In this summary, all that can be attempted is a brief discussion of some of the results obtained by laboratory investigations of several types of patients for whom the hazard of a major surgical operation is more serious than for the average patient. This discussion will be of laboratory data, their significance, and their indications for certain preoperative and postoperative treatment of these patients. In the beginning, let me confess that nothing new is presented, but, on the contrary, I must recall something which is very old and with which all are familiar. When Lister had perfected his antiseptic technic, the surgeons who visited his clinic are said to have commented, "This elaborate method is possible in Lister's operating room, because of the unusual energy, care and enthusiasm present there; but such infinite care of detail will not be possible in other surgeries." This opinion has been completely disproved by