78 PRACTICAL HISTOLOGY. 



a needle. But we possess in the silver method of Reck- 

 linghausen a ready means of demonstrating its existence 

 in an obvious manner; for the ground substance (or 

 intercellular substance) of the connective tissue, and, 

 indeed, of almost every other tissue in the body, possesses 

 the distinctive property of reducing the salts of silver 

 under the action of light, so that the metal is deposited 

 in it either in a free state or, more probably, in combina- 

 tion. The effect of this deposition is, that the ground 

 substance becomes stained of a color varying with the 

 intensity of the light employed, and with oilier conditions, 

 from a light brown to a brownish-black. The iibrous 

 elements participate for the most part in this staining, 

 and are frequently, especially when the preparation has 

 been, as is usual with silver preparations, mounted in 

 glycerine, indistinguishable from the ground substance 

 through which they course, and which also unites the 

 white fibres into the bundles which they form. The 

 cellular elements, on the contrary, remain absolutely 

 unstained, and, moreover, after the action of the silveV 

 salt are no longer affected by those staining fluids which 

 otherwise have a particular aSinity for them ; it is there- 

 fore no longer possible to bring them into view. Where- 

 ever, then, a cell is situated, there appears after the 

 reduction of the silver nothing but a white patch upon 

 or in the brown ground; and if, as is not unfrequently 

 the case, several flattened cells may have occurred 

 together with their edges in juxtaposition, the group 

 appears as a larger white patch intersected by dark lines, 

 these representing a small amount of intercellular sub- 

 stance between the individual cells. The appearance is 

 similar to what is observed in an epithelial tissue after 

 the silver treatment, for in this the intercellular substance 

 is always very small in amount. Such an arrangement 

 of connective tissue cells is on this account designated 

 " epithelioid." The white patches, then, in the silvered 

 preparation of connective tissue represent either depres- 

 sions on the surface of, or actual cavities within, the 

 matrix or ground substance, containing cells, which 

 themselves are not visible, so that the white patches are 

 termed the cell-spaces, or (recalling the analogous case 

 of bone) the lacuna of the connective tissue. 



It is the more appropriate to give them a special desig- 



