This part of his argument is ended with an appeal to practical experience. "The truth, indeed, presents itself obviously before us when we consider what happens in the dissection of living animals: the great artery need not be divided, but a very small branch only (as Galen even proves in regard to man), to have the whole of the blood in the body, as well that of the veins as of the arteries, drained away in the course of no long time--some half hour or less. Butchers are well aware of the fact and can bear witness to it; for, cutting the throat of an ox and so dividing the vessels of the neck, in less than a quarter of an hour they have all the vessels bloodless--the whole mass of blood has escaped. The same thing also occasionally occurs with great rapidity in performing amputations and removing tumours in the human subject.... Moreover it appears ... that the more frequently or forcibly the arteries pulsate, the more speedily will the body be exhausted of its blood during hæmorrhage. Hence also it happens that in fainting fits and in states of alarm when the heart beats more languidly and less forcibly, hæmorrhages are diminished and arrested. "Still further, it is from this, that after death, when the heart has ceased to beat, it is impossible by dividing either the jugular or the femoral veins and arteries by any effort to force out more than one-half of the whole mass of the blood. Neither could the butcher ever bleed the carcass effectually did he neglect to cut the throat of the ox which he has knocked on the head and stunned before the heart had ceased beating." Harvey continues to push his argument to a logical conclusion in the succeeding chapters of his Treatise partly by argument and partly by adducing fresh experimental evidence. But if any one shall here object that a large quantity may pass through (the heart) and yet no necessity be found for a circulation, that all may come from the meat and drink consumed, and quote as an illustration the abundant supply of milk in the mammæ--for a cow will give three, four, and even seven gallons a day, and a woman two or three pints whilst nursing a child or twins, which must manifestly be derived from the food consumed; it may be answered, that the heart by computation does as much and more in the course of an hour or two.