OF BLOOD. 53 



8. Tie up in a piece of bladder or other animal membrane some whipped 

 blood, and place the bag containing the blood in a beaker of distilled water. 



The colouring matter and proteids exhibit but a slight tendency to pass 

 through the membrane ; the soluble salts pass through readily, and their 

 presence can be recognized in the water by the usual tests. 



9. Pour over some fibrin contained in a watch-glass some solution of 

 peroxide of hydrogen. Bubbles of oxygen are given off. If some tincture of 

 guaiacum be added a blue colour is developed. Gluten, potato peelings, and 

 many other substances develop a blue colour under the same conditions. 



X. T/ie Colouring Matter of the Blood. 



1. Observe the solar spectrum, noting the positions of the dark lines 

 D, E, b and F, in relation to the colours. Compare it with the spectrum of 

 a gas flame, which shows no dark lines. 



2. Observe the spectrum of a flame coloured with sodic chloride, noting the 

 position of the bright yellow line. 



3- Oxy-hgemoglobin. Introduce defibrinated blood into a test-tube, 

 and observe its opacity when undiluted. 



a. Dilute by adding five to ten times its bulk of water. Place the test-tube 

 in front of the slit of the spectroscope, direct it to a gas flame. The only light 

 which passes through is that of the red end of the spectrum. 



b. Add water until the green appears. Note the dark space (absorption 

 band.) between the red and green. 



c. Dilute still further until the yellow-green light is distinguishable in the 

 middle of the dark space, dividing the single broad band into two. 



d. After a further addition of water, note that the band nearest the D line 

 is somewhat more sharply defined than the other. The spectrum is still 

 shortened by the absorption of its violet end. 



e. On diluting, until the solution is almost colourless, two faint bands ar 

 still visible. 



f. Map on the diagram the appearances observed in 3, b and d. 



4- Reduced Haemoglobin. To some blood diluted as in 3, d t add a 

 drop of solution of ammonic sulphide, and warm gently. The colour becomes 

 purplish. Place the tube in front of the slit as before, and observe the 

 change which has occurred. A single absorption band, with ill-defined edges, 

 takes the place of the two bands previously observed. Map its position on 

 the diagram. 



5- Alkaline Hsematin. Add to solution of blood, rather stronger 

 than the last, a drop of solution of caustic potash. Warm gently; the colour 

 completely changes. Ah absorption band appears to the left of the line D, 

 and much of the blue end of the spectrum is cut off. 



6. Reduced Alkaline Hsematin. To the solution obtained in 5 

 add a drop or two of ammonic sulphide and warm gently. Observe the 

 change of colour. Dilute if necessary. A strongly marked band is seen to the 

 right side of the line D, and a second less defined, which nearly coincides with 

 the line E. 



