In preparation to become a missionary he studied at Holliston & Wilbraham, MA and Kent's Hill, ME academies, 1835-1839. He studied medicine at Dartmouth & Cambridge Medical colleges. He was licensed to preach by the Boston Quarterly Meeting, Lowell, MA, April 1839 and was ordained an evangelist in Lowell, May 7, 1840. He received his M D from Dartmouth College, 1850; and DD, Hillsdale College, 1881. He sailed for India, May 16,1840 where he was a missionary at Balasore, Orissa, India, October 1840-52; Midnapore, Bengal, 1865-83. Otis returned to the United States, September 1883 and again he sailed from Boston for India, January 23, 1886. He published ''A Medical Guide in Oriya and Bengalee.''