4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



3. Distilled water. 



4. Hydrogen peroxide (H2O2), U.S. P. grade. A 3 percent solution 

 keeps better than stronger solutions and has been found satisfactory. 



5. Borax or sodiiun borate powder (sodium tetraborate, Na2B407- 

 IOH2O), U.S. P. grade or better is preferred. 



6. White glycerin, U.vS.P. grade or better is preferred. The liquid 

 should be obtained and stored in glass containers as it becomes colored 

 in contact with metal. 



7. Trypsin pov/der (purified).^ This material may be sold also as 

 pancreatic protease and pancreatin. It typically contains a wide 

 variety of enzymes as well as trypsin. The commercial preparation 

 must be free of collagenase contamination and must have been 

 purified to the extent that it is free or nearly free of elastase. One 

 method of effective removal of elastase from pig pancreas preparations 

 that resulted in a good yield of trypsin and chymotrypsin was de- 

 scribed by Kunitz and Northrop (1936) ; see also Bal6 and Banga 

 (1950). Highly purified and concentrated trypsin preparations are 

 expensive and unnecessary. Extensive purification may reduce or 

 eliminate desirable enzymes that are produced by the pancreas, 

 particularly the chymotrypsins and the wide variety of other proteases 

 as well as lipolytic and diastatic enzymes. The enzyme potency is 

 often expressed as a ratio. The figure 1:80 usually means that one 

 part will digest 80 parts casein when measured by the specified 

 pancreatin test. Other specifications may include the activity of 

 individual enzymes expressed as units per gram. 



The dry powder is stable and may be stored at room temperature 

 for a considerable length of time. To insure stability and to reduce 

 possible bacterial multiplication, however, I suggest keeping it in a 

 tightly closed container under refrigeration. One hundred grams is 

 suflficient to clear nearly 100 small specimens, if they are properly 

 prepared. 



8. Thymol, N.F. crystals (C10H14O). 



9. Concentrated formaldehyde solution, about 40 percent by vol- 

 ume, U.S. P. 



10. Ethyl alcohol (ethanol), 95 percent, U.S. P. (optional; used in 

 step 10 of "Method" section). Absolute (100 percent) ethyl alcohol 

 is desirable. 



11. Xylene (xylol) (optional; used in step 10 of "Method" section). 



' I have made extensive use of Fisher Scientific Company's "Purified Trypsin 

 Powder" (1 ISO N.F.), Catalog Number T-360. Similarly good results have been 

 obtained from Difco Laboratories' "Trypsin, Difco Certified" (1 :25{) N.F.), Code 

 Number 0152. 



