The staining and refractive properties of bone.

T change in the refractive and stain­ ing properties of bone which occurs after pressure is applied to it was first described by Dreyer1 who applied pressure to the skull? of dead Vervet monkeys by strapping elastic bands under tension around them. The refractive and staining properties of the inner and outer tables of the calvaria of untreated monkeys differ in many sections cut from these bones. The inner table is usually non-birefringent and stains green with Masson’s stain, while the outer table tends to be birefringent and to stain brown. These differences are probably due to the muscular forces which act on it. This paper is a report on further investi­ gations on the effects of stress on bone and was undertaken to find out: (a) what changes occurred as a result of stress applied in vitro on bone; (b) if similar changes could be induced in vivo by func­ tional stresses and (c) whether these changes were permanent or reversible.