The study of the normal and pathologic significance of the blood pressure has been a subject of interest for many years. It was not until mechanical instruments were available, however, that any accurate measurements of blood pressure were taken. Ludwig, in 1847, first obtained a blood pressure tracing. In 1882, almost forty years later, V. Basch invented the tonometer. Roy and Adami in 1890 modified this for external use and Riva Rocca in 1896 manufactured the first practical clinical instrument for taking blood pressures.
During the last two decades, the clinical literature has been filled with blood pressure observations on both man and animal. The normal blood pressure of man has been established by a score of investigators; Alvarez,1 Barach and Marks,2 Cook,3 Dawson,4 Fisher,5 Frau Wolfensohn-Kriss,6 Goepp,7 Greene,8 Kammerer,9 Lee,10 MacKenzie,11 Michael,12 Sallom,13 Smith,14 Sorapure,15 Weysse,16 and Woley.17 The series by Goepp included 9,996 determinations; that of Fisher, 12,647;