Cross-section of keraphyllous and podophyllous laminæ (horny and fleshy leaves): _a_, inmost part of the solid wall; the horn-tubes approach very close to the horny leaves; _b_, body of the podophyllous membrane; _c_, horny portion of a horn-leaf directly continuous with the middle or principal layer of the wall; _c′_, a rudimentary horn-leaf that does not reach the body of the podophyllous membrane; _c″_, cross-section of horny leaves from the sides of which branch many secondary leaves (leaflets) composed of soft (young) horn-cells. These soft cellular horn-leaflets dovetail with the podophyllous or fleshy leaflets; _d_, podophyllous laminæ extending from the body of the podophyllous membrane; _d′_, podophyllous laminæ which have branched in their course to the wall, and thus given rise to _c′_, rudimentary horn-leaves; _d″_, cross-section of podophyllous leaflets extending from the sides of the podophyllous leaves; each two such leaflets secrete a keraphyllous leaflet between them; _e_, injected arterial vessels.] [Illustration: FIG. 37. Vertical section of the horny sole magnified: _a_, funnel-shaped openings which contain the horn-producing villi of the fleshy sole; they are of various sizes; _b_, horn-tubes; _c_, intertubular horn.] [Illustration: FIG. 38. Horny frog, with the posterior portion of the perioplic horn-band and the periople which covers the quarters removed from the hoof as one piece by maceration: _a_, trough-shaped depression of upper surface, which is divided posteriorly into the two upper channels of the frog by _b_, the frog-stay; _c_, part of the frog that is joined to the bar and forms the lateral wall of the depression (channels) on upper surface of frog; _d_, lateral surface of horny frog which, in its upper part, adheres to the bar, but below, at _d′_, lies free; _e_, point or summit of the frog; _f_, perioplic horn-band; _f′_, periople of the quarters.]