ABSORP'TION (Lat. ab, away + sorbere, to swallow). When certain fluids are brought together the molecules of one mix intimately with those of the other and diffusion takes place. if certain solids containing fluids are brought in contact with other liquids, some of passes into the solid and absorption takes place. Gases may also be absorbed simi larly. Diffusion :idling through an animal or vegetable membrane is called osmosis. Much of what is termed absorption in physiology is really osmosis. Most of the tissues of living bodies have the power of absorbing tluids—a property that often continues after death and until decomposition. Animal substances differ in absorbing power according to differences in the liquid. notably if they differ in specific gravity and if the fluids in the substances brought in con tact are miscible. The following table from Chev rent shows the amounts of liquid absorbed by different substances in twenty-four hours: Aetivity of absorption. or osmosis, varies with the freshness of the membrane, being great soon after separation from the principal parts: and varies also with pressure, motion, and tempera ture. Absorption of oxygen by the blood in the lungs is apparently instantaneous, the change in color from dark red to bright red as soon as it arrives at the pulmonary vessels, showing the action of the gas it has taken from the atmosphere. This rapidity of absorption is due to the fact that in the circulation of the lungs the blood is spread out in the fine capil laries over a very large area, and to the inces sant motion of the blood in the capillaries.
Claude Bernard found that if a solution of iodide of potassium were injected into the duet of the parotid gland on one side of a living animal. the saliva discharged by the correspond ing gland on the other side almost instantly afterward contained iodine. In a measureless instant, therefore, the iodine was taken up by the glandular membrane on one side, absorbed by the blood, carried to the heart, absorbed from the blood by the glandular membrane on the other side and furnished to the saliva. It is by this process of absorption that the elements of nutrition are taken from the intestines and eonveyed to the tissues they are to nourish: the hones absorb nmeh ealcareons matter from the blood, cartilages less, and muscles less still; the brain takes more water than does muscle, and musele more than hone. The active prin ciples of drugs and poisons are dissolved by the juices in the stomach, and by osmosis pass, unchanged or slightly modified, into the circu lation. (See LACTEALS ; LYMPHATICS.) Ophnn dissolved by the liquids of the stomach is absorbed by the membranous lining, taken away by the blood and distributed well through the body; at the brain it nets on the brain cells and produces sleep or narcotism or insensibility. The quickness of absorptive action is shown in using hypodermic injections; a few moments after the syringe has punctured the skin of the forearm a severe pain in the foot is sensibly relieved.