vations on the midwifery of the case would be out of place on this page. F g. 64. M. Serres's work, and that of M. G. de St. Hilaire, exhibit a great variety of Teratological foetuses, to which I must merely allude, as the limits of this volume will admit of no extended observations upon them. I have mentioned them here, chiefly with the view to put the Student on his guard as to the midwifery of such cases; and still more in order that he may early learn that these monsters are merely results, not of excess, but of failure in development. The double-headed foetus, Fig. 63, has two stomachs, and probably two hearts, but only one intestinal canal, composed by the union of the two jejunums, or the two iliums, into a single jejunum or ilium, a colon and rectum. This child is a twin, which has not acquired a superfluous head, but which has lost, one a left, and the other a right arm; one the right,. and the other the left half of its thorax-one kidney-half the colon and rectum, half the bladder, testes and penis, and a right or a left leg. This double-headed foetus then has lost, not gained: it has been fused, or, to use a term in horticulture, grafted. The right child has sunk part of its body in that of the left child, which in like manner has sunk the right half of its body in the left half of its twin brother. In Rita-Christina, if both children happened to be asleep, and one should tickle Rita's foot, she would wake and smile: so, if Christina's foot were tickled, it would cause her to laugh, without at all affecting her sister, for the left leg was Christina's and not Rita's, and vice versâ. Happily, when twins are conceived, they inhabit each its own amnion, and in some instances, its own chorion-which insulates them. When the development of the amnion fails, and the two germinal membranes are suffered to come into contact within the womb, they may unite, or weld, or engraft together, under a certain law; but the back of one cannot unite to the abdomen of the other, nor the head of one child to the other's pelvis. In order to unite, only the edges of the still unclosed germinal membrane can weld-that is, the left edge of one with the right edge of the other, and mutatis mutandis. Hence the law of development is binding; that law ordains that the right edge of the membrane, when bent over to shut in the trunk, should unite with the left edge turned inwards in like manner. Hence, it may fuse with the left or the right edge of its foetal twin. e Fig. 65. a If If we might suppose the germinal area of the germinal membrane to be in shape a long oval, like Fig. 65, and a the cephalic pole, b the pelvic pole; c d the brachial, and eƒ the crural regions; we may conceive that no sublunary power could develop a pelvis at a, or a head at b; a leg at c d, or an arm at e f; for even in this microscopic mass the generic law is as imperative and coercive as the attraction of gravitation is for the whole universe. There is nothing generically in common or identical in a and b, or between c d and e f; c unites with d only, and e with f only; when the scaphoidal germinal membrane has become completely bent so as to bring into apposition the edges c e and d f to make the cavity of the belly and thorax, d could not unite with e nor c with f. If in the adjoined diagram, Fig. 66, the two ovals may represent the germinal areas of twins, not separated by amnia, then a and 7 may unite if brought into apposition, or b and m; c and g, and e and i, have no affinity. If d and g, which have affinity, should unite, the result would be a foetus with one head, two arms, and four legs; if ƒ and i be placed in contact in utero, their affinity would cost a left leg for the right hand membrane, and a right leg for that on the left. Thus we should have a Rita-Christina. It is a curious subject of reflection, that of the individuality or du a Fig. 66. i h ality of a creature with one head and two bodies, or with two heads and one body! Rita-Christina was dual, as was Dr. Pfeiffer's monster, Fig. 63; but as to the monster figured in Serres's Plate 12, it is to be doubted whether the personal identity was absolute for each of the children-as there was one common cerebellum. Doubtless it is not possible, in Teratology, to suppose that half of one child should sink into and be totally lost in half of another child, thus making out of two independent personal identities a single one. In nature, the union must take place from the liver upwards only, or from the liver downwards only; whence, it cannot happen that the whole right symmetrical half of the left twin should be sunk in the left symmetrical half of the right twin. We may therefore expect to meet with cephalodym or hepatodym or pelvidym, and not with such a union of two personal identities as would serve to personify the ancient fable of Salmacis and her lover. All such fusions imply loss, not gain of substance-monstrosity by default, and not monstrosity by excess. If a child is born with six fingers on either or each hand, or six toes on either or each foot, it presents a case of excess of development, or monstrosity by excess; and the samples of five-legged calves, &c., that are commonly met with, are, perhaps, cases of monstrosity by excess. There was a singular example of cephalodym here some four years ago: it was a healthy pig with one head, two fore legs, and two abdomens, with four hind legs. It was a remarkable fact that the genitalia of this creature were not under