X PREFACE 



assumed that these problems are of the same kind, and 

 to be approached by the same methods, as other problems 

 of physics and chemistry. This point of view seems the 

 only one possible for the scientific investigator. The 

 organism exhibits a regularity which, although of a 

 special kind, is obviously based upon and presupposes 

 the regularity of its component physico-chemical proc- 

 esses. Investigation of the latter requires the use of 

 the exact methods developed by modern analysis; and 

 these have been shown to yield the same constant and 

 reproducible results in organisms as in non-living 

 systems. In fact, one of the most striking features of 

 organic processes is their exactitude, which is frequently 

 safeguarded by regulatory devices of the utmost delicacy. 

 The investigation of many such processes is purely 

 physico-chemical in its method and results. 



It must be remembered, however, that in living 

 organisms we are dealing with synthetic products of a 

 higher order. When the materials and energies of the 

 surrounding world unite to constitute the organism, 

 new qualities and modes of activity inevitably come into 

 existence; these special properties of living beings form 

 the subject-matter of the biological sciences, as dis- 

 tinguished from the physical sciences. For this reason 

 the physical and chemical characterization of the con- 

 stituents, reactions, and processes whose combination 

 or synthesis produces life is not in itself sufficient; 

 the biological interest centers in the conditions and 

 special mode of this combination, and in the nature 

 of the resulting unity. The problem of the nature 

 of vital organization remains the fundamental one for 

 biology. 



