10 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



9. Rinse specimen in distilled water or soak in borax solution, if 

 large quantities of alkali are suspected to be present in the body- 

 cavities, and then return to the digestion solution if it is usable; 

 othermse, repeat the process, beginning with step 4. Continue 

 digestion until all areas of muscle tissue have disappeared. 



Completion of the clearing process following staining is suggested 

 because virtually all of the stain embedded in the soft tissues is re- 

 moved along with the remaining areas of dark brown or yellowish 

 muscle tissue. 



10 (optional). Some oils and fats that remain after the digestion 

 process may be removed by gradually transferring the specimen 

 through a series of ethyl alcohols in varying strengths, beginning with 

 about 40 percent, thence through 70 percent, 95 percent, to absolute 

 alcohol (if available), and then to xylene. After the xylene, the 

 specimen is transferred downward in the alcohol series to water and 

 washed until all traces of the xylene are removed. 



11 (optional). Guanin or guanin-like substances may be removed 

 by soaking the specimen in a solution of 2 to 4 percent potassium 

 hydroxide for several days. Guanin is seldom dense, opaque, or 

 troublesome in preserved specimens, especially those preserved in 

 formalin. It is almost insoluble in water, only slightly soluble in 

 alcohol, but it is freely soluble in dilute acids and aqueous potassium 

 hydroxide solutions. 



12. Following digestion, many specimens are adequately trans- 

 parent for study in alcohol. To attain uniformity and to avoid 

 storage problems, specimens are worked into glycerin through a series 

 beginning with 40 percent glycerin in distilled water or in stock 

 potassium hydroxide solution (stock solution 4a), followed by 70 

 percent glycerin (stock solution 4b) and full strength glycerin. The 

 potassium hydroxide and glycerin mixtures are preferred to create a 

 slight residual alkaUnity for long-term storage of specimens. A few 

 crystals of thymol are added to the final glycerin to prevent growth of 

 microorganisms, as the digestion products are an ideal medium for 

 such growth. 



For final storage, the specimen is placed in a glass jar with a 

 bakelite top. The jar size should be sufficient to allow complete 

 coverage of the specimen by glycerin but sufficient space between the 

 glycerin and top so that it can be screwed on loosely without danger 

 of glycerin spillage. Metallic containers and tops should be avoided 

 as glycerin reacts in contact with metal, often resulting in colored 

 glycerin. 



Glycerin specimens. — Specimens that have not been successfully 

 cleared by any of the modifications of the Schultze method (Davis 

 and Gore, 1947; Evans, 1948; Hollister, 1934) may be improved or 



