Rashevsky's treatment of general binary relations between sets of biological elements is extended using the novel mathematical concept of lattice-valued relation (1.v.r.). This yields a quantitative measure of the strength of the relations between components of a biological organism, and some illustrative examples are given_ Specific 1.v.r.'s are used to define (more precisely than in Rashevsky's preliminary theory of binary relations) the biologically important relationships amongst hormones, metabolism and energy exchange involved in metabolic reactions. The 'strongest link' between the set of hormones and the set of metabolic reactions is quantified using a special 1.v.r., and other specific biological realisations of lattice-valued relations in abstract-relational biology are presented. L.v.r.'s may also be regarded as a form of G-relation in relational biology, or as a particular case of generating diagrams. Further possible developments of this approach, using more complex tools of the newly developed mathematical theory of lattice-valued relations, such as function space 1.v.r., group 1.v.r., 1.v.r. morphisms, 1.v.r. homology and n-ary 1.v.r.'s are suggested.