Histological sections of the head of Dipsas albifrons . Sagittal section of the head of Dipsas albifrons (MZUSP 17885); Paraffin section, Mallory trichrome staining (A). Higher magnification focusing on the mandibular region and showing the difference in staining between the anterior and the posterior regions of il2, composed by mucous cells (m) and seromucous cells (sm), respectively. A large duct (d-il2) connects the posterior region of the seromucous infralabial gland (il2) to the floor of the mouth (arrowheads); Paraffin section, Hematoxylin-eosin staining (B). Transverse section of the mandibular region showing contact between mucous and seromucous cells of the infralabial gland (il2) with its large duct (arrowheads) localized under the muscle levator anguli oris; Paraffin section, Mallory trichrome (C). Limit between the anterior mucous cells (m) and posterior seromucous cells (sm) of the il2; Historesin, Toluidine blue-fuchsin (D). Alcian blue, pH 2.5, histochemistry also revealing the highly positive result for the mucous cells (m). Nuclear staining with hematoxylin; Historesin (E). PAS histochemistry revealing the highly positive result for the mucous cells (m); Historesin (F). Bromophenol blue histochemistry revealing a positive reaction in the seromucous cells (sm), and contrasting with the negative result of the mucous cells (m); Historesin (G). Abbreviations: cp, compound bone; d, dentary bone; d-il2, duct of ventrolateral, seromucous infralabial gland; Hg, harderian gland; lao, muscle levator anguli oris; ng, nasal gland; oc, oral cavity; oe, oral epithelium; slg, sublingual gland; t, tongue. Scale bar in pictures A-C = 1 mm and D-G = 100 μm. Panels at the upper right corner denote position of the section in A, B, C.