The years between 1919, when Ross was demobilised from the War Office and 1925, when the Ross Institute was founded, are somewhat of a hiatus as far as documentary evidence is concerned. It can be assumed that he returned to private practice during this period and we know that he was employed by the Ministry of Pensions until 1923 at least, when he started his appeal for funds in order to establish the Ross Institute. Because of the scarcity of material in the Ross Collection for this period all that is available has been gathered together under the heading of the Ross Institute, which thus covers the remainders of Ross’ life until his death in 1932.
After two years of fund-raising the Ross Institute and Hospital for Tropical Diseases was incorporated in 1925 and was formally opened by the Prince of Wales in 1926. The public response to the initial target of £50,000 was poor; indeed finance was to prove the major problem throughout the Institute’s years of independence as it was entirely dependent on public subscription. The aim of the Institute was to supplement the work of the two schools of tropical medicine already in existence, i.e. London and Liverpool, in that more emphasis was to be placed on research and on the provision of facilities for training medical men for practice in the tropics. Ross was appointed Director-in-Chief with Sir Aldo Castellani and Sir William Simpson as directors; Sir Malcolm Watson joined the staff shortly afterwards as Principal of the Medical Control and Protozoological Department.
In 1926 Ross, now aged 69, visited Ceylon and in 1927 he visited Malaya, to see the work being done there by Sir Malcolm Watson, and India. These were to be the final expeditions he made as in August 1927 he suffered a stroke which left him paralysed down his left side. Since 1925 his health had been deteriorating because of diabetes mellitus and arteriosclerosis and now the result of those combined with a stroke was to confine him to a wheelchair for the rest of his days. For those reasons he became increasingly a figurehead at the Ross Institute and it was Sir Malcolm Watson who became the controlling director.
After the death of Ross in 1932 the Institute found it more and more difficult to continue as an independent organisation and it was eventually incorporated with the London School of Hygiene and Tropical Medicine in 1934.