[Bf-python] What are "Tail" bones?

[Carlos López]

I'm become crazy, i try to set a group of empties whereas the respective nodes of an armature. But when I access to a "bone.tail", I get an understandable vector, such as for example:

Bone:

RootX=1.958
RootY=0
RootZ=0.818
TipX=2.474
TipY=0
TipZ=-1.673

and I get:

TailX=2.42948...
TailY=0.423836...
TailZ=-0.62377...

It happens in the most cases, but not with "parent" bones (inmediatly child of the armature)
Do i do something wrong? Is it a bug?

Klópes