As to any deficiency of power, my reviewer had omitted to notice that not only the ordinary expansion of the water of the blood by calorie had been assumed, but also its vaporization, or the change of such a portion as was needed into steam, the lungs being _in vacuo_; so that nature here had not failed of her usual abundance. And had not this power been kept in check by the pressure of the surrounding air hindering the perfect vacuum of the lungs, there was reason to fear, rather its excess than its deficiency. As to the reviewer's assertion that heat is generated in every part of the system, and imparted to the _solids_ equally with the fluids--that I positively denied, in the name of common sense. For who does not know that, although there may be some heat elaborated in the stomach, and some during the processes by which the fluids change to solids, that the great source of heat to the system, is in the fluid blood, and not in solid flesh or bone? Our senses of sight and feeling show us, in the case of blushing, that heat comes and goes with the blood. No one believes that the solid parts of his leg warm the blood as much as it warms them. Finally, it discredited the old theory, that it showed no adequate use for the great primary function of respiration, and its constant attendant, animal heat. Breathing and warmth are not ultimate ends. Man breathes to live; he does not live to breathe. He is warm to live; he does not live merely to be warm. Our theory shows that it is these primary agencies which sustain his being; and it sets forth the manner in which they operate for this end. And thus, while it indicates the wisdom of the Almighty in the formation of the animal frame, it shows itself to be His true interpreter. SECTION III. Uses of the Theory--Proofs.--Publication of a Work, in 1849, entitled "Respiration and its Effects, more, especially in relation to Asiatic Cholera and other Sinking Diseases."--Examples. TO DR. MARCY.--The theory of the two chief motive powers which operate at the centre was, we conceive, completed by the addition of steam formed in the vacuum of the lungs, as available to give to the blood its due velocity. We also believe that complete proof _a priori_ had been adduced of the fallacy of the theory that the _primum mobile_ is in the heart; and, also, that proof _a priori_ had been given that it begins at the lungs, and is the product of respiration. It remained to apply this theory to use, and to find proofs _a posteriori_. Although some of my friends regarded my theory as an _ignis fatuus_ which led me into nothing but evil, yet it has enabled me, by plans of exercise, to endure for many years, in-door sedentary labor--and yet enjoy health; and in unusual emergencies, more than once to save my own life and that of others.