MACERATING FLUIDS 489 



Nitric Acid and Potassium Chlorate. About 5 gm. of potassium 

 chlorate are dissolved in 20 c.c. of the acid. Muscle cells are separable in 

 one to six hours. Wash thoroughly in water and examine in water or 

 glycerin. 



Potassium Hydrate. Muscle cells may be teased apart after immersion 

 for about an hour in a 35 per cent, aqueous solution. They may be ex- 

 amined in the same solution or transferred to a saturated aqueous solution 

 of potassium acetate, which prevents further maceration. The solution 

 of potassium hydrate may also be used for isolating epithelial cells. 



Concentrated Sulphuric Acid. The elements of the epidermis, hair and 

 nails may be separated after immersion in this fluid. They should be 

 thoroughly washed in water. 



PERMANENT PREPARATIONS. 



None of the methods described above yield much information re- 

 specting the finer structure of tissues and organs, nor do they yield perma- 

 nent preparations. For ease of reference, the various steps in the pro- 

 duction of a permanent preparation have been grouped under the follow- 

 ing five headings. 



1. Fixation. Under this heading are given formulae for the best fixing 

 fluids, with directions for their use and for the subsequent handling of the 

 tissue until it is placed in 80 per cent, alcohol, in which tissues may be 

 kept for a considerable time. 



2. Imbedding. This includes the various steps for preparing the 

 tissues to be sectioned in paraffin or celloidin, starting from 80 per cent, 

 alcohol. 



3. Cutting and handling sections. Brief directions are given for cutting 

 sections and handling them, until they are ready for staining. 



4. Staining. Formulae and directions for the use of stains, and the 

 after treatment until the preparation is in the appropriate clearing fluid. 



5. Clearing and mounting. The choice of a clearing agent for paraffin 

 and celloidin sections is discussed, together with the methods and media 

 for mounting. 



Since each of the fixing, imbedding and staining methods is considered 

 as a unit, each starting where the previous step ends, the student can 

 easily prepare specimens according to any desired possible combination 

 by referring to the directions for the selected fixative, imbedding method, 

 and stain. 



i. Fixation. 



A good fixative should penetrate and kill tissues quickly; preserve the 

 tissue elements, particularly the nuclei, in the condition in which they are 



