The Similia Principle, the basis of homeopathy, implies that substances initiating symptoms when applied to healthy biological systems can be utilized as remedies to treat a diseased system with similar symptoms. Depending whether the remedy substance was of the same type as the etiologic agent, treatment is classified as either homologous or heterologous. The intact rat is the biological system most utilized in basic science homeopathic research. The Homeopathy Basic Research experiments (HomBRex) database (about 1300 experiments on model biological systems in homeopathic research) was analyzed for homologous and heterologous treatments of disease states of intact rats. The relationship between the Similia Principle and hormesis is discussed.