I might here mention the effects which this has upon all the faculties of the mind, by keeping the understanding clear, the imagination untroubled, and refining those spirits that are necessary for the proper exertion of our intellectual faculties during the present laws of union between soul and body. It is to a neglect in this particular that we must ascribe the spleen which is so frequent in men of studious and sedentary tempers, as well as the vapours to which those of the other sex are so often subject. (118: 5) Had not exercise been absolutely necessary for our well-being, nature would not have made the body so proper for it, by giving such an activity to the limbs and such a pliancy to every part as necessarily produce those compressions, extensions, contortions, dilatations, and all (10) other kinds of motions that are necessary for the preservation of such a system of tubes and glands as has been before mentioned. And that we might not want inducements to engage us in such an exercise of the body as is proper for its welfare, it is so ordered that nothing valuable (15) can be procured without it. Not to mention riches and honour, even food and raiment are not to be come at without the toil of the hands and sweat of the brows. Providence furnishes materials, but expects that we should work them up ourselves. The earth must be laboured (20) before it gives its increase; and when it is forced into its several products, how many hands must they pass through before they are fit for use! Manufactures, trade, and agriculture naturally employ more than nineteen parts of the species in twenty; and as for those who are not (25) obliged to labour, by the condition in which they are born, they are more miserable than the rest of mankind unless they indulge themselves in that voluntary labour which goes by the name of exercise.