Francis Peyton Rous ForMemRS (/raʊs/; October 5, 1879 – February 16, 1970) was an American pathologist at the Rockefeller University known for his works in oncoviruses, blood transfusion and physiology of digestion.

[1] A medical graduate from the Johns Hopkins University, he was discouraged from becoming a practicing physician due to severe tuberculosis.

Due to the disease, he considered himself as unfit to be a physician, or a "real doctor," for which he focused his interest in medical research.

[8] In 1907, he went to Germany for a training course on morbid anatomy at Friedrichstadt Municipal Hospital (Krankenhaus Dresden-Friedrichstadt) in Dresden[6] under Christian Georg Schmorl.

[1] On his way home from Germany, he showed symptoms of pulmonary tuberculosis and was sent to the Adirondack Mountains in northeastern Upstate New York for recovery.

[7] Rous started his Rockefeller research on the tumors in rodents,[12][13] and turned to that of chicken (specifically, a sarcoma) in the early 1910.

A woman brought him a Plymouth Rock hen[6] which had developed a "large irregularly globular mass" on its right breast two months earlier.

Speculating the medical importance, he noted that "there is no reason to suspect on these points [of growth and transmission] that the neoplasm will differ from the better-known tumors of mammals.

In 1911, he made a seminal observation that cell-free filtrate (using Berkefeld filter that separate bacteria and large microbes) of chicken sarcoma could produce a malignant tumor when transferred to other chickens,[15] describing:A transmissible sarcoma of the chicken has been under observation in this laboratory for the past fourteen months, and it has assumed of late a special interest because of its extreme malignancy and a tendency to wide-spread metastasis... small quantities of a cell-free filtrate have sufficed to transmit the growth to susceptible fowls.

And suddenly, in opposition to all these dignified and bearded Herren Professoren who firmly believed what they said, rose the voice of a young American who claimed to have transmitted by a cell-free filtrate a neoplasm—a chicken sarcoma.

Experiments he continued with James B. Murphy and published made conclusive evidences for the cancerous nature of the infection.

[22] Rous continued to work on cancer up to 1915, after which he gave up due to failure to obtain other carcinogenic agents from chicken and mice, and general acceptance of his discovery.

[5] The virus nature of the Rous sarcoma was shown by William Ewart Gye of the National Institute for Medical Research at Hampstead in 1925.

[32] Although an Austrian physician Karl Landsteiner had discovered blood types a decade earlier, the practical usage was not yet developed, as Rous described: "The fate of Landsteiner's effort to call attention to the practical bearing of the group differences in human bloods provides an exquisite instance of knowledge marking time on technique.

He was appointed honorary fellow of the Weizmann Institute of Science and foreign correspondent of the Académie Nationale de Médecine in Paris.

He also received the Kovalenko Medal of the National Academy of Sciences, the Distinguished Service Award of the American Cancer Society, the United Nations Prize for Cancer Research, and the Paul Ehrlich and Ludwig Darmstaedter Prize from the Federal Republic of Germany.

[7] Rous shared the Nobel Prize in Physiology or Medicine in 1966 with Charles Brenton Huggins "for his discovery of tumour-inducing viruses.

Marni (1917–2015) was a children's book editor, and the wife of another Nobel Prize winner, Alan Lloyd Hodgkin.