n] BIOLOGICAL FOUNDATIONS 49 



trace their upward progress. For this to be adequately 

 done, the very fundamentals must be explored, and 

 the quest begin with an enquiry into the original and 

 essential properties of living substance. 



The biologist, looking at life objectively, finds 

 life then manifest itself as the sum of the properties 

 pertaining to a group of peculiar and complicated 

 chemical bodies which are classed together under the 

 general name of protoplasm. 



The form and structure adopted by the lowliest 

 living things at the time of their origin, which then 

 had to serve as the starting-point for all subsequent 

 forms and structures in life, are chiefly due to two 

 properties of these protoplasmic substances one 

 physical, the other chemical. The first is their 

 colloidal nature, which permits of their sharing the 

 definiteness and resistance of solids with the mobility 

 and quick chemical reactions of liquids. The second 

 is their power of assimilation, their power of building- 

 up, out of materials different from and chemically 

 simpler than their own substance, new molecules, 

 identical in composition with the old. Assimilation 

 is molecular reproduction, and is by far the most 

 important property of protoplasm. Whenever an 

 organism performs any action, it must needs do 

 work, expend energy. This energy it procures from 

 the break-down and combination with oxygen of 

 some of the unstable living molecules. Combustion 



H. 4 



