Human Physiology. 



of a great forest. And in animal life there are forces at work, 

 still more mysterious and astonishing ; forces of growth and 

 reparation, nutrition, heat, secretion, motion, muscular action, 

 nervous power, feeling, thought, will animal and psychic 

 forces, which we have scarcely begun to investigate. But these 

 may best be treated of in future chapters. 



CHAPTER III. 



LIFE. 



Organisation What is Life? A Guiding Intelligence Life precedes 

 Organisation Necessity of a Self-existent Cause Genesis of Species 

 The Darwinian Hypothesis Characteristics of the Vegetable King- 

 dom Variety of Products from the same Elements Vital Chemistry 

 Sexual Life in Plants Vital Mechanism Nutritive Contrivances 

 Seed Distribution Plant Aromas Functions of Leaves Contriv- 

 ances for Reproduction Protection Mind. 



WE have glanced at the phenomena of matter, and of the 

 forces which make matter what it is, and which some hold to 

 be all there is of matter. We have now to consider other 

 forces which produce the phenomena, or constitute the condi- 

 tion, which we call Life. Vital Principle is a vague expression, 

 but Life means something it means all the phenomena of 

 living things, and the cause or causes of the phenomena, so far 

 as we can perceive them. The earth, waters, and air are full 

 of organised, living things, which grow from minute germs, and 

 propagate their kind. 



Organised living beings are complex, having varying parts 

 and organs; inorganic and lifeless substances are similat 

 throughout. A block of stone or iron has no special form 

 or organs. Vegetables and animals are composed of liquids 

 and solids; and living things have a certain form, surface, or 



