EXAMPLES 93 



the capillary tube, which is placed in the "revolving 

 apparatus." 



Take a test-tube of 5 cc. of "coefficient jelly," which 

 of course, being cold, is set in the bottom of the tube. 

 Add to it 0.4 cc. (4 units) of Unna's stain; 0.2 cc. 

 (2 units) of alkali solution. Then the tube must have 

 added to it 4.4 cc. of water, to make its total contents 

 up to 10 cc. The colorless "coefficient jelly" will be 

 set at the bottom of the tube, and above this will 

 be 5 cc. of the mixture of stain, alkali, and water. 

 The test-tube is then steeped in boiling water, when 

 the jelly melts, and, as it does so, the stain, alkali, and 

 water pervade the whole of its contents of 10 cc. In 

 reality this 10 cc. of molten jelly is neutral, for the 

 2 units of alkali have just neutralized the original 

 acidity of the "coefficient jelly." When all is melted 

 and mixed, the tube is taken out of the boiling water, 

 and the contents are actually boiled, until they froth up 

 in the tube, by holding the end of the tube in the flame 

 for a few minutes. A drop of the boiling, stained 

 mixture is then run on to the slide. Here it will set 

 firmly in about three minutes, and if it is held up to 

 the light the jelly-film will be found to be quite trans- 

 lucent. A clean cover-glass is prepared, and a drop of 

 the citrated blood is tapped out of the capillary tube on 

 to it. The size of the drop is immaterial. The cover- 

 glass is taken up bet\veen the finger and thumb, in- 

 verted so that the drop of fluid is undermost, and it 

 is allowed to fall flat on to the agar-film on the slide. 

 The blood spreads over the film under the cover-glass, 

 and the slide is then placed in the 37 C. incubator 



