Tannic acid mixed with glutaraldehyde or paraformaldehyde is a strong fixative, which can precipitate amino acids and oligopeptides such as arginine and glutathione. Tissue specimens fixed with this tannin-aldehyde mixture are useful for histochemical studies, including lectin labeling, immunological staining and tissue enzyme digestion.
A human heart with an unusual superior vena cava was dissected. This dissection suggested that the sinus coronarius and its branches (main veins of the heart) were left-sided vessels, and that the anterior cardiac veins were right-sided vessels. It was also suggested that the sinoatrial node near the right superior vena cava was the right-sided center of the conductive system, and that the atrioventricular node close to the sinus coronarius or left superior vena cava and descending into the ventricle was the left-sided center of this system. The left coronary artery was thicker than the right one, and issued circumflex and anterior interventricular arteries. These findings indicate that the human heart mainly consists of left-sided elements.
The cerebral cortex, cerebellar cortex and hippocampus of adult mice were studied by light and electron microscopy of tissue sections. Dark neurons were well stained with nuclear fast red, and clearly distinguishable from light neurons. The dark neurons were classified into active and resting types. Active types were characterized by their well developed Golgi's complexes. Resting types contained poorly developed Golgi's complexes. These findings indicate that active dark neurons are converted into the light neurons via resting dark neurons.