442 J. ARTHUR THOMSON [jine 



any animal living its life in nature, responding effectively to its 

 environment, and to ask ourselves again — How does this act ? We 

 must then confess that the way of the eagle of the air is still too 

 wonderful for us. 



The term physiology is now for the most part restricted to a study 

 of the individual organism, and especially to a study of its internal 

 economy. Just as anatomical analysis may be compared to picking a 

 watch to pieces — an operation which dimly suggests the delights of 

 dissection — so physiological analysis may be compared to a study of 

 the kinetic aspect of the watch, and even when physiology becomes 

 comparative it is still like comparing one kind of watch with another. 

 To save the results from inexcusable partiality and incompleteness it 

 is necessary to sound the natural history note, the recognition of 

 organisms in the plural, as members of a pair, a family, a flock, an 

 association, a fauna, as threads in a web of life, as agents in a complex 

 environment. In our everyday work in the laboratory we have the 

 bad habit of speaking of the earthworm, the crayfish, the skate, but to 

 the naturalist these words are all in the plural. 



It is recorded that young hermit-crabs which had been reared 

 from eggs in an aquarium, and had never seen a shell, at once seized 

 some shells which were dropped into the water, and had begun to 

 explore them before they had reached the bottom. It is idle to say 

 that this effective response is not as essentially part of the nature of 

 the hermit-crab as its gills or gizzard. For the physiologist to ignore 

 the answer which the hermit-crabs made to the stimulus of the shells 

 would be as illegitimate as to ignore their respiration and nutrition. 

 In short, no one can seriously maintain that physiological analysis has 

 only to do with cells, tissues, and organs ; it has equally to do with the 

 intact living creature in its natural surroundings, with its domestic and 

 social relations, with its habits and adaptations, with its struggle for 

 existence and endeavour after wellbeing. Physiological analysis thus 

 completes and corrects itself in " Natural History." 



It is evident that physiological study supplements the anatomical 

 answer to the question — " What ? " The latter, if we are patient, will 

 make a living creature practically translucent, will enable us, without 

 any Eontgen rays, and, with our eyes shut, to see the animal through 

 and through, each organ in its place. But the physiological discipline, 

 if we are patient, will give us more — will give us a working thought- 

 model, an intellectual cinematograph. I do not mean to suggest that 

 there are not other results of anatomical and physiological study besides 

 an increase in our power of visualising ; but that is one result, and a 

 very important one, for clear seeing is often the first step to clearer 

 understanding. 



We have heard wise warnings against the extremely analytic method 

 of modern biology, against the necrology which is always destroying in 

 the effort to understand. I have already recognised the danger in- 



