Abstract
The usual difficulties of quantitative plethysmography are multiplied when the method is applied to the intestine by the occurrence of intestinal contractions which may compress gases trapped within the lumen of the gut, even though the ends of the loop are open, and which, if strong enough, may pull mesentery into the chamber. These difficulties are obviated by the substitution of a simple gravimetric method, which permits, as an added advantage, simultaneous recording of intestinal motility.
A loop 6 to 10 cm in length, whose mesentery is long, is separated by incisions which are converged to the root of the mesentery, care being taken to preserve the loop's blood supply. With the dog lying supine, the loop and its prepared pedicle are lifted over a horizontal rod held in a clamp as close as possible to the root of the pedicle, and the pedicle is sutured to the rod (Fig. 1, a). The loop is threaded upon a light supporting rod (b), and the ends securely fastened. The projecting ends of the supporting rod are attached by means of threads to the horizontal beam of a spring balance (c). The tension of the spring and the leverage are adjusted until the loop on its rod, and the entire pedicle are swung clear of the animal. The loop should lie approximately in the same horizontal plane as the rod which supports the pedicle at the root.
It has been found simpler to record the movements of the horizontal beam indirectly, through a second light magnifying lever (e) as this permits adjustment of leverages without disturbing simultaneous ordinates on the record. If long loops are taken, strong contractions may exert pull on the pedicle, and so interfere with the record.
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