34 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



Vacuoles. 



Chromalin network. 



Linin network. 

 Nuclear fluid. 



Nuclear membrane. 



Exoplas 



Spongioplasm. 

 Hyaloplasm. 



Niideolns. 

 Chromalin net-knot. 



Centrospher 



Foreign indosures. Metaplasm. 

 Fig. 12. Diagram of a cell (Bohm, Davidoff and Huber). 



THE CELL. 



More than two hundred years ago the English 

 botanist, Robert Hook, described cork as made up 

 of "little boxes or cells distinct from one another." 

 In 1838 Schleiden postulated a cellular basis for 

 plants, and according to his conception these cells 

 were minute compartments filled with a fluid sub- 

 stance in each of which floated a nucleus. The fol- 

 lowing year, 1839, Schwann showed that the animal 

 body was likewise built up of cells resembling those 

 described by Schleiden in plants. These observa- 

 tions placed animals and plants on a common struc- 

 tural basis and established the cell theory, now re- 

 garded as one of the great biological discoveries of 



