through various stages of partial block. Through this experiment, Hirschfelder and Erlanger discovered that in order to pass off an atrioventricular block, the auricles must be slowed down. In stimulating the vagus the degree of heart-block increases thereby facilitating the stoppage of the heart block. In an experiment that underwent not long after, Hirschfelder and Erlager studied the effects of time on the stoppage and were able to conclude that the weaker the ventricular muscle, the longer the stoppage. University of Minnesota After moving to Minnesota in 1913, Hirschfelder began pursuing research directed toward pharmacology. It is said that Arthur Hirschfelder was unable to attain a license to practice medicine in Minnesota because when as a medical student at Johns Hopkins, the medical institute did not provide a "physical diagnosis" course which is required and stated in the Minnesota Medical Practice Act. Due to this reason, Hirschfelder directed his focus towards pharmacology. He met Merrill C. Hart, an organic chemist, whom he collaborated with in researching organic compounds to use as anesthesia. Through this research, Hirschfelder and Hart synthesized and discovered local anesthesia made of saligenin to replace the use of cocaine in cystoscopy. This 4% solution drug is mildly antiseptic with the ability to kill 2% of pyogenic cocci bacteria in less than 30 minutes. This anesthesia had poor longevity and was not considered as a clinical option. Later in 1913, Hirschfelder published part II of his book on Diseases of the Heart and Aorta. In this, he discussed the effects of drugs on various cardiac diseases, detailing the pharmacological and therapeutic uses of various drugs. Calcium Salts Hirschfelder listed calcium salts as cardiac stimulants and discovered that calcium lactate, previously used to treat typhoid fever, had no effect on controlling pulse-rate and blood-pressure. However, when researchers injected calcium chloride into the heart, the heart was able to revive to a regular heart rhythm with moderately high blood pressure. Caffeine Through various papers and the plethora experiments occurring around the world of caffeine, Hirschfelder knew caffeine with become the next big thing in the cardiac world. Hirschfelder stresses the consequences of the therapeutic use of caffeine. Upon ingestion, caffeine's ability to relieve drowsiness, Hirschfelder was able to find that its pros were often accompanied by insomnia, nausea, vomiting, vertigo, palpitation, and more. He noticed that these negative side-effects set in at the same time, or earlier, than the time