Born at Dunstable, and at the age of 14 was apprenticed to Mr Harris, a surgeon in Birmingham, with whom he lived for four years during his apprenticeship, and for a subsequent two years attending the Birmingham General Hospital and also the Snow Hill School of Medicine. At the age of 20 he proceeded to University College, London, and for one year was House Surgeon at the hospital whilst Liston was surgeon. He settled in Bedford and soon acquired a leading practice whilst continuing to study for the London University degree. He was prominent as a practical sanitarian, and in face of intense local opposition succeeded in bringing about reforms in the Bedford drainage and water supply. He was a prolific writer and gained the friendship of Benjamin Ward Richardson, to whom is due a warm appreciation of Barker’s writings. Richardson characterized as masterpieces papers on “Cystic Entozoa in the Human Kidney with an Illustrative Case”, published in 1856; on “Disinfection and Deodorization” in 1866, and on “Malaria and Miasmata” in 1859. The ‘Entozoa’ essay obtained the Silver Medal of the Medical Society of London, that on ‘Disinfection’, the Hastings Gold Medal of the British Medical Association, and that on ‘Malaria’, the Fothergillian Gold Medal of the Medical Society in 1858. Among unsuccessful proposals was that in 1864 concerning the erection of town and village kitchens, where the food of the poor might be economically cooked by the aid of scientific knowledge, and that the *British Medical Journal* should publish a register of meteorological phenomena, which in fact was started but discontinued. In addition to numerous occasional publications he was engaged in a collection of photographs of eminent medical men of all countries, with brief analytical notices of their works. The photographic portraits from life were by Ernest Edwards, and 2 quarto volumes were published posthumously in 1867-1868. The second volume includes his obituary notice by Sir Benjamin Ward Richardson, with a portrait. Barker died of typhoid fever on Oct 24th, 1865, having been twice married and becoming the father of six children.