This is known as the Tarsal Gland and I always remove it after I have gutted my deer in the field. I was told when I started many years ago that leaving this gland can cause poor taste in the meat, but I really don' t believe that theory to much anymore. I just simply remove it in the field so the deer can be tagged(this is where the meat seal goes), the deer is ready to be hanged to be skinned and I don' t have to worry about any taint from the gland when skinning(as i use a different knife to skin vs gut). I guess it is personal or taught when it is to be removed but seeing it has to be removed, I just perfer to disgard it in the wild and be done with the task.