THE ORGANISM AND ITS ENVIRONMENT 367 



without Its banks and bed; it Is likewise impossible to consider the 

 organism independent of its environment. As the nature of the 

 terrain determines the direction and flow of the stream, so the 

 environment of the organism, in part at least, determines the trend 

 taken as the energy derived from nutrition forms and maintains the 

 organism. 



Functional adaptations may be referred to changes in the chem- 

 ical and physical reactions within the protoplasm. Let us assume a 

 cell that is in equilibrium with all its surroundings, so that there is 

 a constant inflow of foods and oxygen and a constant outflow of 

 wastes. Assume also that under such ideal conditions the rate of 

 metabolic reactions is identical in all regions of the cell and that the 

 surface membrane is identical with respect to electrical and per- 

 meability properties over the entire boundary. Now suppose a new 

 factor is introduced into the environment; for example, the tem- 

 perature is raised. The first eflfect must be at the cell boundary, so 

 that electrical and permeability characteristics change in accord 

 with the rise in temperature. But a change in the cell boundary also 

 involves changes in the internal regions of the cell, a re-distribution 

 of various substances and an alteration in the rate of metabolism. 

 So, because of a change in the environment, the whole mechanism 

 of life in the protoplasm is shifted, as when the collapse of a small 

 portion of a stream bank causes the stream to shift position. If, in 

 the case we have been considering, the nature of the environmental 

 change is minor, or a substance or condition that the protoplasm 

 may overcome or remove as waste, the cell returns to its original 

 condition, as the river washes away and disposes of small cave-ins 

 of its bank. If, however, the change is great, or a substance of such 

 nature that the energy of metabolism cannot alter or otherwise dis- 

 pose of it, either the life of the protoplasm becomes permanently 

 altered, that is, adapted to the change, or it may become disor- 

 ganized and die, as the stream may alter its course or be obliterated. 

 The environment of every organism is constantly changing; day 



