ALTHOUGH some (as before said) were buried in Sleep, yet others suffered by a very different Extream, and kept continually waking, insomuch that frequent Repetitions of the most efficacious Opiates could not procure the least Composure; in which Case, it is my Opinion, that the Membranes of the Brain are pricked and vellicated by poisonous _Spicula_; besides which also those soft, dewy Moistures upon the Brain, necessary for its Relaxation to sleep, are dissipated and exhaled by the burning Heat of the Fever; so that the Spirits are, as it were, set on Fire, and Inflammations raised, not to be again extinguished, and frequently likewise Sphacelations of the Brain. BUT the most remarkable Symptoms of this Class, is the Palpitation of the Heart, the Ancients conjectur’d that Pestilential _Aura_ to have a specifick Contrariety to the Nature of that Organ; and it must be confessed that in the late Sickness this Complaint was very grievous; but yet I cannot see how this Venom should more particularly be pointed against the Heart than any other of the _Viscera_, unless in Consideration to the greater Importance of its Office in the OEconomy. As soon as the subtile Poison of a Contagion hath insinuated it self into the Mass of Blood, either through the Pores of the Skin, or other more open Passages, there is no doubt, but it imprints upon it very malignant Qualities, which, according to the necessary Laws of Circulation, must arrive at the Heart it self, and affect it with Uneasiness, so that its Palpitation is nothing else than its Struggles to throw off what is Offensive; and it is no wonder to me this happens, because the Heart is composed of such a Contexture of Fibres; for as the Pestilential Venom hath somewhat in it of a saline Nature, and what is acrid, it very naturally stimulates the nervous Parts, and gives to this Organ even convulsive Motions; but of this matter every one hath leave to judge for himself. BUT how vehemently the Heart may beat on this Occasion, appears very manifest from a remarkable Instance; I was sent for to a Youth of about fourteen Years of Age, who had continued free of the Infection, after his Mother and the rest of the Family had been visited by it, when all on a sudden he was seized with such a Palpitation at Heart, That I and several others could hear it at some considerable Distance, and it continued so to do till he died, which was soon after; many Medicines being given without any manner of Success: But in so extraordinary a Case as this, I am apt to conjecture it rather owing to a Pestilential Carbuncle seizing the Heart it self, than from the Vellication and _Stimulus_ only of pungent Particles passing through it.