When Stanley was 9, the family moved to San Luis Obispo County, California, where he studied at Paso Robles High School.

[1] In 1904, he dropped out and worked as a newsboy on the Southern Pacific railway, though he eventually returned to Stanford to finish his degree.

The now-debunked theory that testicular transplant could cause male rejuvenation and age reversal was first proposed in 1889 and grew popular during the 1920s.

[1][6] Stanley believed that these procedures could cure afflictions such as pedophilia, depression, asthma, acne, neurasthenia and melancholia.

[1][7] By 1919, Stanley was recognized by the United Press Dispatch as "an international figure in the surgical world through his successful operations in rejuvenating old and senile prisoners by transplanting the interstitial glands of murderers who have paid the law’s penalty.

[2][15] In December 1941, shortly following the Japanese attack on Pearl Harbor, Stanley was called into service as a lieutenant commander in the United States Navy Reserve.

[4] Meanwhile, U.S. Navy physicians performed medical experiments on San Quentin inmates, many of whom volunteered due to patriotic fervor.

[16] After the war, he returned to his position at San Quentin,[1] though he would find the newly-reorganized California Department of Corrections now uses therapy as the guiding model.

[15] He operated a private practice in San Rafael, California, for a short time,[4] and later worked as a physician on cruise ships.