During World War 1, new medical technologies and practices were developed out of necessity to treat the large number of casualties. X-ray machines became portable and useful for surgeons to locate embedded shrapnel and bullets. Blood transfusions also advanced due to knowledge of blood typing, allowing blood to be stored and saving many lives. Advances were also made in plastic surgery, skin grafts, and prosthetics to treat extensive injuries to soldiers' faces and limbs. While medical knowledge grew from these experiences, infections still posed a major risk to wounded soldiers.