380 METHODS. 



8. 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. 7. 



Preservation in Alcohol. 



When a specimen is to be preserved with alcohol alone, it should be 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 from twelve to twenty-four hours, and finally 

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

 specimen 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: 



1. Stain in toto. (See page 382.) 



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- 

 tion. As soon as the paraffin has set, chill it rapidly with cold water, otherwise 

 the paraffin is likely to crystallize and therefore to cut badly. 



B. To Imbed in Celloidin: 



1. Dehydrate the mass thoroughly in 95 per cent alcohol, four to twenty- 

 four hours. 



2. Place mass for twenty-four hours in alcohol and ether, equal parts. 



3. Place mass in thin syrupy solution of celloidin in equal parts of ether and 

 alcohol for at least twenty-four hours. (If the specimen contains cavities several 

 days are necessary to allow the celloidin to penetrate and fill them.) 



4. Place mass in thick viscid solution of celloidin in equal parts of ether and 

 alcohol for twenty-four hours. 



5. Set mass on block of vulcanite, compressed fiber, or maple-wood, and as 

 soon as a film has formed over the surface of the celloidin (two to five minutes) 



6. Immerse in 80 per cent alcohol for twenty-four hours. 



7. Cut. 



