MANIPULATION OF THE MICROSCOPE. 37 



are often set up in the mounting medium which may be 

 misinterpreted. A still more serious source of error lies 

 in the phenomenon known as the Brownian movement, 

 or pedesis, a dancing, oscillating motion which affects 

 suspensions of finely divided solid particles under cer- 

 tain not very clearly understood conditions. Gamboge 

 or carmine suspended in water shows the Brownian 

 movement well, and should be studied carefully in order 

 that such motion may not be confused with that charac- 

 teristic of the bacteria or other living organisms. 



REFERENCES. 



Bausch, E. Manipulation of the Microscope. Rochester, igoi. 

 Gage, S. H. The Microscope. Ithaca, N. Y., 1904. 



