It's normal for ANY male dog.
What you are seeing is the bulbus glandis (also called a knot). That is what "locks" up a male to a female when they are bred ---- Also referred to "tying up".
When males are excited, you can clearly see it more.
_________________
CoonDawgs.com - A Site Designed for Coon Hunters
American Houndsmen - Vintage Hound Hunting
Coon Dog Cemetery - Key Underwood Coon Dog Memorial Graveyard
HuntingBassets.com - A site dedicated to hunting with Basset Hounds