124 THE MICROSCOPIST. 



plates of different shape (endothelial cells), or cells in which 

 the long axis predominates (cylindrical epithelium), or 

 forms which are intermediate between plates and cylin- 

 ders. Some cells appear ramified or stellate, as in the 

 cells from the pith of a rush, bone-cells, and corpuscles of 

 the cornea. Others may become extraordinarily elongated, 

 as in the formation of fibre, muscle, etc. Some cells are 

 provided with cilia, which are limited to one portion of 

 the surface, and project their free extremities into the 

 cavity which they line. Dr. Beale considers the cilia to 

 be formed material, and their movements not vital, but a 

 result of changes consequent on vital phenomena. 



Every living organism, plant, animal, or man, begins 

 its existence as a minute particle of bioplasm. Every 

 organic form, leaves, iiowers, shells, and all varieties of 

 animals ; and every tissue, cellular, vesicular, hair, bone, 

 skin, muscle, and nerve, originates by subdivision and 

 multiplication and change of bioplasm, and the trans- 

 formation or metamorphosis of bioplasm into formed ma- 

 terial. It is evident, therefore, that there are different 

 kinds of bioplasm indistinguishable by physics and chem- 

 istry, but endowed with different powers.* 



7. Cell-Genesis. Schleiden first showed that the em- 

 bryo of a flowering plant originates in a nucleated cell, 

 and that from such cells all vegetable tissues are devel- 

 oped. The original cells were formed in a p&sma or blas- 

 tema, commonly found in pre-existing cells, the nuclei first 

 appearing and then the cell-membrane. These views were 

 applied by Schwann to animal structure. The latter be- 

 lieved that the extra-cellular formation of cells, or their 

 origin in a free blastema, was most frequent in animals. 

 The researches of succeeding physiologists have, however, 

 led to a general belief that all cells originate from other 

 cells. 



* Beale's Bioplasm. 



