376 NATIVE ALBUMINS AND GLOBULINS. 



present in Urge amount, a red precipitate occurs, but if mere traces are present only the fluid, 

 becomes red.] . __ 



(3) The addition of a few drops of a dilute solution of cupnc sulphate, and the subsequent 

 addition of caustic potash or soda, give a violet colour, which deepens on boiling ; [the same 

 colour is obtained by adding a few drops of Fehling's solution (biuret-reaction)]. 



(4) They are precipitated after strong acidulation by acetic acid and by potassium ferrocyanide. 



(5) "When boiled with concentrated hydrochloric acid, they give a violet-red colour (Lieber- 

 mann'g reaction). 



(6) Sulphuric acid containing molybdic acid gives a blue colour (Frohde). 



(7) Their solution in acetic acid is coloured violet with concentrated sulphuric acid, and shows 

 the absorption-band of hydrobilirubin {Adamkicwicz). 



(8) Iodine is a good microscopic reagent, which strikes a brownish-yellow, while sulphuric 

 acid and cane-sugar give a purplish-violet (K Schultze). 



[(9) When rendered strongly acid with acetic acid and boiled with an equal volume of a con- 

 centrated solution of sodic sulphate, they are precipitated. This method is used for removing 

 proteids from other liquids, as it does not interfere with the presence of other substances. 

 Saturation with sodio-magnesic sulphate precipitates the proteids, but not peptones, and the 

 same is the case with saturation with neutral ammonia sulphate ( 249).] 



[(10) The precipitation of albumin by acids is more delicate when the acid is dissolved in 

 alcohol containing 10 per cent, of ether ; the precipitate is not dissolved by an excess of the 

 reagent.] 



[(11) Most of them are precipitated by strong mineral acids, and metaphosphoric acid, tannic 

 acid (in an acid solution), phospho-wolframic and phospho-molybdic acids (in acid solution); 

 potassio-mercuric iodide (in acid solutions); many metallic salts, e.g., of Cu, Pb, Ag, Hg; chloral, 

 phenol, trichloracetic acid, picric acid, alcohol. Taurocholic acid precipitates albumin and syn- 

 toniu, but not peptone or hemi-albumose ( 275).] 



249. THE ANIMAL PBOTEIDS AND THEIR CHARACTERS. Class I. Native Albumins 

 occur in a natural condition in animal solids and fluids. They are soluble in water, and are 

 not precipitated by alkaline carbonates, NaCl, or by very dilute acids. Their solutions are 

 coagulated by heating at 65 to 73 C. Dried at 40 C, they yield a clear, yellow, amber-coloured, 

 friable mass, "soluble albumin," which is soluble in water. 



(1) Serum-albumin ( 32 and 41). [Its specific rotatory power is -56.] Almost all its 

 salts may be removed from it by dialysis, when it is no longer coagulated by heat. It is 

 coagulated by strong alcohol ; and not very readily precipitated by hydrochloric acid, while the 

 precipitate so formed is easily dissolved on adding more acid. When precipitated, it is readily 

 soluble in strong nitric acid. It is not coagulated when shaken up with ether. The addition 

 of water to the hydrochloric solution precipitates acid-albumin. For its presence in urine, 

 S264. 



(2) Egg-albumin. When injected into the blood-vessels or under the skin, or even when 

 introduced in large quantity into the intestine, part of it appears unchanged in the urine ( 192, 

 4, and 264). When shaken with ether it is precipitated. These two reactions serve to dis- 

 tinguish it from (1). The specific rotation is-35'5, i.e., for yellow light. Amount of S, 1'6 

 per cent. 



(Metalbumin and Paralbumin have been found by Scherer in ropy solutions in ovarian cysts ; 

 they are only partially precipitated by heat. The precipitate thrown down by the action of 

 strong alcohol is soluble in water. ) 



Class II. Globulins are native proteids, insoluble in distilled water, but soluble in dilute 

 neutral saline solutions, i.e., neutral solutions of the alkalies and alkaline earths, e.g., NaCl, 

 KC1, NH 4 C1, MgS0 4 , (but not Na,CO g , Na 2 HP0 4 ), sodium chloride of 1 per cent., and in 

 magnesium sulphate. These solutions are coagulated by heat, and are precipitated by the 

 addition of a large quantity of water. Most of them are precipitated from their sodium chloride 

 solution by the addition of crystals of sodium chloride, and also by saturating their neutral 

 solution at 30 with crystals of magnesium sulphate. When acted upon by dilute acids they 

 yield acid-albumin, and by dilute alkalies, alkali-albumin. 



(1) Globulin (Crystallin) is obtained by passing a stream of CO;, through a watery extract of 

 the crystalline lens. " - 



(2) Vitellin is the chief proteid in the yolk of egg. It is also said to occur in the chyle (?) 

 and in the amniotic fluid ( Wcyl) : Both the foregoing are not precipitated from their neutral 

 solutions by saturation with sodium chloride. 



(3) Para-globulin or Serum-globulin ( 29), and in urine ( 264). 



(4) Fibrinogen ( 29). In the clear jelly-like secretion of the vesiculre seminales of the 

 guinea-] it:, there is a globulin-like body closely resembling fibrinogen. It contains 29 per cent, 

 of albumin, with scarcely any ash. If it be touched with a trace of blood-serum, without 

 mixing them, it gradually and completely forms a solid mass quite like fibrin. 



(6) Myosin is the chief proteid in dead muscle. Its coagulation in muscle post-mortem con- 

 stitutes rigor mortis. If muscle be repeatedly washed, and afterwards treated with a 10 per 



