Luray Cavern
a cave, not large, but remarkable for the vast number and extraordinary shapes of its stalactites, close to Luray village, Va., 90 miles N.
W. of Richmond. Many of these wonderful columns exceed 50 feet in length; numbers of them are hollow, giving out bell-like notes when struck; and the colors range from waxy white to yellow, brown, or rosy red. The cavern, which is lit with electric light, attracts thousands of visitors every year. have a lung which is a simple cavity in southern constellations. It is situated the back communicating directly with between Centaurus and Ara, just under the air, and covered with minute bloodvessels; in bivalve mollusks again, as in the oyster, it is the internal surface of the mantle or skin-lining which is the special organ, with the same essential structure as gills. In the Articulata, as tapeworm, marine worms, Crustacea, as the crab tribe, we find a somewhat similar arrangement to that of the Mollusca, but in insects, insects, and other proper air-breathing Articulata, we have a reg ular series of air-sacs along each side of the body, opening by pores, called spiracles or stigmata, so in the spider-tribe, but in a more concentrated form, and more resembling the lung of the Vertebrata. The gills of fishes come next in the scale, accompanied in many cases with an air bladder, especially in those approaching the Reptilia in their organization, and in some of these it is a double sac, the analogue of the double lung. The lungs of the reptiles are, for the most part, capacious sacs occupying a good deal of the trunk cavity, ty, but not filled, like those of the Mammalia, by an act of inspiration, but chiefly by the process of swallowing. In birds we have the connecting link between the types of structure in the two classes.
Pathology. There are various diseases of the lungs; two of the most important are tubercular phthisis and pneumonia.