The Principal Symptoms indicating the Small-Pox in general.

‘The Small-Pox shew themselves by a greater or smaller Number of Pustules, dispersed over the whole Body, rising in a round Form, and terminating in a whitish Point, having a very red Circle at their Basis; and growing insensibly larger for several Days, till at last they suppurate and dry up. These are the certain Tokens of the Small-Pox:’Tis impossible to mistake them. But that is not enough for a Physician. It is his Business to prognosticate them before their Eruption; or at least to discern them when they begin to come out. He cannot therefore be too careful in observing the Symptoms which indicate them when they are ready to appear, or which accompany them when they just begin to rise.’

Helvetius, An essay on the animal oeconomy.
Together with observations upon the small pox (London, 1723), p. 117.

Apart from pustules the other chief characteristic of the disease according to Sir Richard Blackmore, was a fever which was quickly accompanied by ‘great Pains, sometimes in the Head, sometimes in the Side, sometimes in the Limbs, but much more frequently in the Back, where often they are very acute and scarce sufferable; attended with great Sickness and violent Vomitings, which so nearly resemble a Fit of the Stone, that sometimes the Physician, imposed upon by the Similitude of Symptoms, has pronounced it to be that grievous Distemper.’ As Blackmore’s account makes clear, this very ‘similitude of symptoms’ made the task of treatment very difficult indeed, particularly as different symptoms arose at different stages of the infection.

Sir-Richard-Blackmore
Portrait of Sir Richard Blackmore: Courtesy of the National Library of Medicine.

Helvetius outlined three stages of the disease:

‘The First comprehends all the Time preceding the Eruption, and the Three First Days of the Eruption it self; which commonly ends of the Fourth Day inclusive after it begun.
The Second Stage or Season is from the Fourth to the Ninth Day inclusively; the Time in which the Suppuration is carry’d on and finish’d.
The Third extends from the End of the Suppuration, to such Time as the Pustules dry up and fall of. This usually happens the Fourteenth or Fifteeenth Day. But we are to observe, that pretty often, in the Malignant-Confluent especially, the Pustules subsist, and maintain their Ground much longer.’

Helvetius, An essay on the animal oeconomy.
Together with observations upon the small pox (London, 1723), p. 162.