Woodhull was the first to call to the attention of the service the necessity of co-operation between the medical and line officers in the promotion of military hygiene.

His duties included instruction in military hygiene at the Infantry and Cavalry School at Fort Leavenworth, Kansas, from 1886 to 1890 and command of the Army and Navy Hospital at Hot Springs, Arkansas, from 1892 to 1895.

He was awarded the gold medal of the Military Service Institution for his paper on "The Enlisted Soldier," which was published in its Journal for March 1887.

In 1891, he travelled to England to study the British Army's medical care and published a report in 1894.

He wrote Provisional Manual for Exercise of Company Bearers and Hospital Corp in 1889, and Notes on Military Hygiene for Officers of the Line.