High magnification light micrographs of hematopoietic tissue structures in the liver. (a) Portal triad region (PTR). Numerous hematopoietic cells are seen in the connective tissue of the portal space. Spotted salamanders (Hynobius naevius). (b) Perihepatic subcapsular region (PSR). PSR is usually two to six cell layers thick, almost completely enveloping the hepatic parenchyma, with the visceral peritoneum adjoining (arrows). This tissue contains neutrophils (arrows) and eosinophils. African clawed frog (Xenopus laevis). (c) Inter-hepatic lobular nodule. Numerous hematopoietic cells (arrows) are seen in the sinusoidal capillaries of the hepatic lobule. Sakishima rice frog (Rana sp.). Scale bars = 100 μm.