At the beginning of the 20th century, Charles Shier collected and studied under a microscope a group of patients who were close to seeing a doctor because they had noticeable bulging veins. After he established that this bulge was caused by stagnation of blood in the veins, he came up with tests such as phlebodynamometry and phlebodensometry to determine the condition of the veins in patients. He stated that if the veins are contused, symptoms similar to subcutaneous hemorrhages and bruising may occur.