Paraffin sections of air respiratory organ of catfish measured 24.6 (A), 26.3 (B-E) cm in length, stained with H&E. The arrow head refers to the respiratory epithelium in "A" and differentiating chondrocytes of elastic cartilage in "E". The red arrows refer to areas of interstitially located mesenchymal cells. The black arrows refer to the matrix of the newly formed elastic cartilage. Note: "H" hyaline and "E" elastic cartilage. Scale bars represent 80 μm in "A", 200 μm in "B", 20 μm in "C" 50 μm in "D".
