We have already pointed out the difficulty of determining the presence of twins merely from the appearance of the mother's abdomen; the same will necessarily hold good with regard to one large child. The size of the patient must rarely have any influence in forming our prognosis: in most cases she will have many symptoms, which arise either from pressure or weight in the pelvis, such as difficulty in passing water, oedema of the feet and legs, varicose veins of the thighs and labia, or from cramps, the result of pressure upon the absorbents, veins, or nerves; considerable expansion of the inferior segment of the uterus: all these will give us reason to suspect the presence of a large child even although the abdomen may not be remarkably distended. Where the head is very large, the bones are seldom much ossified; they therefore yield easily, and the head accommodates itself to the shape of the passage: sometimes, however, it is unusually hard, the bones are well ossified and very unyielding, so that even if it be not larger than common, still, from its hardness, it meets with considerable difficulty in passing through the pelvis. Cases have been described where the cranial bones were completely ossified, and the sutures perfect; but this latter is very doubtful. Perfect mentions an instance where the head was "almost one entire ossification, and where it passed through the pelvis with great difficulty." (Perfect's _Cases in Midwifery_, vol. ii. p. 370.) We have also met with cases requiring perforation on account of deformed pelvis, and where the cranial bones had almost the feel of a hard nut or shell; still, however, as already observed, we seldom see any serious impediment to the passage of a large head, so long as it is naturally formed; and this applies also to the other parts of the child. _Form of the child._ On the other hand, where there is an unnatural form of the child, either from a disproportionate size or anormal configuration of certain parts, labour may be rendered not only very difficult but dangerous: thus one of the three great cavities may be distended with an accumulation of fluid, the most common form of which, is the congenital hydrocephalus.