A treatise on physiology and hygiene for educational institutions and general readers .. . e there would be a constantly-recurring tendency to collapse after every breath. The lung-sub-stance essentially consists of these bronchial tubes and terminalair-cells, with the blood-vessels ramifying about them (Fig. 44).At the top of the trachea is the larynx, a sort of box of cartilage,across which are stretched the vocal cords. Here the voice is pro-duced chiefly by the passage of the respired air over these cords,causing them to vibrate. 5. Over the opening of the larynx is found the epiglottis, w
A treatise on physiology and hygiene for educational institutions and general readers .. . e there would be a constantly-recurring tendency to collapse after every breath. The lung-sub-stance essentially consists of these bronchial tubes and terminalair-cells, with the blood-vessels ramifying about them (Fig. 44).At the top of the trachea is the larynx, a sort of box of cartilage,across which are stretched the vocal cords. Here the voice is pro-duced chiefly by the passage of the respired air over these cords,causing them to vibrate. 5. Over the opening of the larynx is found the epiglottis, whichfits like the lid of a box at the entrance to the lungs, and closesduring the act of swallowing, so that food and drink shall pass 4. Office of the bronchial tubes ? What further can you state of them ? 5. The epiglottis ? When it does not close in time, what is the consequence ? RESPIRATION. 157 backward to the oesophagus; or gullet (Fig. 45). Occasionally itdoes not close in time, and some substance intrudes within thelarynx, when we at once discover, by a choking sensation, that. something has gone the wrong way, and, by coughing, weattempt to expel the unwelcome intruder. The epiglottis is one ofthe many safeguards furnished by nature for our security and com-fort, and is planned and put in place long before these organs arebrought into actual use in breathing and in taking food. 6. The air-passages are lined throughout almost their whole ex-tent with mucous membrane, which keeps them in a constantlymoist condition. This membrane has cells of a peculiar kind uponits outer surface. If examined under a powerful microscope, we maysee, even for a considerable time after their removal from the body,that these cells have minute hair-like processes in motion, whichwave like a field of grain under the influence of a breeze (Fig. 46).This is a truly beautiful sight; and since it is found that theselittle cilia, as they are called, always produce currents in one 6. Lining of the
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Keywords: ., bookcentury1800, bookdecade1, booksubjectphysiology, bookyear1884
