On hyperimmunization of rabbits with pneumococcal vaccine, increase in the content of gamma globulin and fall of albumin in the serum are produced. In such hyperimmunized rabbits, investigations of the plasma volume, albumin degradation, and the distribution of the albumin intra- and extravascularly were undertaken by Sterling's method employing rabbit albumin labelled with I131.
The investigations do not suggest any significant alteration in the albumin degradation nor in the distribution between the intra- and extravascular albumin. It was demonstrated that the plasma volume increases simultaneously with increase in the gamma globulin and fall in albumin.
It is concluded that the fall in serum albumin observed is due to a regulative mechanism which attempts to maintain the colloid-osmotic pressure by increasing the plasma volume.