Figure 13 in Studies on spider respiration and circulation by Victor Willem

Figure 13. Schematic structure of a lung. It is depicted in a (longitudinal) vertical section, but the spiracle is shown as if on a rather horizontal section: the lamellae, whose number has been greatly reduced, have been considerably thickened in order to visibly indicate their elements: the cuticular layers, the chitinogenic cells, the dorsal face projections, the (simplified) cuticular productions of the free edge, the cellular columns going from one face to the other, and the sinuses. s, spiracle; m, dilator muscle of the vestibule; v, cuticular wall of the vestibule; Vp, pulmonary vein; Lv, ventral sinus, shown in the background. [There is no reference to this figure in the text]