Another although much rarer consequence of malposition of the child, is that peculiar mode of expulsion which was first noticed by Dr. Denman in 1772. From the supposition that the shoulder receded and the nates came down into the pelvis, in which position the child was born, he called it "_the spontaneous evolution of the foetus_;" but the term _spontaneous expulsion_, as proposed by Dr. Douglas in 1811, is much better adapted, it having been shown by that gentleman that the explanation of this process as given by Dr. Denman was not correct. (_An Explanation of the real Process of the spontaneous Evolution of the Foetus_, by J. C. Douglas, M. D. 2nd ed. 1819, p. 28.,) but that whilst the shoulder rested against the pubes, the side of the thorax and abdomen, followed by the nates, passed in one enormous sweep over the perineum, leaving the head and other arm still to be extricated. The shoulder and thorax thus low and impacted, instead of receding into the uterus, are at each successive pain forced still lower, until the ribs of that side, corresponding with the protruded arm, press on the perineum, and cause it to assume the same form as it would by the pressure of the forehead in a natural labour. At this period, not only the entire of the arm but the shoulder can be perceived externally, with the clavicle lying under the arch of the pubes. By farther uterine contractions the ribs are forced more forwards, appearing at the os externum, as the vertex would in a natural labour, the clavicle having been by degrees forced round on the anterior part of the pubes with the acromion looking towards the mons Veneris. "The arm and shoulder are entirely protruded with one side of the thorax, not only appearing at the os externum, but partly without it: the lower part of the same side of the trunk presses on the perineum, with the breech either in the hollow of the sacrum or at the brim of the pelvis, ready to descend into it, and, by a few farther uterine efforts, the remainder of the trunk, with the lower extremities, is expelled." (Douglas, _op. cit._ p. 28. 2nd ed.) Farther experience has confirmed the correctness of Dr. Douglas's views (_Med. Trans. of the Royal Coll. of Physicians_, vol. vi. 1820;) and, indeed, the original case as related by Dr. Denman himself tends to prove that nothing like an "evolution" of the foetus takes place. I found the arm much swelled, and pushed through the external parts in such a manner that the shoulder nearly reached the perineum. The woman struggled vehemently with her pains, and during their continuance _I perceived the shoulder of the child to descend_.