Black Oxen is a remarkable film largely because it is based on a remarkable book, by Gertrude Atherton, and is (as far at any rate as the part that survives is concerned) quite a faithful representation of the novel.
"Rejuvenation" in its general usage during the period was something of a euphemism and was extremely male-oriented (in effect the "viagra" of its day). The interest in the potential effects of what would eventually be identified as testosterone goes back in some ways way into folklore but its "scientific" application began with a very eccentric French physiologist called Charles-Édouard Brown-Séquard who claimed in 1899 to have regained his youth after injecting himself with filtered extracts from the crushed testicles of young dogs and guinea pigs. In the 1920s and 1930s, Russo-French surgeon Serge Voronoff developed a technique for grafting monkey testicle tissue onto the testicles of men for a similar purpose, but is was the very distinguished endocrinologist Eugen Steinach whose work created the most interest.
Steinach believed that what he called the "Steinach vasoligature" for men (a partial vasechtomy) would effect a rejuventaion and, although the emphasis still remained largely on men and on sexual potency; poet W. B. Yeats, from one of whose verse-plays the title of the book and film comes, was the best-known celebrity to have been "steinached" and to have claimed a rejuvenation and a re-energisation as a result. Steinach did however extend his theory to women, the equivalent being an irradiation of the ovaries (which also rendered the woman infertile) and Atherton was herself one of those who had undergone the treatment and she too claimed to have benefited significantly from it and it was the inspiration for the novel.
This was the time when cosmetic surgery was also coming of age - many people know that actress Sarah Bernhardt had to have her leg amputated but fewer know that she had had had a face-life shortly before that. This was also the time when the generation-gap was beginning to be talked about and seemed in the era of "flapper" 9represented of course by Clara Bow in the film) to create a particularly harsh divide where women were concerned. Atherton believed that Steinach rejuvenations were a form of female empowerment (many women would claim the same today for cosmetic surgery) and she uses the idea of rejuvenation in her novel to review a whole range of related subjects - the situation of the old, the generation gap, the sexuality of women.
In the first part of the film (the part that survives) this is fairly well represented by Lloyd but if the ending of the film is (as some reviewers claim) predictable, it should not be because it is not at all the same as the ending of the book. Lloyd plumps in fact for a much more conventional view that has the heroine agreeing to "act her age" (and in effect "know her place")while the hero goes off with the flapper. Corinne Griffith gives I think a very impressive and subtle performance as a woman with a mature mind but a young body (the ideal as Atherton perceived it) but, in life, as in the film, it was the young Clara Bow (whose performance is nothing remarkable) who proved the eventual beneficiary.
It is thought that the film in its entirety is not beyond the possibilities of being Steinached but given the disappointing ending, it is perhaps better the way it is.