ANIMAL FLUIDS AND TISSUES. 655 



oxalate solution removes the calcium salts by precipitation. The 

 injection causes the production of antithrombin in the injected 

 animal. 



Blood-serum differs from plasma only in containing no fibrinogen 

 and much active thrombin. 



Experiment 74. (Separation of the proteins of blood-plasma and of blood-serum.) 



a. Fibrinogen. To 5 c.c. of salt or oxalate plasma add an equal volume of 

 saturated solution of sodium chloride. Fibrinogen is precipitated, carrying 

 with it the prothrombin. Filter and preserve the nitrate for the separation of 

 albumin and globulin, as detailed below. 



Dissolve the fibrinogen and protlirombiu in a little dilute salt solution, add 

 an excess of calcium chloride, and keep the mixture at 40 C. for a few minutes. 

 Shreds of fibrin are formed and precipitated. 



b. To 25 c.c. of blood-settim, contained in a mortar, add 20 grammes of 

 ammonium sulphate and rub with a pestle until the fluid is saturated with 

 the salt. Filter through dry filter-paper, acidulate the filtrate with acetic 

 acid, and boil. No change occurs, as both proteins have been precipitated 

 completely. 



c. To 25 c.c. of blood-serum add 25 c.c. of a saturated solution of am- 

 monium sulphate; filter; and wash with a saturated solution of the salt. 

 Under this treatment only serum-globulin is precipitated, while serum- 

 albumin is kept in solution. Heat the filtrate to boiling: serum-albumin 

 is coagulated. Place some of the residue left on the filter (globulin) in a 

 test-tube and pour water on it; the protein dissolves by virtue of the small 

 quantity of salt adhering to it. Heat the solution to boiling : coagulation 

 takes place. 



d. Saturate 25 c.c. of serum with magnesium sulphate : serum-globulin is 

 precipitated, serum-albumin remains in solution. 



Serum-albumin and serum- globulin give the ordinary protein reactions. 



A quick method to obtain fibrin is to stir or whip blood with twigs im- 

 mediately after it has been shed. Under these conditions the fibrin 

 does not entangle the blood-corpuscles, but separates as a stringy mass, 

 which adheres to the twigs used for stirring. The remaining part, being 

 made up of the corpuscles suspended in the serum, is designated as defibrin- 

 ated blood. 



Red blood-corpuscles when wet contain of water, 54.63 per cent. ; 

 haemoglobin, 41.1 per cent.; other proteins, 3.9 per cent.; fats 

 (chiefly cholesterin and lecithin), 0.37 per cent. The quantity of 

 water in corpuscles varies widely, and most likely ranges in healthy 

 blood from 76 to 80 per cent. Dried corpuscles contain about 90 

 per cent, of haemoglobin. 



While red blood-corpuscles can be broken up (laked) by the 

 addition of various substances to the blood, the simplest way is by 



