ULMONARY embolism is always P the most tragic of postoperative complications, whiIe postoperative phIebitis is disappointing to the patient as we11 as proIonging hospitaIization and frequentIy incapacitating one for months, so that any measure that wiI1 prevent or reduce their occurrence is deserving of serious consideration. The history of both conditions extends back to the earIier surgica1 pathoIogists, particuIarIy Virchow and WeIch who for practica1 purposes thirty or forty years ago gave us descriptions of their genesis and symptoms which have Ieft IittIe to be added since that time. Most of the recent Iiterature has been more in the way of accumuIation of data dealing with the frequency of the condition, aIthough a few writers have approached this subject from the angIe of prophyIaxis. WiIson in 1912 stated that at St. Mary’s HospitaI the incidence of puImonary emboIism was .07 per cent. Henderson at the Mayo CIinic from 1917 to 1927 found a mortaIity rate of .37 per cent due to this cause. W. A. Lister from the PathoIogicaI Institute of the London HospitaI states that in 4000 major surgicaI procedures there were 194 cases of pulmonary emboIism and 172 cases of emboIism due to fractures. E. C. Lindsey reports a .3 per cent surgica1 mortaIity from this cause. MiIIer and Rogers8 reported I 13 cases from the Massachusetts Genera1 Hospital, 19001927, 76 surgica1 and 37 non-operative. Most Iiterature deaIs with the more fata puImonary emboIism, but the fact that postoperative phIebitis and puImonary embolism primariIy arise in the same manner, and are caused by the same influences renders advisabIe the study of both conditions conjointIy. Any measure which wiI1 favorabIy inffuence the occurrence of one wiI1 have a Iike influence upon the other. With but very Iittle variation most of those who have studied the subject accept Aschoff’s views upon the origin of emboIism and thrombosis as authoritative. He hoIds that thrombosis is the result of a number of variabIes, and that there is not a singIe cause, but quite a number of different conditions which are cIoseIy reIated to the occurrence of thrombosis. Amongst these may be mentioned (I) changes in the bIood pIasma (diminished or increased coaguIabiIity); (2) changes in the 61ood eIements (increased or diminished powers of aggIutination) ; (3) changes in the blood ffow (sIowing and formation of eddies), and (4) changes in the vessel wall itseIf (endotheIia1 damage). Lister deduced from his investigations that impeded venous flow pIus incision into the anterior abdominal waI1 are the principa1 provocative factors in postoperative thrombosis, which is another way of stating that thoracic breathing and muscuIar reIaxation are the main causative factors. Waiters considers that a Iowered metaboIic rate is a decisive factor, or rather that the principa1 cause of the condition is a slowing up of the bIood stream, and to overcome this the administration of