Hunter's great rival among contemporary physiologists was the Italian Lazzaro Spallanzani (1729-1799), one of the most picturesque figures in the history of science. He was not educated either as a scientist or physician, devoting, himself at first to philosophy and the languages, afterwards studying law, and later taking orders. But he was a keen observer of nature and of a questioning and investigating mind, so that he is remembered now chiefly for his discoveries and investigations in the biological sciences. One important demonstration was his controversion of the theory of abiogenesis, or "spontaneous generation," as propounded by Needham and Buffon. At the time of Needham's experiments it had long been observed that when animal or vegetable matter had lain in water for a little time--long enough for it to begin to undergo decomposition--the water became filled with microscopic creatures, the "infusoria animalculis." This would tend to show, either that the water or the animal or vegetable substance contained the "germs" of these minute organisms, or else that they were generated spontaneously. It was known that boiling killed these animalcules, and Needham agreed, therefore, that if he first heated the meat or vegetables, and also the water containing them, and then placed them in hermetically scaled jars--if he did this, and still the animalcules made their appearance, it would be proof-positive that they had been generated spontaneously. Accordingly he made numerous experiments, always with the same results--that after a few days the water was found to swarm with the microscopic creatures. The thing seemed proven beyond question--providing, of course, that there had been no slips in the experiments. But Abbe Spallanzani thought that he detected such slips in Needham's experiment. The possibility of such slips might come in several ways: the contents of the jar might not have been boiled for a sufficient length of time to kill all the germs, or the air might not have been excluded completely by the sealing process. To cover both these contingencies, Spallanzani first hermetically sealed the glass vessels and then boiled them for three-quarters of an hour. Under these circumstances no animalcules ever made their appearance--a conclusive demonstration that rendered Needham's grounds for his theory at once untenable.(2) Allied to these studies of spontaneous generation were Spallanzani's experiments and observations on the physiological processes of generation among higher animals. He experimented with frogs, tortoises, and dogs; and settled beyond question the function of the ovum and spermatozoon. Unfortunately he misinterpreted the part played by the spermatozoa in believing that their surrounding fluid was equally active in the fertilizing process, and it was not until some forty years later (1824) that Dumas corrected this error. THE CHEMICAL THEORY OF DIGESTION