Therapeutic products containing histaminase are obtained from intestinal mucous membrane by treating the fresh membrane or undried waste membrane with a disinfecting agent, freezing, extracting with the buffer solution, and then precipitating with a water-miscible solvent.  Suitable disinfectants are complex mercury compounds or amines of higher fatty acids.  The extraction with a buffer solution is preferably effected in neutral or feebly alkaline condition, and if desired for a long time at a low temperature and then at a raised temperature not above about 45 DEG  C.  The solution may be filtered through a bacterial filter.  The yield may be increased by cooling the water-miscible solvent below 0 DEG  C. before adding it to the buffer solution extract.  The precipitate may be purified by redissolving in a buffer solution and evaporating to dryness under reduced pressure or in the frozen state under greatly reduced pressure.  Suitable buffers are sodium phosphate, ammonia-ammonium-chloride, and glycocoll; glycerin may be added. Suitable solvents are low molecular weight aliphatic ketones such as acetone and methyl-ethylketone, ethers of polyhydric alcohols such as monoethyl ethers of glycol and glycerin.  In examples (1) mucous membrane from fresh intestines is stirred with a solution of sodium chloride and the hydrochlorides of the amines obtained from palm nut oil fatty acids, and the mixture is frozen and ground.  It is then stirred with \baN/10\be phosphate buffer at pH 7,4, centrifuged, and the solution filtered and treated with acetone cooled to -5 DEG  C.; (2) a product obtained in the manner described from waste mucous membrane is redissolved in a phosphate buffer, filtered, concentrated to one-tenth its volume and dried in frozen condition under reduced pressure.  The Specification as open to inspection under Sect. 91 is not limited to the pre-treatment of the membrane by disinfecting and freezing.ALSO:Therapeutic products containing histaminase are obtained from intestinal mucous membrane by treating the fresh membrane or undried waste membrane with a disinfecting agent, freezing, extracting with a buffer solution, and then precipitating with a water-miscible solvent.  Suitable disinfectants are complex mercury compounds or amines of higher fatty acids.  The extraction with a buffer solution is preferably effected in neutral or slightly alkaline condition, and if desired for a long time at low temperature and then at a raised temperature not above about 45 DEG  C.  The solution may be filtered through a bacterial filter.  The yield may be increased by cooling the water-miscible solvent below 0 DEG  C. before adding it to the buffer solution extract.  The precipitate may be purified by redissolving in a buffer solution and evaporating to dryness under reduced pressure or in the frozen state under greatly reduced pressure.  Suitable buffers are sodium phosphate, ammonia-ammonium chloride, and glycocoll; glycerin may be added. Suitable solvents are acetone, methyl ethyl ketone, and ethers of polyhydric alcohols such as monoethyl ethers of glycol and glycerin. In examples: (1) mucous membrane from fresh intestines is stirred with a solution of sodium chloride and the hydrochlorides of the amines obtained from palm nut oil fatty acids, and the mixture is frozen and ground.  It is then stirred with N/10 phosphate buffer at pH 7,4, centrifuged, and the solution filtered and treated with acetone cooled to -5 DEG  C.; (2) a product obtained in the manner described from waste mucous membrane is redissolved in a phosphate buffer, filtered, concentrated to one-tenth its volume, and dried in frozen state under reduced pressure.  The Specification as open to inspection under Sect. 91 is not limited to the pretreatment of the membrane by disinfecting and freezing.