Jenkins graduated from
Moores Hill College (now the University of Evansville) in 1869 and served as a teacher, high school principal and superintendent in the public school systems of
Indiana,
Wisconsin and
California, returning to Moores Hill College in 1876 to take up a post as a professor. In 1883 he was appointed to the faculty of the Indiana State Normal School (now
Indiana State University) at
Terre Haute and he became Professor of Biology at
DePauw University in 1886 where he remained until 1891. In that year he was appointed a founding faculty member at
Stanford University and he remained there until he retired in 1916 when he was Professor Emeritus of Physiology. He collected
specimens on expeditions with
David Starr Jordan and
Barton Warren Evermann and he wrote works on the fishes of the United States of America and of
Hawaii, as well as on invertebrate nervous systems. Jenkins also wrote a series of text books on physiology for
Indiana State University. He was a founder member of the
Indiana Academy of Science and its first treasurer. Among the many scientific societies he was a member of were the
American Association for the Advancement of Science, the
American Physiological Society and the
Cooper Ornithological Society. ==Personal life==