766 M N M N and pairs of extremities. Two distinct heads (with more or less of neck) may surmount a single trunk, broad at the shoulders but with only one pair of arms. The fusion, again, may be from the middle of the thorax downwards, giving two heads and two pairs of shoulders and arms, but only one trunk and one pair of legs. In another variety, the body may be double down to the waist, but the pelvis and lower limbs single. The degree of union in the region of the head, abdomen, or pelvis may be so slight as to permit of two distinct organs or sets of organs in the respective cavities, or so great as to have the viscera in common ; and there is hardly ever an intermediate condition between those extremes. Thus, in the Janus head there may be two brains, or only one brain. The Siamese twins are an instance of union at the umbilical region, with the viscera distinct in every respect except a slight vascular anastomosis and a common process of peritoneum ; but it is more usual for union in that region to be more extensive, and to entail a single set of abdominal and thoracic viscera. The pelvis is one of the commonest regions for double monsters to be joined at, and, as in the head and abdomen, the junction may be slight or total. The Hungarian sisters Helena and Judith (1701-1723) were joined at the sacrum, but had the pelvic cavity and pelvic organs separate ; the same condition obtained in the South Carolina negresses Millie and Christina, known as the "two-headed nightin gale," and in the other recent case of the Bohemian sisters Rosalie and Josepha. More usually the union in the pelvic region is complete, and produces the most fantastic shapes of two trunks (each with head and arms) joining below at various angles, and with three or four lower limbs extending from the region of fusion, sometimes in a lateral direction, sometimes downwards. A very curious kind of double monster is produced by two otherwise distinct foetuses joining at the crown of the head and keeping the axis of their bodies in a line. It is only in rare instances that double monsters survive their birth, and the preserved specimens of them are mostly of fcetal size. Unequal Double Monsters, Foetus in Fcetu. There are some well-authenticated instances of this most curious of all anomalies. The most celebrated of these parasite- bearing monsters was a Genoese, Lazarus Johannes Baptista Colloredo, born in 1716, who was figured as a child by Licetus, and again by Bartholinus at the age of twenty- eight as a young man of average stature. The parasite adhered to the lower end of his breast-bone, and was a tolerably well-formed child, wanting only one leg ; it breathed, slept at intervals, and moved its body, but it had no separate nutritive functions. The parasite is more apt to be a miniature acardiac and acephalous fragment, as in the case of the one borne in front of the abdomen of a Chinaman figured by I. Geoffroy St-Hilaire. Some times the parasite is contained in a pouch under the skin of the abdominal wall, and in another class (of which there is a specimen in the Hunterian Museum) it has actually been included, by the closure of the ventral laminae, within the abdominal cavity of the foetus, a true fuetus infcetu. Shapeless parasitic fragments containing masses of bone, cartilage, and other tissue are found also in the space behind the breast-bone (mediastinal teratoma), or growing from the base of the skull and protruding through the mouth (" epignathous teratoma," appearing to be seated on the jaw), and, most frequently of all, attached to the sacrum. These last pass by a most interesting transition into common forms of congenital sacral tumours (which may be of enormous size), consisting mainly of one kind of tissue having its physiological type in the curious gland- like body (coccygeal gland) in which the middle sacral artery comes to an end. The congenital sacral tumours have a tendency to become cystic, and they are probably related to the more perfect congenital cysts of the neck region, where there is another minute gland-like body of the same nature as the coccygeal at the point of bifurcation of the common carotid artery. Other tumours of the body, especially certain of the sarcomatous class, may be regarded from the point of view of monstra per excessum ; but such cases suggest not so much a question of aberrant development within the blastoderm as of the indwelling spontaneity of a single post-embryonic tissue; and they fall to be con sidered more properly, along with tumours in general, in the article PATHOLOGY (q.v.). The scientific