Mother, Nurse and Infant / A Manual Especially Adapted for the Guidance of Mothers and Monthly Nurses, Comprising Full Instruction in Regard To Pregnancy, Preparation for Child-birth, and the Care of Mother and Child, and Designed to Impart so Much Knowledge of Anatomy, Physiology, Midwifery, and the Proper Use of Medicines as Will Serve Intelligently to Direct the Wife, Mother and Nurse in All Emergencies.

by S. P. Sackett

CHAPTER I.
OF THE PELVIS.

The formative organs of generation are situated within a large cavity, called the cavity of the pelvis, the walls of which are composed of bones and soft parts. This basin (in Latin, pelvis) is an irregular, long cavity, situated at the base of the spinal column, and above the inferior extremities. In the adult the bony pelvis may be divided into four parts or bones, viz: the os sacrum, two ossa innominata, and the os coccygis, but in early life they are more minutely divisible.

THE SACRUM.

The sacrum (Fig. [1]) terminates the vertebral column, and is perhaps the most important bone in the pelvis, obstetrically considered, as it enters largely into the various deformities of the pelvis. In the adult it is of a triangular shape, the base of the triangle being above and inclining forwards, the apex below and somewhat backwards; its length is from four to four and a half inches; its breadth about four inches, and the greatest thickness, two and a half inches. The internal surface is concave to the amount of half an inch, crossed by four transverse lines, marking the former division by cartilage; here are four pair of holes, through which pass numerous nervous filaments, which afterwards form part of the great sciatic nerve.

Fig. 1–	A	represents the internal or anterior surface of the sacrum.
	B B	represents the articular processes.
	C C	represents the anterior sacral foramen.
	D	represents the articulating surface.

It is placed at the posterior part of the pelvis, where it appears like a wedge forced in between the ossa innominata, immediately below the vertebral column and directly above the coccyx.

THE OSSA INNOMINATA.

The os innominata (nameless bone, Fig. [2]) is of a very irregular figure, and the pair occupy the lateral and anterior parts of the pelvis. The external or femoral surface is turned backwards and downwards, as well as outward; at its superior part, inferiorly it looks downwards. Towards the front, the external face presents the cotyloid cavity, or the acetabulum; a little more in advance and below is the subpubic or obturator foramen, which is nearly closed by the obturator ligament.