The blood is a mixture of many fluids, which, in a state of health, are so combined, that the whole passes freely through its appointed vessels; but if by the loss of the thinner parts, the rest becomes too gross to be thus carried through, it will stop where the circulation has least power; and having thus stopped it will accumulate; heaping by degrees obstruction on obstruction. Health and chearfulness, and the quiet exercise of mind, depend upon a perfect circulation: is it a wonder then, when this becomes impeded the body looses of its health, and the temper of its sprightliness? to be otherwise would be the miracle; and he inhumanly insults the afflicted, who calls all this a voluntary frowardness. Its slightest state brings with it sickness, anguish and oppression; and innumerable ills follow its advancing steps, unless prevented by timely care; till life itself grows burthensome. The disease was common in antient Greece; and her physicians understood it, better than those perhaps of later times, in any other country; who though happy in many advantages these fathers of the science could not have, yet want the great assistance of frequent watching it in all its stages. Those venerable writers have delivered its nature, and its cure: in the first every thing now shews they were right; and what they have said as to the latter will be found equally true and certain. This, so far as present experience has confirmed it, and no farther, will be here laid before the afflicted in a few plain words. SECT. II. Persons Subject to it. Fatigue of mind, and great exertion of its powers often give birth to this disease; and always tend to encrease it. The finer spirits are wasted by the labour of the brain: the Philosopher rises from his study more exhausted than the Peasant leaves his drudgery; without the benefit that he has from exercise. Greatness of mind, and steady virtue; determined resolution, and manly firmness, when put in action, and intent upon their object, all also lead to it: perhaps whatever tends to the ennobling of the soul has equal share in bringing on this weakness of the body. From this we may learn easily who are the men most subject to it; the grave and studious, those of a sedate temper and enlarged understanding, the learned and wise, the virtuous and the valiant: those whom it were the interest of the world to wish were free from this and every other illness; and who perhaps, except for this alloy, would have too large a portion of human happiness. Though these are most, it is not these alone, who are subject to it. There are countries where it is endemial, and in other places some have the seeds of it in their constitution; and in some it takes rise from accidents. In these last it is the easiest of cure; and in the first most difficult.