A contribution to the pathology of the thymus gland / by Leonard S. Dudgeon.

  • Leonard Dudgeon
Date:
1905
Catalogue details

Licence: In copyright

Credit: A contribution to the pathology of the thymus gland / by Leonard S. Dudgeon. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    of unequal size, separated by an intervening fissure. Tlie main portion of the gland is situated within the thorax, but both lobes send prolongation upwards for a short distance into the neck, sometimes reaching to the level of the thyroid. The thoracic portion of the gland lies in the superior and anterior mediastina, and extends downwards as far as the level of the fourth co.stal cartilage, lying on the surface of the pericardium, and superficial to the in- nominate veins. I have frequently noticed, in large and enlarged thymus glands, a small intermediate or third lobe, and other observers have had a similar experience. In the large majority of cases, however, such as one sees in the post-mortem room of a children’s hospital, the thymus gland has either one or two lobes. According to liektoen, “ Small accessory thymic glands may occasionally be found about the periphery of the thymus body ”; but I have never seen any- thing to justify the statement. It is also stated that the gland may be completely absent, but one would have to satisfy oneself by microscopical examination of the connective tissue from the normal thymic area before such a statement could be accepted as true. Sir John Simon remarks, “I have never noticed absence of the thymus except in cases of true acephalism.” The blood supply is derived from the inferior thyroid, internal mammary and possibly other arteries, and the gland is drained by the inferior thyroid, internal mammary, and both innominate veins. The nerve supply, according to most authors, is derived from the vagus and sympathetic trunks. The cavity in the centre of each lobe is one of the most conspicuous features of large and enlarged thymus glands. The size of the cavity varies according to the freshness of the tissues. If we leave a thymus gland exposed to the air for some hours, we shall find at the end of that time that there is a large cavity in each lobe, filled with thick, yellow, often blood-stained fluid very similar to pus. The presence of this fluid has frequently given rise to various mistakes, more especially to the diagnosis of abscess formation. Sir Astley Cooper compared this fluid to chyle. If we squeeze a perfectly fresh and normal gland, this fluid wells up in all directions, but it apparently increases by the breaking down of the gland tissue, and will eventually give rise to a definite cavity in the centre of the lobe. I consider that this fluid arises from a liquefaction of the elements of the thymus, and it consists almost entirely of lymphocytes. Histology. Before considering the pathological changes, it may be well to refer to a few essential points of the normal histology of the gland. The thymus gland is enveloped by a sheath of connective tissue, which sends off septa from its deep surface; these pass into the gland substance and separate the lobules from each other. Each lobule is composed of clusters of adenoid tissue with a small amount of connective tissue intervening. A follicle consists of an outer cortical and an uiner or medullary portion, but in the former the lymphoid cells are closely packed, whilst in the medulla of the gland they are much less numerous, and the retiform matrix is coarser. The medulla contains the concentric corpuscles of Hassall. These bodies, which are first observed about the fourth month of foetal life, are spherical in shape, and consist of flattened cells arranged concentrically around one or more, central cells, and are frequently enclosed in n further group of flattened cells, i.e. they are compound. I consider, however, that the central portion of Ilassall’s corpuscles has often undergone some form of degeneration. These concentric bodies are remnants of the epithelial structures from which the gland was originally developed, and occur as islets owing to the
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