John Henry Welsh (August 25, 1901 – November 26, 2002) was an American physiologist who pioneered early work on serotonin as a neurotransmitter in invertebrates.
He taught summer courses in invertebrate physiology at the Marine Biological Laboratory in Woods Hole for nearly 40 years.
Welsh attended Berea College, in Kentucky, attracted by an aunt who was teaching there following missionary work in Africa.
[1] Welsh became a full time graduate student of G. H. Parker, beginning in 1927; his thesis research on the photoresponsiveness of shrimp eyes was published in 1930, the year after he had received his Ph.D. (and an M. A. in 1928).
[3] Other students included Betty M. Twarog, who first described the role of serotonin as a neurotransmitter, Talbot Waterman, a pioneer in underwater animal orientation, and George Camougis, who founded one of the U.S.'s first environmental consulting companies.