10 E. J. LUND 



in this one property — namely, the chemical nature of the grain 

 — and its effects. 



An approximately constant medium was provided by using 

 tap water. This precaution is important, for, as will be shown, 

 the nature of the medium often affects or determines the kind 

 of results which are obtained. Distilled water was also used 

 but it was found that this extra precaution was not necessary 

 in most of the experiments, and since distilled water is toxic 

 if the organisms are left in it too long or the change is too rapid, 

 it could not have been used in many of the experiments, even 

 if it had been otherwise desu^able to do so. 



The organisms were starved in 400 cc. of tap water for eight- 

 een to twenty-four hours previous to each experiment. At the 

 end of this time they were free from food and residues. Thus 

 an optically clear, active and perfectly normal cell was obtained 

 with which to begin work in all the experiments where uniform- 

 ity in this respect was desired. All the factors with which we 

 are dealing except the 'physiological states' of the organisms 

 themselves are known and uniform to within narrow limits, while 

 the one of which we wish to 'test the effects can be controlled 

 and varied. 



INTERNAL RELATIONS AFFECTING THE FEEDING PROCESS 



1. The relation of the physiological state of the organism to the 



feeding process 



By the words 'physiological state' is here meant the condition 

 as a whole, of the equilibria in the physical and chemical reac- 

 tion system, the cell, at a certain time in the duration of its 

 existence.^ 



This condition or state is to be thought of as being limited to 

 the space which the organism occupies, or is, in other words, 

 internal. However, it is obviously absurd for anyone to attempt 



' This definition is justified because in so far as the facts are at present 

 known, this is the only kind^of system with which we have to deal in the cell, 

 and therefore in the present state of knowledge the only logical universal assump- 

 tion for experimental purposes is to define 'physiological states' in terms of such 

 known systems, until the universality of the assumption is disproved; 



