1. Trypanosoma gambiense showed marked difference in pathogenicity for rabbits as indicated by the tissue invasiveness of the muscle longissimus dorsi. 2. Two cases of rabbits infected with Trypanosoma gambiense produced the lesions in the muscle. The masses of great number of Trypanosomes appear- ing in the tissue spaces of interstitium of the muscles and hyperplasia of the reticular cells and lymphoid cells in the interstitium of these muscles are observed as the results of pathological changes.