[1] Working with Animal Rights International, a group he founded in 1974, Spira is particularly remembered for his successful campaign in 1976 against animal testing at the American Museum of Natural History, where cats were being experimented on for sex research, and for his full-page advertisement in 1980 in The New York Times that featured a rabbit with sticking plaster over the eyes, and the caption, "How many rabbits does Revlon blind for beauty's sake?

Henry was sent to a Roman Catholic school run by nuns, where lessons were conducted in Spanish, until his father ran out of money and could no longer afford the fees.

[citation needed] In 1943, while at Stuyvesant High School, he became involved with Hashomer Hatzair, a left-wing, non-religious, Zionist group that helped to prepare young Jews to live on kibbutzim in Palestine.

Australian philosopher Peter Singer writes that the anti-materialism and independence of mind that Spira learned from his time with Hashomer Hatzair – where he went by his Hebrew name, Noah – stayed with him for the rest of his life.

Spira decided to leave home when he was sixteen, taking lodgings and an afternoon job in a machine shop, and attending school in the mornings.

Singer suggests that the broader impact of the series beyond the narrow readership of the socialist newspaper taught Spira a lesson: that "careful research can often turn up internal contradictions in what a large organization says and does.

"[3]: 28–29 Spira was also involved in the Committee for NMU Democracy in the early 1960s, during a time when dissidents faced beatings and threats of violence by supporters of union president Joseph Curran.

"[3]: 35–40 In 1958, he graduated as a mature student from Brooklyn College in New York, and in 1966 began teaching English literature in a Manhattan public high school.

Singer's article was a review of Animals, Men and Morals (1971) by three Oxford philosophers, John Harris and Roslind and Stanley Godlovitch.

[4] Another well-known campaign targeted cosmetics giant Revlon's use of the Draize test, which involves dripping substances into animals' eyes, usually rabbits, to determine whether they are toxic.

Spira took a photograph of a primate who had been imprisoned for months in a Bethesda Naval Hospital chair to the Black Star Wire Service, which sent the picture around the world.

He proved especially adept at leveraging the power of the larger animal welfare organizations, such as the Humane Society of the United States, to advance his campaigns.