Page:EB1911 - Volume 18.djvu/771

 department of morphological science treating of deviations from the normal development of the embryo. The term “embryo” is conventionally limited, in human anatomy, to the ovum in the first three months of its intra-uterine existence, while it is still developing or acquiring the rudiments of its form, the term “foetus” being applied to it in the subsequent months during which the organism grows on the lines of development already laid down. It is mostly in the first or embryonic period that those deviations from the normal occur which present themselves as monstrosities at the time of birth; these early traces of deviation within the embryo may be slight, but they “grow with its growth and strengthen with its strength,” until they amount to irreparable defects or accretions, often incompatible with extra-uterine life. The name of “teratology,” introduced by Étienne Geoffroy St Hilaire (1822), is derived from , the equivalent of monstrum; teratology is a term new enough to have none but scientific associations, while the Latin word has a long record of superstitions identified with it. The myths of siren, satyr, Janus, cyclops and the like, with the corresponding figures in Northern mythology, find a remote anatomical basis in monstrosities which have, for the most part, no life except in the foetal state. The mythology of giants and dwarfs is, of course; better founded. The term monster was originally used in the same sense as portent. Luther speaks of the birth of a monstrous calf, evidently the subject of contemporary talk, as pointing to some great impending change, and he expresses the hope that the catastrophe might be the Last Day itself. The rise of more scientific views will be sketched in the course of the article.

Although monstrosities, both in the human species and in other animals, tend to repeat certain definite types of erroneous development, they do not fall readily into classes. The most usual grouping (originally suggested by G. L. L. Buffon, 1800) is into monstra per excessum, monstra per defectum, and monstra per fabricam alienam. It seems useful, however, to place the more simple cases of excess and of defect side by side, and it is necessary, above all, to separate the double monsters from the single, the theory of the former being a distinct chapter in teratology.

1. Monstrosities in a Single Body.—The abnormality may extend to the body throughout, as in well-proportioned giants and dwarfs; or it may affect a certain region or member, as—to take the simplest case—when there is a finger or toe too many or too few. It is very common for one malformation to be correlated with several others, as in the extreme case of acardiac monsters, in which the non-development of the heart is associated with the non-development of the head, and with other radical defects.

Giants are conventionally limited to persons over 7 ft. in height. The normal proportions of the frame are adhered to more or less closely, except in the skull, which is relatively small; but accurate measurements, even in the best-proportioned cases, prove, when reduced to a scale, that other parts besides the skull—notably the thigh-bone and the foot—may be undersized though overgrown. In persons who are merely very tall the great stature depends often on the inordinate length of the lower limbs; but in persons over 7 ft. the lower limbs are not markedly disproportionate. In many cases the muscles and viscera are not sufficient for the overgrown frame, and the individuals are usually, but not always, of feeble intelligence and languid disposition, and short-lived. The brain-case especially is undersized—the Irish giant in the museum of Trinity College, Dublin, is the single exception to this rule—but the bones of the face, and especially the lower jaw, are on a large scale. Giants are never born of gigantic parents; in fact, sterility usually goes with this monstrosity. Their size is sometimes excessive at birth, but more often the indications of great stature do not appear till later, it may be as late as the ninth year; they attain their full height before the twenty-first year. They have been more frequently male than female.

Dwarfs are conventionally limited to persons under 4 ft. They are more likely than giants to have the modulus of the body perfect. Where, disproportion occurs in the true dwarf it takes, the form of a large-sized head, broad shoulders and capacious chest, and undersized lower limbs. Dwarfs with rickets are perhaps to be distinguished from true dwarfs; these are cases in which the spine is curved, and sometimes the bones of the limbs bent and the pelvis deformed. As in the case of giants, dwarfs are seldom the progeny of dwarfs, who are, in fact, usually sterile; the unnatural smallness may be obvious at birth, but is more likely to make itself manifest in the years of growth. Dwarfs are much more easily brought up than giants, and are stronger and longer-lived; they have usually also strong passions and acute intelligence. The legends of the dwarfs and giants are on the whole well based on fact. (See and .)

Redundancy and Defect in Single Parts.—The simplest case of this redundancy is a sixth digit, well formed, and provided with muscles (or tendons), nerves, and blood vessels like the others; it is usually a repetition of the little finger or toe, and it may be present on one or both hands, or on one or both feet, or in all four extremities, as in the giant of Gath. The want of one, two, or more digits on hand or foot, or on both, is another simple anomaly; and, like the redundancy, it is apt to repeat itself in the same family. J. F. Meckel saw a girl who had an extra digit on each extremity, while a sister wanted four of the fingers of one hand. Where the supernumerary digits are more than one on each extremity, the whole set are apt to be rudimentary or stunted; they look as if two or more of the embryonic buds had been subject to cleavage down the middle and to arrest of longitudinal growth. There are several authentic instances of a whole lower limb appearing at birth as two withered halves, as if from embryonic cleavage. Other redundancies of the skeleton are extra vertebrae (sometimes the coccygeal, giving the appearance of a rudimentary tail), or an extra rib. A double row of teeth is occasionally met with; the most interesting case of this anomaly is that in which the rudiments of a double row exist from the first, but the phenomenon is sometimes produced by the milk teeth persisting along with the second set. Among redundancies of the soft parts, by far the most frequent relate to the mammary glands and especially to the nipples. These organs are normally paired amongst mammals, and the glands of each pair are placed symmetrically on a curved line running from the axilla towards the pubes. When many pairs occur, the glands of each pair diverge less from the median line than those of the immediately anterior pair, the abdominal glands lying close together, those towards the axilla being farther apart. When only a single pair is normally present, the pair is abdominal, pectoral or axillary; and whether the normal be one pair or many pairs, additional glands are not infrequent, but occupy the expected position on the mammary lines, Accessory glands or nipples in human beings, if anterior to the normal pair, lie farther from the median ventral line, and vice versa. Among the sense-organs there is a remarkable instance recorded of doubling of the appendages of the left eye, but not of the eyeball itself; the left half of the frontal bone is double, making two eye-sockets on that side, and the extra orbit has an eyebrow and eyelid. The external ear (pinna) has also been found double on one side and its orifice has frequently been found doubled in man and lower animals, and the additional ears lie in a definite relation to the branchial clefts of the embryo. Doubling of any of the internal organs or parts of organs may occur and innumerable cases have been recorded.

 Monstrosities from Defective Closure in the Middle Line.—Under this head come some of the commonest congenital malformations, including slight deficiencies such as harelip, and serious defects such as a gap in the crown of the head with absence of the brain. The embryo is originally a circular flattened disk spread out on one pole of the yolk, and it is formed into a cylindrical body (with four appendages) by the free margins of the disk, or rather its ventral laminae, folding inwards to meet in the middle line and so close in the pelvic, abdominal, thoracic,