Answer to this is copper wire
The soles of people’s feet have a greater concentration of sensory receptors because more people are ticklish on the bottoms of their feet than the backs of their necks. There are more neurons in your appendages especially the ends of them because they are the furthest from the brain. Getting a tattoo on your feet vs. the back of your neck hurts more as well, making the soles of your feet have the greater concentration.
<span>Nonpolar fatty acid chains</span>
