2O2 HOW TO WORK 



s i i!i-,t;inccs to be tested, and for diluting fluids required by the micro- 

 scopical observer. 



289. Alcohol. Alcohol of different strengths will be required for 

 the purpose of dissolving certain substances, and for separating them 

 from other constituents, which are insoluble in this reagent. If a 

 we ik alcohol is required, the strong spirit should always be diluted 

 with distilled water, and it is better to prepare a considerable quan- 

 tity at a time. It is convenient to have two or three bottles which 

 will hold about two quarts each. The strength of each should be 

 written upon a label attached to the bottle. The importance of 

 alcohol as a preservative solution has been referred to in p. 53. 



2O. Ether, Chloroform. An ounce or two of ether will be quite 

 sufficient for microscopical purposes. It should be kept in a stop- 

 pered bottle, provided Avith a. glass cap, to prevent loss by evapora- 

 tion. A little should also be kept in one of the small glass bottles 

 with capillary orifices, p. 209, for the convenience of applying to 

 cells containing highly refracting globules, resembling oil, &c., under 

 the microscope. Chloroform must be kept in capped and stoppered 

 bottles, carefully protected from the light. 



291. Effects of Alcohol and Ether. Alcohol coagulates albuminous 

 matters. Germinal matter is always rendered granular by this reagent. 

 Many transparent tissues are corrugated, and rendered more or less 

 opaque by alcohol. It dissolves certain forms of fatty matter, 

 resinous materials, and many kinds of vegetable and animal colouring 

 matter. 



Ether is of great use for dissolving various kinds of fatty matter. 

 In many cases, however (as, for example, in common milk), the oil 

 globule is covered with a caseous or albuminous investment, which 

 protects it from the action of the ether. In this case it is necessary 

 to add a drop of acetic acid, or solution of potash or soda, to dissolve 

 the membrane, when the ether will at once act upon the fat. 



Chloroform is a valuable fluid for dissolving Canada balsam, 



P- 5 1 - 



292. Nitric Acid of two different degrees of concentration should 



be kept, the strongest that can be procured, and a solution containing 

 about twenty per cent, of the strong acid. This last is the acid most 

 used by the microscopist, especially in separating muscular fibre cells. 

 It is prepared by mixing one part of the strong commercial acid with 

 five parts of distilled water. 



293. Sulphuric Acid is sometimes required undiluted, but a small 

 bottle of diluted acid (one of acid to five of water) should also be at 

 hand. The pure colourless acid should always be procured ; it is to 



