2. A neurologic or pharmacologic state in which painful stimuli are so moderated that, though still perceived, they are no longer painful: Dr. Jones, the neurologist, studied the effect of the new medication on the alganesthesia of patients from the combat zone.
Beyond the pleasures and assurances of touch, there is always the looming possibility of pain. As a survival mechanism, pain warns our brains of danger and tells us to act to correct or avoid the cause.
Pain receptors, free nerve endings, are spread over a larger area than any of the other sensory receptors. They completely ignore light contact, and only fire up if the stimuli threaten to damage the tissue.
There are more pain receptors in the skin than other types of skin sensors, but they are not evenly distributed; for example, the neck and eyelids are densely covered, but there are few receptors on the sole of the feet and on the ball of the thumb, which is why the needle prick for a blood sample is often done on the thumb.