The pituitary body or hypophysis cerebri is a small body situated in the sella turcica. It is elongated from side to side, and is connected with the brain by a stalk which is continuous with the infundibulum of the third ventricle. It consists of two lobes, anterior and posterior, with an intermediate boundary layer. The two lobes are very different in structure. The posterior lobe presents chiefly bundles of spindle-shaped cells partly pigmented. The anterior lobe has the structure of a ductless gland, and is regarded as similar in structure and function to the thyroid gland, consisting, like it, of saccules lined with epithelium. In the intermediate zone there are spaces lined with ciliated epithelium.

Fig. 349. - From complex tumour of pineal gland, a, cartilage; b, gland tissue developing cysts; c, sarcomatous tissue.

Fig. 350. - Tumour of pineal gland, o, tumour; b, pedicle attached in situation of pineal gland; c, corpora quadrigemina; d, thalamus opticus; e, third ventricle; f, optic nerve; g, portion of tumour in aqueduct of Sylvius and fourth ventricle.

The analogy between the pituitary body and the thyroid gland has led to observations as to its condition in diseases of the thyroid, such as goitre and cretinism, and in cases where the thyroid has been removed. Removal of the thyroid in animals and man is followed by enlargement of the pituitary body, so that it weighs double the amount of the normal body (the normal weight in man is about "5 or •6 gramme). The body has also been found enlarged in cases of myxoedema and cretinism, in which diseases atrophic conditions of the thyroid exist, but it is doubtful if the enlargement is constant. In all these cases it is the glandular anterior lobe which increases in size.

Tumours also occur in the pituitary body. Most of the tumours have been connected with the anterior lobe, but a few are recorded in which the infundibulum or posterior lobe has been affected. The forms of tumours met with correspond with the glandular structure of the anterior lobe. Adenoma, consisting of a simple enlargement of the gland, is the form most frequently described. Weigert describes a case in which the tumour was as large as a hen's egg. These tumours are sometimes designated by the term struma pituitaria, this term again indicating a relation to the thyroid gland. Cysts which may be serous or colloid also occur. Teratoma is a rarer form. Sarcoma has been met with in some cases (Fig. 351).

Fig. 351. - Sarcoma of pituitary body.

It is of great interest that Acromegaly is found, if not universally, at least in a large proportion of cases, to be associated with enlargement of the pituitary body, and the enlargement is glandular and may be cystic. The enlarged gland may be as large as a hen's egg. There is great enlargement of the sella turcica and deformity of the parts around.

Literature

Pineal Gland - Weigert, Virch. Arch., 1875, lxv.; Falkson, ibid., 1879, lxxv.; Turner, Path. Trans., 1885, xxxv.; Coats, ibid., 1887, xxxviii.; Mihalkovics, Centralb. f. d. med. Wiss., 1874; Baldwin Spencer, (Pineal eye) Quart. Jour, of microscop. Sc, Oct., 1886. Pituitary body - see Literature fully in Boyce and Beadles, Journ. of path., i., 378, 1893; Weigert, Virch. Arch., lxv., 1875; Marie and Souza-Leite, Essays on Acromegaly, New Syd. Soc, 1891.