6 PRACTICAL PHYSIOLOGY. [l. 



EGG-ALBUMIN. SERUM-ALBUMIN. 



(iii.) The precipitate with (iii.) The corresponding pre- 



nitric acid is soluble with diffi- cipitate is much more soluble 



culty in excess of the acid. in excess of acid. 



(iv.) The precipitate obtained (iv.) The corresponding pre- 



by boiling is but slightly soluble cipitate is soluble in strong 



in boiling nitric acid. nitric acid. 



(v.) Its solution is not pre- (v.) Gives the same reactions 



cipitated by MgS0 4 , but is as in ( 5, I. /.). 

 completely precipitated by 

 (NH 4 ),S0 4 . 



[(vi.) When injected under [(vi.) When injected under 



the skin, or introduced in large the skin, it does not appear in 



quantities into the stomach or the urine.] 

 rectum, it is given off by the 

 urine.] 



(3.) Lact- Albumin, see " Milk." 



6. II. Globulins are insoluble in pure water, soluble in dilute 

 saline solutions e.g., NaCl, MgS0 4 , (NH 4 ) 2 SO 4 but insoluble in 

 concentrated or saturated solutions of neutral salts. Their solu- 

 tions in these salts are coagulated by heat. They are soluble in 

 dilute acids and alkalies, yielding acid- and alkali-albumin respec- 

 tively. Most of them are precipitated from their saline solution by 

 saturation with sodic chloride, magnesium sulphate, and some other 

 neutral salts. 



(i.) Serum-Globulin. It forms about half of the total proteids 

 of blood-serum. It is insoluble in water, readily soluble in dilute 

 saline solutions (NaCl, MgS0 4 ). Its solutions give the general 

 reactions for proteids. Its NaCl solution coagulates at about 



75 C. 



(a.) Neutralise 5 cc. of blood-serum with a few drops of dilute 

 sulphuric acid (o.i per cent.), then add 75 cc. of distilled water, 

 and allow the precipitate to settle. Pour off the fluid and divide 

 the precipitate into two portions, noting that it is insoluble in 

 water, but soluble in excess of acid. 



(b.) Boil a portion of the neutralised fluid = coagulation. 



(c.) Saturate blood-serum in a test-tube with magnesium sulphate, 

 shaking briskly for some time. Serum-globulin separates out and 

 floats on the surface. Filter, and test the filtrate for serum- 

 albumin. 



(d.) Place 5 cc. of blood-serum in a tube, and pour a saturated 

 solution of magnesium sulphate down the side of the tube to form 

 a layer at the bottom of the tube. Where the two fluids meet 

 there is a white deposit of serum-globulin. 