a common influence of its cerebro-spinal system. When the animal was in heat, it was either as to the genitalia of the right or those of the left trunk; but they were not observed to be in heat or rut at the same time, one trunk appearing to become the subject of the periodical excitement about ten days after the other ha ceased to be so. What was the real condition of the identity of this monster! The instances of monstrosity by default of development are sufficiently numerous; as, for example, in the cases of spina bifida, of anencephalous and acephalous foetuses, and of foetuses with imperfect limbs; and those with imperforation of the rectum, and with other atresias. The Student will have little trouble to understand and explain these strange freaks of nature, if, in all cases, he will remember that the monstrosity is dependent either upon fusion of the parts of two different children, or excess in the development of otherwise natural parts, or on cessation, during the embryonal stage of life of that growth and progress which, but for the arrestation, would have finished and rendered complete, parts that now exhibit the appearance of the most shocking deformity. We meet with numerous cases of ectopy; cases in which organs or parts are displaced or deviated. In Fig. 62, page 217, is the picture of a child born here under my care. It lived for several days. The tumor on its belly is an exomphalos, consisting of the entire liver of the infant, which was contained within the root of the umbilical cord. There was no covering of this liver save the deciduous matter of the cord. Of course when the cord should fall after five or ten days, the liver would be wholly exposed. Such an accident renders the child absolutely non-viable. I possess another specimen, in which every abdominal viscus is outside of the belly inclosed within the umbilical cord. Duration of Pregnancy.-The duration of gestation is ordinarily computed to be nine months or 280 days; and the Women, who understand these questions by a traditionary learning, commonly make their calculations with sufficient accuracy. According to the Civil Code in France, a pregnancy may properly be held to continue until the 300th day; which is allowing a latitude of twenty days beyond term. I have been surprised to find how prevalent has been in all ages the opinion that a great latitude exists as to the duration of pregnancy, and that some of the ablest men of our profession, both ancient, medieval, and modern, have admitted a latitude far greater than that allowed in the French Code. I rejoice that this is the case, because, having myself had reason to believe that pregnancy may endure even beyond twelve months, as I shall relate in another page, I conceive it desirable that the truth should be established for the conservation of the credit and peace of individuals or families, in cases where such extraordinary postponement of the term might give rise to the greatest injustice, as well as unhappiness. A great controversy arose in Europe in 1764, which was carried on by various writers until 1770, and brought out the opinions of the most celebrated medical men of the time; a collection of pieces on this subject, in three volumes, is in my library. The dispute arose on the question of legitimacy of a child, whose father, Charles, born January 15th, 1689, was more than 72 years old when he married Renée, Marchioness of Ingreville, who was at the time 30 years of age. He lived four years with his wife, and had no children. On the night of 7th8th of Oct., 1762, he fell sick with fever, and violent oppression, which continued until his death. During his illness, his wife Renée did not sleep in his apartment. He died with gangrene of the leg, on the 17th of Nov., æt. 76 years. More than three months after his death, Renée gave signs of being pregnant. She was observed and carefully assisted by order of the collateral heirs, and gave birth to a son, Oct. 3d, 1763. From Oct. 8th, 1762, to Oct. 3d, 1763, is one year, lacking five days. The question was submitted to various leading medical persons for their opinions as to the legitimacy of the child, and the said three volumes exhibit the most striking examples of the disagreement charged among doctors, many strongly denying the possibility of Renée's purity, and others as earnestly vindicating the legitimacy of her son. It would seem that the most common and ordinary observations and proofs are incapable of expelling from the public mind opinions long established, upon whatever foundation. There is hardly to be found an old wife in the country, who does not know that the term of incubation of the barn-door fowl is uncertain; and that, though it ordinarily lasts twenty-one days, the chick may be found to escape from its shell on the twentieth, or to linger in it, sometimes, to the twenty-second or twenty-third day. Similar facts as regards the gestation of our domestic quadrupeds are abundant, and sufficient to demonstrate the latitudinarian character of what is called term. To show the differences in gestation, I subjoin the following tables which I find in M. Rainard, Traité complet de la Parturition des principales Femelles Domestiques, tom. i. p. 233, et seq. The date of the Covering was noted as to fifteen mares, of which eight foaled after 340 days, three after 342 days, three after 343 days, and only one at 346 days. Brugnone, in like manner, in fifty-five mares found that the foaling took place in |