When you can measure what you are speaking about and express it in numbers, you know something about it, but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.—Lord Kelvin. We shall see that the connection between physical diseases and the external configuration of the body is less close than has been assumed....—Jonathan Hutchinson: The Pedigree of Disease, London, 1884. Since the publication of our first paper on this subject1an opportunity was taken of reviewing the literature dealing with this subject in greater detail. After a thorough search of the older literature it was surprising to find how little attention had actually been paid to the matter in what could be considered a useful sense. The most plausible reason for this appears to be that for many centuries the subject was confused by