Otocephalic are derivatives of the cyclocephalic, but the tendency to atrophy is more marked, since it extends to a greater number of organs. They are characterized in particular by modifications from the side of the aural apparatus, the ears approaching the median line or even united there. Ordinarily there exists as well atrophy more or less marked of the inferior region of the skull, and also absence of the maxillae, and greater part of the face. The arrest in development having included the ethmoid as well as the inferior portion of the face, the ears are drawn inwards and downwards. The two lateral hemispheres of the brain are fused, imperfectly developed, and surrounded by a large amount of cephalo-rachidian fluid. The eyes may be separated, or united in the same orbit, distinct or fused. In the more advanced degree of monster, the atrophy extends to the complete absence of the organs of vision.
Saint-Hilaire divides the otocephalic foetuses into five species: the two eyes are well separated, the two ears are united. The palate bone is bent so that the dental arches touch.
.401•Nia.
There exists but one auditory meatus. The name of this variety is due to the fact that it resembles the sphenoid bone.
Otocephalic (true).—The nose is atrophied, the eyes fused, the Ma3083 imperfect, the ears united or fused.
Edocephalic.—So called because the nasal appendage resembles a penis. In these foetuses there exists a nose similar to that found in certain cyclo cephalic fcctuses. Above it a single eye. Below it a transverse opening which looks like a mouth, but which represents the auditory meati united in the median line. These foetuses have no mouth, and only rudimentary maxilla. A single orbit contains the eye or the two eyes. In a very pronounced instance, Tiedmann noted above the eye a snout, and below it the skin hung down like a second snout.
Opoctphalic.—Where there exists a single or two eyes in one orbit, two ears near together or united, two atrophied maxillae, but neither mouth nor nasal appendage. The eye and its appendages form the greater part of the face, whence the name given to the species, which has frequently been found in animals, and only rarely in the human race.
Triocephalic.—Where there is absence of eyes. All the anomalies de scribed in the other varieties may be present. The entire head is only a little spheroidal swelling. This variety is very rare in man if it exists at all, but common enough in animals.
Simple Omphalosite Monsters.
These monsters lack many organs, and, therefore, they die as soon as the cord is cut. They live, in other words, by the umbilicus, whence their name. An interesting point in their history is that they result from a twin pregnancy, where one foetus is relatively well formed, while the other is a monstrosity, and has a heart very incomplete, even rudi mentary. The twins have a single placenta, and, as Meckel and Cazeaux have shown, there exists in this placenta anastomosis between the um - bilical arteries and veins of the fcetuses. In the omphalosite embryo the circulation is reversed. It is from the umbilical cord passing from the
placenta to the normal fcetus that the funis of the omphalosite is derived. The heart of the normal foetus sends its blood to the placenta by the um bilical arteries, but a portion of this blood penetrates into the umbilical arteries of the omphalosite. The blood returns from it by the umbilical vein, and passes through the cord of the normal foetus to the placenta. The circulation of the monster, hence, constitutes a species of diverticu him of the circulation of the normal foetus. The omphalosite, therefore, receives the blood which contains its nutritive elements, not by the um bilical vein, like the normal foetus, but by the umbilical artery.
The presence of a foetus with normal heart is hence essential to the existence of an omphalosite. According to Claudius, gemellarity not only allows the development of the omphalosite during intrauterine life, but it is the cause of the monstrosity. When two foetuses, of equal volume, develop simultaneously in the same uterus, each has its own life; but if one of them, well formed at the outset, is feebler than the other, the most vigorous heart will cause the blood pressure in the placenta to become too strong for the weaker. Little by little the heart of the latter will cease to be able to functionate, and the omphalosite is formed. This theory is purely hypothetical. We believe, with Dareste and Saint-Hilaire, that there is actually no proof that gemellarity is the cause of the monstrosity.
Paracephalic Fo3tusee.—" These monsters are peculiar in the shape of their bodies, which in almost every respect varies markedly from the nor mal. Their limbs are imperfect not only in shape, but in the number of fingers. A great part of the thoracic and abdominal viscera may be absent. The head is very imperfect." (Saint-Hilaire.) The character istic feature, indeed, about this monstrosity is the head, which is simply a mass at the upper part of the trunk. Both skull and the face are impli cated in the atrophy. Theoretically this monstrosity constitutes an im portant link uniting acephalic foetuses to those which we have just studied. The cervical vertebrae exist, although they may be atrophied so that the head can scarcely be differentiated from the trunk. The limbs are always very imperfect. The diaphragm is sometimes complete, but may be en tirely wanting, so that the thoracic and abdominal cavities constitute a single one. The lungs are not present, or are represented only by a few vesicles; the heart may be only rudimentary, the circulatory system is very imperfect. Of all the organs, the genitourinary are altered the least. The changes in the nervous centres are quite general. Saint-Ililaire says that these monsters have never been observed in•animals. In the human race, such monsters have always been expelled in case of a twin pregnancy, where there were two sets of membranes, but only a single placenta. The foetuses are always of the same sex, usually female.