. The endocrine organs; an introduction to the study of internal secretion . IG. 28.—Part of lobule of the thymus of a child. Magnified 60 , cortex ; m., medulla ; 6., b., large blood-vessels in connective tissue trabeculee. by an increase in connective tissue, the whole organ becoming smaller andoften embedded in a mass of fat. Occasionally it remains fully developed ;such cases are generally associated with an unusual development of lym-phatic tissue in the body, the condition being termed status lymphaticus. In its developed condition the thymus consists of two main lobes, oneon
. The endocrine organs; an introduction to the study of internal secretion . IG. 28.—Part of lobule of the thymus of a child. Magnified 60 , cortex ; m., medulla ; 6., b., large blood-vessels in connective tissue trabeculee. by an increase in connective tissue, the whole organ becoming smaller andoften embedded in a mass of fat. Occasionally it remains fully developed ;such cases are generally associated with an unusual development of lym-phatic tissue in the body, the condition being termed status lymphaticus. In its developed condition the thymus consists of two main lobes, oneon each side, the lobes themselves being subdivided into lobules and thewhole strung together in an irregular manner along a strand of connectivetissue which sends offsets into the lobes, subdividing the lobules from oneanother and sending partial septa into the individual lobules. The con- 45 46 The Endocrine Organs nective tissue conveys blood-vessels, lymphatics, and nerves to and fromthe organ. Each lobule is composed of a cortex which is very dark in stained sections. FIG. 29.—Medulla of thymus of child. Magnified 300 diameters. The smalldarkly stained cells are lymphocytes. The preparation shows two or threeconcentric corpuscles, and blood-vessels. and a medulla which is lighter (rig. 28). The difference is due to the largenumber of lymphoid cells in the cortex, which is densely packed with them. The medulla is formed ofa cell-reticulum as a basis, in themeshes of which are a considerablenumber of lymphoid cells; and inaddition the characteristic concen-tric corpuscles of Hassal, whichare formed by nests of epitheliumcells surrounding one or more cellswhich occupy the centre of the nest(figs. 29, 30). Some of the concen-tric corpuscles are compound, havingmore than one centre. Occasionallythe medulla is found to containsmall ciliated cavities, and rarelystriated muscle-fibres are seen with-
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