Cephalo-caudal differences in testis differentiation. Data is from a 1-year-old male. A chart of the testis is shown with the anterior part (APT) and the first testis lobe (1TL). The diagram shows two testis parameters measured at different points between its connection to the lung and its posterior extremity: the surface of the testis when observed in cross sections and the circularity of those sections. (a), (b) and (c) show sections stained with hematoxylin-eosin-light green, performed in three different regions indicated on the diagram and on the chart of the testis. BV = blood vessel, Cy = Cyst, ED = efferent duct, IT = interstitial tissue, Lo = lobule, PGC = primordial germ cells, SC = somatic cell.