In anemia the red corpuscles are diminished and the white corpuscles and blood plaques increased in number. After excessive bleeding normal salt solution is injected, subcutaneously or by rectum, as being nearly equivalent to blood serum in composition, and the renewal of the solid elements is left to time. The length of time needed for their restoration is about a week, except in the case of the hemoglobin, which takes longer.
CHAPTER IX.
THE LUNGS AND RESPIRATION.
Besides the heart and the great vessels the chest contains the lungs, the chief organ of respiration, which, with the rest of the respiratory system, will now be treated. The nose and mouth, through which the air first enters the body, have already been spoken of. From them the air passes through the larynx to the trachea, thence to the bronchi, and so to the lungs, where the supply of oxygen for the tissues is taken from the air by the hemoglobin of the blood.
The Larynx.—[The larynx] lies in front of the pharynx at the upper and fore part of the neck, where it causes a considerable projection, known as Adam’s apple. It is a triangular box, base up, flattened at the back, in front, and at the sides, but becoming cylindrical below. Above it opens into the bottom of the pharynx and below into the trachea. It is lined with mucous membrane. Its opening at the base of the tongue is closed during swallowing by a little door-like valve of fibro-cartilage, the epiglottis, to prevent the entrance of food.
Nine cartilages go to make up the larynx, of which the most important are the thyroid and cricoid cartilages and the epiglottis already mentioned. The [thyroid] is the largest and is open behind, its two alæ or wings meeting in an acute angle in front and forming the Adam’s apple, always more prominent in the male than in the female. It is attached above to the hyoid bone and has cornua or horns on either side, top and bottom. The cricoid or ring-like cartilage resembles a seal ring with the stone placed posteriorly. It is stronger than the thyroid and forms the lower part of the cavity of the larynx. Inside and resting on the upper border of the cricoid are the two smaller arytenoid or pitcher-like cartilages, pyramidal in shape, and surmounting these again the two cornicula laryngis. The two cuneiform cartilages are in the free borders of the folds of mucous membrane which extend from the apex of the arytenoids to the sides of the epiglottis. Numerous small muscles serve to bind these various cartilages together.
At the angle of the thyroid cartilage in front are attached the [epiglottis] at the top and just below that the superior or false vocal cords, two folds of mucous membrane enclosing the superior thyro-arytenoid ligaments. Lower still are found the inferior or true vocal cords, which are formed by the inferior thyro-arytenoid ligaments covered with a thin, tightly fitting mucous membrane. Both sets of vocal cords as well as the epiglottis may be seen by means of a head and a throat mirror. Between the true vocal cords is a narrow triangular interval called the glottis. It is by means of the vibrations of these cords that sound is produced. The false vocal cords cannot produce sound, though they can modify it indirectly. Quality of voice, as treble, base, etc., depends upon the size of the larynx and the length and elasticity of the vocal cords. Modulation is produced by changing the form of the cavity of the mouth and nose. In whispering the lips take the place of the vocal cords and produce sound by the vibration of their muscular walls.
Instead of tracheotomy laryngotomy is sometimes done in the depression between the thyroid and the cricoid, which may be felt on the living. Foreign bodies sometimes get into the larynx and have to be removed, or the mucous membrane may become inflamed, causing laryngitis. Syphilis attacks the larynx, and tuberculosis and cancer of the larynx occur, these last two being generally fatal. Edema of the glottis may also occur.
