After graduating from UT in 1893, Marion Dorset entered the University of Pennsylvania to study medicine. After one year there, he joined the US Department of Agriculture at the insistence of Dr. Charles Dabney, UT president on leave to serve as assistant secretary of agriculture. He completed his MD degree at George Washington University in 1896 while attending school in the evenings.
At his research job at USDA, Dorset discovered the cause of hog cholera (a filterable virus) and developed a serum for it. The eradication of hog cholera is his best-known accomplishment, but he also developed a rapid diagnostic test for pullorum, a devastating disease of chickens, that has saved poultry farmers millions of dollars. The purple ink, which replaced easily lost clip-on tags, used by government graders on meat to indicate that the meat is healthy and wholesome is a Dorset invention.
The Tennessee Legislature honored Dorset by including him in the Tennessee Agricultural Hall of Fame in 1951. He was a member of the Association for the Advancement of Science, the American Chemical Society, and the American Public Health Association. Iowa State University conferred the DVM upon him in 1915. He was inducted into the Alumni Academic Hall of Fame in 1994.