In investigating the nature of the causes which produce malposition of the child, which, from the above observations, is evidently a circumstance of rare occurrence, the question naturally suggests itself, by what means is the long diameter of the child in so large a majority of cases kept parallel with that of the uterus? This depends in great measure on the form and size of the uterus. Where the uterus is not unduly distended with the liquor amnii, and where it preserves its natural oval figure, it is scarcely possible that the child should present in any other way than with its cephalic or pelvic extremity foremost. There can be no doubt that the first early contractions of the uterus in the commencement of labour have a great effect in regulating the position of the child; for, by the gentle and equable pressure which they exert upon it, they not only maintain it in the proper direction, but tend materially to correct any slight deviations from the right position. Hence, therefore, we find that where any cause has existed to impair or derange the action of these precursory contractions of the uterus, the child is apt to lie across, or, in other words, to present with the arm or shoulder. Thus, for instance, if the uterus be much distended with liquor amnii, the contractions of its parietes can have little influence upon the child's position; this will be particularly the case where the accumulation is very considerable, for here the uterus becomes more or less globular, and presents but little variation as to the length of its diameter in any direction. The form of the uterus is no less worthy of attention as a cause of malposition, and is also in a great measure influenced by the character of its early contractions. Thus in a uterus for the first time pregnant, they generally act equally on all sides: hence it is why in primiparæ the uterus is so exactly oval, and why we so rarely meet with faulty presentations. Sir Fielding Ould, of Dublin, was the first and almost the only practitioner in this country who noticed the influence which the early contractions of the uterus have in determining the position of the child. "The first labour pains, which are very short, continue their repetition for two or three hours, or perhaps for more, before there is the least effect produced upon the os tincæ, which time must certainly be employed in turning the head towards the orifice." (_Treatise of Midwifery_, p. 14.) Wigand, in reasoning upon the physical impossibility of a child presenting wrong, where the uterus is of the natural configuration, says that "the chief cause of faulty position of the child does not depend so much upon the child itself, as upon the deviation of the uterus from its natural elliptical or pyriform shape." (Wigand, vol. ii. p. 107.)