344 SOME OTHER HISTOL<3GICAL METHODS. 



to which has been added enough dahlia to give an almost 

 saturated solution. After staining, the preparations are 

 transferred to alcohol, which washes out the stain from all 

 but the plasma-cells, and may then be mounted in the resin - 

 turpentine solution. 



The degree to which the colour is removed by this process 

 of washing out depends on the degree of acidity of the stain- 

 ing fluid. " A solution that contained only 1\ c.c. of glacial 

 acetic acid, yet stained the preparation with moderate in- 

 tensity." Smaller proportions of acetic acid may therefore 

 be taken for preparations in which there is much connective 

 tissue, but for structures in which cells predominate the more 

 -strongly acidulated solutions are to be preferred. 



Mucus-cells and fat-cells are also sometimes stained by 

 these solutions. 



Other media. In a similar way other soluble anilins may 

 be employed (in the form of a fluid containing 7 4 c.c. of 

 acetic acid), primula, iodine-violet, methyl-violet, purpurin, 

 safranin, fuchsin; of these, methyl-violet gives the best results. 



686. Plasma-cells (KORYBUTT-DASZKIEWICZ'S Methods) (ibid., xv, 

 1878, p. 7). Frogs were kept for two months (in summer) without food, then 

 placed in a reservoir of running water and well fed for four weeks. " Plasma- 

 cells " were then found in abundance. The nerves were first treated with 

 osmic acid of 1'200, and then stained with a slightly acidulated ammonia- 

 carmine. Fuchsin gives the finest stains, but the colour is not permanent. 



The best method for permanent preparations is to stain with dahlia, 

 methyl- violet, fuchsin, or other anilin stains, dehydrate in alcohol, and mount 

 in turpentine. Turpentine in which resin is dissolved is a very useful 

 medium for teasing. It is well to first harden the tissues in osmic acid. 



687. Plasma-Cells (NOEDMANN, Beitr. z. Kenntniss d. Mastzellen, 

 Inauguraldiss., Helmstedt, 1884). Nordmann finds it useful to employ a 

 solution of vesuvin containing 4 to 5 per cent, of hydrochloric acid. Sections 

 should remain for a few minutes in the solution, and then be dehydrated with 

 absolute alcohol. The paper quoted contains a detailed discussion of the 

 microchemical reactions of granule-cells. 



688. Elastic Tissue. Two of the most salient characters of 

 elastic fibres are that they have a great affinity for osmium, 

 staining with much more rapidity than most other tissue 

 elements, and that they are not changed by caustic soda or 

 potash. A further character is that they have a great affinity 

 for cei't.mi anilin dyes, especially Victoria blue. 



For a review of the methods of BALZER, UNNA, LUSTGARTEN, 



