BATH, a large chamber in which patients sit under increased atmospheric pressure for a greater or shorter period. An attempt at this kind of treat ment was made as early as 1662, by Dr. Henshaw, but failed owinr. to the imperfection of the apparatus. The apparatus, as now used, is the invention of M. Emile Laburio, of Paris, who in 1832 conducted a series of careful experiments upon the effects of the atmo spheric air at different densities upon the human frame. The bath is a chamber 9 ft. in diameter and 12:ft. high; it is constrUcted.Of ikon platCS riveted together like those of a boiler of a steam-engine, so as to be perfectly air-tight; it is provided with two close fitting iron doors, which can be opened without affecting the pressure of the air within the chamber; the interior is lined with wood, and furnished with seats; a steam-engine of seven-horse power works a pair of large air-pumps, communicating indirectly with the chamber by a pipe that opens by means of numerous small holes in the bottom of the floor, so that the air enters imperceptibly into the chamber; from the roof, a pipe similarly arranged allows the breathed air to escape. Each of these tubes is supplied with a screw valve, by means of which the inlet and exit of the air are regulated. Two barometers hang on the walls of the chamber, to show the rate of increase and decrease of pressure. The pressure is raised at the rate of 1 lb. every 4 minutes, and the lower
ing takes place at the same rate.- The pressure is usually raised to 7 lbs. per sq. inch, in addition to the usual pressure of the atmosphere. The period generally prescribed for remaining in the bath is 2 hours.
The diseases in which the compressed-air bath is said to be most efficient are pbthisis. asthma, and chronic bronchitis. The effects are attributed to two causes: 1. A greater quantity of air, and consequently of oxygen, is inhaled in a given time; and not only so, but the amount absorbed is increased in proportion to the pressure of the gas against the walls of the air-vesicles. The increased absorption of oxygen and excretion of carbonic acid enables the lungs to perform their functions more efficiently, and thereby removes any congestion existing in these organs. 2. The increased mechanical pressure of the air upon the mucous membranes, when in a state of chronic congestion, has a bracing effect, and imparts renewed vigor to the entire structure of the lungs and bronchi. At Ben-Iihydding, the compressed-air bath is used in cases of the kind above named, along with the usual appliances of the water-cure.