I.] 



MILK, FIBRES, VEGETABLE ORGANISMS. 



101 



field. The larger ones appear coloured yellow, but the finer ones 

 cannot be seen distinctly as yellow bodies. 



(/>.) Note the finer granules, which exhibit a slow 

 dancing movement. They are never at rest. This is 

 called Brownian movement, and appears to be due to 

 inequalities of temperature in different strata of the 

 fluid. This movement is exhibited by all finely- 

 divided particles suspended in a fluid, e.g., China ink, 

 Berlin blue, provided the particles be small enough, 

 and the fluid in which they arc suspended be not too 

 viscid. The fine granules in salivary corpuscles ex- 

 hibit this movement. (Lesson IV. 1, d). 



1. Air-Bubbles in Gum or Water (H). Make a solution of gum 



FIG. 54 . Rico- 

 Starch. 



55- i- Bubble of air in water (A) when the lower surface is in focus ; (I',) Middle, and 

 (C) Upper surface of focus. 2. Bubble of air in Canada balsam. 3. Globule of oil in 

 water 



