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RESPIRATION

1603

RETORT

Respiration,   Organs    of,   are   of   two

kinds:  Gills  arid  lungs. The former are

adapted for respiration in water, the latter for action in free air. Gills are found in clams, crayfish, squids and other invertebrates as well as in all fishes. The essence of respiration consists in an exchange of oxygen and carbon dioxide (COS) between the blood and the air. Special organs of respira-tion are not necessary to accomplish this end. The earthworm, for example, breathes through the skin; that is. the blood comes close to the surface in thin-walled vessels, and the exchange between it and the air is accomplished. In the simplest animals, like the amceba, where, there is no blood, the breathing is done by the protoplasm of the body, but the exchange of carbon dioxide for oxygen is essentially the same as in higher animals. It must also be understood that respiration ^ (q v.} in plants is of the same nature as in animals. The old statement that plants breathe carbon dioxide (carbonic acid gas) in the sunlight, giving off oxygen, and in darkness reverse the process is not true. In breathing they take in oxygen and give up carbon dioxide at all times, and the process is more active in sunlight than in darkness. It is easy to point out how the erroneous idea in reference to their breathing arose. Plants use carbon dioxide in their process of nourishment, and they return free oxygen to the air as a left-over product. This comes mainly from the process of starch-formation; and, as that process takes place in the sunlight, it was at first supposed that the oxygen was set free in daylight from the process of respiration.

Fishes possess gills throughout life; the amphibia have them in larval stages, and, in some forms, both gills and lungs exist in the same individual. Lungs make their first appearance in the dipnoi (q.i>.) and occur in all animals of a higher grade. Lungs are developed ^n all animals as sac-like expansions of the walls of the pharynx, blood vessels are spread over them, and air is introduced into the inside. In the human body the lungs

become very complicated. The windpipe divides into two main branches — the bronchi. These enter the lungs, and are subdivided again and again into the bronchial tubes, which branch like the twigs of a tree. The smallest divisions enter into air-sacs, which are lobulated and have very thin walls. A network of capillaries is spread over the thin walls of the air-sacs, and it is in these capillaries that the exchanges between air and blood go on. The blood does not anywhere come into actual contact with the air, but the exchange of gases is made (by osmosis) through the thin membranes of the air-sacs and the capillaries. The substance of the lungs is spongy, and considerable elastic tissue enters into their structure, which allows them to expand and contract. It is not possible in an illustration to give a true picture of the complexity of the lungs. Not only bronchial tubes branch through their substance, but blood-vessels which carry blood to be aerated, others which carry arterial blood to nourish the lungs, besides lymphatics and nerves, branch through. The oxygen received by the lungs is carried to the minutest parts of the tissues, and is there given up in exchange for carbon dioxide. It therefore is clear that there are an external respiration taking place in the lungs and also an internal respiration taking place in the tissues throughout the body. The latter is the more important part of the process of respiration. The air is* renewed in the lungs through the action of the diaphragm and other muscles. For the amount of air breathed and other details see Huxley's Lessons in Elementary Physiology or any other good textbook of physiology.

Reszke (resh'ke), Jean de, an operatic singer (tenor), was born at Warsaw, Poland, on Jan. 14, 1853. He attained a reputation as a singer while a boy; and, although he had been destined for a lawyer, he soon quitted his profession for the operatic stage. He appeared in 1874 in Venice and in 1875 in London, singing a barytone part; but was convinced that his voice is more truly a tenor. Accordingly he re-appeared in 1879 as a tenor, and is now recognized as one of the world's finest artists in Robert le Diable, Faust, Lohengrin, Aida, Le Cid, Tristran and Romeo and Juliet. Jean de Reszke was a favorite performer for a long period of years at the Metropolitan Opera House, New York. Retort', a vessel employed by chemists for distilling or effecting decomposition by means of heat. It may be made of glass,

WINDPIPE, BRONCHI AND ONE   LUNG

JEAN DE RESZKE