284 



TECHNICAL MICROSCOPY. 



analogous formations ; No. 4, for blood-cells ; No. 5, for epithelial 

 cells, connective-tissue, and pus-cells, if the nuclei are to be shown 

 also ; No. 6, for connective-tissue, muscles, and nerves ; No. 7, for 

 glands; and, finally, No. 8, for cartilage-tissue. 



Beale mentions a fluid prepared according to the following 

 recipe: To 6 ounces of methylated alcohol and 3 drams of 

 creosote, chalk-dust is added until the mixture forms a soft paste. 

 This paste is diluted by careful pounding in a mortar with 

 64 ounces of water, which is gradually poured in, then mixed 

 with a few small lumps of camphor and allowed to stand for 

 about a fortnight. Finally, it is filtered, and preserved in a well- 

 stoppered bottle. A similar mixture was used by Thwaites for the 

 preservation of Desmidiacece. 



We have enumerated the various preservative fluids employed, 

 and will now describe the method of hermetic sealing which is 

 necessary for most of them. The rules to be observed have refer- 

 ence, in the first place, to the base upon which the cover-glass is 

 put to avoid pressure, and, secondly, to the permanent cementing 



of the edge of the cover-glass. 

 If the preparations are not 

 too thick, it will suffice to 

 paint a ridge of cement or 

 varnish upon the slide by 

 means of a brush (Fig. 158), 

 and of such a shape and size 

 that its outer margin projects 

 somewhat when the cover- 

 FIG. 158. glass is applied. When the 



ridge of cement has partially dried, the preparation is placed in the 

 enclosed space, and the latter is filled with the preservative fluid 

 selected. If we have added too much of the fluid, the excess can 

 be easily removed with a brush. It is convenient to put the 



cover-glass on first at 

 one end only (Fig. 

 159), and then to lower 

 it gradually to a hori- 

 zontal position, so that 

 FIG. 159. it adheres to the frame 



of varnish by its edges. 

 If then a little fluid escapes, it may be removed with blotting 



