He was at once appointed professor of anatomy in the Vermont Medical College, and in the same year accepted the chair of anatomy in the
Berkshire Medical College, and in 1833 also that of surgery. In 1836 he was appointed professor of surgery in the
Cincinnati Medical College, and afterward spent some time in the hospitals of Paris and London. In 1839 he became professor of surgery in the New York College of Physicians and Surgeons, which post he resigned after a service of 30 years, but accepted that of professor of clinical surgery. In the spring of 1840, appreciating the want of practical demonstration in teaching surgery, and the difficulty in securing cases for illustration in colleges that were unconnected with hospitals, he visited with his students two or three of the city dispensaries, selected interesting cases, and had them taken to the College of Physicians and Surgeons, where the anatomical theatre offered superior advantages for making diagnoses and performing operations before the class. This was the first college clinic in the United States. In 1843, he organized the
New York Pathological Society, and in 1846 a society for the relief of widows and orphans of medical men. He organized the
New York Academy of Medicine in 1847, of which he was president for many years after 1856. In 1846, with Dr. James R. Wood, he secured the necessary legislation to reorganize the city almshouse into what is now
Bellevue Hospital, and was appointed one of its visiting surgeons. In 1864–1866 he was active in procuring legislation to create the
New York City Board of Health, made many visits to
Albany in its behalf, and was one of its members from its organization. In 1865 he was elected president of the New York State Inebriate Asylum at
Binghamton, succeeding
Valentine Mott. This was the first institution ever established for the treatment of
inebriety as a disease. His treatment of his patients being based on the theory that
alcohol is essentially a
poison, that it cannot be considered as food, and should be used only in exceptional cases and under the advice of a physician. In 1870 he received the degree of
LL.D. from the
college of New Jersey at Princeton. Parker was the first to point out a condition which is known as concussion of the nerves, as distinguished from concussion of the nerve centres, and which had been previously mistaken for one of inflammation. The operation of cystotomy for the relief of chronic
cystitis, and also that for the cure of
abscess of the
appendix vermiformis, are among his contributions to the art of surgery. He died in New York City in 1884. ==Publications==