...F. Giannessi; B. Fattori; R. Ruffoli; A. Gagliardo ABSTRACT The paratympanic organ (PO) in birds is a specialised sensory organ whose function is still unknown. G. Vitali, who first described the PO from observations of the behaviour of PO-lesioned pigeons, proposed that this organ was needed...

... with much scepticism, later with over-enthusiasm and unwarranted generalisation to all lesion situations, together with even less warranted attribution of various beneficial functional properties. Today, as the pendulum swings into a more reasonable position, some of the original observations, which...

... fibres chemotactically to their target fields during development, but is involved in target-controlled neuronal cell death and in regulation of the density of innervation of target tissues. In non-neuronal cells of the sciatic nerve, NGF synthesis is up-regulated during development and after nerve lesion...