6 CHEMICAL PHYSIOLOGY. 



(c.) To 5 cc. of blood-serum in a test-tube, add an excess 

 of crystals of magnesic sulphate, and shake briskly for some 

 time. On standing, a white precipitate of serum-globulin 

 falls. 



Pour off the supernatant fluid, and observe that the pre- 

 cipitate is redissolved on the addition of water. Filter the 

 supernatant fluid and test it for other proteids, which it 

 still contains viz., serum-albumin. 



(d.) Take 5 cc. of blood-serum and pour a saturated solu- 

 tion of magnesic sulphate down the side of the glass to form 

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

 meet, there is a copious white deposit of serum-globulin. 



(e.) Treat another portion of serum to saturation with 

 crystals of sodic chloride, and observe the same results. 



(f.) Take another portion of serum, precipitate the serum- 

 globulin with magnesic sulphate, and filter. To the filtrate 

 add powdered sodic sulphate in excess, which gives a further 

 precipitate. The filtrate still gives the reactions for pro- 

 teids. 



(3.) Fibrinogen, see " Blood." 



7. IIL Derived Albumins are insoluble in pure water and in 

 solutions of sodic chloride, but readily soluble in dilute hydro- 

 chloric acid and dilute alkalies. The solutions are not coagulated 

 by heat. 



(1. ) Alkali-albumin, or Alkali-albuminate Preparation of Solu- 

 tion. Prepare a 5 per cent, solution of egg-albumin, as directed 

 in Lesson I., 1. 



(a.) To the egg-albumin add a few drops of solution of 

 caustic soda or potash (0-1 per cent.), and heat it gently for 

 a few minutes -- alkali-albumin. Boil the fluid ; it does not 

 coagulate. 



(b.) Test the reaction, it is alkaline. 



(c.) Cool some of the alkali-albumin and colour it with 

 litmus solution. Neutralise it carefully with very dilute 

 acid = a precipitate on neutralisation, which is soluble in 

 excess of the acid. 



