WITH THE MICROSCOPE. 20$ 



When we wish to obtain portions of glandular structure isolated 

 from one another, it is a good plan to soak the tissue for some days 

 in dilute nitric acid (one part of acid to six or seven of water), when 

 the areolar tissue becomes softened. At the same time the gland 

 structure is rendered more firm, and may be isolated very readily 

 with the aid of needles. In this manner the gastric glands, the 

 secreting follicles of the pancreas, and salivary glands may often be 

 very satisfactorily demonstrated. 



By boiling animal tissues in strong nitric acid, they become 

 destroyed, while any siliceous constituents remain behind unaltered. 

 In this manner, the siliceous skeletons of the DiatomacecR may be 

 separated from any organic matter with which they may be combined. 

 This is one of the processes employed for obtaining these beautiful 

 objects, frorn^ guano. 



Sulphuric Acid. Hydrochloric Acid. Concentrated sulphuric 

 acid causes epidermic structures to swell up very much, and the cells 

 to separate from each other so as to be readily isolated. Boiling acid 

 completely dissolves them. In the examination of hair, strong sul- 

 phuric acid will be found to render the outline of the cells very 

 distinct. 



Hydrochloric acid is usually employed for dissolving out the 

 mineral constituents of certain tissues, such as bone or teeth. As a 

 rule, it is better to use dilute acid (one of acid to three or four of 

 water), in which case, however, a longer time must of course be 

 allowed, than when the acid is concentrated. 



298. Solution of Potash should be kept of two or three different 

 degrees of strength. One, the strongest which can be obtained ; 

 another, made by mixing one part of the strong potash with three 

 or four of water; and a solution consisting of one part of liquor 

 potassse to eight or ten of water will be found of a useful strength 

 for the examination of many preparations. 



299. Solution of Soda is generally required very dilute. It may be 

 made by mixing one part of the strong solution of the shops with 

 five or six of water ; but this, for many purposes, will require to be 

 still further diluted. Or, about twenty-five grains of the fused soda 

 may be dissolved in an ounce of distilled water. 



soo. Ammonia,. Solution of ammonia, made by mixing one 

 part of the strongest liquor ammonias (British Pharmacopoeia) with 

 three of water, will be found sufficiently strong for all the purposes 

 for which this reagent will be required. 



3O1. Effects of Alkalies on Organic Structures. The action of 

 alkalies, even when cold in a very dilute state, is to dissolve most 

 animal textures. Cell-membranes are frequently almost instantly 



