(From Bregma 1501 to moisten ). In infants these bones are not only tender, but very moist; and sometimes so in adults. They are also called sinciput, parietaria,and medium testae. They are two bones on the upper part of the head, of an irregular square figure, nearly of the same thickness all over, and divided into an upper and lower part by a circular line; on the upper part they are covered only by the integuments, on the lower by the crotaphite muscle; towards the posterior and upper part, there is a hole through which the vessels of the dura mater communicate with those of the scalp. These bones have a large extent, but are the weakest in the human body. The trepan may be applied to any part of this bone, except on the lateral parts of the posterior lower edge of it, the lateral sinuses lying under them. It often happens that tumours are formed on these bones in infants, which contain a fluid, and conceal the osseous substance. These tumours should be left to nature, and their contents will be taken up by the absorbent system.