92 



PRACTICAL PHYSIOLOGY. 



[XIL 



rubbing with well washed white sand). Replace the pulp in the boiling water 

 and add 3-4 grams of caustic potash {i.e., for 100 grams liver). Heat on a 

 water-bath and evaporate until about 203 cc. of fluid remains for 100 grams 

 liver. If a pellicle fonns on the surfiice, heat the whole in a beaker covered 

 with a watch-glass until the pellicle is dissolved. Allow to cool. Neutralise 

 with dilute liydrochloric acid and precipitate the })roteids by adding alter- 

 nately hydrochloric acid and potassio mercuric iodide in small quantities, 

 until no further precipitation occurs. Filter through a thick filter to remove 

 the deposit of proteids. Remove the deposit from the filter with a spatula, 

 and rub it up in a mortar with water containing hydrochloric acid and 

 potassio mercuric iodide, and again filter the pulp. Repeat this process 

 several times to get out all the glycogen. Mix the filtrates and add 2 volumes 

 of 96 per cent, alcohol, stirring briskly all the time ; this precipitates the 

 glycogen. Allow it to stand in a cool place for a night ; filter, and wash the 

 precipitate thoroughly, first with 62 per cent, and then with 96 per cent. 



Fig. 47. — Hot-Air Oven. O. Gas regulator ; E. Thermometer. 



alcohol. Usually the glycogen contains a trace of albumin. To remove the 

 latter, redissolve the moist glycogen in warm water, and after cooling, repre- 

 cipitate with HCl and potassiomercuric iodide and proceed as above. Wash 

 the glycogen with alcohol and then with ether, and dry it by exposure to the 

 air. This method gives the most satisfactory results. 



{d.) Instead of a rat or rabbit's liver, use oysters or the edible mussel, and 

 prepare a solution of glycogen by methods {a. ) or (*.). 



(e.) Use the other half of the liver of the rat or rabbit that has 

 been kept warm, and make a similar extract of it. 



2. Precipitate the Glycogen.— Evaporate the filtrate of (a.) or 

 (&.) to a small bulk, and precipitate the glycogen as a white 

 powder by adding a large amount of alcohol — at least 60 per cent. 



