Figure 7. Experiment E4. The support effect of a tripartite pneumatic system with one pair of ventral and a median dorsal pneumatic tube was studied. 7.1. Si was 435 mm aboveground at a pressure of 0.15 bar, with the dorsal balloon being under tension (arrow) and ventral balloons and segments under pressure and pushing proximally towards the pivot board. 7.2. Si reached 475 mm as one intersegmental wedge (marked in red) was inserted ventrally between the two proximalmost segments. 7.3. At a pressure of 0.15 bar and with the absence of intersegmental wedges, 54 g of iron powder were necessary to achieve siE1.