*

vious derangement of health, nor of the fatal hemorrhage, attending the rupture, and the facility of injecting all the vessels notwithstanding nature's custom to attempt the abolition of arterial canals which run towards mortifying parts.

The circular apertures in the decidua opposite the openings of the Fallopian tubes are worthy of notice, because this membrane is often said to consist of two layers; the exterior perforated opposite the openings of the tubes, but the interior continuous. The ovum, passing from the Fallopian tube, is thought to go through the opening in the external layer against the internal, and this, being pushed before the ovum, to become the decidua reflexa t. These apertures were unfortu

* See Mr. Langstaff's case. Vol. VII.

† Dr. Hunter, (Anatomical Description of the Human Gravid Uterus and its Contents. 1794. p. 55.) speaking of the contents of the uterus after the earlier months of pregnancy, says, "When the decidua is pretty thick it is often divisible into two or more laminæ. Its outer stratum or lamella is perforated at each Fallopian tube, and at the os uteri."

I noticed no opening in the decidua at the cervix uteri, when inspecting its inner surface, yet Dr. Hunter in the preceding quotation speaks of a perforation "at the os uteri." Dr. Baillie, who completed the work, informs us (p. 77, see also Trans. of a Society, &c. Vol. II. p. 66. sqq.) that John Hunter, "in a case of very early conception, probably not more than two weeks," found the decidua, "upon opening the uterus, to be as fine at the beginning of the cervix as the retina, but without any hole in it there." "In more advanced pregnancy," he continues, "that part of the decidua which lines

nately not examined before the parts had lain in spirits and the decidua become contracted. Nor was it before this that I attempted to separate the decidua into layers. Should any member of the Society meet with an opportunity, it would be highly interesting to inquire into these points while the parts are recent *.

the inner surface of the uterus, and which will in the progress of the description be distinguished by the name of the decidua vera, seems to lose itself at the beginning of the cervix, and has evidently there an opening. The decidua which covers the external surface of the chorion, becomes gradually thinner as pregnancy advances, but has no opening in it at the cervix uteri or any where else."

* A bristle passed from the tubes into the uterus in Dr. Clarke's case (1. c. p. 221). But it might be replied that the bristle made itself an opening in the inner layer of the decidua. The openings in the decidua presented themselves spontaneously to my view on exposing its cavity. Yet it must be remembered, that Mr. Burns, in his Midwifery, says, the decidua passes in some cases a little way into the Fallopian tubes; and if the assertion is correct, and mine was one of these cases, there might be an appearance of aperture when no aperture existed.

ON

THE LIGAMENTS

OF THE

HUMAN OSSICULA AUDITUS.

BY THOMAS WILLIAM CHEVALIER, Esq.

Read April 27, 1824.

IT is generally allowed at the present day, that all new facts, however apparently fruitless when recently discovered, should be recorded for the consideration of the many who are devoting their time and their talents to philosophical pursuits. And indeed it is only by those generous principles of conduct, whereby the mind of the world has been, at the earliest period, employed upon the observations of individuals, that we can possibly account for the recent advancement of science.

To a medical student of the present day, even the period of his own pupilage presents instances in which the progress of Pathology appears to have been the immediate result of perseverance in anatomical research; while the diseases which most resist the skill, and baffle the reasoning of the nosologist, for example, those of the nerves, of the skin, of the ear, &c.-are precisely those concern

ing which our anatomical knowledge has been hitherto most glaringly deficient.

My attention having been accidentally directed about six or seven years ago, to a minute investigation of the human organ of hearing, and having been unable to quit so interesting a subject, I began to consider whether the ossicula auditus might not, like other bones of which an accurate movement is required, be restrained and directed by a set of ligaments.

Though joints so minute must have very small ligaments, if any, I hoped that the accurate knowledge of them, might at least enable me to form a decided opinion upon the question, whether the mechanism contained in the cavity of the tympanum, adapts itself to the force alone, or also to the specific and individual characteristics of those impulses which it transmits.

The columella in the ears of birds is weakest in those that sing best. It bends under almost the slightest discernible impulse that can be communicated to the membrana tympani of these animals. If, for example, the membrana tympani of the thrush, or of the nightingale, were to receive the rude impulse of a touch, such a force would be immediately impressed upon the contents of the labyrinth as to injure them, were it not for the extreme flexibility of the columella. So that the pre

servation of the delicate auditory nerve of these birds appears due to the weakness of the recipient or conductor of all they hear; and this defensive provision appears one important use of the sole ossiculum,—or rather of the sole cartilago auditus, that they possess. But one other purpose is evidently answered by the columella in the ears of birds, viz. the diminution of the area of the membrana tympani to that of the fenestra vestibuli.

In man, the incus does not communicate immediately with the stapes, but, as every one knows, through a double ball-and-socket joint; and the stapedius muscle is so placed, that it cannot fail, as often as it acts, to draw the latter bone from its usual position, under the arm of the incus; and to relieve the contents of the labyrinth from the direct impression of too violent a shock (Fig. 2. No. 12).

It is proper to remark, that very few of the ligaments of the body are so precisely similar, with respect to their forms and positions in different subjects, as to answer accurately the descriptions of Weitbretch; although his work upon those parts is the admiration of all who have once employed it in dissection, and can never be excelled. Accordingly, the ligaments of the ossicula auditus (which I have described in the explanation of the drawings as new to me) have not always precisely the same position or form. Several are of a quadrangular shape, but they have their angles in different indi