DIRECTIONS FOR IMBEDDING. 365 



for study, to remove the formaldehyde by treating them with fresh 70 per cent, 

 alcohol. 



6. FLEMMING'S FLUID. 



Formula; I per cent, solution of chromic acid, 50 c.c. 



2 per cent, solution of osmic acid, 12 c.c. 



Glacial acetic acid, 3 c.c. 



The solution must be used freshly made, and must not be kept in the dark. The 

 specimens must be of small size and as fresh as possible. They are kept in the 

 fluid from twenty-four to forty-eight hours, then washed in running water from 

 four to twenty-four hours, then transferred to alcohols of gradually increasing 

 strength. The fluid is useful chiefly for cytological work. 



7. HERMANN'S FLUID. 



Formula : I per cent, platinum chloride in distilled water, 60 c.c. 



2 per cent, osmic acid in distilled water, 8 c.c. 



Glacial acetic acid, 4 c.c. 



Used in the same manner and with the same precautions as No. 6. 



Preservation in Alcohol. 



When a specimen is first put into alcohol, it should be transferred gradually, 

 being put first in 30 or 50 per cent, alcohol for an hour or more, then into 60 per 

 cent, for several hours, 70 per cent, for twelve to twenty-four hours, and finally 

 into 80 per cent., in which it should be kept until required for use. If the speci- 

 men is to be sectioned, it must be placed in 95 per cent, alcohol, which must be 

 renewed at least once, and be allowed to act for twenty-four hours or more, unless 

 the specimen is very small, when a somewhat shorter time may suffice. 



Directions for Imbedding Specimens to be Microtomed. 



A. To Imbed in Paraffin: 



-I. Stain in toto. (Seepages 367 and 368.) 



2. Dehydrate in alcohol from three to twenty-four hours. 



3. Place in oil of cloves and turpentine (equal parts), one to twenty-four 

 hours. 



4. Place in fresh cloves and turpentine for one to twenty-four hours. 



5. Place in soft paraffin at 54 C. for thirty to ninety minutes. 



6. Place in hard paraffin at 54 C. for thirty to ninety minutes. 



7. Warm a glass plate to about 70 C. ; place on it a paper tray or metal 

 imbedding frame ; fill the box with hard paraffin at 54 C. Warm a spatula and 

 with it remove the specimen to the tray or frame, and arrange it in a proper posi- 



