  The equations of motion of an isospin-carrying particle in a Yang-Mills and
gravitational field were first proposed in 1968 by Kerner, who considered
geodesics in a Kaluza-Klein-type framework. Two years later the flat space
Kerner equations were completed by considering also the motion of the isospin
by Wong, who used a field-theoretical approach. Their groundbreaking work was
then followed by a long series of rediscoveries whose history is reviewed. The
concept of isospin charge and the physical meaning of its motion are discussed.
Conserved quantities are studied for Wu-Yang monopoles and for diatomic
molecules by using van Holten's algorithm.
