28 PRINCIPLES OF PHYSIOLOGY 



A condition of fully developed organization 

 is reached, for each kind of living thing, 

 reproductive processes occur, the processes 

 of life go on more slowly and less completely, 

 and finally some part of the machinery of 

 life breaks down, and death occurs. This is 

 the last stage in the evolution of that particular 

 organism. After death of the tissues of the 

 body, it is submitted to the action of external 

 agencies, both physical, chemical, and vital 

 (the vital being due to the activities of 

 micro-organisms of an inferior order), and 

 these ultimately reduce it to the simple 

 elements of which the body was at first com- 

 posed. 



12. A living being is affected during every 

 moment of its life by the medium in which it 

 lives. The medium furnishes the material 

 necessary for its existence. Dead matter is 

 supplied to take the place of the living matter 

 that has died after having done its work. 

 External modes of energy, such as heat, light, 

 and electricity, act upon it, and energy is 

 supplied also by the chemical changes brought 

 about ultimately, but by many subsidiary 



