On the anatomy and physiology of the coccygeal gland

British Medical Journal

1868, Vol. 1, No. 367 (Jan. 11), pp. 25-26.

Macalister, A.

Demonstrator of Anatomy, Royal College of Surgeons, Ireland; Surgeon to the Adelaide Hospital.

In the posterior part of the ano-perineal region, a small aciniform body was first noticed by Professor Luschka of Tubingen, and described by him in Virchow's Archiv for 1860, Band 18, and in Anatomie des menschen, vol. ii, part 2, p. 187, under the name Steissdruse, or the coccygeal gland, as an adenoid appendage to the nervous system resembling the pituitary body in the cranial cavity. After him, Krause (Zeitschrift f. Ration. Med., band 10, heft 2), Heschl (Osterreich. Zeitschrift fur Prackt Heilkunde, 1860, No. 14), Henle (Jahresbericht, 1860), and Kolliker (Gewebelehre, 4 Aufl., heft 2, 539), have referred to it with more or less minuteness; and, within the last three years, Julius Arnold of Heidelberg and Dr. G. Meyer of Gotttingen have made it the subject of elaborate memoirs, and have given us a very full account of its structure and of its probable affinities. These descriptions, however, differ in some respects in their details; and to a few of these as yet unsettled points I would wish to direct attention in the present paper, as I hope to have a future opportunity of publishing more extended observations on the anatomical and physiological relations of this and several corresponding organs.

In order to expose this body, it is necessary to make a careful dissection of the post-anal part of the perineum, removing the integuments and clearing the fat and areolar tissue off the central part of the levator ani, just where that muscle and its fellow of the opposite side unite to form the tendinous ano-coccygeal raphe or ligament. In the course of this examination, it will be found that, nearly two lines in front of the extreme tip of the last ossicle of the coccyx, there it a small oval opening, two lines in length and one in breadth, bordered by a rounded tendinous lip, in which there are a number of circular fibres. Luschka figures this a little nearer to the exact tip of the coccyx than I have ever seen it; for 1 have always found a distinct coalescence between the two levatores ani for from half a line to two lines behind the opening. Descending through this opening will be found a minute pedicle, usually single,

But sometimes double or branching, inclined forwards and perfectly separated from the borders of the opening which it traverses. This cord descends for about a line and half and ends in the true coccygeal body, a pinkish grey mass, in size compared by Lushka to a lentil, being the eighth of an inch broad and about the tenth of an inch long. It is usually to be found as a single lobulated body; but I have seen It as a cluster of separate acini united by the branches of the pedicle; otherwise, but rarely, it may take the form of a reniform, globose, or bilobate mass. It is said to be equal to a small pea in size; but when its surrounding fibro-areolar capsule is removed, it is not quite so large at usually stated. Its thickness is variable, and can be much increased by injection. At first, it is with difficulty distinguished from the surrounding adipose tissue; but its colour, its density, its shape and attachments, will serve to distinguish its lobules from the fat granules in the vicinity. When compound, I have counted from three to seven lobes, which usually are all about the same size, each about as large as a poppy-seed. (Arnold.)

From the arteries and nerves external to the pelvis, it does not seem to receive any supplies, although the filaments of the fifth sacral and coccygeal nerves and the branches of the most posterior of the inferior haemorrhoidal arteries ramify in its neighbourhood.

But the true connections of this body are found when the levator ani is carefully dissected on its upper surface, and when we trace downwards the terminal coccygeal branch of the middle sacral artery, and the descending plexiform filaments of the ganglion impar. And here let me direct attention to a slight inaccuracy in many anatomical works on the subject of the middle sacral artery; it is usually described as terminating by dividing into two branches, each of which unites with the lateral sacral artery of its own side; but no mention is made of the arteria coccygea media, a tortuous but constant trunk, which is continued behind the ganglion impar to the upper surface of the before-mentioned aperture In the levator ani. This vessel forms an important element in the pedicle above mentioned, and is peculiar for exhibiting numerous lateral sacculi of an oval, fusiform, or reticulated nature. These were first described in man by Arnold; but are very easily seen when the artery is filled with injection. Indeed, it is very necessary before proceeding la the examination of the coccygeal body, to fill this vessel with some fine injection, which is easily done from the middle sacral opposite about the fourth piece of the sacrum. This arteria coccygea media conducts downward the sympathetic filaments from the coccygeal ganglion, and many of these are lost on the coats of the gland, and some penetrate as far as the walls of its component vesicle. G. Meyer has described two series of these fibres: the first, a pale series of gelatinous threads, terminating in the walls of the globules; and the second, a fine interlacing series, with double contour lines, indicating a double tube; these were by no means so distinct nor so easily followed.

