50 LABORATORY EXERCISES. 



25. STUDY OF BEEF BLOOD. (Dem.) 



Materials : Concentrated nitric acid and ammonia, iodine solution, 

 Fehling's solution; test-tubes, alcohol-lamp, platinum-foil, bottle 

 and rubber stopper; three bottles of blood prepared as follows: 



Bottle No. 1. Take a bottle to the slaughter-house and get the 

 butcher to fill it with fresh blood. Carefully set it aside (in cold 

 storage room if possible), taking care not to jar in the least the con- 

 tents. At the end of several days the solid clot should be sur- 

 rounded by a transparent serum of a pale straw color. Label the 

 bottle Clotted Blood. 



Bottle No. 2. Get the butcher to collect some blood in a pail and 

 whip it rapidly for some time with a brush-broom or with his hands. 

 Fill bottle No. 2 with the red liquid remaining in the pail, labelling 

 it Defibrinated Blood. 



Bottle No. 3. Collect the stringy substance clinging to the broom, 

 wash it with water until it is white, and place it in bottle No. 3, in 

 a 4$ solution of formalin * or in 80$ alcohol ; label it Blood Fibrin. 



A. Study of clotted blood. 



1. Describe the preparation of clotted blood 



(see Bottle No. i under Materials above). 



2. Pour off all the liquid serum into another 



bottle of the same size. 



a. What proportion of blood appears to 



be serum? 



b. What is the color of the serum ? 



3. The solid mass left behind in Bottle No. i 



is the blood-clot. 



a. Hold the bottle in a horizontal posi- 



tion and compare the shape of the 

 clot with that of the bottle. 



b. What is the size of the clot compared 



with the size of the bottle? (See 

 2, a above.) 



* 4% formalin is prepared by diluting 1 volume of formalin with 

 10 volumes of water, 



