OBSERVATIONS ON CALVARIAL GROWTH IN RACHITIC AND HEALING RATS

The histology of the rachitic and healing sutures, ectocranial and endocranial surfaces of the rat calvarium is described in this paper. Osteoid margins were evident on all surfaces observed at seven days in rachitic rats and were seen to increase in equal amounts on either side of the sutures as the disease process continues, while the osteoid accretion on the ectocranial and endocranial surface revealed differential growth rates throughout the experimental period. The pattern of osteoid deposition is suggestive of a process of calvarial reshaping from the younger animals to the older ones. The marrow spaces were gradually occluded by the osteoid deposition on their margins. On induction of healing by vitamin D, the osteoid was calcified and then differentially resorbed by osteoclasis. The first osteoclasts were seen at the anterior lambdoidal suture two days after vitamin D administration. At the end of four days of healing, osteoclasts were evident at the coronal, the anterior lambdoidal and the posterior lambdoidal sutures as well as the endosteal sides of the ectocranial and endocranial surfaces. There were no osteoclasts in contact with uncalcified osteoid throughout the entire experimental period. Only the osteoid assumed to be overgrowth was resorbed, while osteoid in some areas was calcified and then retained. At the end of a ten day healing period, the calvarium of the experimental animal was virtually identical to that of the control animal, with the exception of some localized osteoclasis continuing. A rachitogenic diet supporting excellent health and growth in the albino rat is described in this paper. Copyright © 1969 Wiley‐Liss, Inc.