_Nates presentations._ "After the presentations of the cranium those of the nates are the most frequent in point of occurrence, and also the most natural," says the celebrated Boer, in the work already quoted. Under the term _nates_ presentations, we include those of the knees and feet, as these latter presentations can only be looked upon as modifications of the former. Professor Naegelé, jun., in his new edition of the admirable essay upon the mechanism of labour, published by his father, in Meckel's _Archiv. für die Physiologie_, has very properly brought these different positions under one head, viz. "positions of the pelvic extremity of the child:" as, however, we possess no word in English to express this, we shall attain the same object by considering knee and footling births as mere modifications of breech presentations. "As regards the relative situation of the limbs to the body of the child, the position is the same as in the two genera of head presentations above described, viz. the knees are usually drawn up to the abdomen, the feet close to the nates, so that not unfrequently they may both be felt together at the beginning of labour, and afterwards descend into the pelvis and are born together. Sometimes the feet (or perhaps only one foot) are felt higher above the brim than the nates; in which case, as the nates descend they rise, and are turned upon the abdomen and breast of the child, and descend with these parts as labour advances. Frequently it is the reverse: the feet are somewhat lower than the nates; they are felt in the os uteri at the beginning of labour, and descend before them as labour advances. It is rare that the knees come down before the nates during the farther progress of labour, and it is not probable that they are ever found alone in the os uteri at the commencement of it." (H. F. Naegelé, _Mechanismus der Geburt_, 1838, p. 57.) The nates may present in two ways, either with the back of the child forwards, or with its abdomen forwards: of these the former occurs most frequently; thus of 161 cases which were accurately ascertained at the lying-in hospital of Heidelburg, 121 were observed with the back of the child forwards, and 40 with it backwards: in either of these positions the transverse diameter of the child's pelvis always corresponds to one or other of the oblique diameters.