Publisher Summary M. L. Tsetlin's concepts about nonindividualized control in the system of a multilevel regulation of movements were experimentally confirmed in a special series of experiments designed to study the restructuring of the interaction system among the nerve mechanisms on the spinal level. This chapter describes the experimental setup and the basic results. Gurfinkel’ and Pal’tsev have demonstrated the presence of cross influences in a human spinal cord: the knee jerk produced on one side changed in a specific way the state of the segmentary structures on the opposite side. The changes were revealed by monosynaptic testing. The data indicate that in a multilevel control system, the supporting motor apparatus in single-type movements restructures the interaction system of the auxiliary elements of the lower level, and the character of the restructuring is determined by the type of motor task.