THE BLOOD. 21 



4. Action of Saline Solution. 



(a.) Take 2 cc. of defibrinated blood in a test-tube, label 

 it D, add 5 volumes of a 10 per cent, solution of sodic 

 chloride. Observe the change of colour. It becomes a very 

 bright florid red, more brick-red than the original blood 

 itself. Compare its colour with that in A, B, and C. It is 

 opaque. 



5. Haemoglobin does not Dialyse. 



(a.) Place a watery solution of defibrinated blood in a 

 dialyser, and suspend it in a large vessel of distilled water. 

 Carefully test the dialyser beforehand to see that there are 

 no holes in it. If there are any fine pores, close them with 

 a little white of egg, and coagulate it with a hot iron. 



(b.) After several hours observe that no haemoglobin has 

 passed into the water. 



(c.) Test the diffusate for chlorides. 



6. Phenomena of Coagulation. Place a small porcelain capsule 

 on the table ; decapitate a rat, and allow the blood to flow into 

 the capsule. Within a few minutes the blood congeals, and when 

 the vessel is tilted the blood no longer flows as a fluid, but as a 

 solid. It then coagulates completely. Allow it to stand, and 

 after an hour or so, pale-yellow coloured drops of a fluid the 

 serum are seen on the surface, being squeezed out of the red 

 mass, the latter being the clot. 



7. Frog's Blood Coagulation of the Plasma. Place 5 cc. of 

 normal saline (0'75 per cent, salt solution) in a test-tube sur- 

 rounded with ice. Expose the heart of a pithed frog, and cut 

 into the ventricle, allowing the blood as it escapes to flow into 

 the normal saline. Mix the two, and the corpuscles (owing to 

 their greater specific gravity) after a time subside. After they 

 have subsided remove the supernatant fluid the plasma mixed 

 with normal saline by means of a pipette. Place it in a watch- 

 glass, and observe that it coagulates. 



8. Mammalian Blood. 



(A.) Study coagulated blood obtained from the slaughter- 

 house. Run the blood of a sheep or ox into a tall cylindrical 



