Externally the palpating fingers at the pelvic brim will note the absence of the hard, round head, and feel a mass, softer, quite irregular in shape, and less defined than customary. Movements also may be appreciated that would be too far down in the uterus if the head was presenting. Next the hard, spherical tumor of the head can be outlined somewhere in the fundus, and the heart tones, instead of being below the umbilicus will be on the same level or even higher. Vaginally the cervix is not filled out, the presenting part does not come down, but after labor has begun the distinctive features of the breech gradually become more evident, as they are driven into the pelvis. One or both feet, or the buttocks, may be recognized. The examining finger may possibly enter the anus and be stained with meconium or pinched by the sphincter, which differentiates this orifice from the mouth. One after another the characteristic landmarks appear until the diagnosis can not be doubtful. As soon as the sacrum is found or the legs definitely placed, the position can be named. _Mechanism._—The hips always enter the inlet in one of the oblique diameters and the back is turned to the same part of the uterine wall as in the corresponding vertex positions. The acts described in the mechanism for vertex deliveries show a somewhat different order. Descent is first, then comes internal anterior rotation, which brings the anterior hip under the symphysis and its delivery is quickly followed by the posterior hip, which rolls out over the perineum. The body advances, as a rule, with the back toward the front of the mother. The shoulders with arms folded move under the pubic arch and then the head delivers in a state of flexion. The head, of course, has no caput and it is not moulded. This mechanism may be greatly impeded or complicated at any stage of the movement. The advance may be retarded to a pathological degree, the belly may be large and as it passes along the canal one or both arms may be stripped up alongside the head or even into the back of the neck. The head may be arrested at the inlet by the arms, by its degree of deflexion, or by pelvic contraction. The rotation may not take place, or it may be abnormal, and the belly of the child look forward toward the mother’s. Any of these variations adds further to the difficulty of the labor and to the danger of the partners in the event. Artificial aid may be required which brings with it the possibility of sepsis. The fœtal mortality which averages five per cent is due mostly to asphyxiation. Interference with the supply of oxygen begins as soon as the cord passes the vulva and the child must be delivered in eight minutes from that time, or perish. Partial detachment of the placenta may also cut off the oxygen to a fatal degree, and the child may be unable to breathe when born on account of mucus sucked into the trachea by premature efforts at respiration.