a method and apparatus for investigating various parameters of biofluids , such as blood , particularly protein and cellular concentrations and cellular volume utilises the application of at least two a . c . frequencies , preferably simultaneously , in the range 0 . 1 to 60 mhz to a sample of the fluid and receiving and resolving the frequencies after passage through the fluid . the received frequencies are processed to derive corresponding d . c . voltage amplitudes which are mathematically processed to provide a numeric output correlating with a parameter under investigation , a new parameter named instant sedimentation rate is disclosed .