In Leonardo da Vinci’s anatomical drawings, the penis is connected directly to the brain.
A 1986 article “On the sexual intercourse drawings of Leonardo da Vinci” explains why this connection, still commonly proposed today (although mostly as a metaphor it must be said), was thought to be anatomical fact by the great master.
“A brief glance at the male character in Fig. 3 reveals the amazing internal ‘plumbing’ designed by Leonardo to describe Aristotelian physiology. He has drawn two canals in the penis, the lower of which is connected to the urogenital tract via the urethra, while the upper canal passes to the spinal cord by means of three vessels. The close-up of the penis demonstrates these two canals in fine detail. In ancient Greek writing, the ‘essence’ of a baby was provided by the ‘universal seed stuff’ of the male. This procreative ingredient was derived from animal spirit, a physiological material necessary for muscular activity. The animal spirit was manufactured from arterial blood at the base of the brain and was transferred to all parts of the body through the nerves. Hence da Vinci’s spinal connection to the penis.”
And before I hear a “Yeah, right on Leo!” from the ladies, I note a remarkably similar vagina – spinal cord connection also makes an appearance in the diagram.