Consideration about the Conceptions, being like unto an _Ovum_ in the Womb, proposes a Parallel between these Animalcles and Insects; and insinuates, that as the latter cast their Skins, and appear of another Shape, so the other which at first seem like Tadpoles, may cast their outer Skin, and then be round; and that this may be the occasion of the round Figure of the Conception in the Womb. To this it may be replied, that according to Mr. _Leewenhoeck_'s own Sentiment, the Animalcles cannot come forward, if they do not find the _Punctum_ or proper place for their Nourishment, to which it seems they must have some _Adhæsion_. Now the Conception in _Viviparis_ is not fastned unto the Womb for many days, nor does adhere to any point of it; so that it seems this roundish Body is not the Animalcle thus chang'd after having cast an outer Skin, but is rather the _Cicatricula_ or little Egg, into which the Animalcle has entred as its _Punctum_ or place of nourishment; else I do not see why they should not be adhering to the Womb from the first Conception, or why (as I have said) many hundreds of them are not conceiv'd and formed together, _&c._ _A short Discourse concerning Concoction: Read at a Meeting of the Royal Society, _May ... 1699_, by _Clopton Havers_, M. D. Fellow of the Royal Society._ The manner in which the Digestion of the Aliment is performed, is a thing not very easie to be understood and explained. However, it has not escap'd the Conjectures of some Philosophical Men, who having curiously observ'd the _Phænomena_ of Nature, and enquired into their Causes, have, amongst other things, endeavour'd to account for this. But their Sentiments about it have been various, and the Hypothesis, by which they have studied to explain it, very different. Some have thought the Concoction of the Food to be a kind of Elixation; and that the grosser and more solid Parts being, as it were, boil'd in the Liquid by the Heat of the Stomach, and the Parts adjacent to it, as the Liver, Spleen, and Omentum, are by a long and continued Elixation, first render'd more tender, and then colliquated, and dissolved into minuter Particles, so as to mix more equally with the Fluid, and with that to make one Pulpament, or chylous Mass. And _Hippocrates_, tho' he does not plainly call it an Elixation, yet seems to attribute the Concoction of the Food to the Heat of the Stomach, as the Cause of it, _Sect. 4. Libro de salubri victus ratione_. So where he takes notice of the voiding of such Fæces, as appear to be like the Food that has been eaten; he adds, _Constat enim, sane ventriculum, ciborum copiam, ut concoquat, calefacere non posse_. And there are other Passages in the same Book, from which we may conclude, that he suppos'd the Heat of the Stomach to be the great Cause of the Digestion of the Food.