GENERAL PROPERTIES I THE CORPUSCLES. 421 



destroyed. Solutions whose osmotic pressure is the same as 

 that of the plasma are said to be isosmotic or isotonic with the 

 blood, those whose pressure is lower are designated as hypotonic, 

 and those whose pressure is higher as hypertonic* The salt 

 that is contained in the plasma in largest amounts is sodium 

 chlorid. In mammalian serum it exists to an amount equal 

 to 0.56 per cent, and is probably responsible for the greater 

 part (60 per cent.) of the osmotic pressure shown by this liquid. 

 In making isotonic solutions this salt is, therefore, generally 

 employed. A solution containing nine-tenths of 1 per cent, of 

 sodium chlorid (NaCl, 0.9 per cent.) gives the same osmotic 

 pressure as plasma as determined by the effect of each on the 

 lowering of the freezing-point (see Appendix, Diffusion, Osmosis, 

 and Osmotic Pressure). Such a solution mixed with blood 

 should not and does not alter the water contents of the corpuscles. 

 One may, in fact, use a 0.7 per cent, solution of sodium chlorid 

 without causing any noticeable hemolysis. This strength of solu- 

 tion or, preferably, 0.9 per cent, is frequently employed in infusions 

 and experimental work; it constitutes what is known in the labora- 

 tories as normal saUne or physiological saline. If, however, one 

 uses a lower concentration, some of the corpuscles are hemolyzed, 

 and the number of corpuscles destroyed and the rapidity of 

 the hemolysis increase rapidly with the lowering of the osmotic 

 pressure-! While a 0.9 per cent, solution of sodium chlorid 

 suffices in most cases for infusions and for diluting blood, 

 it does not entirely replace the normal plasma or serum, since 

 these liquids, in adcUtion to the sodium salts, contain salts of 

 calcium, potassium, magnesium, etc., each of which has doubtless 

 a certain specific importance. In diluting blood outside the body, 

 when the dilution is large, better results are obtained Ijy using what 

 is known as Ringer's mixture, which consists of the physiological 

 saline solution plus small amounts of potassium and calcium 

 chlorid. One formula for Ringer's solution is : 



Sodium chlorid 0.9 per cent. 



Calcium chlorid 0.026 '* '^ 



Potassium chlorid 0.03 " " 



Hemolysis Caused by the Action of Hemolysins. — It has long been 



* For a full consideration of osmotic pressure in its relations to physio- 

 logical processes, see Hamburger, "Osmotischer Druck und lonenlehre," 

 Wiesbaden, 1902. 



t According to Brachmachari ("Studies in Hemolysis," Calcutta, 1913) 

 the red corpuscles in human blood begin to hemolyze in ^q solutions of sodium 

 chlorid, and the hemolysis increases rapidly between this concentration and ^ 

 solutions. Some corpuscles, however, retain hemoglobin even when the blood 

 is diluted with nine times its volume of distilled water. 



