Born at Lancaster of a medical family settled there for a hundred years. His grandfather and father both practised in the town. His father, Christopher Johnson, senr, was an Edinburgh graduate, and for more than half a century a leading practitioner who cultivated both literature and science. His eldest brother, James Johnson, a graduate of Dublin, practised in Lancaster as a physician. Christopher Johnson, junr, also studied in Dublin at the Royal College of Surgeons and at the Meath Hospital, further at Guy's Hospital, and settled in Lancaster, first as assistant to, and then in partnership with, his father. He and his brother James encouraged a group of young men to study chemistry, one of whom, Edward Frankland, was the distinguished Professor of Chemistry and a FRS. The chemical studies were carried on in the evening at the Mechanics Institute. He was appointed Surgeon to the Lancaster Infirmary and sat on the Committee of Management; he was also Certifying Factory Surgeon for the District. In 1879 he was President of the Lancashire and Cheshire Branch of the British Medical Association, and at the second visit of the Association to Lancaster in 1886 he read a paper on "Sanitary Reform a Hundred Years ago". He was a member of the Corporation, was Mayor in 1857 and 1858, and served on the Boards of several Charities, and on the Central Committee of the Royal Albert Asylum for Idiots. He read papers on scientific subjects to various local societies, had a keen sense of humour, and told good stories in the Lancashire dialect. A man much trusted and of sterling worth. He was made JP for the Borough of Lancaster in 1858, and for the County of Lancashire in 1882. For some years before his death he suffered from serious heart trouble, but continued on duty until his sudden death on November 6th, 1894, at 12 Castle Park, Lancaster, and was honoured with a public funeral by his fellow-townsmen.