The Russian-born Dr. Serge Voronoff of France was the initiator of the "monkey glands" fad of the 1920s and 1930s, persuading dozens of men that pieces of monkey testicle implanted in their own testes would give them increased potency. He came up with this idea after noting that eunuchs aged faster than the non-castrated. Voroneff wrote a book about his process in 1926, which spread the idea around the world. A Dr. Leighton Jones was famous for the same procedure in Australia, and cases of this transplant being done are known in the U.S., Italy, Russia, Brazil, Chile, and India. It was sometimes difficult to procure the monkeys needed, and monkey houses to raise the animals sprouted near Voroneff's location. (Since the vivisection of animals was illegal in England, human testes were substituted.)

Voroneff's procedure: "The monkey gland would be cut in pieces of about two centimeters long by a half centimeter wide and a few millimeters deep. The surgeon would then introduce two grafts in the scrotum, which he fixed with stitches taken off after eight days." (Gillyboeuf) He later tried grafting monkey ovaries in women, but did not continue this line of thought, though it is sometimes credited as an ancestor of hormone replacement therapy for menopausal women.

On a similar note, John Romulus Brinkley (1885-1941) was well-known in the U.S. for using goat glands for the same supposed restoration of male fertility and virility; he started performing these implantations in 1918. Brinkley was licensed as a doctor in Kansas; the license was revoked in 1930, when he had already become rich from his practice, so he moved to Texas, just across the border from a Mexican radio transmitter on which he advertised his services prescribing supposed drug remedies.

The gland-implantation fad was widespread enough that Irving Berlin, William Faulkner, George Bernard Shaw, and the 14th edition of the Encyclopedia Britannica all refer to monkey glands in some way. Pablo Picasso is said to have been a patient of Voronoff's. And a cocktail called a Monkey Gland is found in bartending guides starting about 1930. Recipes vary, but usually go something like this:

1 ounce gin
1 ounce orange juice
1 dash grenadine
1 dash anise (probably originally absinthe; Pernod or Benedictine are often substituted now)

Sources:
Gillybeauf, Thierry. "The Famous Doctor Who Inserts Monkeyglands In Millionaires" Spring: The Journal of the E.E. Cummings Society Vol. 9, 2000 http://www.gvsu.edu/english/cummings/issue9/Gillybo9.htm
Tosches, Nick. Where Dead Voices Gather. Boston: Little, Brown, and Company, 2001.
http://www.bbc.co.uk/wales/bllcks/facts/french.shtml
http://www.tsha.utexas.edu/handbook/online/articles/view/BB/fbr55.html
http://pw1.netcom.com/~mikalm/brinkley.htm
http://www.lakemac.infohunt.nsw.gov.au/library/lhist/suburb/lmp&p/eraring.htm
http://emilychesley.com/lit_re/graf.htm
http://www.yourlifesource.com/estprog.htm
http://www.new1.com/MaryCleereHaran/nytimes.htm
http://hotwired.lycos.com/cocktail/98/46/index3a.html