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LEFT HAZELTON 490 HEALTH INSURANCE a. warm friend of President Roosevelt, and also of President Harding, who ap- pointed him Postmaster-General in his cabinet, HAZELTON, a city in Luzerne co.. Pa., on the Pennsylvania, the Wilkes- Barre and Hazelton, and the Lehigh Valley railroads; 115 miles N. W. of Philadelphia. It is the center of the Le- high anthracite coal region, with 40 mines in the vicinity. Besides its coal mining and shipping interests, the city has railroad shops, iron works, and ex- tensive manufactures of flax, brooms, silk, macaroni, chewing gum, and coffins. It is the seat of the Miners' State hospital; has electric lights and street railways, public high school, Hazelton Seminary, daily and weekly newspapers, and 2 National banks. Pop. (1910) 25,452; (1920) 32,267. HAZLITT, WILLIAM, an English author and critic; born in 1778. Edu- cated for the clerical profession, Hazlitt, after a brief attempt at an art career, decided to enter literature, and in 1805 produced his "Principles of Human Ac- tion." This was the germ of a long and successful literary career, during which he gave to the world his "Lectures on the Literature of the Elizabethan Age"; "Table Talk"; "Lectures on the English Poets"; "The Spirit of the Age," and "Life of Napoleon Bonaparte." He died in 1830. HEAD, in anatomy, the skull, or crani- um. Part of the head consists of an os- seous ovoidal capsule for the protection of the brain. The face proper consists of the upper and lower jaws. The skull in old age becomes composite like the sacrum in the adult. The margins, or sutures, of the cranial bones, 22 in num- her excluding the hyoid bone, correspond to the articular processes in the trunk. In youth the flat cranial bones are con- nected by a double lamina of cartilage; notwithstanding the junction of the mar- gins, they grow by the increase of one cartilage and the ossification of the other. Like the arch in the movable vertebrae, we have the arch in the head; in the lower part there are bones phy- siologically connected with the head bones of the neck. There are three seg- ments in the head: (a) The posterior, ' beginning from the cervical vertebrae below the occipital segment, consisting of a single bone, in reality four bones; a part of it lies in the base of the cra- nium at the back of the face, but the greater part extends up the back of the cranium. It consists of a ring, lateral sides, and an arch, (b) The anterior, consisting of the frontal and ethmoid bones. The only vestige here of the ver- tebral foramen is the foramen caecum, (c) The central segment; in the middle line below, and cut in two halves by the moesial plane, is the sphenoid bone, but along with it are two bones, the tem- poral, attached to its outer portions or great wings, composing the basis of the arch completed by the two parietal bones. These segments are divided by the lamb» doidal sutures and coronal. The head is divided into a base and a vault, or cal- varium; the inner aspect is called the cerebral, the other the superficial, ex- ternal, etc., aspect. The bone on the outside of the cranium is not so dense aa it is on the inside, in accordance with a law of construction in all animal and vegetable bodies, a law of part, and a law of place. Some anatomists count four segments, the two temporal bones constituting the fourth. The vertebrata have a head homologous in its anatomy with that of man. That of the A^imdosa is homologous in functions, but not in parts. The cephalopodous and gasterop- odous mollusks have heads, the Conchif- era, sometimes called Acephala, want them. Most animals of lower organiza- tion than these are destitute of heads. HEALTH ASSOCIATION, AMERI- CAN PUBLIC, an association of public officials and other individuals interested in the promotion of sanitary science in its relation to municipal government. The organization had its origin in 1872, when, on April 18, an informal con- ference was held in New York City, at which were represented five States and five cities. A committee was appointed to draw up a constitution for a national institute of sanitary science. In the fol- lowing September the constitution was formally adopted and officers were elected. The association has since pub- lished a great deal of literature on public sanitation and has devoted much energy to education along these lines. Its official organ is "The American Jour- nal of Public Health." HEALTH INSURANCE, a form of insurance which insures its beneficiaries against need in time of illness and com- pensates for the loss of employment during periods of illness. It is one of those departments of the general field of insurance which was taken up reluc- tantly by private enterprise, on account of the difficulty of protecting the insur- ance companies against fraud. Health insurance may be divided now into three distinct classes; commercial, mutual, and social. Commercial health insurance has developed only to a limited extent, and that only within the past few years, being generally connected with the busi- ness of casualty companies. Mutual