In 1977 we had the opportunity to use a socalled „mechanical oscillator technique“ which was developed by O. Kratky and coworkers (1969) for the continuous measurement of the mechanical density of fluids. The device is constructed by A. Paar KG in Graz. The working group at the Department of physiology performed measurements in animal experiments and also in a patient during hemodialysis. A summary of the first results were published at the 13. International Conference on Medical and Biological Engineering (1982). Here I report about the Doctors Dissertation by F. Vauti in 1984. The following data were recorded: body temperature, heart rate, blood pressure. blood density, plasma density, hematocrit, hematocrit, number of erythrocytes and of leucocytes, were measured in capillary blood - during day and night. In addition to the results in Dr. Vauti’s Dissertation, measurements performed in a healthy person in a laboratory of the Surgical Clinic have been made. The most surprising result was that the oscillations of the arterial blood density werde synchronized with the respiration. In summary, all measurements demonstrated synchronizations: 1.Density of blood and time of day and 2. Density of blood and respiration. T. Kenner: Physiological Measurement in Circulation Research. Med. Prog. Technol. 9, 67 – 74 (1992) F. Vauti : Der Einfluss der circadianen Rhythmik auf hämatologische und cardiovasculäre Parameter beim Menschen in der Orthostase unter besonderer Berücksichtigung der transkapillären Flüssigkeitsverschiebung. INAUGURAL-DISSERTATION, Graz, 1984.