8o THE POPULAR SCIENCE MONTHLY 



conditions, for the fountain of action escapes them as the fountain of 

 youth receded before the searching eyes of Ponce de Leon. Neverthe- 

 less, the treasures on the road of the deluded are no less valuable than 

 those strewn on the pathway of the sane, if they will but pick them up, 

 and all the wealth of our much boasted " causal " biology has been 

 brought home by men who were not lucky enough to get what they 

 were after, but wise enough to take what they could find. 



Those who have parted with their entire wealth of prejudice in the 

 matter of causation can safely begin to discuss the question whether 

 scientific explanations, explanations by means of chains of events, can 

 be legitimately applied to vital action, and furthermore whether such 

 explanations are useful. At the outset, however, they meet with a 

 grave difficulty, for at the present time no one knows exactly what it is 

 that needs to be explained. Some tell us, life is motion; others call it 

 a chemical-physical process; whereas some declare it synonymous with 

 consciousness. Herbert Spencer, after cudgeling his brains for many 

 years, arrived at a statement which seemed to him, as it has to many 

 since then, the best possible. " Life," he says, " is the continuous ad- 

 justment between internal relations and external relations." 



Unfortunately none of these definitions is really satisfactory. Who, 

 on being told that life is the continuous adjustment between internal 

 and external relations, can feel that now he has the secret firmly in his 

 grasp? Indeed at present a hard and fast definition is scarcely pos- 

 sible, and, if it were, would add more to the comfort of the dialectician 

 than to the progress of knowledge. When we understand life the defi- 

 nition will come of itself, and then no one will care to use it. 



Most of the biological work of to-day is an attempt to find out ex- 

 actly how living things make their living, and the biologist, regardless 

 of his party affiliations, is happy to say that all who study these ques- 

 tions agree that living things make use of machinery. Is not the 

 respiratory system a machine by which oxygen is taken from the 

 air and carbon dioxid given off to it? Is not the digestive system 

 a factory which changes food-materials into simpler compounds that 

 are absorbed? 



The machinery of living things is very remarkable, complex, and 

 adequate. It may not always be wholly adequate, but certainly in gen- 

 eral it is sufficiently so. Sometimes it can be improved by surgery, by 

 the prescription of glasses, hearing trumpets, false-teeth and tonics, 

 but on the whole it is adequate, it is fit. Indeed, fitness more or less 

 pronounced, but fitness, nevertheless, is the leading characteristic of 

 living machinery and its processes, and under shifting external con- 

 ditions, distinguishes them clearly from things not alive. No man 

 need take the time to adjust himself consciously when he deals with his 

 fellowmen, with horses, dogs and with building materials. Our famil- 



