used,but at Chain's suggestion, they tried the much less dangerous amyl nitrite, and found that it also worked. Penicillin-bearing solvent was easily separated, but now they encountered the problem that had stymied earlier attempts: recovering the penicillin from the solvent. Heatley reasoned that if the penicillin could pass from water to solvent when the solution was acidic, maybe it would pass back again if the solution was alkaline. Florey told him to give it a try. This method, which Heatley called "reverse extraction", was found to work. Chain hit upon the idea of freeze drying to enable the water to be removed without damaged the penicillin. The team had thus developed a complete process for growing, extracting and purifying penicillin, resulting in a dry, brown powder. By early 1942, they could prepare highly purified compound, and had derived the chemical formula. Meanwhile, the team showed that Penicillium extract killed different bacteria. Gardner and Orr-Ewing tested it against gonococcus (against which it was most effective), meningococcus, streptococcus, staphylococcus, anthrax bacteria, actinomyces and the organisms that caused tetanus and gangrene. Florey and Jennings experiments on rats, mice, rabbits and cats in which penicillin was administered in various ways, and found no evidence of toxicity. On 25 May 1940, Florey injected eight mice with a virulent strain of streptococcus, and then four of them with penicillin. A day later all four of the untreated mice were dead, but all of the treated ones were still alive, although one died two days later. Over the following weeks Jennings and Florey repeat the performed experiment with ever-larger batches mice, and with different bacteria. They found that penicillin was also effective against staphylococcus and gangrene. They published their findings in The Lancet on 24 August 1940. Florey reminded his staff that promising as their results were, a man weighed 3,000 times as much as a mouse. In February 1941, Florey and Chain treated their first patient, Albert Alexander, who had had a small sore at the corner of his mouth, which then spread, leading to a severe facial infection involving streptococci and staphylococci. His whole face, eyes and scalp were swollen to the extent that he had had an eye removed to relieve the pain. Within a day of being given penicillin, he started to recover. However, the researchers did not have enough penicillin to help him to a full recovery, and he relapsed and died.