• (n.) The soft tissue, or substance, which, in developing bone, ultimately undergoes ossification.
(os´te-o-jen″) the substance composing the inner layer of the periosteum, from which bone is formed.
Os'te·o·gen noun [ Osteo- + -gen .] (Physiol.) The soft tissue, or substance, which, in developing bone, ultimately undergoes ossification. 
Type: Term Pronunciation: os′tē-ō-jen Definitions: 1. A bone matrix-producing tissue or layer.