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Rh the walls of the buildings of ancient towns, like Pompeii, where, as was to be expected, most of them have been preserved, those from other ancient cities buried by the eruptions of Vesuvius and from Rome being very small in number. All the various classes of these inscriptions—public and private advertisements, citations for the municipal elections, and private scribblings of the most diverse (and sometimes most indecent) character, one partly collected by Chr. Wordsworth (Inscriptiones Pompeianae, &c., London, 1837, 1846)—are now arranged by Zangemeister in the Corpus, vol. iv. with supplement (some specimens in Wil. 1951 sq.), whence their peculiar palaeographic and epigraphic rules may be learned. And, lastly, as related to some of these advertisements, though widely differing from them in age and character, may be mentioned the so-called diptycha consularia, monuments, in the first instance, of the still very respectable skill in this branch of sculpture to be found at this late period. They are carved-ivory tablets, in the form of pugillaria, and seem to have been invitations to the solemnities connected with the accession of high magistrates, especially to the spectacles of the circus and amphitheatre; for they contain, along with representations of such spectacles, the names, and often the portraits, of high functionaries, mostly of the 5th and 6th centuries. Since Gori’s well-known work on this class of monuments (Thesaurus veterum diptychorum, &c., 3 vols., Florence, 1759) no comprehensive collection of them has been published, but a full list is given by H. de Villefosse in the Gazette Archéologique of 1884; as specimens see C.I.L. ii. 2699, and v. 8120, 1–9.

—As a “Textbook” of Roman epigraphy R. Cagnat, Cours d’épigraphie latine (3rd ed., Paris, 1898, with supplement, 1904) can be heartily recommended. But students must be warned against Zell’s Handbuch der römischen Epigraphik (2 vols., Heidelberg, 1850–1852), an unsatisfactory work which is open to serious criticism. J. C. Egbert’s Introduction to the Study of Latin Inscriptions (1896) is designed for American and English students. For Christian inscriptions Le Blant’s Manuel d’épigraphie chrétienne d’après les marbres de la Gaule (Paris, 1869) may still be consulted with advantage.

 INSECT, the anglicized form of the Late Lat. insectum, used by Pliny in his Natural History as the equivalent of the Gr. . Aristotle had included in one class “Entoma” the six-legged arthropods which form the modern zoological class of the Hexapoda or Insecta, besides the Arachnida, the centipedes and the millipedes. The word was introduced to English readers in a translation (1601) of Pliny’s Natural History by Philemon Holland, who defined “insects” as “little vermine or smal creatures which have (as it were) a cut or division betwene their heads and bodies, as pismires, flies, grashoppers, under which are comprehended earthworms, caterpilers, &c.” Few zoological terms have been more loosely used both by scientific and popular writers. The definition just quoted might include all animals belonging to the groups of the Arthropoda and Annelida, and U. Aldrovandi in De animalibus insectis (1602) almost contemporaneously distinguished between “terrestrial insects,” including woodlice, earthworms and slugs, and “aquatic insects,” comprising annelids and starfishes. Perhaps the widest meaning ever attached to the word was that of R.A.F. de Réaumur, who “would willingly refer to the class of insects all animals whose form would not allow them to be placed in the class of ordinary quadrupeds, in that of birds, or in that of fishes. The size of an animal should not suffice to exclude it from the number of insects. . . . A crocodile would be a terrible insect; I should have no difficulty, however, in giving it that name. All reptiles belong to the class of insects, for the same reasons that earthworms belong to it.”

The class Insecta of Linnaeus (1758) was co-extensive with the Arthropoda of modern zoologists. The general practice for many years past among naturalists has been to restrict the terms “Insecta” and “insect” to the class of Arthropods with three pairs of legs in the adult condition: bees, flies, moths, bugs, grasshoppers, springtails are “insects,” but not spiders, centipedes nor crabs, far less earthworms, and still less slugs, starfishes or coral polyps.

For a general account of the structure, development and relationships of insects, see and, while details of the form, habits and classification of insects will be found in articles on the various orders or groups of orders, and in special articles on the more familiar divisions (,, , , &c.). The history of the study of insects is sketched under.

 INSECTIVORA, an order of non-volant placental mammals of small size, with a dentition adapted to an insect-diet. In nearly all cases these creatures are nocturnal, and the majority are terrestrial, many burrowing in the ground, although a few are arboreal and others aquatic. They have plantigrade or partially plantigrade feet, that is to say, they apply the whole or the greater portion of the soles to the ground when walking; and there are generally five toes, each terminating in a claw, and the first never being opposable to the others in either the fore or hind limb. A full series of differentiated teeth, including temporary or deciduous milk-molars, is developed, and the cheek-teeth have distinct roots and are crowned with sharp cusps, which in some instances are three in number and arranged in a triangle. Very frequently the number of the teeth is the typical forty-four, arranged as i., c. , p. , m. , but occasionally there is a fourth pair of molars, while the incisors may be reduced to two pairs above and one below, and the canine is frequently like an incisor or a premolar. The skull is of a primitive type, often with vacuities on the palate, as in marsupials, with a small brain-chamber, and the tympanic bone generally ring-like instead of forming a bladder-shaped bulla; except in the African Potamogale, clavicles, or collar-bones, are always present; the humerus generally has a perforation on the inner side of its lower extremity; and a centrale bone is usually present in the carpus. In the brain the smooth hemispheres are so short as to leave the cerebellum and sometimes even the corpora quadrigemina exposed. The uterus is two-horned; the placenta, so far as known, is deciduate and discoidal; the testes are abdominal or inguinal; and the teats usually numerous. The body in several instances is covered with sharp spines in place of hair.

The great majority of the Insectivora are nocturnal in their habits, and their whole structure indicates an extremely low grade of organisation, fully as low as that of marsupials. It is noteworthy that the dentition in several of the groups approximates to that of the extinct mammals of the Jurassic epoch (see ), and exhibits more or less distinctly the primitive tritubercular type. Although the past history of the group is very imperfectly known, it seems probable that the Insectivora are nearly related to the original primitive mammalian stock. Indeed, it has been stated that were it not for the apparently advanced type of placenta, they might easily be regarded as the little modified descendants of the ancestors of most other mammals. Probably they are in some way related to the creodont carnivores (see ), but if, as has been suggested, the latter are akin to the primitive ungulates, the connexion would seem to be less close than has been sometimes supposed.

Representatives of this order are found throughout the temperate and tropical parts of both hemispheres, with the exception of South America (where only a few shrews have effected an entrance from the north) and Australia, and exhibit much variety both in organization and in habit. The greater number are cursorial, but some (Talpa, Chrysochloris, Oryzorictes) are burrowing, others (Limnogale, Potamogale, Nectogale, Myogale) aquatic, and some (Tupaiidae) arboreal. To the great majority the term insectivorous is applicable, although Potamogale is said to feed on fish, and the moles live chiefly on worms. Notwithstanding the nature of their food, much variety prevails in the form and number of the teeth, and while in many cases the division into incisors, canines, premolars and molars may be readily traced, in others, forming the great majority of the species, such as the shrews, this is difficult.

In most cases the brain-cavity is of small relative capacity, and in no instance is the brain-case elevated to any considerable extent above the face-line. The facial part of the skull is generally much produced, and the premaxillary and nasal bones well developed; but the cheek, or zygomatic arch, is usually slender or deficient, the latter being the case in most of the species, and post-orbital processes of the frontals are found only in the Tupaiidae and Macroscelididae. The number of dorsal vertebrae varies from 13 in Tupaia to 19 in Centetes, of lumbar from 3 in Chrysochloris to 6 in Talpa and Sorex, and of caudal from