463. The nutrient portion of the food is poured into the left subclavian vein, (24, 27, fig. 88,) at the lower part of the neck, and is carried to the right cavities of the heart. The fluid in these cavities consists of the chyle incorporated with the impure blood. Neither of these two elements is fitted to promote the growth or repair the waste of the body. They must be subjected to a process, by which the first can be converted into blood, and the second freed of its carbonic acid gas and water. This is effected by the _Respiratory Organs_. ANATOMY OF THE RESPIRATORY ORGANS. 464. The RESPIRATORY ORGANS are the _Lungs_, (lights,) the _Tra´che-a_, (windpipe,) the _Bronch´i-a_, (subdivisions of the trachea,) and the _Air-Ves´i-cles_, (air-cells at the extremities of the bronchia.) The _Di´a-phragm_, (midriff,) _Ribs_, and several _Muscles_, also aid in the respiratory process. 465. The LUNGS are conical organs, one on each side of the chest, embracing the heart, (fig. 88,) and separated from each other by a membranous partition. The color of the lungs is a pinkish gray, mottled, and variously marked with black. Each lung is divided into lobes, by a long and deep fissure, which extends from the posterior surface of the upper part of the organ, downward and forward, nearly to the anterior angle of the base. In the right lung, the upper lobe is subdivided by a second fissure. This lung is larger and shorter than the left. It has three lobes, while the left has only two. -=-=-=-=-=-=-=-=-=-=-=-= 463. What fluids are conveyed into the right cavities of the heart? What is necessary before they can be adapted to the wants of the body? By what organs are these changes effected? 464-474. _Give the anatomy of the respiratory organs._ 464. Name the respiratory organs. What organs also aid in the respiratory process? 465. Describe the lungs. -=-=-=-=-=-=-=-=-=-=-=-= [Illustration: Fig. 89. A back view of the heart and lungs. The posterior walls of the chest are removed. 1, 2, 3, The upper, middle, and lower lobes of the right lung. 8, 9, 10, The two lobes of the left lung. 6, 13, The diaphragm. 7, 7, 14, 14, The pleura that lines the ribs. 4, 11, The pleura that lines the mediastine. 5, 12, 12, The portion of the pleura that covers the diaphragm. 15, The trachea, 16, The larynx. 19, 19, The right and left bronchia. 20, The heart. 29, The lower part of the spinal column.] -=-=-=-=-=-=-=-=-=-=-=-= Explain fig. 89. -=-=-=-=-=-=-=-=-=-=-=-= 466. Each lung is enclosed, and its structure maintained by a serous membrane, called the _pleu´ra_, which invests it as far as the root, and is thence reflected upon the walls of the chest. The lungs, however, are on the outside of the pleura, in the same way as the head is on the outside of a cap doubled upon itself. The reflected pleuræ in the middle of the thorax form a partition, which divides the chest into two cavities. This partition is called the _me-di-as-ti´num_.