Forstaaelse af matrix klassen fra Managed DirectX

Jeg proever foelgende:

Matrix m = new Matrix();

m.Translate(new Vector3(55555, 0, 0));
System.Diagnostics.Debug.WriteLine(m.ToString());
m.RotateX(0);
System.Diagnostics.Debug.WriteLine(m.ToString());

Resultatet er:

Determinant: 1
M11: 1
M12: 0
M13: 0
M14: 0
M21: 0
M22: 1
M23: 0
M24: 0
M31: 0
M32: 0
M33: 1
M34: 0
M41: 55555
M42: 0
M43: 0
M44: 1

Determinant: 1
M11: 1
M12: 0
M13: 0
M14: 0
M21: 0
M22: 1
M23: 0
M24: 0
M31: 0
M32: 0
M33: 1
M34: 0
M41: 0
M42: 0
M43: 0
M44: 1

Hvordan kan det vaere at M41 vaerdien forsvinder i efter rotering?