2o8 THE MICHOSCOPE AND HOW TO USE IT. 



gland, and allow to stand for three weeks. Press the glycerine 

 through muslin to remove the gland tissue. The glycerine is a 

 solvent for the t7-ypsin of the pancreas, just as it is for other 

 soluble ferments. One cc. of the glycerine filtrate is added to 19 

 cc. of I per cent, solution of sodic carbonate. The fluid becomes 

 turbid, but after filtration a pale yellow fluid is obtained. The 

 tissue to be digested is placed in this fluid, and the whole is kept 

 at a temperature of 40° C. in a water bath. Sections of softened 

 bone digested by this method are preserved in a 10 per cent, solu- 

 tion of common salt (Birch). 



Artificial Gastric Digestion for Skin, etc.— This was intro- 

 duced by Dr. Stirling several years ago, but, as it is Httle known, 

 I have ventured to insert it here. It is invaluable for ascertaining 

 the arrangement of the elastic fibres and muscular tissues in the 

 skin. It depends for its value on the fact that certain substances 

 are digested more rapidly than others, and so are rapidly 

 removed. Make the gastric juice by mixing i cc. of pure hydro- 

 chloric acid with 500 cc. water, and add i gramme of pepsin, or a 

 few drops of a glycerine extract of the gastric mucous membrane. 

 It is well to keep the mixture at 38° C. for two or three hours 

 before using. The piece of skin to be digested is stretched 

 over a small glass ring and firmly tied to it. It is then placed in 

 some (200 cc.) of the digesting fluid, which is kept at a temper- 

 ature of 38'' C. in an ordinary water bath for a period varying 

 from three to eight hours — the time depending on the age and 

 size of the piece of skin. After partial digestion the skin is placed 

 in water for twelve hours, when it swells up and becomes ex- 

 tremely transparent. It may be kept most advantageously in a 

 10 per cent, solution of common salt, and may be hardened in one 

 of the ordinary hardening fluids, and afterwards stained with log- 

 wood and carmine. It is also applicable to other tissues. I 

 would advise readers to try the method, and am sure they will 

 be satisfied with the results. 



