CHAP. VIII.
Of the BONES of the PELVIS.
I Doubt not in the least but This and the proceeding Chapter will seem needless, and appear superfluous to some Persons, in the Practice of MIDWIFERY; namely, to such as know not the New Improvements of this Art: But especially to such as are accustom’d to the Use of Instruments, they’ll appear altogether Useless and Vain; since such Practitioners can easily (upon any Occasion, without the curious Anatomical Knowledge of these Parts) first slay the INFANT, and then either deliver or kill the WOMAN, as Chance may direct their SHARPS.
BUT for my Part, because I have no Notion of such sort of Weapons, I shall endeavour to acquit my self more honourably, and teach my Followers another way, and That without Blood-shed; as I hope will hereafter more amply appear.
AND First therefore in speaking of the Bones of the PELVIS, I shall begin with the OSSA Innominata; which are two large Bones joined to the Sides of the OS SACRUM. They are compos’d of Three distinct Pieces, each of which has its respective Name: The First and superior is call’d Os Ilium; because the Guts Ilia lie upon it directly. It is Large and almost of a Semicircular Figure, a little Convex and Uneven on its External Side; as it is Concave and Smooth on the Internal. In short, it is join’d to the Sides of the three Superior Vertebræ of the Os Sacrum, and is Larger in WOMEN than in MEN.
THE Second and Anterior is call’d Os Pubis; which is united in the Forepart to its Fellow-BONE of the other Side, by an intervening Cartilage: By the Extension of which Cartilage, the Ossa Pubis in Young Women, sometimes recede a little from One another, to facilitate a difficult Birth.
THE Third is the Inferiour and Posteriour, call’d Os Ischium, or Coxendix, which has a large Cavity call’d Acetabulum Coxendicis; and This receives the Head of the Os Femoris; the Supercilium or Top of which Cavity joins the Os Pubis.
THESE Three Bones, until the Age of Puberty, may be seen distinctly, tho’ afterwards they grow together, and become one BONE, without leaving any Mark of Division. They adhere on each side to the Os Sacrum by two Strong Ligaments; the Upper of which passes from the Posteriour Acute Process of the Ischium to the Sacrum; as the Lower joins the Tuberculum Ischii to the Sacrum.
THESE Bones in WOMEN are more distant or separated from One another, and are smaller than in MEN; especially the Os Pubis, to the end that the Cavity of the PELVIS, and the Angle betwixt the Os Pubis and Ischium, may be the Larger, for the more commodious Bearing of the Infant, and the more easy Exclusion of it in Birth. But from hence I would no ways infer, that the Ossa Pubis and Ilia sever themselves in time of LABOUR; (notwithstanding the Opinion of some Authors) for I am fully satisfied of the contrary: Because I have conducted more than one Woman in my Time, upon walking out of one Chamber into another, immediately after DELIVERY; which could never have happen’d in Case of such a distant or dislocated Separation.
THESE Bones call’d Innominata are of wonderful Use and Service: For besides that they form the PELVIS, and defend every Part of its Contents, they also give Connexion and Juncture of the rest of the Body, to the Thigh-Bones; as they likewise give Rise and Origin to many Muscles, and are the Basis of Support of the Spine of the Back, as well as of all the Superior Parts. Whence I come à propos to descant a little upon this particular Part, as far as concerns our present Purpose.
THE Spine then is that Bony Column or Ridge, which extends itself down the Back from the Head to the Fundament, containing the Spinal Marrow, and resembling the Letter S in figure.
IN This Spina therefore we must consider its Fivefold Division; namely, into Neck, Back, Loins, Os Sacrum, and Os Coccygis. The First Three consist of 24 Vertebræ; whereof the Neck has 7, the Back 12, and 5 belong to the Loins. Those of the Neck bend inwards; those of the Back outwards, for enlarging the Cavity of the Thorax; Those of the Loins bend inwards again; and Those of the Os Sacrum outwards, to enlarge the Cavity of the PELVIS.
THE Vertebræ of the two last concern us most in this Place; wherefore I shall say no more of the rest, save only by the By, or coincidently, as they fall in my way. Those of the Loins then are the Thickest and Broadest, and the Last of them is the Largest of all the Vertebræ; as their Cartilages are thicker and stronger than any of the Others, and their Acute Processes are at a greater Distance from one another. From whence it comes to pass, that the greatest Motion of the Back is perform’d by the Vertebræ of the Loins.
THE Vertebræ of the Os Sacrum grow so close together in Adults, that they make but one large solid BONE, of a Triangular Figure; and yet not without the Mark of a four or five-fold Division: As in Children, it consists of many more Pieces or Divisions. However, its Basis is tyed to the last Vertebræ of the Loins, and the Upper part of its Sides to the Ilia; as its Point is to the Os Coccygis.
THE Os Coccygis is also in Adults, for the most part, but one entire BONE; tho’ in younger Persons it is compos’d of 3 or 4 small Divisions; Of which the Lower is still less than the Upper; till the Last ends in a small Cartilage. It is join’d in its Glenoide Cavity to the Extremity of the Os Sacrum; being short and bent inwards: It supports the Intestinum Rectum, and yields to the Pressure of the INFANT in Travail: But MIDWIVES ought not to thrust it back or repel it with Violence; No, they should rather handle it gently, if they would prevent dangerous Consequences, as well as great Pain to the Woman in LABOUR.
FROM hence it is manifest, that they are mistaken who imagine that the Opening and Enlargement of the PELVIS, in making way for the INFANT, does depend upon the Separation of the Ossa Pubis: For it much more depends upon the yielding of the Os Sacrum, or its giving way naturally; especially This Part of it call’d Os Coccygis. Neither doth the Straitness of the Upper Part of the PELVIS so much occasion a difficult BIRTH, as the small Distance that is betwixt the Points of the Ossa Pubis, call’d Ossa Sedentaria or Seat-Bones, and the Os Coccygis: No indeed, neither of These can be any great Hindrance to the Passage of the Infant; since all Bones, never so closely knit together with Ligaments, may be moved extensively upon occasion, by carefully and gently stretching the said Ligaments. But, in short, it most commonly happens, that the Ill Position of the Infant itself, or the bad Condition and Situation of the Womb, or Both, occasion a difficult or preternatural Birth.
BUT I would here farther observe yet, that as these Bones differ frequently both in Form and Size, according to the different Constitution of the Body; so neither are they always of the same Substance: For in some Women, we find a great many Nervous and Cartilaginous Ligaments, which penetrate into the solid Substance of the Bones themselves; in which the Ligaments are so fast bound together, that it is hard to distinguish whether they are One or More Bones. From whence, however, it will hereafter appear, that One Woman is more easily delivered than Another; the Bones in One being more firm and immoveable, altogether resisting any Relaxation; which in Another are more loose and pliable, easily give way and yield freely to the Force of the Endeavouring and Struggling INFANT.
THE Contents of this Section will appear more evident, by looking curiously upon a Female SKELETON: In which (for Distinction’s-sake I recite This) that the lower Parts of the Seat-Bones, are generally more distant, and not so much bent inwards, down towards the Point of the Os Coccygis, as in a Male SKELETON. Which Difference, in short, the Omniscient Creator has so order’d, for preventing difficult BIRTHS; and yet, notwithstanding all this wise Provision of Nature, they happen too often in the World. However, having thus, in fine, described the Pelvis and its Bones, as far as is requisite for MIDWIVES, I come next, more particularly to describe that astonishing Piece of God’s Handy-work, to which all the afore-mention’d Parts are ordain’d to minister, and that both conjunctly and severally, without any Exception: viz.