THE PLACE OF BIOLOGY. 81 



to take our data one by one ; for, as I shall presently 

 show in more detail, it is characteristic of a living 

 organism that the details of form, movement, chemical 

 composition, and change which we distinguish in it 

 are essentially, and not merely accidentally, connected 

 with one another. We are accustomed to the fact that 

 a limb, or even a bone, of a certain build is associated 

 with a whole body of a certain build. We know also 

 that if an animal is breathing we may expect to find 

 its heart beating and all its other organs in a state of 

 more or less evident activity. We associate together 

 the details of structure and activity as those of a living 

 animal ; we think and speak of it as alive, and we 

 regard its structure and activities as the expression or 

 manifestation of its life. What I - wish to maintain 

 is that in so regarding a living organism we use a hypo- 

 thesis which is for biology just as intelligible, just as 

 elementary, just as true to the facts known, and just 

 as good a scientific working hypothesis, as is the hypo- 

 thesis of the indestructibility of matter for physics 

 and chemistry. 



The mechanistic theory of life assumes that in ultimate 

 analysis it is only an accident that material particles 

 of which the living body is composed are aggregated 

 and combined in the form actually met with, and 

 another accident that they display the activities actually 

 observed in the living body. This follows from the 

 conception of organisms as simply material systems in 

 motion or at rest ; for the physical world as it is ordin- 

 arily conceived consists of matter and energy which are 

 eternal and unchangeable, while of their actual distri- 

 bution no explanation is given except that it depends on 



