I. ISOLATED TWINS.
In 1877, Beason divided the causes into predisposing and determining,. Among the first he noted: Excessive size of the pelvis, a single sac, small foetuses and faulty accommodation. Among the second, spasmodic and tetanic contraction of the uterus, the projection of the sac containing the superior fcetus below the first presenting fcetus, the premature rupture of the membranes of the second fcetus.
a. The Foetuses present by the Vertex. (Fig. 207.)—Usually the heads present successively at the superior strait, and there is no difficulty. Sometimes, however, the head of the second fcetus is placed on the neck of the first, presenting together in the sxcavation. If the foetuses are small they may be expelled spontaneously, but otherwise intervention is neces sary.
b. One Rehm presents by the Breech, the otter by the Head. (Fig. 208). —In case the legs are extended, the head of the second child may engage at the same time as the extremity of the first. The head of the first may hook on to that of the second child, and drag it down. Delivery is only possible where the foetuses are small, and the uterine contractions strong and sustained. In certain instances, it has been possible to push up the head of the second child, and thus to deliver that of the first. (Cases of Budin (Fig. 208), Perrochaud, Sidney, Calise, Walter.) The forceps has been used by Hohl, Carriere, Balfour, Tellkampf, Eichorn, Brain, Genth, Depaul, and others. Craniotomy and decapitation have been practised by numerous others.
c. The first Infant presents by the Head, the second by the Breech.—A case has been recorded by Mauriceau, where the sac of the second infant projected below the head of the first, and constituted the obstacle.
d. The Twins present by the Breech.—If the breeches are complete they cannot engage simultaneously; if the legs are extended the feet may de scend together. (Cases of Arnaud, of Schultze, of Plessmann.) e. The first Fail us presents by the Head, the second by the eases have been reported: One of Morgagni (Fig. 209), one of Solayres.
f. The first Fcetus presents by the Breech, the second by the Trunk.— One case of Baudelocque's, another of Dunal's. (Fig. 210.) g. The first F031118 presents by the Trunk, the other by the Breech.—A case has been recorded by Bartscher.
The above are the cases found in literature by Beason. In the major ity the diagnosis was not made till labor. It is difficult to lay down rules for treatment. One rule should be absolute, and this is to abstain from the administration of ergot, which can only compromise the life of the foetus, and complicate the necessary intervention.
In the exceptional cases, where the twins 'occupy the same amniotic sac, the cords may intertwine and knot. Muller has collected eight cases, and to these we would add those of Ygonin, Fricker, Sleinwachter and Gueniot.
Composite Monsters (Autosites)..
Autosite composite monsters include: Ensomphalic, monomphalic, sycephalic, monocephalic, sysomic, monosomic foetuses.
Ensomphalic Fetuses.—" These foetuses are each practically complete, although united together, and are able to accomplish independently almost all the vital functions. Each has its own umbilicus, and, during intrauterine life, its umbilical cord." (Saint-Hilaire.) Each is nor mally constituted, except at the point of fusion; they are viable, and if they usually die, it is because they are born before term, or there is some difficulty during delivery. They may be distinguished into: Pygopagi, metopagi, and cephalopagi.
Pygopagi.—Where the fusion is back to back. The sacrums are united from the first or the second sacral vertebra. The rectum is double above, and single below. They are viable, and a number have reached the adult age. (IIel•ne Judith, Millie-Christine.) The union of the sa . crums is the reason why there has always been hesitancy in separating the two individuals. In one case where this was attempted, they quickly died.