HERMAPHRODITISM TN DOUBLE MONSTERS.
One of the most curious facts in the history of double monsters is the great rarity of an opposite or hermaphroditic sexual type in their two component bodies, the genital organs of both bodies being almost always either both female or both male.
Physiological science affords us at present no satisfactory clue to the explanation of this singular circumstance. From two cases of double monstrous embryos observed in the egg of the domestic fowl by Wolff. and Baer,-f and from a similar case met with in the egg of the goose by Dr. Allen Thomson, it appears certain that double monsters sometimes originate upon a single yolk, probably in consequence of the existence of two eicatricuhe upon this yolk,t or of two germinal points (or two of the vesi cles of Purkinje and Wagner) upon a single cicatricula. In such a case the two bodies of the double monster are so early and intimately united together as to form, almost from the commencement of development, a single sys tem; and therefore the fact of the uniformity of their sexual character is the less remarkable. But in other instances when the double mon ster originates (as from the phenomena of in cubation in double-yolked eggs we know to be frequently the case,) on two separate yolks or in two separate embryos becoming fused or united together, at a more advanced stage of develop ment, it appears more extraordinary that the sexes of the two conjoined foetuses should be so constantly uniform as they seem to be in monsters perfectly double. This uniformity only becomes the more singular when we re flect that twin children are not at all unfrequently of opposite sexes.§ The fact itself, however we may explain it, of the comparatively extreme rarity of both male and female sexual organs upon double monsters seems sufficiently established by va rious careful investigations made into the sub ject. Thus out of furty-two perfectly double monsters which Haller' was able to collect at the time at which he wrote, there were only two that were supposed to be of double sex, or, in other words, that had one body male, and the other female. Among double-headed monsters with single lower extremities, he found an hermaphroditic type more common, and adduces three examples of it.
In re-investigating this matter, the late Pro fessor Aleckelt could discover among the nu merous class of monsters with perfectly double bodies united anteriorly or laterally by the tho rax and abdomen, only one very doubtful case of exception to the above general fact. In the class of double monsters united in the region of the pelvis he mentions two exceptional cases from Valentin: and llasenest;§ of double headed monsters with single bodies, he quotes three similar cases from Lemery,11 Bacher,IT and Bilsius ;" and of monsters with a single head and double body he adduces two cases from Brissaustt and Condamine,lt in which in a like manner one body of the monster was supposed to have female, and the other male sexual organs. Several of these cases, how ever, certainly rest upon too doubtful authority and insufficient observation.
Isidore St. llilaire has still further extended the data on which the above general fact is founded, by sliming that the same uniformity of sex holds good with respect to double para sitical monsters,§§ and even in monstrosities double by inclusion. Thus out of this last in teresting class of double monsters, he alludesilll to ten distinct cases in which the sex of the included being was ascertained. In six out of these ten cases the including and included body were both male; and in the other four they were both female.
On the whole, therefore, we must consider as founded on a proper inductinn from the ex isting data, the axiom of Aleckel,—" Sexuum diversorum indieia in eodem organism°, quan tumvis duplicitate peceet, non dari, sed unum tantum But while all the data hitherto collected with regard to this subject would seem to point it thus out as one of the most constant and best ascertained laws in te ratology, still we are not altogether disposed to consider it with Zeviani* and Lesauvaget as subject to no exceptions whatever. In the study of monstrosities, as in the study of other departments of medical science, we find many general, but no universal laws.