Lazzaro Spallanzani (1729-1799) was an important Italian physiologist who made countless contributions to the study of anatomical and reproductive functions and animal and microscopic life. His most important experiments dealt with how sexual reproduction actually occurred. Sure, we knew about the sperm and the egg, but we didn't figure out until remarkably late in human history how all the parts fit together (no pun intended). And it took a celibate Catholic priest to do it.

Born in Modena, he was the son of a lawyer. He studied the classics, philosophy, mathematics, and languages at the Jesuit school in Reggio. Though he eventually took holy orders in 1757 and worked as a priest, he never joined the Jesuit order. Instead he went to Bologna to study law, but his interests soon turned towards science. He also held various teaching posts, becoming professor of logic, metaphysics, and Greek at Reggio College in 1754 and professor of physics at the University of Modena in 1760.

Through all this, plus penning the occasional work of literary criticism, all of Spallanzani's spare energy was directed towards his scientific experiments. In 1766, he published a work examining the physics of how stones bounce when thrown across a body of water. In 1767, he first turned to biology, writing an attack on the theory of "vital atoms", theoretical particles which were the source of physiological activity. He, like Antonie van Leeuwenhoek, though these "vital atoms" were microorganisms, which they of course were, which he proved through a series of experiments with boiling gravy, showing that the leftover particles were microorganisms introduced through the air and not part of the original substance. 1768 produced the results of his experiments in animal regeneration and transplantation, one of which was a successful transplant of the head of one snail onto the body of another one. In 1773, he studied blood circulation in the lungs and organs and the chemicals in digestive juice.

But you want to hear about sex, right? The sperm and the egg were discovered in the 17th century, and it was assumed that both played a role, but no one quite stumbled on the obvious yet. By the next century, the prevailing theory was "remote fertilization": the sperm and the egg merely needed to be in the same neighborhood and the egg would be exposed to the invisible aura seminalis ("spermatic vapor"). Presumably ether or phlogiston were not acceptable substitutes.

Spallanzani believed this nonsense, but his experiments separating toad eggs and semen proved that physical contact was necessary between the egg and the sperm. He gathered a quantity of frog sperm by clothing male frogs in makeshift taffeta "pants" (dear God, could I make this stuff up?) and setting them loose on female frogs. When the males mounted the females, they ejaculated into the pants, allowing Spallanzani to collect it for his research. He then placed the sperm and the eggs into separate containers, where the "vapor" could reach the eggs but there was no physical contact. No dice. But when he mixed the eggs and the seminal fluid, instant tadpole soup.

And thus some of the first experiments in artificial insemination. But he wasn't finished there. Frogs were one thing, mammals another. So he isolated a male and a female dog from one another, masturbated the dog to collect the sperm, and inseminated the bitch with it. Soon he had plenty of puppies to give away.

Despite his successes, he could never manage to crossbreed cats and dogs.

Through these strange experiments, Spallanzani became famous in scientific circles. He was offered a chair at the University of Pavia in 1769, which is where he would stay for the rest of his life. His popularity brought jealous accusations of malpractice, which he emerged from unscathed. Later experiments involved the electrically charged torpedo fish, the senses of the bat, and the conversion of oxygen to carbon dioxide in the body. He also traveled extensively, penning accounts of his trips to Constantinople and Sicily.

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