INTRODUCTION 7 



stimulate all living organisms. The organisms are sensitive, 

 and respond to these stimuli. Supplying food to animal or 

 plant is applying a stimulus, as well as providing the means 

 to further and continued action. The response to the stimu- 

 lus may vary with the organism, be immediate or delayed, 

 be external and visible to the eye, or merely internal; but 

 every organism lives, both because the conditions make liv- 

 ing possible, and also in accordance with and in response to 

 the many and diverse stimuli exerted upon it by these con- 

 ditions. The different reactions of different organisms to 

 the same stimulus do not imply any special or peculiar 

 vital force ; on the contrary, they imply the special or pecul- 

 iar structure of these different organisms. The force of 

 gravitation pulls some things down, but it is the same 

 force which keeps other things up. The Eiffel Tower, con- 

 structed in opposition to the force of gravitation, stands 

 now because of it. So all living organisms, subjected to 

 like forces and supplied with like materials, behave accord- 

 ing to the characteristic habits of each species and the 

 peculiar habits of each individual. 



II. THE LIVING MATTER AND THE ACTIVELY LIVING 

 STRUCTURE 



As Hertwig has so strongly emphasized,* the living and 

 active protoplasm is to be regarded not as a ■ cheinical 

 compound or an association of chemical compounds, but 

 rather as an orderly arrangement of these into a definite 

 structure, of which water is an indispensable constituent. 

 Some of the water contained within the cell should be con- 

 sidered to be as much a constructive constituent of the liv- 

 ing protoplast as the water is of the crystal of copper 

 sulphate. As, without a certain amount of water, one can 

 never have crystals, no matter how much copper sulphate 

 may be present, so also, without the necessary amount of 

 water we can never have active protoplasm. When the 

 water of constitution is withdrawn, all the activities of the 



* Hertwig, Oscar. Die Zelle und die Gewebe, Bd. I., p. 15. The Cell- 

 translation by Campbell, vol. I. 



