These differential parameters and in particuilar the equations obtained by putting them equal to zero play an important role in all questions connected with the study of the orthogonality of directions in higher spaces. In ? 1 I set up four fundamental theorems concerning determinants, using ordinary (not symbolic) notation. In ? 2 the symbolic method is applied to the construction of four important formulas which are used in the sequel and furnish at the same time numerous relations betweeni differential parameters. In ? 3 the directions orthogonal to all directions in a space of X dimensions given by the equations U', ..., U= const. are determined and ? 4 contains a general investigation of the conditions under which one space V', . n, -= const. contains directions which are orthogonal to all directions of another space U', .., U-A = const., and the determination of these directions.