Survey of the Literature Effect on Amphibians Effect on Mammals Size of Blood Vessel Blood Pressure Heart Rate Autonomic Nervous System Original Experiments Experiments During Amytal Anesthesia Effects After Intravenous Administration Effects After Local Administration Experiments During Ether Anesthesia Effects After Intravenous Administration Effects After Local Administration Experiments After Recovery from Ether Anesthesia Effects After Intravenous Administration Effects After Local Administration Effects of Caffeine, on Animals with Low Blood Pressure Experiments During Amytal Anesthesia Comment Summary SURVEY OF THE LITERATURE The effect of caffeine and its compounds on circulatory phenomena has long been of interest to physiologists, pharmacologists and clinicians. Since the isolation of the drug in 1820 by Runge, research has piled on research, until at present the literature is extensive. Stuhlman and Falck1not only mentioned this fact, but enumerated fifty-one articles published between 1820 and 1856. Most of the study has been centered on