RESUMO
The present study aimed to compare between the anatomy, histology and histochemistry of two species belonging to two different families namely Muridae and Dipodidae. Muridae is the largest family of rodents in the world; it is represented in this work by fat sand rat Psammomys obesus. Four-toed jerboa Allactaga tetradactyla represents the other family, Dipodidae. Psammomys obesus lives in coastal presaharan region; the preferred habitat is saline marshes ,and wadis where halophytic plants were abundant. However, Allactaga tetradactyla, inhabites the salt marshes and clay desert areas of coastal plains. The investigated animals were collected from desert, weighed and transferred alive to the laboratory in separate cages then anaesthetized with ether, after which they were carefully dissected, organs are taken out and prepared for the histological and histochemical studies. The nucleocytoplasmic index of liver cells was calculated, kidney weighed and the relative thickness of cortex,, outer and inner medulla was measured and total glomerular number was recorded. The liver, as in mammalian species, is consists of five separate lobes. The mitotic index of Psammomys obesus is smaller than that found in Allactaga tetradactyla. This may he due to the increased activity of'Allactaga tetradactyla. In the kidney, the cortex is classified into three regions namely superficial, midcortical and juxtamedullary zones. Both number and diameter of glomeruli, glomerular volume and relative glomerular blood volume is greater in Psammomys obesus than that in Allactaga tetradactyla. These observations indicate the ability of Psammomys obesus to produce highly concentrated urine than that of'Allactaga tetradactyla