amine this question, I am still, even when considering the Siamese, not in any way doubtful that double deformities are not produced by fusion, but by segmentation. True, when one sees two such individuals, with perfect development of all parts, who are only united at one point, it is possible to think that a subsequent fusion of embryos, which are otherwise fully developed, might be possible; nevertheless, there are very important obstacles to oppose the adoption of this theory, and from the fact that with an otherwise faultless development of the individuals, but slight deformities are present, I think the adherents of the fusion theory, if they reason on it, would doubt the truth of their doctrine. It is quite clear, that fusion of two embryos, one with another, is only possible when they are not separated by their various coverings. With the theory of fusion, we must then take for granted, that in consequence of those mechanical changes which brought the two bodies into contact, the enveloping folds were destroyed, the bodies came into actual contact and then fused, an assertion which is, however, very doubtful. On the other hand, I must draw attention to the fact, that in all cases in which fusion was discovered on the surface of children otherwise perfectly developed (and there is not a small number of cases in which the pelvis or the head of a fœtus was fused to a portion of the amnion), in every instance there were uniformly great deformities presented in the child, under consideration; deformities which are produced during the intra-uterine life of the single fœtus, may always be traced back to some inflammatory process. These fœtal inflammations extend themselves more irregularly than those during extra-uterine life. We, therefore, find at the birth of such a child, the region affected over a more extended area than is the case in individuals after birth. A simple adhesion between the head and the ovarian membranes, of not greater area and seriousness than most people have not only once but several times in their lungs, suffices to produce a hydrocephalic, and perhaps an ancephalic in

fant. These serious results are also produced by the inflammatory process in other parts of the foetal body.

But no one has ever discovered anything in double monstrosities which would point out the existence of such foetal inflammations. While not in other instances, (where union of the surface of the body with adjacent parts has occurred, could with certainty demonstrate the results of the inflammatory action,) still at present every trace of any tissue is wanting in cases of double deformity, that we might consider as the result of any inflammatory action. We would have to go back to an exceedingly early period of fœtal life; we would have to take for granted that in the very beginning two ova had lain so closely together that their first development had brought them in contact and produced a union between them. In this case it would be very remarkable that two eggs of this sort should in other respects go through their normal development without any disturbance, and that they should fuse at that very point, where the development of external and adjacent parts would tend to separate them from each other.

This theory of fusion must contend, however, with still greater difficulties, as it is often asked, Whence do these two ova come? One is then always referred to a single ovarian follicle. When one has the opportunity to examine the ovary of a mother of twins-one finds in the case of twins of the same sex but a single ruptured sac-always, but one large corpus luteum, and it is easily inferred that both individuals are formed from a single ovum.

When we consider, that in every well authenticated case of adherent or united twins both children without exception were of the same sex, that, one doubtful case excepted, it has never been observed that a male and female child were grown together, that rather homologous, or two male or two female children were attached; that the physical development was always in direct proportion to the mental, and when internal or external differences appeared, these first showed themselves during the progress of life, and are explained by

different disturbances; when we then see, that in the majority of cases there is to all appearances the greatest similarity, we will then, with right, be able to assert, that the law which is now generally accepted, also holds good in the case of these twins, namely, that they were produced, not by the fusion of two ova, but by the segmentation (division) of a single one.

I will add another observation, which, I think, determines this opinion. We have direct observations in the case of fish and lower animals, i. e., those by Gegenbaur (Wurzberg Transactions, Vol. II., page 166), on the snail, in regard to the division of a single egg and the development of a double animal from one egg. This was directly observed in the egg. It is not a theory, but a proven fact. No one has seen, on the other hand, two eggs fused and double monstrosities formed out of them. The case of segmentation was then observed. The case of fusion is but an hypothesis, and, plausible as this theory may be at a first glance, you will still, when you investigate it more closely, decide in favor of the segmentation theory as being the more probable.

We have, unfortunately, no series of observations in regard to the behavior of the ovarian membranes in such cases; however, the observations arrived at agree in so much, that but one placenta a simple chorion-one amnion-and never a plurality of these was present. These conditions would be difficult of explanation if we were to consider the value of the theory of originally separate ova, while easily explained if a single ovum were present, which only after partial development gives rise to two infants.

The theory of segmentation is also acceptable, as from this stand-point duplicities in every instance may be explained, a double finger, as well as a double individual. No one will, if any person has a sixth finger, think that this duplication was produced by the fusion of two buds, while the production of this monstrosity by division is very plausible. This simplicity, this searching application, is, as it

seems to me, a very decided advantage of the theory which I advocate, in contra-distinction to the theory of fusion.

It is to be regretted that we possess, in respect to the majority of the cases of duplication, but a meagre report as concerns their family record. I have taken pains to collect the suitable material, but nevertheless, I have in but one of the cases, which in other respects is of great interest, in that of Boehm, found the statement, that in the family of the mother two cases of simple twins had occurred before the united twins were born.

Chang and Eng, whose youth is described in a pamphlet published by their direction, deny that twins had ever been born in any branches of their family. They had, it is true, very fruitful parents, who were blessed by nine children, among whom the twins count as two; four before them and three after, but among these there were no more twins. They themselves have succeeded, during a wedded life with two sisters, the daughters of an American divine, to procreate eighteen children; but when I asked them if they had not also twins, they were greatly frightened, and said that it had already gone better than they ever expected.

However, it would be very interesting, and I would direct the attention of all confrères, who, in the course of their practice may have had opportunity to make observations on double deformities, to determine by means of the family history, whether twins had ever occurred previously, as it would be an argument in favor of the theory as offered by me, if it could be proven that these duplications could be compared to the common instances of twin births.

In respect to the antecedents of Chang and Eng, I will add that they are descended from Chinese parents who had emigrated to Siam, and that their birthplace was the city of Macklong, which is situated about sixty miles from the capital, Bangkock. The twins describe their first appearance upon the world's stage, as a rather pitiable one. Their delivery was easily secured, because they were very small. In their early life they suffered but little from illness; only

during their sixth or seventh year were they afflicted by variola; and, soon after, by the measles, by which diseases they were simultaneously attacked. In the year 1833, while in Ohio, they suffered severely from an attack of intermittent fever, during which they were simultaneously affected by attacks of chills. In 1819, a severe epidemic of Asiatic cholera visited Siam, during which a part of their family died. Their father died also, so that in their eighth year they had but their mother to support them, in very indigent circumstances. They soon endeavored to earn their own livelihood by manual labor. They began by making cocoa-nut oil; later, they began peddling, the artificial breeding of ducks, fishing, etc. By means of these efforts, which prospered, they lived considerably on the ocean. According to their statement, they soon perfected themselves in rowing, which I easily believed, as they were enabled to row as one man, and thereby employed considerable force. As they were never sea-sick, their predilection for seafaring is explained, and this has never left them. They also learned to swim, and, as they say, acquired considerable proficiency in this.

In 1829, they were persuaded by a sea-captain to go to America, and later, on to England. The captain led them from place to place, and pocketed their money. Only when they acquired full freedom, did they by journeys through the United States, England, France and Holland, gain sufficient means to enable them to marry and found an establishment. During the late war they lost their entire fortune, and were then necessitated to make a new journey to Europe. Hence, we see them, for the first time, in Germany.

The second question which presents itself, and which was erroneously stated in England, that this is their motive for coming here, is, Is such a case fitted for operation?

As far as this is concerned, I must next state that we have, in the literature on the subject, two well authenticated cases in which an operation was followed by success. However, both of these cases were very young, and, as is remark