Corns
A corn is small areas of very thick skin. A corn is roughly round in shape. Corns press into the deeper layers of skin and can be painful.

Hard corns commonly occur on the top of the smaller toes or on the outer side of the little toe. These are the areas where poorly fitted shoes tend to rub most.
Soft corns sometimes form in between the toes, most commonly between the fourth and fifth toes. These are softer because the sweat between the toes keeps them moist. Soft corns sometimes become infected.
Calluses
A callus is larger, broader and has a less well defined edge than a corn. These tend to form on the underside of the foot (the sole). Commonly they form over the bony area just underneath the toes. This area takes much weight when walking. They may be painless but can become painful
http://www.patient.co.uk/showdoc/23068875/

Hard corns are usually located on the top of the toe or on the side of the small toe. Soft corns resemble open sores and develop between the toes as they rub against each other
http://www.aofas.org/i4a/pages/index.cfm?pageid=3358

Le cor pulpaire
Il se rencontre sur le bout de l'orteil...
http://www.e-podologie.com/casclinique/orteils/46.html