Accessory lobes of Lachi
Transverse section of the spinal cord of a chicken (HE): position of the accessory lobe of Lachi
The accessory lobes lie dorsal to the lateral or denticulate ligament (ligamentum denticulatum) which attaches the pia mater to the arachnoidea and dura mater to provide stability to the spinal cord. In the lumbosacral region of birds, this lateral ligament is very well developed and has a transverse and a longitudinal component. On the picture above however, this division is not visible.
An arachnoidal trabecule covers each accessory lobe at the (ventro)lateral site. On the dorsal site, the accessory lobes are only covered by loose pia mater so there is close contact with the fluid in the subarachnoidal space.