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 usually called Ductus Thoracicus, there are numerous Valves, which hinder the Return of the Chyle to the common Receptacle, so that it can be moved forwards, but not backwards.

Since this Passage of the Chyle has been discovered, it has been by some believed, that the Milk is conveyed into the Breasts, by little Vessels, from the Ductus Thoracicus. The whole Oeconomy of that Affair has been particularly described very lately by Mr. Nuck; before whose Time it was but imperfectly known. He says therefore, that the Breasts are Heaps of Glands, supplied with Blood by innumerable Ramifications of the Axillary and Thoracick Arteries; some of which passing through the Breast-bone, unite with the Vessels of the opposite Side. These Arteries, which are unconceivably small, part with the Milk in those small Glands, into small Pipes, four or five of which meeting together, make one small Trunk; of these small Trunks, the large Pipes, which terminate in the Nipple, are made up; though before they arrive thither, they straiten into so small a Compass, that a stiff Hair will just pass through. The Nipple, which is a Fibrous Body, has seven or eight, or more Holes, through which every Pipe emits its Milk upon