Division of Biochemical Development and Molecular Diseases, Joseph Stokes, Jr Research Institute, Children's Hospital of Philadelphia and the Department of Pediatrics, Medical School of the University of Pennsylvania, Philadelphia, Pennsylvania 19104, U.S.A. and *Department of Physiology, University of Texas Southwestern Medical School, Dallas, Texas 75275, U.S.A.
(Received 6 January 1977)
It has been shown that diet and endocrine regulation are two factors influencing perinatal development of various intestinal enzymes (e.g. Koldovsky, 1972; Koldovsky, Jumawan & Palmieri, 1975; Yeh & Moog, 1975). So far, most studies have been performed in vivo; studies using organ cultures are hampered by the short viability of the preparations (Trier, 1976). Ferguson, Gerskowitch & Russell (1973) introduced an ingenious method of implanting under the kidney capsula of adult mice isografts of foetal small intestine, and these developed in a similar manner to normal intestine in situ. Since the isografts were never exposed to external stimuli (food, etc.),
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