50 



CHAPTER III. 

 THE FORCES IN THE ORGANISM. 



No living naturalist is able to give an accurate definition of 

 an organism or life itself. However great the progress made in 

 biology during the last century, however great the store of obser- 

 vations made and facts discovered, we are as far as ever from 

 the desired goal of a definition of life and from a real knowledge 

 of the conditions of life, the most important object of our 

 researches. Though girders, stones, and mortar are indispens- 

 able to the builder of a house, the main thing is the plan of 

 the architect who unites the scattered parts in one harmonic 

 whole. While former ages and naturalists were content to 

 describe the structure and shape of animals and plants, to give 

 them names and classify them according to the degree of simi- 

 larity, we demand to-day to know not only how an organism is 

 constructed, but also why it is so constructed, how it originated, 

 how its various organs were evolved, what their functions are, 

 and by what laws the different vital functions are regulated. 



Not so long ago there existed between the inanimate, in- 

 organic Nature and the world of animals and plants an abyss 

 over which no bridge led, nor, indeed, could lead, according to 

 the then almost general belief. Whilst in inorganic Nature 

 all changes took place according to the unalterable laws of 

 mechanics, physics and chemistry, the phenomena of life remained 

 a profound mystery. But as science was unwilling to renounce 

 even an attempt to explain the seemingly inexplicable, there 

 arose the convenient assumption of the presence in each 

 organism of a specific, mysterious, unknowable source of force, 

 which under the sonorous name of vital force vis vitalis long 

 haunted the realms of science. Though by this assumption 

 knowledge had not been advanced a single step, and though 



