ANATOMY AND PHYSIOLOGY 



that animal tissues differed radically from this con- 

 struction. The elementary particles of vegetables 

 "were regarded to a certain extent as individuals 

 which composed the entire plant, while, on the other 

 hand, no such view was taken of the elementary parts 

 of animals." 



ROBERT BROWN AND THE CELL NUCLEUS 



In the year 1833 a further insight into the nature of 

 the ultimate particles of plants was gained through the 

 observation of the English microscopist Robert Brown, 

 who, in the course of his microscopic studies of the epi- 

 dermis of orchids, discovered in the cells " an opaque 

 spot," which he named the nucleus. Doubtless the 

 same "spot" had been seen often enough before by 

 other observers, but Brown was the first to recognize it 

 as a component part of the vegetable cell and to give 

 it a name. 



" I shall conclude my observations on Orchideae," 

 said Brown, " with a notice of some points of their gen- 

 eral structure, which chiefly relate to the cellular 

 tissue. /In each cell of the epidermis of a great part of 

 this family, especially of those with membranous 

 leaves, a single circular areola, generally somewhat 

 opaque than the membrane of the cell, is observ- 

 able. This areola, which is more or less distinctly 

 granular, is slightly convex, and although it seems to 

 be on the surface is in reality covered by the outer 

 lamina of the cell. There is no regularity as to its 

 place in the cell ; it is not unfrequently, however, cen- 

 tral or nearly so. 



