/usr/include/OGRE/Volume/ is in libogre-1.9-dev 1.9.0+dfsg1-7+b4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/OGRE/Volume/OgreVolumeCSGSource.h
/usr/include/OGRE/Volume/OgreVolumeCacheSource.h
/usr/include/OGRE/Volume/OgreVolumeChunk.h
/usr/include/OGRE/Volume/OgreVolumeChunkHandler.h
/usr/include/OGRE/Volume/OgreVolumeDualGridGenerator.h
/usr/include/OGRE/Volume/OgreVolumeGridSource.h
/usr/include/OGRE/Volume/OgreVolumeHalfFloatGridSource.h
/usr/include/OGRE/Volume/OgreVolumeIsoSurface.h
/usr/include/OGRE/Volume/OgreVolumeIsoSurfaceMC.h
/usr/include/OGRE/Volume/OgreVolumeIsoSurfaceTablesMC.h
/usr/include/OGRE/Volume/OgreVolumeMeshBuilder.h
/usr/include/OGRE/Volume/OgreVolumeOctreeNode.h
/usr/include/OGRE/Volume/OgreVolumeOctreeNodeSplitPolicy.h
/usr/include/OGRE/Volume/OgreVolumePrerequisites.h
/usr/include/OGRE/Volume/OgreVolumeSimplexNoise.h
/usr/include/OGRE/Volume/OgreVolumeSource.h
/usr/include/OGRE/Volume/OgreVolumeTextureSource.h