appreciation of monsters hardly began before the 18th century ; even so great a rationalist in surgical practice as Ambroise Pare (1517-1590), although he was attracted as a scholar in later life to the subject, did not advance in it materially beyond the fantastic and credulous standpoint of the time, which is exem plified in the elaborate treatise of Lycosthenes, Prodigiorum acosten- torum chronicon, Basel, 1557. Throughout the 17th century fabulous monsters continued to be described along with actual specimens ; the embryological studies of Harvey (1651) were doubtless calculated to help in the growth of rational opinion about monsters, though Harvey himself mentions them only casually. The first systematic discussion of them from a strictly objective or anatomical point of view occurs in various writings of Haller from 1735 to 1753, and the subject continued after that to engage a large amount of precise and philosophical thought on the part of Caspar Friedrich Wolff (1735-1794), who first stated the relation of monstrosities to em bryonic deviations in words that even now hardly require to be altered, and of Blumenbach, Summering, Autenrieth, Tiedemann, and others. The engrossing interest of the subject in the early part of the 19th century is shown by the fact that J. F. Meckel s Handbuch dcr pathologischcn Anatomic (1817) was largely occupied with congenital malformations. Geoffroy St-Hilaire, the father, gave them a prominent place in his Philosophic Anatomiquc (Paris, 1822), and his son Isidore made them the subject of a special and very elaborate treatise in 3 vols. (Paris, 1832-37), illustrated by a small and inadequate atlas of plates. Monstrosities were at this period a prominent part of all text-books of morbid anatomy. From 1840 to 1850 may be regarded as the period in which human tera tology reached its highest point ; in 1840-42 the special treatise of Vrolik was published (2 vols., Amsterdam), containing an introduc tion on the normal development, and his sumptuous and incompar able atlas to the same followed in 1849; in 1841 Otto published at Warsaw a description of 600 monsters with 30 folio plates ; and in 1842 the embryologist Bischoff contributed to Wagner s Handicort- crbuch dcr Physiologic, vol. i., an article on teratology as elucidated by the best information on mammalian development. An article by Allen Thomson in the London and Edinburgh Monthly Journal of Medical Science,, July 1844, followed by a critical survey in the next number, is of the first importance for the theory of double monsters, and it is one of the few notable English contributions to animal teratology apart from museum catalogues, the general article in Todd s Cyclopedia of Anatomy and Physiology having been written by Vrolik, while the special subject of Hermaphroditism is treated of in a long and learned article by J. Y. Simpson (reprinted in his collected works). One of the latest important works on monsters is that by Forster (Jena, 1861), Die Missbildungen dcs Menschcn systematisch dargestellt, with an atlas of 26 4to plates containing 524 figures (on a small scale), of which 162 were drawn from original specimens, mostly in the Wiirzburg Museum ; this work has a very great variety of illustrations from all sources, and most copious bibliographical references. The newest treatise is Ahlfeld s Miss bildungen dcs Menschcn (Leipsic, 1880-82), with an extensive atlas of folio plates, as comprehensive as Forster s and on a larger scale. Monsters have of late been assigned a comparatively subordinate position in pathological teaching, owing, doubtless, to the more im mediate interest of microscopic and experimental pathology. Among recent pathological text-books that of Perls (Stuttgart, 1877-79) may be named as containing an adequate treatment of the subject. The two most considerable contributors to teratology recently have been Panum (Berlin, 1860), and Dareste (Paris, 1877), both of whom have occupied themselves mainly with producing monstrosities arti ficially in the bird s egg by varying the temperature in the hatching oven. See also L. Gerlach, Die EntuHiungswcise dcr Dopjiclmisslil- dungen bei den Mhercn IVirbelthicrcn, Stuttgart, 1883. (C. C.) MONSTRELET, ENGUERKAND DE (ob. 1453) (who, rather owing to accident than to merit, held, until within the present century, the same position as chronicler of French affairs during the early part of the 15th century as Froissart deservedly holds with regard to the last half of the 14th), was born at an uncertain date, apparently
not later than 1400, and died in July 1453. He was of