Rat embryo E15. Frontal section of the submandibular gland region. (a) Haematoxylin‐eosin staining. Primordium of the submandibular gland parenchyma (P) and sublingual gland parenchyma (SL). CM, Meckel's cartilage; G, parasympathetic submandibular ganglion; L, lingual nerve; T, tongue. (b) HNK‐1 immunoperoxidase labelling. Primordium of the submandibular gland parenchyma (P) and sublingual gland parenchyma (SL). CM, Meckel's cartilage; G, parasympathetic submandibular ganglion; L, lingual nerve. (c) HNK‐1 immunoperoxidase labelling contrasted with haematoxylin‐eosin. Primordium of the submandibular gland parenchyma (P) and sublingual gland parenchyma (SL). G, parasympathetic submandibular ganglion.