The Lax-Nelson Lagrangian theory of an arbitrary dielectric crystal in interaction with the electromagnetic field will be applied to several interactions. The elastooptic effect will be studied in a crystal near a second-order phase transition. This will explore how the asymmetry of the linear elastic stiffness tensor, produced by coupling to rotation and recently predicted by this theory, can be measured. The recent prediction of this theory that natural optical activity can arise form three distinct mechanisms in crystals and produce terms having two types of frequency dispersion will be extended to magnetically induced optical activity (Faraday effect). The acoustic analog of optical activity, acoustic activity will also be explored. The frequency shift of optic modes caused by the application of stress or an electric field will be calculated and related to the elastooptic effect. A resolution to the Minkowski-Abraham controversy will be presented based on the general conservation laws of real momentum and pseudo-momentum expressed in the spatial and material coordinate systems respectively and upon our previous analysis of the general nonlinear stress tensor of a dielectric crystal in interaction with the electromagnetic field. The Lagrangian theory will be generalized to include intrinsic spin of the particles composing the crystal lattice. This will allow treatment of ferromagnetic and ferrimagnetic interactions. This will be accomplished by the introduction of Grassman variables.
