Abstract
The intestinal intrinsic reflexes are comparatively studied using the small intestine in situ as well as in vitro of dogs, rabbits and guinea pigs.
1. When the contraction waves propagate along the wall of the small intestine in situ, the effect of the mucosal intrinsic reflex generally consists of the reinforcement of the waves above and their weakening below the spot stimulated. This effect occasionally can be mixed with that described in 2.
2. When the propagating waves are hardly seen in the small intestine in situ, as is the case in guinea pigs, there occurs just above the spot stimulated a rise in tone superimposed by pulsations which send out the waves, the one travelling orad, whereas the other travelling anad but inhibited in its course.
3. In dogs and rabbits stretching the wall of the small intestine in situ produces usually an extracontraction followed by the inhibition of motility both above and below the stimulated spot. In guinea pigs the same stimulus as above initiates easily a series of extracontractions, while an inhibition, which may be expected to follow them, is not conspicuous.
4. In the small intestine in vitro the effect of the intrinsic reflexes are abolished completely in a short time (about 30 minutes.) after its isolation. However, the extracontractions produced by stretching the intestinal wall are fairly strong. From the results described above it may be concluded that the so-called reflex peristalsis, observed in guinea-pig small intestine in vitro, is not neurogenic but myogenic in its nature.
