Physiology itself teaches us these things. A frugal meal taken in the open air will nourish the body far better than a sumptuous repast in a close room, where the air is impure, because all the functions of the body are more active in the open air, and assimilation is more complete. In like manner a frugal meal eaten in common with beloved and sympathetic persons is much more nutritious than the food a humble, harassed secretary would partake at the lordly table of a capricious master. Liberty in this case is the cry that explains all. _Parva domus sed mea_ (a little house, but my own), has been quoted ever since the Roman epoch to indicate which is the most healthful of houses. Where our lives are oppressed, there can be no health for us, even though we eat of princely banquets or in splendid buildings. * * * * * =With man the life of the body depends on the life of the spirit=.--Physiology gives an exhaustive explanation of the mechanism of such phenomena. Moral activities have such an exact correspondence with the functions of the body that it is possible to appreciate by means of these the various emotional states of grief, anger, weariness, and pleasure. In _grief_, for instance, the action of the heart becomes feebler, as under a paralyzing influence; all the blood-vessels contract, and the blood circulates more slowly, the glands no longer secrete their juices normally, and these disturbances manifest themselves in a pallor of the face, an appearance of weariness in the drooping body, a mouth parched from lack of saliva, indigestion caused by insufficiency of the gastric juice, and cold hands. If prolonged, grief results in mal-nutrition and consequent wasting, and predisposes the debilitated body to infectious diseases. _Weariness_ is like a rapid paralysis of the heart; it may induce fainting, as expressed in the popular phrase "dead tired"; but a reflex action will nearly always restore the sufferer, like an automatic safety-valve; thus a yawn, that is to say, a deep, spasmodic inspiration, which dilates the pulmonary alveoli, causes the blood to flow to the heart like a suction pump, and sets it in motion again. In _anger_ there is a kind of tetanic contraction of all the capillaries, causing extreme pallor, and the expulsion of an extra quantity of bile from the liver. _Pleasure_ causes dilatation of the blood-vessels; the circulation, and consequently all the functions of secretion and assimilation are facilitated; the face is suffused with color, the gastric juice and the saliva are perceptible as that healthy appetite and that watering of the mouth which invite us to supply fresh nourishment to the body; all the tissues work actively to expel their toxins, and to assimilate fresh nourishment; the enlarged lungs store up large quantities of oxygen, which burn up all refuse, leaving no trace of poisonous germs. It is an injection of health.