BLOOD. 195 



tion for proteose and peptone by saturating with ammonium sul- 

 phate according to directions given on page 114. 



(e) Crystallisation of Sodium Chloride. Place the remainder 

 of the filtrate in a watch glass and evaporate it on a water-bath. 

 Examine the crystals under the microscope and compare them with 

 those in Fig. 60, page 200. 



6. Test for Iron. Incinerate a small portion of the coagulum 

 from the last experiment (5) in a porcelain crucible. Cool, dis- 

 solve the residue in dilute hydrochloric acid and test for iron by 

 potassium ferrocyanide or ammonium thiocyanate. Which of 

 the constituents of the blood contains the iron? 



7. Laky Blood. Note the opacity of ordinary defibrinated 

 blood. Place a few cubic centimeters of this blood in a test-tube 

 and add water, a little at a time, until the blood is rendered trans- 

 parent. It is now laky blood. How does the water act in causing 

 this transparency? Examine a drop of laky blood under the micro- 

 scope. How does its' microscopical appearance differ from that of 

 unaltered blood? What other agents may be used to render blood 

 laky? 



FIG. 57. 





Q 



\ 



EFFECT OF WATER ON ERYTHROCYTES. 



8. Osmotic Pressure. Place a few cubic centimeters of blood 

 in each of three test-tubes. Lake the blood in the first tube accord- 

 ing to directions given in the last experiment (7) : add an equal 

 volume of isotonic (0.9 per cent) sodium chloride to the blood in 

 the second tube, and an equal volume of 10 per cent sodium chloride 

 to the blood in the third tube. Mix thoroughly by shaking and 

 after a few moments examine a drop from each of the three tubes 



