Histomorphometric and scanning electron microscopic analysis were perf
ormed on 74 embryos and foetuses and on 20 sheep (early post-natal to
adult age). Histodifferentiation of the reticulum took place at 33 day
s of foetal life. Reticular ribs were observed as evaginations of the
epithelial stratum germinativum at 64 days. Neutral mucopolysaccharide
s first appeared in epithelial cells at 46 foetal days, thereafter to
decrease gradually in number, subsequently stabilising in postnatal li
fe. Acid mucopolysaccharides, mucins and mucoid compounds were not det
ected. Growth curves and formulae were constructed for each tissue lay
er. Initial test involved multiplicative (y=axb), linear (y=a+bx) and
polynomial model (y=a+bx+cx2+dx3).