There is still another reason why a scientific treatment of the consumption of wealth has been delayed. It could not be developed until medicine and hygiene had provided us with satisfactory standards of the needs of the human body. When food, for example, was still regarded purely as a matter of individual likes and dislikes, it was impossible to discuss at all adequately the sufficiency or insufficiency of the food consumption of a given class. But now that we know that the varying tastes simply express in different ways the need for so much proteid, carbo-hydrates and fats, we have a firm basis on which to work. It is true that it is not yet quite so firm as we could wish; the scientists have not yet succeeded even for a single class in fixing a dietary standard which would be accepted by all in particular, and recently the investigations of Professor Chittenden have suggested that the amount of proteid hitherto thought essential may be excessive. Moreover, little attention has yet been paid to the need of different food for different work. Yet it seems probable, to say the least, that the sedentary worker, using his brain and not his muscles, may require lighter and daintier food than the labourer in the fields or the docks, and may really suffer as seriously if that better food be denied him as does the latter if he fails to secure a sufficiency of coarser and cheaper nutriment. This question would be of great importance in investigating the expenditure of the clerk class. But although the scientists have here failed to provide the students of domestic expenditure with all the data required, yet there is sufficient knowledge of the general principles of dietetics to enable us to base our study of food consumption on a fairly sound basis. In the same way a standard of housing accommodation establishing the minimum of space per head necessary for health is generally recognised; and on these and similar calculations, correlated with the cost of house-room and commodities, it will be possible to build up a science of consumption which will be really a science and not a series of guesses and vague generalities. It is true, again, that it is easier to deal with the grades of society practising the roughest and least-skilled labour than with those engaged in the higher forms of brain-work, but we can at all events set ourselves to discover what _is_ the average distribution of the expenditure of men earning £1000 a year, and can afterwards appeal to the hygienists to decide for us what kind of food, house-room, and recreation is essential for a man who makes his living by the higher activities of the intellect. A very close connection between economics and hygiene is essential if the division of our subject that deals with consumption is to be adequately treated.