Extraction with Ammonium Chlorid and Hydrochloric Acid.—The residue, after exhaustion with cold water, is extracted with a solution of ammonium chlorid containing 150 grams of the salt in a liter. This method of extraction is entirely similar to that with water just described. Globulins and myosin pass into solution by this treatment. The residual mass is washed as free as possible of the solvent and is then further extracted with dilute hydrochloric acid containing four cubic centimeters of the fuming acid in a liter. The treatment with dilute acid is continued until no further substance passes into solution. This is determined by neutralizing a portion of the extract with sodium carbonate, or by the direct addition of potassium ferrocyanid. In either case absence of a precipitate indicates that no nitrogenous matters are present in the solution.
Extraction with Alkali.—The residue from the acid extraction is washed with water until the acid is removed and then extracted in a similar manner with a dilute solution of sodium or potassium hydroxid containing not to exceed two grams of the caustic to the liter. When this residue is finally washed with water and a little acetic acid, it will be found that practically all the purely albuminous bodies contained in the tissues have been extracted with the exception of any fibrin, which the blood, present in the tissues at the commencement of the extraction, may have contained. The extract should be acidified with acetic as soon as obtained.
Extraction with Boiling Water.—The residual matter boiled for some time with water will part with its collagen, which, when transformed by the heat into glutin, passes into solution.
The sarcolemma, membranes, elastic fibers and keratin remain undissolved.
413. Contents of the Several Extracts.—By the systematic treatment of muscular tissues in the manner just described, the nitrogenous bodies they contain are separated into five classes, viz.:
Cold Water Extract.—This contains serum albumin, serum globulin, muscle albumin, myosin, mucin and peptone.
Ammonium Chlorid Extract.—This solution contains the globulins and also in many cases some myosin and serum globulin.
Hydrochloric Acid Extract.—When the extractive matter removed by hydrochloric acid, thrown out by sodium carbonate and well washed with water, has a neutral reaction, it consists of syntonin, when acid, of an albuminate.
Alkali Extract.—The acid albumin of the animal tissue is found in the alkaline solution and may be thrown out by making the solution slightly acid.
Insoluble Residue.—The fifth class contains the insoluble nitrogenous bodies mentioned above.