On the function of the colonic spindle ( Fusus coli ) of the rabbit

Abstract

In previous notes 1 attention was drawn to an apparently undescribed, macroscopic, spindle-shaped, sphincter-bearing structure which connects the transverse colon of the rabbit with the descending colon.

One of the main functions of this organ apparently is to prevent, under normal conditions, the passage of scybala before they have been deprived of most of their water content. This seems to be accomplished largely by mechanical pressure exerted on the moisture-soaked scybala by the muscular spindle, the passage of the pellet into the descending colon being prevented by contraction of the sphincter at the spindle neck.

Evidence for this action is furnished by inspection of the active spindle in the living animal, and by inspecting and weighing the scybala in the order of their location in the transverse colon, the spindle and in the descending colon. In the living rabbit under morphin narcosis, where peristalsis has been accelerated by the intravenous injection of 0.1 to 0.3 mg. of physostigmin, one may occasionally see a spurt of fluid spiralling through the neck of the spindle into the descending colon, as a powerful per-istaltic contraction of the spindle tries to drive the mass through the closing sphincter. Obvious differences in the size, appearance and consistency of the various scybala in the different sections of the region in question also indicate the same fact. The most conclusive evidence of this mechanical dehydrating action of the spindle is however obtained when the scybala of these regions are weighed. The accompanying graph illustrates this statement; the normal weights are those which were obtained immediately after autopsy; the the weights of the same scybala are those obtained after clrying to a practically constant weight at room temperature, The weights on the same ordinate with the same symbol represent the same scybaltim in the normal and the dehydrated state; those on different ordinates are different scybala; only two series of observations from different animals are recorded, as they well illustrate what is generally found under normal conditions.