The use of animals in the search for new drugs is not always reliable. Physiological differences between species can produce various results. There have been major medical break throughs without the aid of animals. X-rays were developed without the use of animals, as well as the vaccine for yellow fever. Penicillin may have never gotten past preliminary testing if it were tested on guinea pigs because the drug is fatal for the rodents. Penicillin was also discovered without the use of animals. Salicylates