The thickness, shape and arrangement of elastic fibres within the nuchal ligament from various animal species.

As shown by statistical evaluation carried out within various animal species (e.g. ruminants, equids, carnivores and proboscidates) the thickness of elastic fibres of the nuchal ligament is a specific character, i.e. unrelated to the somatic size of taxonomically different specimens. On the whole, ruminants are characterized by thicker elastic fibres than those from equids and carnivores. Moreover, within ruminants a correlation between the thickness of elastic fibres and body size has consistently been found. However, this condition occurs only when comparison between zoologically related species is drawn. During postnatal growth clearcut structural changes were brought to light, represented by the following phenomena simultaneously taking place: a) increase in thickness and lenght of preexisting elastic fibres; b) a progressive increase in the number of fibre splittings as well as of collaterals given off by individual fibres along their extension; c) neoformation of elastic fibres, and their addition to preexisting ones. In the bovines, already at six months of postnatal life, the elastic fibres of larger caliber have attained their full size.