Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/239

Rh   DIGBY, (1603–1665), an eminent English physical philosopher, born at Gothurst, Bucking hamshire, on the llth July 1603, was descended from an ancient and illustrious family. His great-grandfather had distinguished himself at B.osworth on the side of Henry VII. ; and his father, Sir Everard Digoy, was one of the leading Eoman Catholic gentry at the time of the Gun powder Plot. Having risen in arms on that occasion, Sir Everard was executed at Lundoii, January 27, 1606. The young philosopher was educated by his guardians in the Protestant faith. Having finished his education at Oxford, he went abroad in 1621, and travelled in France, Spain, and Italy. On his return he was knighted, and received from Charles I. the appointments of gentle man of the bed-chamber, commissioner of the navy, and governor of Trinity House. At the head of a small squadron, which he equipped at his own expense, he sailed in 1628 against the Algerines, and afterwards defeated the Venetians near the port of Scanderoon. During a brief stay in Paris he joined the Church of Rome. Having returned to England in 1638, he espoused the cause of the king, and was imprisoned in Winchester House, by order of the Parliament. He was, however, liberated at the request of the French queen- dowager in 1643, and retired to France, where he was taken into the confidence of the court, and. enjoyed the friendship of Descartes and other learned men. Here he wrote his Treatise on the Nature of Bodies, his Treatise on the Soul, PeripateticJc Institutions, and other works. He visited England, after the defeat of the Royalist party, but the Parliament refused to allow him to remain. Banished from England upon pain of death if he returned, he resumed his residence in France, where he was treated with the highest respect, and was intrusted with an embassy to several of the courts of Italy. He returned again to his native country during the Protectorate of Cromwell, and seemed to be more zealous for the advance ment of the interests of the Commonwealth than befitted a staunch royalist. He used his influence to reconcile the Catholics to the Protectorate on condition of their being secured the free exercise of their religion. With Crom well he was on terms of intimate friendship, the bond of sympathy being probably not so much politics as a common interest in the new-born science of physics. At the Restoration he returned finally to London, where he died in 1665. He married Venetia Anastasia, the daughter of Sir Edward Stanley of Shropshire, &quot; a lady of an extraordinary beauty and of as extraordinary a fame.&quot; His whimsical experiments to preserve her beauty by the in vention of new cosmetics procured him as much notoriety as his sympathetic powder for the cure of wounds at a distance. He was appointed one of the council of the Royal Society at the time of its first establishment, and he took a very active part in its management. Besides the works already mentioned, Digby wrote A Conference about a Choice of Religion, Paris, 1638; Letters on the same sub ject, Lond. 1651 ; Observations on Religio Medici, Lond. 1643; A Treatise of Adhering to God, Lond. 1654; On the Cure of Wounds ~by the Powder of Sympathy, Lond. 1658 ; and a Discourse on Vegetation.  DIGESTIVE ORGANS. The organs of digestion, or alimentary apparatus, are for the purpose of receiving the food or aliment ; of converting that portion of the food which is digestible into chyle, so that it may be absorbed and applied to the nourishment of the body ; and of trans mitting that which is indigestible onwards to be excreted. In the Protozoa there is no special digestive apparatus, but the particles of food are introduced into the general substance of the body, where they undergo digestion and assimilation. But in animals generally there is a definite digestive cavity or stomach, which communicates with the surface by a distinct opening or mouth, through which the food is introduced into the stomach. As a rule a second opening, or anus, is also in communication with the stomach, at which the indigestible parts of the food are excreted. As animals increase in structural complexity the digestive apparatus has additional parts superadded to it. In man and all the more highly organized animals it con sists of an elongated tube, the Alimentary Canal, divided into various compartments, into which numerous Glands pour their secretions to be used in the digestive process. In most vertebrates, the great class of birds being excepted, the compartment of the canal called the mouth, or oral cavity, contains a hard masticatory apparatus, the Teeth, which play an important part in breaking down the food. As the digestive organs in the human body are so con structed as to illustrate one of the most perfect forms of an alimentary apparatus, they will form the special subject of description in this article.

The is a tube about 28 feet long, which traverses almost the entire length of the axial part of the body. In man arid all other vertebrates, it lies in relation to the ventral surface of the bodies of the vertebrae. It commences on the face at the orifice of the mouth, and terminates on the surface of the lower part of the trunk at the orifice of the anus. It is divided into a series of segments, or compartments, which communicate with each other, from above downwards, in the longitudinal axis of the canal. These compartments are named mouth, pharynx, oesophagus, stomach, small intestine (subdivided into duodenum, jejunum, and ileum), and large intestine (sub divided into caecum, colon, and rectum). The canal is lined by a mucous membrane, called the alimentary mucous membrane, which is continuous with the nasal mucous membrane, with the respiratory mucous membrane, and at the anal and oral orifices with the integument, Outside this mucous membrane is the submucous coat, and external to it is the muscular wall of the canal. By the contraction of the muscular wall the food is propelled along the canal from above downwards. Opening on the surface of the mucous membrane are the orifices of the ducts of numerous glands, the secretions of which, mingling with the food, act chemically on it, so as to render it soluble and capable of being absorbed.

The Mouth, Oral Cavity, or Buccal Cavity, is the dilated commencement of the alimentary canal, in which the food is masticated and mingled with the secretion of the salivary and mucous glands. It is situated in the face, and extends from the lips in front to the pharynx behind. It is bounded above by the hard and soft palate, with the uvula ; below by the lower jaw, the mucous membrane of the floor of the mouth, and the tongue ; on each side by the cheek ; and in front by the lips, between which is the aperture of communication with the surface of the face. Behind it freely communicates with the pharynx through the isthmus faucium. The muscles situated in the lips, cheeks, floor of the mouth, tongue, and soft palate enter into the formation of the walls of the mouth. The mouth is lined by a red-coloured mucous membrane, which becomes continuous posteriorly with that of the pharynx, and at the margins of the lips with the skin of the face. The mucous membrane covering the alveolar portions of the jaws, and surrounding the necks of the teeth, is called the gum. From the outer surface of each jaw it is reflected to the inner surface of the cheeks and lips. From the inner surface of the lower jaw the mucous membrane is reflected to the floor of the mouth, and a broad band, 