Numerous clinical trials require drawing a limited quantity of blood, for instance to decide how much glucose in somebody with diabetes or the hematocrit level in a competitor. This method can be effortlessly done in light of the fact that of slender activity, the capacity of a fluid to stream up a little cylinder against gravity, as displayed in Figure. At the point when your finger is pricked, a drop of blood structures and keeps intact because of surface pressure — the uneven intermolecular attractions at the outer layer of the drop. Then, at that point, when the open finish of a tight width glass tube contacts the drop of blood, the cement powers between the particles in the blood and those at the glass surface draw the blood up the cylinder. How far the blood goes up the cylinder relies upon the measurement of the cylinder (also, the kind of liquid). A little cylinder has a generally enormous surface region for a given volume of blood, which results in bigger (relative) appealing powers, permitting the blood to be drawn farther up the cylinder. The actual fluid is kept intact by its own firm powers. At the point when the heaviness of the fluid in the cylinder produces a descending force equivalent to the vertical power related with slim activity, the fluid quits rising.