2O6 HOW TO WORK 



dissolved, while the nucleus (germinal matter) appears to be altered 

 but slightly. 



Alkalies are also employed for dissolving certain crystalline 

 substances which are occasionally found in animal tissues, such, for 

 instance, as the u rates. 



The action of potash and soda upon animal structures is very 

 similar. Both dissolve substances of an albuminous nature, but the 

 effect of soda is more gradual, and it has been found that for most 

 purposes in microscopical research, the reagent possesses advantages 

 over potash. 



The solution of potash required by the microscopist is the 

 ordinary liquor potassa of the pharmacopoeia, and the solution of 

 soda is prepared in the same manner. These solutions may be 

 diluted with water to the required strength. Potash and soda are 

 employed where a tissue is to be rendered more transparent for the 

 purpose of demonstrating the arrangement of the nerves or other 

 anatomical elements not soluble in this reagent. 



These reagents dissolve the layer of epithelium covering mucous 

 membranes, or render it perfectly transparent, so that the arrange- 

 ment of the structures beneath the basement membrane can be 

 easily demonstrated. In investigating the arrangement of the nerves 

 and vessels in papillae and other structures, they are very valuable, 

 especially the soda solution. 



For the purpose above-mentioned, the alkalies should be diluted 

 with water. The changes are expedited by the application of heat, 

 which, however, must not be too great, for fear of complete solution 

 taking place. The structure may be heated with the solution in a 

 test tube. 



Some animal textures become hardened by prolonged maceration 

 in carbonate of potash, but this plan does not appear to be so 

 generally useful as others previously indicated. Epidermic structures 

 are not much altered by this salt. 



The introduction of different chemical solutions by injection, 

 will be discussed in Part V. I strongly recommend this plan of 

 subjecting the tissue to the action of the reagent. See also 

 Part V. 



302. Nitrate of Barjtcs. A cold saturated solution of the salt 

 forms a test solution of convenient strength. It should be filtered 

 before use. A solution of nitrate of barytes is employed as a test 

 for sulphuric and phosphoric acids. The precipitated sulphate of 

 baryta being insoluble both in acids and alkalies ; while the 

 phosphate of baryta is readily soluble in acids, but insoluble in 

 ammonia. 





