At this period, then, the fever is fully formed; the series of morbid phenomena is complete: any thing more that happens is referrible to degree and to duration, and must be the result of one or other of these circumstances, or of their combined operation. And we now see that the organs affected, constitute precisely that system of organs which has been described as forming the febrile circle: that the symptoms which denote the fever are just the symptoms which indicate a derangement in the several functions performed by these organs; and that the order in which they become successively involved is exactly that which has been assigned. As soon as the preternatural heat comes on, pain begins to be felt in the head. Dr. Clutterbuck, in describing the general character of the ordinary fever of London states[23] that “the _first_ symptom almost invariably complained of is more or less of uneasiness of the head.” If by uneasiness he meant pain, there is, if there be any truth in the preceding observations, a long train of symptoms to intervene before this symptom occurs. That it does ultimately occur is certain: but commonly its place in the series is much later than is here assigned: it is disordered function of the brain, indicated by loss of mental energy, that appears to form the first symptom in this morbid train. The pain, when it does come, is sometimes slight at first, and occasionally it remains slight throughout the disease; at other times it is pretty severe. Cases sometimes occur, in which, instead of pain, there is only a sense of giddiness, and now and then the uneasy feeling is described as that of lightness: or, on the contrary, as that of heaviness or weight. But whether the feeling be pain, and that pain be slight or severe, or whether it be giddiness, or lightness, or heaviness, it indicates a similar condition of the organ, and requires a similar treatment.