withdrawing of the stimulus, or its naturally losing its force, could only have the same effect with fasting or fatigue; but the debility of the stomach, the confusion of the head, and other effects which attend a dose of opium, demonstrate that it acts partially, and not equally over the whole body. The Science of Life indeed says that these effects are owing to the improper omission of the medicine, or not repeating the doses in due time. This may be; but no improper exhibition of food, or want of due repetition, will produce such symptoms; which undoubtedly is a proof that food stimulates the system in one way, and opium in another. 6. If any medicine could be found that acted as an universal stimulus or exciter of the whole system, it could not like others be expelled, by any particular evacuation; but, by destroying the balance between the force of the acting powers and the subject on which they act, would most certainly kill, unless very powerful means were used to counteract its effect. The only stimulant we are acquainted with which acts equally on the whole system, and which can be readily exhibited as a medicine, is that pure kind of air called by Dr. Priestley _dephlogisticated_, by Scheele _empyrean_, and by the French chemists and their followers _oxygen_. The exciting powers of this air, when breathed instead of the ordinary atmosphere, are astonishing. It not only augments the appetite, but the power of the muscles, and the inclination to use them; so that without any intoxication or delirium the person cannot refrain from action; and it not only exhilarates the spirits in an extraordinary manner, but beautifies the face. Did the cure of diseases therefore, or any set of them, depend on mere excitation, no other medicine but _oxygen_ would be necessary. What effects it may have in diseases of debility is not yet ascertained; but to persons in health it certainly proves fatal: their bodies are unable to bear its powerful action, and of consequence they waste, and would die of consumptions, if its effects were not counteracted. Nor is this at all an easy matter; for Dr. Beddoes informs us that, by breathing this air for a short time each day, only for three weeks, he found himself in great danger of a consumption, and was obliged to use much butter and fat meat in his diet, besides giving up the use of the air altogether, in order to get clear of its mischievous effects.