LIFE AND DEATH. 275 



the fluid around and are burnt off in the form of 

 carbon-dioxide and water, heat being of course 

 evolved. This is the fundamental process of 

 Respiration. 



It is probably the alternation of these pro- 

 cesses of Assimilation the building up into the 

 protoplasmic structure of new complex labile 

 molecules and Destructioti the shattering of 

 such molecules with redistribution, oxidation, etc., 

 of their fragments which constitute the funda- 

 mental process of life. Different authorities 

 attempt to explain the details of these processes 

 in various ways, but there is practical agreement 

 on the one point, that life consists in the 

 alternate building up of new protoplasm from 

 the food-materials Assimilation and the breaking 

 down of the molecular complexes to simpler ones 

 Disintegration, or Dis-assijuilation, as we may 

 call it. During the periods when assimilation 

 prevails, and the protoplasm increases in mass, 

 we recognise Growth, and since this is usually 

 associated with the vigorous imbibition of water, 

 owing to the powerful osmotic attractions for 

 that liquid exhibited by some of the products, 

 and with consequent further stretching of the 

 invisible molecular plexus, the growth may be so 

 evident in increased size, that we are accustomed 

 to look upon the visible increase in volume alone 

 as growth ; but it is essential to understand that 

 growth of the protoplasm is always proceeding 

 during life, even when as many older molecules 

 are being shattered and dispersed as new ones 



