144 



PRACTICAL HISTOLOGY. 



[VII. 



30 to 50 per cent, alcohol, the alcohol being renewed frequently 

 until no colouring matter is given off. They can then be preserved 

 in strong alcohol, but on prolonged keeping the nuclei change 

 somewhat. 



1. T.S. Tail of Larva of Salamander (H). Stain a section for 

 12-24 hours, or even longer, in a solution of safranin (p. 75) a 

 saturated alcoholic solution diluted with half its volume of water. 



In dealing with such delicate sections, 

 it is well to " fix " the section on a 

 slide beforehand, especially if it be 

 cut in paraffin. The section may be 

 fixed by albumin and glycerine, the 

 paraffin removed by turpentine or 



FIG. 107. V.S. Epidermis of a Young T -,nn1iflin A ffpv efaininrr \viQliin cjnirif 

 Salamander with Kesting Nuclei, naplltlia. Attei Staining, wasll 111 *pll it 



Monaster and Blaster Stages of and place ill acid alcohol (lOOCC. 



ami i lSfa^in, C x i 3oo Chr d absolute alcohol to 3-5 drops of 



hydrochloric acid). This rapidly de- 

 colorises it (J-i min.). Instead of acid alcohol the absolute alcohol 

 may be used. It removes the surplus stain more slowly. The 

 difficulty is just to hit the moment when the dye is washed out of 

 the nuclear matrix, the fibrils being still stained. The section is 

 then transferred to absolute alcohol and clarified, and mounted in 

 xylol-balsam. The best agent to clarify the section is cedar-wood 



oil, as it does not dissolve 

 the safranin, which clove-oil 

 does. 



(a.) Observe the layers of 

 epithelium of the epidermis 

 (fig. 107). In several of 

 the nuclei the characteristic 

 mitotic figures are to be 

 seen, and in one or two 

 sections it is not difficult to 

 pick out examples of nearly 

 FIG. 108. -Mitotic Figures from the Epidermis .^ t | ie stages of nuclear 

 of a Young Salamander. Chromic acid and . . ^ 



safranin, x 300. division. While the nuclear 



fibres are well seen in 



safranin-stained specimens, the nuclear spindle is not usually well 

 seen. 



2. Surface-Scraping of tha Epidermis, Cornea, or External 

 Gills. Instead of making a section, scrape the surface of the skin 

 of the tail, or break up the external gills in water, or stain (safranin) 

 and mount the cornea in xylol-balsam. Stain either with safranin 

 or logwood, mount in balsam, and numerous mitotic figures will be 

 found (fig. 1 08). 



