Placoid
a term used to designate a variety of scales covering the bodies of the elasmobranchiate fishes (sharks, skates, rays, etc.), the Placoidei of Agassiz. These structures consist of detached bony grains, tubercles, or plates, of which the latter are not uncommonly un armed with spines.
PLAGUE, a peculiarly malignant fever of the continued and contagious type, now believed to be almost identical with the worst kinds of typhus fever. It is produced by the absorption of a poison generated by decaying animal matter combined with heat, moisture, and bad ventilation. At first there is great restlessness, followed ultimately by corresponding exhaustion, and death supervenes in two or three days. Grand Cairo is the chief known focus of the plague, the spread of which, in different directions, is at least attempted to be checked by quarantine. The plague seems to have been the black death of the 14th century. It was known by the name of plague when, in 1665, it slew in London 68,596 people, about onethird of the population. In the summer of 1896 a very malignant form of disease, known as the "bubonic" plague, made its appearance in Bombay, India, and spread with great rapidity. The number of cases and deaths finally became so large that more than 450,000 people-one-half of the population, fled from the city. The bubonic plague receives its name from the fact that it attacks the lymphatic glands in the neck, armpits, groin, and other parts of the body. In general, the disease is spread in the same manner as cholera, except that the cholera germ must enter the intestinal tract, while the germ of the plague may attack any part of the mucous membrane, or be attended by even the minutest abrasion of the skin. But while this germ is so virile and so easily taken into the system, it is one of the most easily killed by disinfection. One per cent. of quicklime will destroy it.
The Ten Plagues of Egypt were 10 inflictions divinely sent upon the Egyptians to compel them to emancipate the Israelites from bondage and allow them to quit the land. (Exod. vii: 14, xii: 30. For the use of the word plague see ix: 14, xi: 1.)