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2. I. P. Pavlov, Complete Collection of Works [in Russian], Moscow-Leningrad.,2 book 2, (1951), p. 536.
3. I. K. Smirnov, Byull. éksper. biol., 8, (1962), p. 122.
4. E. N. Speranskaya, Methods of Operations of the Digestive Tract [in Russian], Moscow., (1962).
5. W. N. Boldyreff, Ergebn. Physiol., Bd. 24, S. 399 (1925).