Abstract
1. A non-recirculatory perfusion system has been developed suitable for the perfusion of the hind limbs of small experimental animals.2. By means of it a solution of T. 1824-labelled serum albumin has been introduced into the vascular compartment of the hind limbs of female rats under isogravimetric conditions. Excision and analysis of certain muscles has been used to provide information concerning the percentage distribution of the labelled albumin within these muscles.3. Experiments have been carried out in vivo employing [(131)I]labelled serum albumin and [(51)Cr]labelled erythrocytes in order to compare the vascular volumes determined under in vivo conditions and in perfusions, and to estimate the capillary haematocrit in vivo.4. The physiological validity of the methods used and the results obtained has been discussed.