In the second class are included such cases as (1) the various forms of cyctopia, cm coalescence of the eyes; these malformations are not very rare in the human subject, And arc of frequent occurrence in pigs and other animals; although usually horn alive, these monsters are not viable; <2) coalescence of time lowerextrendues either into a com mon. limb, which supports two feet, or into an undefined taillike mass; (3) minor amal gamations, which do not affect vitality, as more or less perfect coalescence of the fingers and toes.
The third class embraces such cases as (1) fissures of the cranium, which arc generally due to hydrocephalus in the fetus; (2) harelip and cleft palet; (3) fissures on the neck, whose origin is due to the respiratory clefts—which, during the formation of the embryo, appear in the cervical region, not uniting at an early stage, as in the normal condition, but remaining more or less open; (4) fissures of the vertebral arches of the spinal column, occasioning the affection known as spina bifida; (5) fissures of the thorax, in which case the lungs or heart are more or less exposed; (6) fissures of the abdomen.
The malformations of the fourth class include congenital closure of the anus, the mouth, the nostrils, etc.
The malformations of the fifth class may be arranged in two divisions, according as certain parts are too large, or there arc supernumerary organs.
The sixth class is very extensive, and embraces many varieties. One or more parts may be disproportionately large—as, for example, the head iu cases of congenital hydro cephalus; or there may be one or several supernumerary organs—a sub-class which pre sents a very great range, from the simplest cases, in which a single joint of a finger is supernumerary, to those of a highly complicated nature, when two or even three bodies are united by some one point. There may be a single head and trunk and supernumer ary parts—as, for example, supernumerary teeth, vertebra (giving rise to the formation of a tai; in the human subject), ribs, =mime, fingers, toes, etc.; or there may be mal formations with more than one head and trunk—double, or even triplet monsters This sub-class is divisible into two groups, according as the united individuals are equally developed, or as only one is developed; the second being more or less atrophied, and forming a parasitic appendage to the first. As examples of the first group, we mention
(I) duplication of the bead and upper 'yid of the vertebral column; (2) duplication of the head, neck, and upper extremities, while the chestand abdomen are single, or fused into one another (in this group, we must place the twin-monster Rita Christina, who was born in Sardinia in Mar., 1829, and was brought alive to Paris, where she died in the November of that year); (3) almost complete duplication, with separation of the two bodies, except at a single spot, as in the case of the Siamese twins; (4) triplet monsters. such as the child with three heads born in 1s32 in Catania (see Geoffrey St. Hilaire, ilistoire des Anomalies de l'Oryanisation, vol. iii. p. 327). To the second group belong such cases as the following: (I) a perfect individual may bear on its head another head, with traces of the rest of the body; (2) on a weil-developed body, a second, smaller and defective one, may be situated, which, after birth, does not increase in size; (3) in a more or less perfectly developed individual, there may be concealed, commonly in the abdomen, parts of a second individual—a condition which has received the name of fretas in fatu, and which is most probably caused by the inclusion of one germ by another.
To the sixth class belong (1) those cases in which there is a reversing of the position of the internal organs—when the heart and spleen lie upon the right, and the liver and ctecum on the left side; (2) anomalies in the course and distribution of individual vessels.
The malformations constituting the sevenn class have been sufficiently noticed in the article IIERMAPHICODITISM.
The term teratology (from the Greek words gras, a prodigy, and Milos, a discourse) is now frequently applied to the history and science of monstrosities. For further infor mation on this subject, the reader is referred to Geoffrey St. Hilaire, Histoire des Anom alies de l'Organisation (3 vols. 1832-36); Otto, Monstrorum Sexcentoruin, Descriptio Analomica, (1841); and to the article "Teratology," by Vrolik, in The Cyclopedia of Anatomy and Physiology.