Accessory lobes of Lachi

Transverse section of the lumbosacral vertebral column and spinal cord of a chicken (HE) (1)

In the lumbosacral region in birds, segmentally organized ventrolateral protrusions of the spinal cord form accessory lobes (accessory lobes of Lachi) (nuclei marginales). These lobes consist of multipolar neurons, myelinated and unmyelinated axons, glycogen cells, glial cells and capillaries. The accessory lobes are believed to have a mechanosensory function, more specifically to form an extralabyrinthine organ of equilibrium.

The accessory lobes were previously called major nuclei of Hoffman von Kolliker, analogues to the minor nuclei of Hoffman, which  are small zones of marginal neurons in the white matter of the spinal cord in the neck region.

In pigeons, ten pairs of accessory lobes are distributed from T6/L1 to S5/S6.

The transverse section above is a more oblique section in which the accessory lobe is made visible at only one side.