8 PRACTICAL PHYSIOLOGY [l. 



Place undiluted egg-white in a test-tube, and add strong caustic 

 potash. The whole mass becomes a jelly, so that the tube can be 

 inverted without the mass falling out. 



({/.) Its solution gives the general reactions for proteids under 

 1 (A.). 



(2.) Acid- Albumin [or Syntonin]. 



Preparation. (A.) To dilute egg-albumin, add o.i per cent, sul- 

 phuric acid, and warm gently for several minutes = acid-albumin. 



(B.) To finely-minced muscle, e.g., of frog, add ten times its volume of 

 dilute hydrochloric acid (4 cc. of acid in I litre of water), and allow it to 

 stand for several hours, taking care to stir it frequently ; filter, the filtrate 

 is a solution of a globulin combined with an acid, and has been called 

 syntonin. 



(C.) Allow concentrated hydrochloric acid to act on fibrin for a time, and 

 filter. 



(D.) It may be prepared by dissolving myosin in excess of . I per cent. HC1, 

 and after a time neutralising the solution with sodic carbonate. 



(E. ) To undiluted egg-white, add acetic acid = a jelly of acid-albumin. 



Use the clear nitrate from (A.) or (B.) for testing. 



(a.) The reaction is acid to litmus paper. 



(b.) Boil the solution ; it does not coagulate. 



(&) Add litmus solution, and neutralise with very dilute caustic 

 soda = a precipitate soluble in excess of the alkali or acid. 



(d.) Kepeat (c.), but add sodium phosphate before neutralising ; 

 the acid-albumin is precipitated when the fluid is neutralised ; 

 so that sodium phosphate does not interfere with its precipita- 

 tion. 



(e.) Add strong nitric acid = a precipitate which dissolves on 

 heating, producing an intense yellow colour. 



(/*.) It is precipitated like globulins by saturation with neutral salts, e.g., 

 NaCl, MgS0 4 , (NH 4 ),S0 4 . 

 (</.) Boiled with lime- water = partial coagulation. 



8. IV. Caseinogen, the chief proteid of milk was formerly 

 regarded as a derived albumin. It is precipitated by acid. Like 

 globulins it is precipitated by saturating milk with Nad or MgS0 4 , 

 but it is not coagulated by heat. (See " Milk.") 



9. V. Proteoses or Albumoses. In the peptic and tryptic 

 digestion of proteids these bodies are formed as intermediate pro- 

 ducts. In peptic digestion of albumin, acid-albumin is first formed, 

 and finally peptone. Between the two is the group of proteoses or 

 albumoses. There are several of them, and they were formerly 

 grouped together as hemi-albumose. These proteoses have been 

 subdivided into albumoses, globuloses, caseoses, &c., according as 

 they are derived from albumin, globulin, or casein. (See " Diges- 

 tion.") Witte's peptone usually contains a small amount of 



