What is the theme in The Cabinet of Curiosities by Douglas Preston?

Murder to further science is a theme. Enoch Leng killed young, poor people so that he might experiment with their bodies and find ways to prolong his own life. Leng, a trained scientist, believed it was in the name of science that he was killing these innocents. When a construction crew breaks through the ground on the sight of Shottum's Cabinet of Natural Productions and Curiosities, they discover the skeletons of thirty-six of Leng's victims. Each one shows damage to the bottom section of the spinal cord where the cauda equina is located. This bundle of nerves is the largest section of nerves in the human body and Leng hoped that they would provide him with the important element of his life prolonging serum.