines, the silver lines that surround the 

 epithelial cells. The omentum is a thin serous membrane 

 with a simple layer of squamous epithelium on both sur- 

 faces. Between the epithelial coverings there is fibrous 

 tissue, and at the trabeculae there are, in addition, fat cells, 

 bloodvessels, and nerves. 



(H.) Examine the silver lines upon the trabeculae. 

 The silver blackens what appears to be an interstitial sub- 

 stance that cements the cells together. If, however, the 

 tissue have been for more than three or four minutes in the 

 silver solution, the nucleus, and, to a less extent, the peri- 

 nuclear part of the scale, become darkened. Over the 

 bands of tissue between the spaces in the areolar portion 

 of the membrane, the silver lines are often imperfect. 

 Profile views of the nuclei of the epithelial plates that clasp 

 the fibrous bundles in this situation will probably be readily 

 seen. 



Seal up the preparation. All glycerine projecting 

 beyond the margin of the cover-glass must be removed 

 with a pipette (Fig. 45), and, if necessary, the slide must 

 be washed with bibulous paper dipped in water. Paint a 

 ring of gold size around the margin of the cover-glass, and 



