and to apply it to its proper Uses, and prepare it for its proper Vessels. Besides the Power of Exercise on the Secretions of Particles purely Excrementitious, and the better Mixture of those which are Homogeneous; it is to be consider’d, that there are in the Oeconomy Secretions made to return with Advantage into the Blood, out of which they are made; and the Consideration of the Nature of these does afford us fresh Reasons to set a Value upon the Use of Exercise, because the Body is so fram’d and adapted, as to require it, in order to the furthering and increasing these Operations; and if in the Business of Fermentation, which is only a gradual Separation of the Must from the Spirituous Particles of the Liquor, we find that the Motion of the Vessels in which the Liquor fomenting is contain’d, does so much improve that Operation, as we are convinc’d it does, by the Effects of the Carriage by Sea on Wines and other Liquors in Casks; of how much greater Importance must the Motion of the Body be, in order to the perfecting the Animal Fluids, in a System of Mechanism so contriv’d, as to expect and demand such an Assistance? Where the Solids are so fine-spun, as to determine the very Shape of the Particles of a Fluid; and where they are so dispos’d, that a Fluid never passes by ’em but it carries off some Melioration and Improvement, and therefore cannot well arrive too frequently at those Passages where it receives so happy an Alteration. Let us suppose the Blood to pass the most extreme Parts twelve times in an Hour, when the Body is not mov’d; if the Motion of the Body encreases this to fifteen or sixteen times in an Hour, it will necessarily follow, that the Quantity of the Secretions by the Liver, the Spleen, the Brain, and the rest of the Glands, which separate the beneficial Juices, of which I am speaking; the quantity of these, I say, must needs be augmented; which in Process of Time, when this is brought to a Habit, must be of some Consequence. To insist but on one of these Secretions; I take it to be no Paradox, that the more a Man stirs himself, the more Animal Spirits are made in the Brain; tho’ it will be strait retorted, that by the very same Motion and Exercise, there will be a Waste of the Spirits by Perspiration, more than proportionable to the Overplus that is made in the Brain; and tho’ I grant this, it will not suffice to discompensate the Benefit which the Blood reaps from the Augmentation of the Quantity of the Animal Spirits infus’d into it (if I may so speak) from the Brain; because the true Animal Spirits have their Work to do in the Blood, before they come to pass off at the Skin; they are not of that Fugitive Make, which at first Thought most Men are apt to suppose ’em to be; they seem to be destin’d to contemperate the Acrimony of the Blood, to embrue it with a Plastick Quality, and may serve to execute other Functions, besides that of Motion; so that it is