MOUNTING CELLS 



449 



A 



B 



suitable distance, and cutting out the piece between them, any 

 required elongation of the cavity may be obtained (B, C, ])). 



Sunk-cells. r ^his name is given to round or oval hollows, exca 

 vated by grinding in the substance of glass slides, which for this 

 purpose should be 

 thicker than ordinary. 

 They are shown in fig. 

 377, A, B, C. Such 

 cells have the advan- 

 tage not only of com- 

 parative cheapness, but 

 also of durability, as 

 they are not liable to 

 injury by a sudden jar, 

 such as sometimes 

 causes the detachment 

 of a cemented plate or 

 ring. For objects whose 

 shape adapts them to 

 the form and depth of 

 tlie cavity, such cells 

 will be found very con- 

 venient. It naturally 

 suggests itself as an 

 objection to the use of 

 such cells that the con- 

 cavity of their bottom 

 must so deflect the 

 light-rays as to distort or 

 filled either with water 



FIG. 377. Plate-glass sunk-cells. 



obscure the image 



but as the cavity is 



or some other liquid of higher refractive 

 power, the deflection is so slight as to be practically inoperative. 

 l!e fore mounting objects in such cells the microscopist should see 

 that their concave surfaces are free from scratches or roughnesses. 



Built-up Cells. When cells are required of forms or dimensions 

 not otherwise procurable, 



they may be built t<j> 

 separate pieces of 



of 



cemented together. 



glass 

 Large 



mounting 



cells, suitable foi 

 zoophytes or 

 similar flat objects, may be 

 easily constructed after 

 the following method : A 

 piece of plate-glass, of a 

 thickness that shall give 

 the desired depth to the 

 cell, is to be cut to the 

 dimensions of its outside 

 wall ; and a strip is then 

 each of its edges, of such 



FIG. STS. Built UP cells. 



to be cut off with the diamond from 

 breadth as shall leave the interior piece 



qual in its dimensions to the cavity of the cell that 



is desired. 

 G G 



