The author researched the degenerating nerve fibres anatomically on the brain and the spinal cord of dogs by Marchi's method, after removing the parts of each motor area for fore-limb, bind-limb and the mixed area for both limbs. The results were as follows: 1) The efferent fibres from each part of motor cortex and from the premoter cortex are intricated underneath the cortex. 2) The area for fore-limb contains 17 % of Betz's cells for hind-limb; the area for hind-limb contains 9 % of Betz's cells fore-limb, and the mixed area for bothlimbs contains 44 % of Betz's cells for fore-limb and 56 % of Betz's cells for hind-limb; that is to say, the Betz's cells for hind-limb extended much more into the area for fore-limb than those for fore-limb into the area for hind-limb. 3) One of the Neurons from the area 6aα of premotor cortex pass through the homolateral Nucleus caudatus terminated into the homolateral Nucleus lentiformis. 4) The motor cortex of dogs contains many extrapyramidal tracts. The area for forelimb contains them much more than the area for hind-limb, and in the midst of two areas the mixed area for both limbs is situated.