Let Ha, Hb, Hc be the altitude feet; Ma, Mb, Mc the midpoints of the sides; Xa, Xb, Xc the orthocenters of HaMbMc, HbMcMa, HcMaMb (altimedial triangles) and xa, xb, xc the orthocenters of MaHbHc, MbHcHa, McHaHb. The lines Xaxa, Xbxb, Xcxc concur.