When examined, this structure presents several parts; the first of which is the general capsule, usually imperfect above, made up of fibro-areolar tissue, surrounding and uniting the lobules. This consists of threads of white fibrous tissue with a few nucleated cells interspersed in their meshes. H. Luschka has described some true nerve-cells, and mentions that into these the nerve-fibres are traceable, but this arrangement has not been detected either by Meyer or Arnold, and I have not satisfied myself of the existence of such an union, which, however, I would regard as highly probable.

Each lobule besides, seems to have a special capsule, similar in nature to the general investment of the organ, and in this, Krause believes that unstriped fibres exist with no trace of ganglion cells; Luschka, on the contrary, believes that the capsule is hyaline; I regard it, however, as most probably muscular, although, indeed, its appearance as such to extremely indistinct. Within this each lobe is seen to consist of a closely united group of thick walled fusiform vesicles, lined by a delicate epithelial layer, embedded in a stroma of nucleated fibres, aptly compared by Luschka to the connective tissue of a sympathetic ganglion. Each of these thick walled vesicles is believed by Luschka to be a closed gland-follicle, containing a cellular and granular substance, indeed, at first sight, many of these appear very like the cortical cell-masses of the zona fascicularis of the suprarenal capsule. The upper end of each, however, is continuous with the minute terminal branches of the coccygea media artery and Arnold describes them as fusiform, aneurismal and tortuous vessels; fact, a dense cluster of branches similar to those already mentioned on the lower part of the middle sacral, with largely developed muscular and epithelial coats. The walls of some of these appear hyaline, but I believe them to be composed of true unstriped muscle. Within the lobules, and between the vessels proper, are polygonal, angular, or caudate cells, which resemble, more or less, those of a sympathetic ganglion, but are even more caudate, more acutely angled and prolonged than the nervine cells of sympathetic tissue. Future observers may perhaps be enabled to trace sympathetic filaments into these

We have thus six tissues entering into the composition of this body. 1. The general fibro-areolar capsule; 2. The special muscle capsule; 3. The aneurysmal vessels making up the largest part of its bulk; 4. The two sets of nerve-fibres; 5. Cells, tome of which are undoubtedly nervous, and, 6. The epithelium cell-lining.

The influence of sex m the development of this body, seems not to be very strongly marked; I have found it oftener in the form of separate lobules in males than in females, but I do not think this is anything but an accidental variation. In the eighth and ninth months of intrauterine life the component vesicles of each lobule are less closely united, and the lobules more separate than in the adult. I will not allude to the comparative anatomy of the organ at present, except to notice that I have seen the middle sacrals in the ostrich, monk-vulture and goose terminating in a tuft of interlacing and anastomising capillaries, but without any appearance absolutely similar to the coccygeal body. Meyer found it in the cat on the second caudal vertebra, but did not see it in the dog, rat, or mouse; and Krause found it larger in macacus cynomolgus than in man, but in the neighbouring species, macacus nemestrimus and sinicus, I have not found it at all conspicuous in point of size or development.

When compared with other tissues in the body, we find there are several to which it is more or less closely allied. Luschka compares it with the pituitary gland, the posterior lobe of which it slightly resembles in appearance, but we have none of the caudate or stellate cells in the latter body, nor have we the thick-walled capillaries in the former, but a closer ally is to be found in that other structure first pointed out by the same distinguished anatomist, the "intercarotic ganglion," a small ovate acuminated body, from two lines to a quarter of an inch in length, lying between the carotid arteries, which is composed of a dense rete of interlacing arteries, with very many sympathetic nerve-fibres, forming a close plexus, intermixed with undoubted nerve-cells. Now if we regard the caudate and stellate cells as nervous, and if we believe in the accuracy of Professor Luschka's observations of the junction of nerve-vesicles and fibres in this body, we will be led to the conclusion that this body is not only a small rete mirabile, but likewise centre of nerve-power, or a terminal sympathetic ganglion. It evidently has nothing in common with secretory glands, as its closed follicles are certainly vascular and not truly adenoid.

In conclusion, I would suggest that unless the name coccygeal gland has been too firmly established in anatomical literature, we should adopt the name suggested by Dr. Julius Arnold, and call this organ the glomerulus arterio-coccygeus; as the word gland has been forced to travel so far beyond the bounds of its legitimate meaning, and should as far as possible be limited in range to bodies possessing secretory functions.

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