6o 



A MANUAL OF PHYSIOLOGY 



corpuscles settle. The plasma can then be siphoned or pipetted off. 

 Instead of dog's blood, the blood of an ox or pig may be obtained at 

 the slaughter-house. 



4. Preparation of Fibrin-Ferment. Precipitate blood-serum with 

 ten times its volume of alcohol. Let it stand for several weeks, then 

 extract the precipitate with water. The water dissolves out the 

 fibrin-ferment, but not the other coagulated proteids. 



5. Serum. Test the reaction, and determine, both by the hydro- 

 meter and the pycnometer,or specific gravity bottle, the specific gravity 

 of the serum provided, or of the serum obtained in experiment 3. 



Serum Proteids. (i) Saturate serum with magnesium sulphate 

 crystals at 30 C. The serum-globulin is precipitated. Filter off. 





FIG. 13. THOMA-ZEISS H^EMOCYTOMETER. 



M, mouth-piece of tube G, by which blood is sucked into 5 ; E, bead for mixing ; 

 a, view of slide from above ; b, in section ; c, squares in middle of B, as seen under 

 microscope. 



Wash the precipitate on the filter with a saturated solution of mag- 

 nesium sulphate. Dissolve the precipitate by the addition of a 

 little distilled water, and perform the following tests for globulins : 



(a) Saturate with magnesium sulphate. A precipitate is obtained. 



(b) Drop into a large quantity of water, and a flocculent precipitate 

 falls down, (c) Heat. Coagulation occurs. Determine the tempera- 

 ture of coagulation (p. 21). 



(2) To a portion of the filtrate from (i) add sodium sulphate to 

 saturation. The serum-albumin is precipitated. (Neither magnesium 

 sulphate nor sodium sulphate precipitates serum-albumin alone, but 

 the double salt sodio-magnesium sulphate precipitates it, and this is 

 formed when sodium sulphate is added to magnesium sulphate.) 



(3) Dilute another portion of the filtrate from (i) with its own 

 bulk of water. Slightly acidulate with dilute acetic acid, and determine 

 the temperature of heat coagulation. 



(4) Precipitate the serum-globulin from another portion of serum 

 by adding to it an equal volume of saturated solution of ammonium 



