In 2012 release, you could pick a headcrab’s and houndeye’s corpse. Now you can only pick the ones that were placed within the level (that were never alive in the game to start with) but not the ones you generated by killing actual enemies. These corpses placed within the level also spill blood for a few seconds upon loading a saved game, but they are actually supposed to be dead and bleeded-out long time ago, like the dismembered bullsquid in Questionable Ethics, lying on a table in the room where you get the crossbow.
