Abstract
Various characteristics were investigated as functions of age on an experimental material consisting of 42 snakes Natrix natrix. In the first group consisting of 19 animals from 1 to 15 years of age the force to thermal contraction of the collagen fibre increases progressively with age without ever reaching a plateau one encounters in the case of mammals. The percentage of the total hydroxyproline content of collagen remained constant regardless of age, whereas the percentage of hydroxyproline "liberated" during thermal contraction decreased with age. The ageing of collagen therefore takes place at different rates in cold-blooded and warm-blooded animals. In another group consisting of 23 animals aged from 3 to 16 years, the investigation of oxygen consumption showed that basal metabolism remains virtually constant up to the extreme age, contrary to what is the rule in warm-blooded vertebrates.