536 POWDERED DRUGS 



index than Canada balsam, and unstained tissues come out more sharply in it than 

 in the Canada balsam. 



Decalcification. Three per cent, of nitric acid in 70 per cent, alcohol is a good 

 decalcifying agent. The material should be left in the solution for several days. 

 Chromic acid has a decalcifying action; a I per cent, to 2 per cent, solution should 

 be used, and the material should be left in this until decalcification is found to be 

 complete. 



Decolorizing. Material which has become brown in alcohol may be decolorized 

 in the following solution: To each 100 mils of alcohol is added from 0.2 to 0.5 mil of 

 concentrated sulphuric acid and as much potassium chlorate as can be transferred 

 on the point of a knife. The material is to lie in this solution for eight to ten days, 

 and is then to be washed a few times in pure alcohol, the material standing for 

 some time in each change of alcohol. 



Dehydration. This is best accomplished by cutting the material into as small 

 pieces as possible, and then placing it in 20 per cent, alcohol, and then into as- 

 cending grades of alcohol of 10 per cent, increase at intervals of about two hours. 

 Microtome sections mounted on the slide may be transferred to strong alcohol 

 without injury. In passing from water or aqueous stains to Canada balsam, the 

 material should first come into strong alcohol, and then into xylol to insure complete 

 dehydration, and to infiltrate the material with a solvent of balsam namely, 

 xylol. Aniline is also a good dehydrating agent. The preparations may pass 

 directly from water into the aniline and from the aniline into the balsam. A 

 stick of potassium hydrate placed in the aniline will keep the latter dehydrated. 

 Potassium hydrate is not soluble in aniline. Very thin microtome sections which 

 are found not to be injured by drying may be allowed to dry, and then may be 

 placed in xylol and thereafter transferred to balsam. 



Desilicification. This is accomplished by hydrofluoric acid. A glass vessel is 

 coated on the inside with melted paraffin to prevent the action of the acid on the 

 glass. Alcohol is then poured into the vessel and the material is immersed in the 

 alcohol; then the hydrofluoric acid is added, drop by drop. The process should be 

 completed in a few minutes. Care must be taken not to breathe the fumes of the 

 acid, since they attack the mucous membranes. 



Diastase. This may be prepared as follows: Germinate barley in the incubator 

 between pieces of blotting-paper until the plumule has reached a length of about 

 2 mm. ; then dry the barley on the water-bath and grind to a fine powder. When 

 a diastatic solution is desired, pour over 10 Gm. of the powdered barley I liter of 

 water containing 2 mils of chloroform: let stand for ten hours at about I5C. and 

 filter. The water filtered off will contain the diastase in solution. Add a little 

 chloroform and preserve in a dark place. Starch-grains may be mounted in this 

 solution under a cover-glass and kept from drying in a moist incubator, and the 

 effect of the diastase on the starch may be studied from time to time under the 

 microscope; or a i per cent, starch may be made to which about an equal amount 

 of the diastatic solution may be added, and then at intervals samples from the 

 mixture of starch and diastase may be tested with a solution of iodine. The starch 

 will, after a time, be changed into dextrines and grape-sugar, and will no longer 

 give a blue color when tested with a solution of iodine. 



Digestive Fluids. To remove from sections aleurone grains which are so numer- 

 ous as to obscure the nucleus, the sections should be treated for twenty-four hours 

 with a digestive fluid prepared by mixing I part of pepsin-glycerine with i part of 

 pancreatin-glycerine, and 20 parts of a 0.3 per cent, solution of hydrochloric acid. 

 Differences in the character of the protoplasmic cell-contents, and particularly in 

 the dividing nucleus, may be demonstrated by treating sections of fixed material 



