VI. Experimental researches on spontaneous generation

The experiments are twenty in number, and were performed during the summer of 1863. The substances used were in ten experiments milk, and in ten, fragments of meat and water. These were in all cases placed in a bulb of glass about 2½ inches in diameter, and having two narrow and long necks. The experiments are divided into five series of four experiments each. In one series the bulbs were filled with air previously passed through a porcelain tube containing fragments of pumice-stone and heated to vivid redness in a furnace. In the others they were filled respectively with carbonic acid, hydrogen, oxygen, and nitrogen gases. In each series two experiments were made with milk, and two with meat ; and each substance was boiled in one case, and not boiled in the other. The joints of the apparatus were formed either by means of non-vulcanized caoutchouctubing, or india-rubber corks previously boiled in a solution of potash ; and in every case, at the end of the experiment, the necks of the bulb were sealed by the lamp. The time of boiling such of the substances as were boiled varied from five to twenty minutes, and the boiling took place in the bulbs, and with the stream of gas or air still passing through. The substances were always allowed to cool in the same stream of gas before the bulbs were sealed. The microscopic examination of the contents of the bulbs took place at various times, from three to four months after their enclosure.