X-ray diffractometer analyses show that in bone diaphyses of dog, wolf, ox, aurochs, domestic pig and wild boar, the hydroxyapatite crystais are probably oriented with the basal pinacoid at right angles to the long axes of the bones; in some areas of the distal epihyses they parallel the long axes of the bones. No difference is found in the orientation of the crystals either between domestic and wild animais or between carnivores, ruminants and omnivores. -- AATA