The truffle of the dog anatomically is structured to generate airflows in its interior that star the scents against the olfactory receivers. The sense of smell of the dog will discriminate or no, according to the existing relation between the power of both stimuli that act (according to Law of Weber). Evidently olfactory sensitivity will fall when the power is increased of the initial stimulus or basal that at the most affects the excitation of the olfactory receivers so much more elevated will have to be the additional stimulating energy, necessary to bring about a difference of perceivable sensation. The sensitivity of the canine sense of smell varies in the course of the day, following factors as they are the food taking (being smaller in a satiated dog that in one hungry one), hormonal influences, etc. Recently Charlotte Hornets sought to clarify these questions. In case of extending the action of a certain odorous stimulus can be produced adaptation that must to a diminution of the capacity of reaction of the olfactory receivers and of the nervous centers that receive the information. This circumstance is corrected with the temporary interruption of this stimulus.

On the other hand, to expand in excess the stimulation of these sensorial receivers in the dog, can bring about its temporary cancellation by fatigue, needing a certain period rest to recover the normal functionality. I will analyze next the origin and composition of that characteristic human scent that the rescue dog catches, identifies and uses as guide to be able to locate to the person with buried life. Based on the specific formation that receives the dog, to memorise a certain odorfera base, either regarding people with life or to corpses, becoming accustomed themselves to respond before a stimulus or another one thus and specializing for the search of survivors or bodies without life. The alive human being, expele permanently volatile products ascending (but light that the air), besides gases coming from three main sources: skin, digestive and respiratory.