TUBE-CELLS. 



239 



FiQ. 65. 



nesses, which greatly interfere with the appearance of the picture. 

 Cells of this kind may he obtained, from Messrs. Jackson, Ox- 

 ford Street, either of round or oval form, and not only ground 

 out of slides of the usual size (3 in. by 1) and thickness, but also 

 hollowed in pieces of plate-glass of larger dimensions. 



137. Beep and Built-up Cells. — The deep cells which are re- 

 quired for mounting Injections and other microscopic prepara- 

 tions of considerable size and thickness, mat/ be made by drilling 

 through a piece of thick plate glass (Fig. 64, d) ; but for the reason 

 already given, the drilled cells are now seldom used, their place 

 having been taken, either by tube-cells, or by the deep built-up 

 cells to be presently described. The tube-eelh are made by cut- 

 ting transverse sections of thick-walled glass tubes of the required 

 size, grinding the surfaces of these rings to the desired thinness, 

 and then cementing them to the glass slides with marine glue. 

 Not only may round cells (Fig. 65, a, b), of any diameter and any 

 depth that the Microscopist can possibly require, be made by this 

 simple method, but oval, 

 square-shaped, or oblong 

 cells (c, d) are now made, of 

 the forms and sizes that he 

 is most likely to want, by 

 flattening the round glass- 

 tube whilst hot, or by blow- 

 ing it within a mould. The 

 facility with which such cells 

 may be made, and the se- 

 curity they afford, have 

 caused the deep cells built 

 up of separate strips of glass 

 (Fig. 66) to be comparatively 

 little employed, except in 

 cases where some very un- 

 usual size or shape (a) may 

 be required, or where it is 

 necessary that not merely 

 the top and bottom, but also 

 the sides of the object, should 

 be clearly seen (b). The perfect construction of these requires 

 a nicety of workmanship which few amateurs possess, and the 

 expenditure of more time than Microscopists generally have to 

 spare ; and as it is consequently preferable to obtain them ready 

 made, directions for making them need not here be given. A 

 new plan of making deep cells, however, has been lately intro- 

 duced by Dr. L. Beale ; which, though it does not give them 

 side walls possessing the same flatness with those of the built-up 

 cells, adapts them to serve most of the purposes for which these 

 are required, and makes them more secure against leakage ; 

 whilst it has the advantage of being so easy and simple, that 



Tube-Cells, Round and Quadrangular. 



