36 PRACTICAL PHYSIOLOGY. [V. 



altered. The blood becomes darker in colour and transparent. This is the 

 laky condition due to the discharge of the haemoglobin from the corpuscles. 

 Place the vessel with the fluid blood on the table, and it clots or forms a firm 

 jelly. 



13. Salted Plasma Influence of Neutral Salts on Coagu- 

 lation. At the slaughter-house, allow blood to run into an equal 

 volume of saturated solution of sodium sulphate (or one quarter 

 of its volume of a saturated solution of magnesium sulphate) ; 

 mix. The blood does not clot, but remains fluid. Place the 

 vessel aside on ice, and note that the corpuscles subside, leaving 

 a narrow clear yellowish layer on the surface the plasma mixed 

 with the saline solution, and known as salted plasma. To obtain 

 sufficient plasma, the blood must be " centrifugalised " (page 43), 

 to separate the corpuscles from the plasma. 



(a.) Heat undiluted salted plasma to 60 C. The fibrinogen is 

 precipitated at 56 C. Filter. The filtrate will not coagulate, 

 even after the addition of fibrin-ferment and CaCl 2 , as there is no 

 fibrinogen present. 



(f>.) Place 1 5 cc. of the salted plasma in a tall, narrow, cylindrical, 

 stoppered glass tube. Add crystals of sodium chloride, and shake 

 the whole vigorously, when a white flocculent precipitate is thrown 

 down. Allow the precipitate to subside. Decant the supernatant 

 fluid. Filter through a filter moistened with a saturated solution 

 of sodic chloride, and wash the precipitate on the filter with a 

 saturated solution of sodic chloride. This is the plasmine of Denis. 

 With a spatula, scrape the washed precipitate off the filter. 



Dissolve the plasmine in a small quantity of distilled water, 

 and filter quickly. The filtrate, if set aside, will clot after a 

 time. It is better to do the several operations rapidly to ensure 

 success, but I have frequently found coagulation occur when the 

 plasmine was not dissolved in water until many hours after it was 

 deposited. 



14. Oxalats Plasma. --Oxalate of potassium prevents blood from 

 coagulating when present to the extent of 0.2 per cent. Dissolve 

 i gram of potassium oxalate in 10-20 cc. of normal saline, place 

 it in a vessel capable of holding 500 cc., and allow blood to run 

 in to fill the vessel. Mix the two fluids. The blood does not 

 coagulate, but remains fluid. Centrifugalise it to obtain the 

 oxalate plasma, which may be siphoned off. The oxalate pre- 

 cipitates as oxalate of lime- the calcium which is necessary for 

 coagulation. 



(rt.) To oxalate plasma, add a few drops of a 2 per cent, 

 calcium chloride solution = coagulation, and more quickly at 

 40 C. 



