Richly Myelinated Hypothalamus
The mamillary body (BC13) forms the caudal segment of the hypothalamus. It appears as a round bulge, a myelinated region that is surrounded by a prominent capsule. The latter is formed by afferent and efferent fiber tracts, namely, medially by fibers of the mamillothalamic fasciculus (Vicq d'Azyr’sbundle) and the mamillotegmental fasciculus (Gudden's tract), and laterally by fibers of the fornix.
The mamillary body is divided into a medial and a lateral nucleus. The large medial nu-cleus (B14) contains small neurons. It isspheroid and makes up the round body that is visible at the base of the brain. The lateralnucleus (B15) is dorsolaterally attached tothe medial nucleus like a small cap. The mamillary body is surrounded by nuclear regions of the poorly myelinated hypo-thalamus, namely, the premamillary nucleus (C16) and the tuberomamillary nucleus(B17).