130 



PRACTICAL HISTOLOGY. 



[IV. 



the cells do not correspond with those of the upper layer. In 

 focussing through the membrane, note the plexus of elastic fibres 

 in it. 



(c.) To see the nuclei of the endothelial cells, stain another piece 

 of the silvered omentum in logwood and mount it iti balsam. 



The omentum of a young rabbit is chosen because it is nearly a 

 complete membrane with few fenestrse or holes in it. 



12. Omentum of Cat (L and H). Mount in balsam a small 

 piece of the silvered omentum of a cat (Method, p. 77). In cutting 

 the omentum into small pieces, the easiest way is to spread it out, or 

 rather float it out, on a sheet of paper, and then cut the paper and 

 omentum into pieces of the necessary size. The pieces are thus 



less liable to fold up, and are 

 more readily manipulated on 

 the slide. 



(a.) (L) Observe a mesh 

 work of trabecula3 (T) bound- 

 ing open polygonal spaces (tig. 

 91, 111). In the larger tra- 

 beculse may be seen blood- 

 vessels (c), an artery or a 

 vein, or both, surrounded 

 here and there by groups of 

 large clear cells fat-cells (/). 

 All the trabeculse are com- 

 pletely covered with endo- 

 thelial cells, whose outlines, 

 mapped out by silver lines, 



can J ust be recognised. 



(&.) (H) Select a large 



Silver lines, and a. Nuclei of theendothelmm; ', \./ ,, . 



m. Meshes; b. Nuclei of the connective-tissue Strand With a blood-VCSSel 111 



FIG. Qi.-Omentum of Cat Silvered. T = Trabe- 

 cula, with c. Blood-vessel; /. Fat-cells; s. 



xic silver nitrate and hacmatoxylin ' it (T). Focus the silver lines 



(s) on its upper surface, and 



gradually depress the lens until the fibrous tissue composing the 

 strand comes into view, and, still lowering the lens, bring the 

 endothelium on the under surface into view. 



(c.) Select a fine trabecula, and note the silver lines on it; also 

 observe the fibrous tissue of which it is composed. 



(tL) If desired, a preparation may be stained with logwood to 

 reveal the nuclei of the cells of the endothelium (a), as well as 

 those of the fibrous tissue composing the membrane (l>). The 

 nuclei of the endothelial cells are superficial, and usually spherical 

 (a) ; those of the connective-tissue corpuscles are in the substance 

 of the membrane, and arc usually more flattened and somewhat 

 oval (b). 



