Lazzaro Spallanzani Biography (1729-1799)
- biologist, physiologist
Spallanzani was born on January 12, 1729, in Scandiano, Italy. He attended the University of Bologna and began his studies in law. However, his cousin, Laura Bassi, a professor of physics and mathematics, introduced him to a broadrange of scientific studies. Spallanzani altered his educational course and,in 1754, he earned a Ph.D. in philosophy. He joined the priesthood to supporthimself while he studied natural phenomena, hoping to determine explanationsfor such events as a stone skipping on water, the regeneration of decapitated snail heads, and the electric discharge of torpedo fish. Over the course ofhis career, Spallanzani would examine the pits of spitting volcanoes, the world of reproduction, the waters of eels, the dark depths of the bat's home, and the intricacies of the vascular system.
Yet Spallanzani's greatest contribution was in the area of spontaneous generation of microorganisms. The theory of spontaneous generation held that livingcreatures could develop from lifeless matter, especially from decaying matter. For instance, Aristotle believed that animal life generated spontaneouslyfrom mud, dung, or decaying timber. Other scientists believed alligators arose from Nile River mud, worms came from Thames River mud, and mites came fromcheese.
Francesco Redi, (1626-1697) an Italian physician and naturalist, conducted experiments in the seventeenth century that first dispelled the myths of spontaneous generation. Using the theory that decaying products only served as a nesting site for maggots to lay eggs, Redi showed that, in hot weather, maggotswould appear on exposed meat or dead animals. If the fresh meat was placed in a jar covered with a fine gauze, no maggots appeared.
Spallanzani, meanwhile, set out in 1765 to prove that microorganisms existedbecause they were already present in some form in the solution, the container, or the air. He took solutions which he knew would "breed" organisms and boiled them for up to an hour. The flasks were hermetically sealed to keep out contaminated air. Nothing grew.
But proponents of the spontaneous generation theory dismissed Spallanzani's experiments, saying only that the boiling process had destroyed elements vitalto the propagation of the organisms. It was not until Louis Pasteur's experiments on bacteria a century later that Spallanzani was proved right. Spallanzani's work regarding spontaneous generation eventually led to means of food preservation through heat sterilization and canning.
Spallanzani also turned his attention to the circulatory system. Viewing thesystem of blood vessels within a hen's egg in 1771, he was able to determinethat an arteriovenous network existed in a warm-blooded animal. With furtherstudy of the circulatory system, in which Spallanzani studied the changes that occur upon impending death as well as the effects of wounds on various parts of the system, he eventually developed a theory of blood pressure. He determined that the arterial pulse was not due simply to displacement of the cardiac muscle, but to an intentional and forceful push of blood against the vascular walls.
One of his next inquiries involved the fertilization of eggs. He began with the mating practices of frogs and toads. By 1785, when he was working with dogs, he induced the first case of artificial insemination. Spallanzani's curiosity surrounding natural phenomena took him on an expedition to the volcanoesof Vesuvius, Stromboli, Vulcano, and Etna. During his travels, he climbed towithin five feet of red-hot lava in order to measure its flow. He suffered burned feet as he descended into the bowels of Vulcano. He was rendered unconscious by the gases at Etna. Spallanzani's volcanic studies earned him status as a pioneer in the volcanology.
One of Spallanzani's final investigations took him into the dark world of bats. He was fascinated by their ability to maneuver without light. Even blinded, the bats could travel and eat without interruption or hesitation. Spallanzani went through the senses one by one, trying to discover which one governedthe habits of the bat. Through the process of elimination, he found that plugging up the bats' ears rendered them directionless. While Spallanzani accepted the theory of echolocation, this theory wasn't explained until 1941, when Donald R. Griffin described the bat's sensitivity to sound waves. Spallanzanidied on February 11, 1799, in Pavia, Italy.