COAGULATION OF BLOOD 



161 



7. Reaction of Blood Plasma. Wet a piece of red litmus-paper in 

 saturated magnesium sulphate solution, then touch one end of the strip with 

 a drop of blood drawn from your finger under sterile conditions. After a 

 few moments wash off the excess of corpuscles in neutral distilled water. 

 The blue at the point of contact with the blood indicates alkalinity. 



8. The Specific Gravity of Blood. From standard mixtures of 

 chloroform and benzol with specific gravity of i . 050, i . 060, and i . 070 make 

 up a set of specific-gravity solutions of 1.050, 1.052, 1.054, etc., to 1.070. 

 These standards may be kept in stoppered 4-dram vials, or in test-tubes. 

 The specific gravity of blood is determined by inserting with a pipet a 

 drop of freshly drawn blood into the middle of one of the solutions, say 

 i .056. Since the blood does not mix with the chloroform and benzol, the 

 drop will rise or sink according to its relative specific gravity. By a few 

 trials one may quickly find a specific gravity in which the drop of blood 

 floats without rising or sinking. This represents the specific gravity of the 

 drop of blood. 



This method permits rapid clinical application and has proven of con- 

 siderable interest in the hands of clinicians. 



9. The Isotonicity of Blood. The absorption or loss of water by the 

 corpuscles of blood in solutions of other concentrations than that of 

 blood plasma can be used as a 



means of determining the isoton- 

 icity of blood. Make up a series 

 of solutions of sodium chloride, 

 varying by tenths, from 0.5 to 1.2 

 per cent. Prepare a series of 

 slides with vaselin rings and 

 mount drops of human blood in 

 drops of saline of 0.4, 0.6, 0.8, i, 

 1.2 and 1.4 per cent., examine 

 immediately then every ten min- 

 utes under a high-power micro- 

 scope. The corpuscles of some 

 of the slides will swell up and 

 may disintegrate, others will 

 show crenation as in figure 126. 

 In the isotonic solutions the cor- 

 puscles will appear of their nor- 

 mal size and condition. 



10. Coagulation of Blood. a. formal Clot. Anesthetize a dog, insert 

 a cannula into the carotid or femoral artery, and draw samples of blood 

 into two or three clean, dry test tubes. Draw one sample into a test- 

 tube that has had its sides oiled. Note the exact time at which the blood 



FIG. 132. Microscopic View of Clot Showing 

 Fibrin Network. 



