20 EPITHELIUM AND ITS BIOPLASM. 



embryo leaf consists. The bioplasm is perfectly 

 transparent and looks like pure water. The cavity in 

 which it lies has been termed a i<pace or vacuole which 

 was supposed to be occupied by mei'e passive fluid. 

 But the colourless material is living bioplasm, and so 

 important that the walls of the spaces (cellar walls) 

 could not have been formed except by its agency. 



32. Cartilage and its bioplasm. — In a piece of 

 cartilage or gristle it is easy to see the little masses 

 of transparent structiireless bioplasm, and distinguish 

 these from the firm cartilage material which inter- 

 venes, and which has been formed by them. The 

 structure of cartilage will be again referred to. 



33. Epithelium and its bioplasm. — If a little of 

 the soft matter be removed from the inside of the 

 cheek, and examined under a magnifying power of 

 two hundred diameters, it will be found to consist of 

 numerous little particles (elementary parts or cells),, 

 every one of which contains in the central part an 

 oval mass of living matter, around which is a firmer 

 material that has been formed by the bioplasm, 

 and was deposited layer within layer. Often very 

 distinct concentric rings may be seen, owing io this 

 mode of deposition. The younger the particles of 

 epithelium* the larger is the mass of soft colourless 

 living bi(.)plasm in proportion to the formed material 

 of which the outer part consists, and which has 

 ceased to manifest vital properties or powers. 



34, Mucus and its bioplasm, — If a little viscid 

 mucus be coughed up and examined under the mi- 

 croscope it will be found to be very transparent, and to 

 exhibit streaky lines here and there. At short dis- 

 tances will be observed oval particles of transparent 



* Epithelium, from i-jri upon, and QaWio to sprout, for it 

 used to be supposed that epithelium grew or sprouted from 

 membrane. Epithelium really is formed by biopla&m -which 

 sprang from preexisting bioplasm ; the bioplasm existed before 

 the membrane and therefore could not haTC sprung from it. 



