CHAP, x VITALITY 181 



used to say, ' a living body is a vortex of chemical and 

 molecular change " ; and the image of a vortex ex- 

 presses the fundamental fact of persistence in spite of 

 ceaseless change. Huxley compared the organism to 

 the whirlpool below the Falls of Niagara, always chang- 

 ing, yet remaining strikingly the same year after year. 

 Part of the secret of life is certainly that the chemical 

 processes are so regulated and correlated that, in spite 

 of the ceaseless change, the organism retains its integrity 

 for days or years or centuries. And along with this 

 must be associated two facts that each kind of living 

 creature has its own chemical individuality and a specific 

 organisation. Chemically the creature is a vortex, but 

 structurally it has an architecture, and the two are 

 mutually conditioned. To start with, the creature is a 

 complicated, condensed system of molecules in a colloidal 

 state, a system with characteristic reactions and rates, 

 which, as it lives, grows and differentiates, forms a 

 characteristic framework or substratum. As Prof. Child 

 suggests, the image of a stream and its bed may be 

 useful ; the stream has a character and it expresses 

 part of its character in the bed it makes, which in turn 

 influences the flow of the stream. The three important 

 facts are, that there is this ceaseless metabolism, that it 

 is specific for each kind of creature and is associated 

 with a specific organisation, and that both are capable 

 of persistence for a variable length of time. 



2. The Capacity for Growth, Reproduction, and 

 Development. Organisms are essentially characterised 

 by this triad of qualities, which may be usefully thought 

 of together, (a) There are delicately poised, ephemeral 

 organisms which live, to use a homely expression, from 

 hand to mouth. They are going concerns, they balance 

 their accounts, but they trade on a very restricted capital 

 and cannot survive a crisis. Organisms could not have 

 gone far if they had not had a capacity for accumulating 

 energy, and this leads to growth. Organic growth 

 differs from crystal growth in utilising materials quite 

 different from those that compose the growing substance, 

 in implying active assimilation rather than passive accre- 



