Dr. Jacob Chason, a former professor and chairman of the Pathology Department at Wayne State University who was recognized as a leading authority in his field, died of complications from Parkinson\'s disease Nov. 22 at his home in Dallas . He was 90. For more than five decades, Dr. Chason served in every conceivable capacity in the field of pathology and was renowned for his range of expertise. \"His impact was enormous,\" said Dr. Margarita Palutke, professor of pathology at Wayne State University . \"He was one of the leading neuropathologists in the area. Just as importantly, he was always very supportive of the residents and younger staff. He set the grade as far as the field was concerned.\" Born in Monroe , Dr. Chason attended the University of Michigan where he received his bachelor\'s degree in 1937 and his medical degree in 1940. During World War II he enlisted in the Army as a battalion surgeon and served with the 81st Infantry Division in the South Pacific, attaining the rank of major. He was discharged in 1946. After the war he became director of laboratories at the Veteran\'s Administration Hospital in Allen Park . That same year he joined the faculty of Wayne State University School of Medicine as an assistant professor of pathology. In 1958, he was promoted to full professor. In 1966, Dr. Chason became chairman of the Pathology Department, a position he held until 1978.