 Complete the following phrase:  The beginning of the American Civil War interrupted Corsons education as he enlisted in Company K of the 4th Pennsylvania Infantry in April 1861, and mustered out as a sergeant in July 1861. Returning to Penn late that year, he served as a medical cadet at the army hospital on Cherry and Brad Streets while studying at the school. He enlisted in the 6th Pennsylvania Reserves 35th Pennsylvania Volunteers as an assistant surgeon in March 1863 after graduating with an MD degree, participating in the Battles of Gettysburg, Falling Waters, Manassas Gap, 