Based on Capillary Gate Theory and Tissue Repair Theory, this paper describes the “Stress Repair Mechanism” (SRM) that maintains and repairs vertebrate tissues. It accounts for most of the mysterious manifestations of allostasis that remain unexplained by Hypothalamic-Pituitary-Axis (HPA) hormones and thereby enables the Universal Theory of Medicine predicted by Hans Selye. SRM activity explains hemodynamic physiology, capillary hemostasis, infarction, Korotkoff sounds, blood pressure, hypertension, diabetes, allostasis, allostatic load, anesthesia, analgesia, atherosclerosis, apoptosis, malignancy, eclampsia, sepsis, Multi-System Organ Failure (MSOF), the surgical stress syndrome, the fight or flight response, and numerous other manifestations of physiology and pathology. SRM function comprises the autonomic nervous system, the vascular endothelium, and the dynamic enzymatic interaction of blood-borne hepatic Factors VII, VIIIC, IX and X that produces thrombin, soluble fibrin and insoluble fibrin, whose combined effects account for all SRM manifestations. The vascular endothelium is a diaphanous neuroendocrine organ that lines all blood vessels and is the sole constituent of capillary walls. It secretes tissue factor into extravascular tissues, and insulates those tissues from the hepatic enzymes, so that tissue disruption exposes tissue factor to the enzymatic interaction and activates tissue repair. The vascular endothelium also releases nitric oxide and von Willebrand Factor into blood in accord with autonomic balance to regulate the enzymatic interaction to govern tissue perfusion and organ function. Therefore, continuously fluctuating combinations of nervous stimuli that affect autonomic balance and forces that disrupt tissues determine SRM activity.