Apothecary

An apothecary is a Space Marine specialist, equivalent to a Medic. Armed with standard Space Marine gear and a Narthecium. If a Marine is too damaged to be saved, or has died, it is the Apothecary's duty to extract the gene seed from his dead brother. They also monitor Space Marine Initiates to make sure they're healthy or to check for unhealthy mutations.

When they aren't busy extracting miscellaneous items from a Space Marine's anus, Apothecaries work tirelessly to find a cure for Space AIDS, because Space Marines can't stop fucking each other. That totally wasn't a subtle jab at stupid chapter rivalries.