ASSIMILATION 



"motility"": and irritability evinced l>y motility is characteristic 

 of all living beings save when in the temporary condition of 

 " rest." 



Again, in the case of the cannon, the gunner after its dis- 

 charge has to replenish it for future action with a fresh cartridge : 

 the Amoeba or leucocyte can replenish itself — it " feeds." When 

 it comes in contact with a fragment of suitable material, it 

 enwraps it by its pseudopodia (Fig. 3), and its edges coalesce 

 where they touch on the far side as completely as we can join up 

 the edges of dough round the apple in a dumpling. It dissolves 

 all that can be dissolved — i.e. it " digests " it, and then absorbs 

 the dissolved material into its substance, both to replace what 

 it has lost by its previous activity and to supply fuel for future 



Fig. 3. — Amoeba devouring a ])lant cell ; lour successive stages of ingestion 

 (From Verworu.) 



liberation of energy ; this process is termed " nutrition," and is 

 another characteristic of living beings. 



Again, as a second result of the nutrition, part of the food 

 taken in goes to effect an increase of the living protoplasm, and 

 that of every part, not merely of the surface— it is " assimilated " : 

 while the rest of the food is transformed into reserves, or con- 

 sumed and directly applied to the liberation of energy. The 

 increase in bvdk due to nutrition is tlius twofold : part is the 

 increase of the protoplasm itself — " assimilative growth," part is 

 the storage of reserves — " accumulative growth " : these reserves 

 being availal)le in ttirn by digestion, whether for future true 

 growtli or for consumption to liberate energy for the work of 

 the cell. 



We can conceive that our cannon might have an automatic 

 feed for the supply of fresh cartridges after each sliot ; but not 

 that it could make provision for an increase of its own bulk, so 

 as to irain in calibre and strenutli, nor even iur tlie restoration 



