HEPATIC RESPIRATORY COMPENSATION AND BLOOD-VOLUME IN THE FROG (RANA-ESCULENTA)

In the frog, Rana esculenta (L.), the liver can change in volume by over 25%, depending on the respiratory conditions of the animal: in well-oxygenated specimens the organ can hoard about half of the total amount of erythrocytes in ifs sinusoids, and release them into the bloodstream under conditions of hypoxia. This phenomenon can be observed at a temperature of 6 degrees C by comparing the liver volumes and haematic values of chlorobutanol-anaesthetized animals exposed to the air or submerged in still water (a condition which induces hypoxia): the blood volume remains constant, at about 5 ml per 100 g of body weight, but red blood cell count and haematocrit value differ by as much as 50%. At 18 degrees C there is an increase in oxygen demand and in anaesthetized animals, which rely totally on cutaneous respiration, the compensatory liver mechanism can no longer be observed, since all the available erythrocytes are already circulating in a blood volume which, depending on respiratory conditions, can vary between about 7 and 8 ml/100 g. At 30 degrees C, cutaneous respiration alone does not allow the anaesthetized animals to survive long enough to stabilize their haematic parameters.