32 



METHODS OF SEPARATING LIQUOR SANGUIN1S. [BOOK I. 



three concentric compartments. Into the central and external of these 

 are placed small lumps of ice, whilst into the intermediate compartment 

 blood is received as it issues from the vessels of the animal. The middle 

 compartment being very narrow (its width, not exceeding half an inch) the 

 whole of the liquid, which it contains, is rapidly reduced to the temperature 

 of melting ice. In the course of about two hours the corpuscles have 

 subsided to the lower part of the partition containing the blood, and 

 considerable quantities of pure plasma may be drawn off, with the aid of a 

 syphon or pipette. 



--3/4 



FIG. 9. DK SANDERSON'S APPARATUS FOR COLLECTING LIQUOR SANGUINIS. (Hand- 

 book for the Physiological Laboratory.} 



2. Plasma may be much more easily obtained, though mixed 

 with water and saline matters, by mixing blood, immediately on its 

 being shed, with solutions of certain neutral salts of sodium, potas- 

 sium or magnesium, or by dissolving suitable quantities of such 

 salts in the blood before coagulation has occurred. From such 

 mixtures of blood and neutral salts the corpuscles separate by sub- 

 sidence, and the plasma may be obtained by decantation or filtration. 

 The following are the proportions in which sodium sulphate arid 

 magnesium sulphate, which are the salts chiefly employed, should 

 be added to blood in order to prevent coagulation and lead to the 

 separation of the liquor sanguinis. 



a. One part of finely powdered sodium sulphate is added to 

 12 parts of blood and the powder is gently stirred with the blood to 

 hasten its solution. Instead of employing the solid salt in the 



