It is the purpose of the communication to outline the viability of organismic tissues using selected examples for continued and catastrophic development, variation in the species specific life span, in the species specific size, metabolism, and different characteristics of cellular renewal from a species specific view. Finally, the application of tissue viability to medical research and clinical therapy was approached. It is the author's belief that a broader application of species specific facts to medicine would be an advantage to enhance our understanding of basic life processes and simultaneously human medicine.