Vivisection - artificial direct effect on the organs and tissues of an animal in acute experience. Vivisection is often ends with the death of the animal. However it gives an opportunity to study the activity of organs and systems in the body in conditions close to natural. Vivisection allows more precisely to trace changes of physiological processes in natural impacts on them, and artificial (different types of stimuli, transplantation, exposure to chemicals). The pain reduction is achieved anesthesia. It should be remembered that the data of vivisection cannot be unconditionally transferred to humans.