CH. VII] 



ISOLATION OF ELEMENTS 



175 



stained. The stain makes the structural features somewhat plainer ; it also accen- 

 tuates some features and does not affect others so markedly. 



I 263. Permanent Preparations of Isolated Cells.— If one desires to make a 

 permanent preparation of isolated cells it may be done by placing a drop of glycerin 

 at the edge of the cover and allowing it to diffuse under the cover, or the diffusion 

 may be hurried by using a piece of blotting paper, as shown in Fig. 140. One 

 may also make a new preparation and either with or without staining mix the 

 cells with a drop of glycerin on the slide and then cover, or one may use glycerin 

 jelly (\ 254, 326). 



Fig. 145. Adjustable lens holder with universal joint. This is especially use- 

 ful J vt gross dissections, and for dissecting the partly isolated elements with needles 

 (Leitz: Wm. Krafft, N. Y.). 



\ 264. Isolation of Musculer Fibers. — For this the formal dissociator may be 

 used {\ 260, 324), but the nitric acid method is more successful (§ 330). The fresh 

 muscle is placed in this in a glass vessel. At the ordinary temperature of a sitting 

 room (20 degrees centigrade) the connective tissue will be so far gelatinized in 

 from one to three days that it is easy to separate the fascicles and fibers either with 

 needles or by shaking in a test tube or reagent vial (Fig. 143) with water. It 

 takes longer for some muscles to dissociate than others, even at the same temper- 

 ture, so one must try occasionally to see if the action is sufficient. When it is, the 

 acid is poured off and the muscles washed gently with water to remove the acid. 

 If one is ready to make the preparations at once they may be isolated and mounted 

 in water. If it is desired to keep the specimen indefinitely or several days, the 

 water should be poured off and a half saturated solution of alum added ($ 314). 

 The alum solution is also advantageous if the specimens are to be stained. The 



