Bruxonian or Particle Movements. 175 



chemical sense that its employment is hardly to be approved at 

 the present day. Particle, in the meantime, is a more neutral 

 word, and will be adopted here. 



If we take some, say about a tenth of a grain of, fine, dried 

 mud or clay, and place it on a slip of glass used for microscopic 

 work; remove the larger gritty particles; place a drop of water 

 on the rest ; cover it with a thin cover glass ; we shall have made 

 a "preparation" ready for examination. Now take a micro- 

 scope with, say, :|^-inch objective, giving a magnification of about 

 400 diameters, and look at the preparation. The smaller par- 

 ticles will be seen to be in a state of rapid oscillation. The 

 movement seen is what is known as the Brunonian movement. 

 We may imagine that the object which is moving is some form of 

 life, some organism which the water has allowed to resume 

 activity after lying dormant as dead while dried. But this is not 

 so. We may take another illustration. Get a paint-box of 

 water colours. We may take almost any colour at random, but, 

 by preference, choose gamboge, a yellow gum. Rub a little 

 down with water on a glass slip and make a "preparation " in 

 the usual manner. The particles are seen under the micro- 

 scope, as before, in lively Brunonian or Brownian movement. 

 There can be no question of animalculse coming to life in this 

 case. It is a common or popular idea that w^here movement is 

 there is life, and where life is there must be movement. A 

 moment's thought dispels the idea, for we see clouds moving as 

 we see birds moving, we see the river moving as we see fish 

 moving, and we see dust particles moving, and we see a plant 

 like the Mimosa sensitiva moving; yet we do not confuse the 

 various kinds of movement, those of organised life or of inorganic 

 material. 



The various microscopic movements met with, and called by 

 him "molecular movements," are thus classified by the late 

 Professor Hughes Bennett in his text-book on Physiology : — • 



1. Those described by Robert Brown, hence Brunonian. They 



are independent of organic structure, and are therefore 

 purely physical. 



2. Those in the interior of cells, as Chara, Vallisneria, and 



Tradescantia. It has been disputed whether these are 

 vital or physical. 



