THE CELL 47 



other. Analysis shows (see table on p. 43) that the 

 substances most abundant in the plant are carbo- 

 hydrates, and the microscope confirms this fact, showing 

 that carbohydrates form the cell -wall, appear in the 

 shape of grains of starch, or are dissolved in the cell-sap 

 in the form of sugar. Analysis shows that in relative 

 abundance albuminoids take the second place, and also 

 that the younger parts of a plant are comparatively 

 richer in nitrogenous substances than older parts ; the 

 microscope demonstrates that protoplasm consists chiefly 

 of albuminous substances, containing nitrogen, and that 

 this protoplasm is the predominating constituent in 

 young cells. Lastly, both microscope and analysis 

 point to the presence of fatty substances in the plant 

 and in the cell. 



We have now made acquaintance with the principal 

 substances contained in a vegetable cell. Already we 

 had come to the conclusion that the cell builds up 

 all these substances from gases, salts, etc., which 

 surround it. In other words it must feed from the 

 outside. Every cell must draw its food from the soil, 

 from the air, or from some neighbouring cell. A 

 question naturally arises here : in what way can this cell, 

 this little bladder without any opening, or any mouth 

 or jaw, attract and absorb surrounding substances ? 



To explain this first phase in the nutrition of the 

 vegetable cell we must turn aside from it for a while, 

 we must turn aside even from botany itself, and study 

 some purely physical phenomena ; we must study 

 certain general properties of matter manifested in dead 

 as well as in living nature. We shall often use this 

 method in the future. It is the only sure method 

 whenever we wish to find the explanation of vital 

 phenomena ; for, in the language of physiologists, to 

 explain means to reduce complicated vital processes to 

 more simple physico-chemical phenomena. 



