another Confirmation of this Theory, whose _Moleculæ_ are still less than the preceeding, as appears by their Eruption with greater Flatness, and less Extension of the Obstructed Vessels. Thus also we see that in all these Diseases where the Contagious Matter is more Virulent than ordinary, or the Constitution of the Year more productive of these Diseases, or join'd with a Hot Tense and Scorbutic Disposition, Diarrhea's, Dysenteries, Purple Spots, Hemorrhages, Phrensies, Convulsions, Inflammations, _&c._ equally accompany these as Pestilential Diseases. From what has been said in this and the foregoing Chapters may be deduced the Reasons of the greater or less Virulency of the Small-Pox, Measles, _&c._ in some Years more than others; As also why these Diseases shou'd rage with the greatest Violence when join'd with, or immediately preceeding a Pestilential Constitution of the Air. Hence also appears the Reason why Pains of the Head, Stomach, Loins and Back, preceed the Eruption of the Pustules, these Parts as nearest the Heart being soonest obstructed, and the _Impetus_ of the Blood against the obstructed Canals much greater than in the rest of the Body. As also why the Pustules should appear so much sooner in the Face, Neck and Breast, than other Parts of the Body, as appears from _Prop. 2_. Hence likewise appears the Reason why the Fever, Vomiting, Pains, _&c._ preceeding the Eruption of the Pustules should cease or be much diminish'd upon their Appearance; The _Moleculæ_, by the Force of the Circulating Fluids, being driven into and fixt in the Cutaneous Glands, and Secretory Vessels, whereby the Capillary Arteries being freed from them, a more easy Passage is allowed to the Circulating Fluids. Hence also appears the Reason why the Fever gradually increases with the Augmentation of the Pustules, the Contiguous Vessels being compress'd by their Distention, and the Obstructions in the Secretory Vessels made more Numerous; whence the Quantity of the Perspirable Matter being Diminished, and the Canals streightned, the Vessels will be more full, and the Pulse more strong and frequent. Hence likewise it will follow, that the more numerous the Obstructions are, and more pungent the Contagious Matter, the more Violent the Symptoms will be, and the Matter of the Pustules when suppurated become an Acrid and pungent gleety Substance, or Laudable _Pus_. As also why the Time of Suppuration shou'd vary in Proportion to the Virulency of the obstructing Matter; and consequently the Reason of the Difference between the _Distinct_ and _Confluent Small-Pox_. Hence also it will appear, that Bleeding, in the Beginning of the Disease, ought only to be Administred where the _Impetus_ of the Circulating Fluids is so great, that notwithstanding the Diminution of the Force of the Blood by it, the protrusive Force of the Circulating Mass will exceed the _Impetus_ made on the Obstructing Matter by the Vibrations of the _Fibres_, and likewise why on its