38 THE PREPARATION OF THE JELLY FILM 



salts. The red cells will haemolyse immediately. The 

 white cells are worth watching. As soon as they 

 come to rest, or even before that, the polynuclear 

 leucocytes seem to swell up, the granules exhibit 

 "furious" Brownian movements, and in a few moments 

 the cell totters and then bursts. Water kills blood- 

 cells instantly if there are no salts present. Let the 

 experiment be repeated, but, instead of using merely 

 agar and water, now make the jelly with sodium 

 chloride in the strength of "normal saline solution." 

 It can be made thus: Melt a few cubic centimetres 

 of 2-per-cent agar jelly and place 1 cc. in a test- 

 tube. Prepare a solution of 1 . 8-per-cent sodium 

 chloride in water. To the 1 cc. of molten 2-per- 

 cent agar jelly add 1 cc. of the sodium-chloride 

 solution. The test-tube will now hold 2 cc. of a 

 1-per-cent agar jelly containing 0.9-per-cent sodium 

 chloride, i.e. "normal saline solution." The whole 

 is melted again, and a drop poured on a slide. If 

 some blood is now examined on this jelly, it will be 

 seen that the red cells do not "lake" immediately. 

 The leucocytes, however, again die very quickly, as is 

 seen by their swelling up, the onset of "dancing" 

 movements of the granules, and by rapid bursting, 

 although the rupture will not be quite so rapid as 

 when only water was present. 



Now let the experiment be repeated a third time, 

 but instead of adding a solution which contains only 

 sodium chloride, let it contain in addition some sodium 

 citrate, thus: To 1 cc. of 2-per-cent agar jelly add 

 1 cc. of a solution containing 1 . 8-per-cent sodium 



