“…Thiry-Vella loops, which date to the 1800s, were used to study enzymatic activity (Johnston, 1932) and absorption (Raudin et al, 1933;Newman and Taylor, 1958). Problems with maintenance of a functional epithelium in the absence of a constant exposure of the mucosa to chyme led researchers to develop other cannulation procedures such as reentry cannulas (Phillipson, 1952;Harrison and Hill, 1962; Goodall and Kay, 1965) and double reentry cannulas (Homey et al, 1972(Homey et al, , 1973Phillips et al, 1978). Also, widespread use of cannulas installed in a variety of locations along the gastrointestinal tract, designed simply to sample digesta and intended to be used in conjunction with inert digesta markers, came into use and continue to be widely used.…”