Page:Collier's New Encyclopedia v. 07.djvu/241

PERISSODACTYALA 187 PERITONITIS has been known for centuries, its develop- ment into an efficient instrument has been comparatively recent. PERISSODACTYLA, in Owen's classi- fication, a section of Ungulata. The hind feet are odd toed in all, and the fore feet in all but the Tapiridse and the Bron- totheridx. Dorsolumbar vertebrae never less than 23. Femur with a third tro- chanter. Horns, if present, not paired, except in the extinct Diceratherium. Usually there is but one horn; if two are present, they are in the median line of the head, one behind the other, not sup- ported by bony horn cores. The section is now usually divided into seven fami- lies, four extinct. fluid, like the liquid white of an egg, al- lowing the two sides, when rubbed to- gether, to glide over each other, as if oiled, without check or the slightest fric- tion. The outside of this is rough and granulated. The peculiarity of the in- ner and outer sides of this immense bag lies in this, that the surface of the fir.st is close, smooth, moist, and shiny, and, however firmly pressed, can never grow together, or keep long in contact; while that of the other is rough, dry, and ad- heres firmly to all with which it comes in contact. This external side, then, ad- heres to the muscles of the abdomen, and to every portion of the intestines, but in such a manner that between every con- volution, or twist of the bowels, a fold DIAGRAM OF SUBMARINE SHOWING POSITION OP PERISCOPE PERISTYLE, an open court within a house, having a colonnade around it, by which the principal apartments were reached; the exact reverse of the perip- teros, though the same in character, the one being inside, the other outside a building. PERITONEUM, one of the most dif- ficult parts in the human anatomy for a teacher to explain intelligibly to his pupils, and the last that the student is able thoroughly to understand. From birth till death, the bowels are constantly moving and gliding over each other, in a worm-like perpetual motion, called peris- taltic motion. It will be self-evident that this day and night friction of such deli- cate textures as those composing the in- teguments would, in the 70 years of man's life, wear out, or at least in time most seriously injure them. To prevent this friction, nature has provided the peritoneum, an immense shut-bag. The inside — that portion out of sight — pre- sents, when cut open, a smooth, glairy surface, studded with innumerable ves- sels, always pouring out a thin, smooth of peritoneum accompanies it, so that between the bowel above or below there is always the two glairy sides rubbing against each other, and allowing the in- testines to glide about without let or hindrance, the bowels being always on the outside of the bag, but always glid- ing over the two inner sides. The peri- toneum is a serous membrane, and, in the same way as it covers the bowels, lines and invests every organ in the abdominal and pelvic cavities. PERITONITIS, inflammation of the peritoneum; it is exceedingly painful and dangerous, from its extent and connec- tion with important organs. Peritonitis may exist either as an acute or chronic disease. In the former there is usually great pain and tenderness of the abdo- men, accompanied with fever, and a fre- quent, small, and hard pulse. Some- times, at first, the pain is confined to one spot, but it generally soon extends over the whole of the abdomen. It is very severe, and much increased by any mo- tion, even coughing, sneezing, or drawing a long breath. Its causes are various, as