_Impaction of twins in the passage._--It is very rare to have twins enter the passages together so as to become firmly impacted. As a rule, each of the twins has its own separate membranes, and as the water bags of one will naturally first enter and be the first to burst, so the calf which occupied those membranes will be the first to enter the passage and the other will be thereby excluded. When the membranes of both have burst without either calf having become engaged in the pelvis, it becomes possible for the fore legs of one and the hind legs of the other to enter at one time, and if the straining is very violent they may become firmly impacted. (Pl. XVIII, fig. 1.) The condition may be recognized by the fact that two of the presenting feet have their fronts turned forward, while the two others have their fronts turned backward. If the four feet belonged to one natural calf, they would all have the same direction. By means of this difference in direction we can easily select the two feet of one calf, place running nooses upon them just above the hoofs or fetlocks, and have an assistant drag upon the ropes while the feet of the other calf are pushed back. In selecting one of the twins to come first several considerations should have weight. The one that is most advanced in the passage is, of course, the first choice. Though the fore feet of one are presented, yet if the head is not in place the calf presenting by its hind feet is to be chosen as being less liable to obstruct. Again, if for either calf one limb only is presented and the other missing, the one presenting two feet should be selected to come first. As soon as one calf has been advanced so as to occupy the pelvis the other will be crowded back so that it will not seriously obstruct. _Fore limbs curved at the knee--Limbs sprawling outward._--In this case not only are the knees somewhat bent in a curve, but the calf has a position as if it rested on its breastbone, while the legs were drawn apart and directed to the right and left. The shoulder blades being drawn outward from the chest and the elbows turned out, the muscles extending from the trunk to the limb are unduly stretched and keep the knees bent and the feet directed outward so as to press on the sides of the passages. They become retarded in their progress as compared with the more rapidly advancing head, and may bruise or even lacerate the walls of the vagina. It would seem easy to rectify this by extending the legs, but the already tense and overstretched muscles operate against extension in the present position, and it is not easy to rotate the limbs so as to apply the shoulder flat against the side of the chest. Under these circumstances a repeller (Pl. XX, fig. 7) may be planted in the breast and the body of the calf pushed backward into the womb, when the limbs will extend easily under traction and the presentation becomes at once natural.