native heat can convert into perfect blood. They deny, however, that the bile can by any means be thus trans- formed into blood; although the blood, they say, is readily changed into bile, an event which they conceive takes place in melancholic diseases, through an excess of the concocting heat.
Now, if all this were true, and there be no retrogressive move- ment, viz. from black bile to bile, from bile to blood, they would be brought to the dilemma of having to admit that all the juices were present for the production of black bile, and that this was a principal and most highly concocted nutriment. It would further be imperative on them to recognize a kind of twofold blood, viz. one consisting of the entire mass of fluid contained in the veins, and composed of the four humours aforesaid; and another consisting of the purer, more fluid and spirituous portion, the fluid, which in. the stricter sense they call blood, which some of them contend is contained in the arteries apart from the rest, and which they then depute upon sundry special offices. On their own showing, therefore, the pure blood is no aliment for the body, but a certain mixed fluid, or rather black bile, to which the rest of the humours tend.
Aristotle, 1 too, although he thought that the blood existed as a means of nourishing the body, still believed that it was composed as it were of several portions, viz. of a thicker arid black portion which subsides to the bottom of the basin when the blood coagulates, and this portion he held to be of an in- ferior nature ; 2 " for the blood," he says, " if it be entire, is of a red colour and sweet taste ; but if vitiated either by nature or disease, it is blacker." He also will have it fibrous in part or partly composed of fibres, which being removed, he con- tinues, 3 the blood neither sets nor becomes any thicker. He farther admitted a sanies in the blood : " Sanies is unconcocted blood, or blood not yet completely concocted, or which is as yet dilute like serum." And this part, he says, is of a colder nature. The fibrous he believed to be the earthy por- tion of the blood.
According to the view of the Stagirite, therefore, the blood
DC Part, Anim. lib. ii, cap. 3. a De Hist. Anini. lib. iii, cap. 19. 3 Ibid.
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