There are appropriate and probably redondant receptors responding to imbalances of either the IC or EC space. Regulation of the EC space seems to evolve different distinct mechanisms for its two components i.e. volemic and interstitial space. They both elicit dipsic and natriophilic responses. Neurophysiology and neurochemistry of dipsic responses to the different types of dehydration is briefly reviewed. Hydromineral homeorheusis (1) can be achieved even without any participation of the orodigestive exteroreceptors, since animals survive without drinking, by self injecting water through an implanted atrial catheter. However, the contribution of exteroreceptors, particularly the oral ones, allow, in ordinary conditions, and even more in exceptionally stressing circumstances, to compensate for all imbalances more rapidly and in a more appropriate and amplified way. So, in everyday's conditions, drinking, in spite of its non-regulatory (i.e. non-triggered by actual imbalances of the inner milieu) appearance, results in an anticipatory and "luxurious" hydromineral regulation. This kind of ingestive behaviour is more adaptive than any behaviour which would tend only to correct imbalances after they happened.