1. In the first, the patient lies insensible, with delirium, perhaps so violent that he cannot be kept in bed without restraint; with extreme restlessness and constant watchfulness; with rapid and panting respiration; with a tender abdomen, perhaps with frequent and involuntary stools, a dry, black, and hard tongue, a quick, yet weak pulse, and the skin universally and pungently hot. 2. In the second he lies insensible, with a cold and dusky skin; with a swollen and livid countenance; with a heavy and oppressed respiration; with a pulse perhaps not to be felt, or, if distinguishable, either so rapid that it cannot be counted, so small that it is like a thread beneath the finger, and so weak that it is lost by the slightest pressure, or else slow, irregular, and intermittent. In this state, the patient is almost as completely paralyzed as in apoplexy, and the attack is almost as rapidly fatal as apoplexy. It constitutes what has been called congestive fever. Fortunately, these intense forms of the disease are of rare occurrence: they are witnessed only in solitary instances, and they arise either from exposure to a highly-concentrated poison, or from some condition of the constitution, by which that power to resist the influence of noxious agents, which is characteristic of life, is more than commonly diminished or exhausted. They have been conceived to form exquisite specimens of diseases of debility. But where is the debility? Not in the disease, for that is of giant strength; not in the patient, for remove, if you can but remove, a part of the load that oppresses him, and instantly an intensity of action will be set up in the whole system, perhaps as great as it is capable of exerting, and certainly greater than it is capable of sustaining without the most imminent danger. The brain is overwhelmed by the intensity of its affection; the energy that should animate the system, and of which it is the great source, is withheld: but that energy is suspended, not destroyed; and the debility which seems to be the result is not real, but apparent, not direct, but indirect. The giant that lies prostrate on the earth, mastered by superior power, has still a giant’s strength, though he does not at that moment put it forth: give him but the chance of throwing off the load that keeps him down, and he will soon shew you that he is not weak. I have always been struck with the extraordinary clearness and decision with which the acuteness of Sydenham enabled him to make this important distinction, perhaps in the very first case that occurred to him, in which the discrimination was required. Having described, in his own powerful manner, an excellent specimen of congestive fever to which he was called, he states that he ordered the patient to be bled: that the bye-standers regarded the suggestion with horror: that the man seemed at the point of death; that to them it appeared that the abstraction of