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Their exchanges must in all cases take place through the capillary walls and the layer of cells lining the alveoli. The small pits are alveoli, and the vessels in their walls are chiefly capillaries. The air enters and leaves the lungs by the same system of tubes.
*Interchange of Gases in the Lungs.*—During each inspiration the air from the outside fills the entire system of bronchial tubes, but the alveoli are largely filled, at the same time, by the air which the last expiratory effort has left in the passages.
By the action of currents and eddies and by the rapid diffusion of gas particles, the air from the outside mixes with that in the alveoli and comes in contact with the membranous walls. Here the oxygen, after being dissolved by the moisture in the membrane, diffuses into the blood. The carbon dioxide, on the other hand, being in excess in the blood, diffuses toward the air in the alveoli.
The epithelial cells are not arranged on any definite plan, but are closely packed in irregularly shaped alveoli. If the alveoli are large and the intervening stroma is scanty and delicate, the tumour is soft and brain-like, and is described as a medullary or encephaloid cancer.
For protoplasm does not fill the cell as a compact mass, but spreads itself out and builds itself up in the most delicate network or meshwork, of which it forms the threads and walls, enclosing innumerable vacuoles and alveoli, and Bütschli succeeded in making a surprisingly good imitation of this “structure” by mechanical means.
Drops of oil intimately mixed with potash and placed between glass plates formed a very similar emulsion-like or foam-like structure with a visible network and with enclosed alveoli.
In many cases the upper front teeth, instead of the natural curve outwards, which the row presents, had been pressed so as to appear as if the line of alveoli in which they were planted had an inward curve.
Name the divisions of the lungs. Trace air from the outside atmosphere into the alveoli. Trace the blood from the right ventricle to the alveoli and back again to the left auricle. How are the air passages kept clean and open? Describe the pleura. Into what divisions does it separate the thoracic cavity? Describe and name uses of the diaphragm.
A name given to certain substances, such as soda, potash, and the like, which have the power of combining with acids. Pertaining to the alveoli, the cavities for the reception of the teeth. A single-celled, protoplasmic organism, which is constantly changing its form by protrusions and withdrawals of its substance. Amoeboid. Like an amoeba.
The alveoli contained a secretion which was almost certainly milk, O'Donoghue states that the entire series of growth changes in these animals up to twenty-one days after heat in identical with that which occurs in normally pregnant animals. Kinderh.
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