He concluded that bats do not need vision for navigation; although he failed to find the reason. At the time other scientists were sceptical and ridiculed his findings. A contemporary of Spallanzani, the Swiss physician and naturalist Louis Jurine, learned of Spallanzani's experiments, investigated the possible mechanism of bat navigation. He discovered that bat flight was disoriented when their ears were plugged. But Spallanzani did not believe that it was about hearing since bats flew very silently. He repeated his experiments by using improved ear plugs using turpentine, wax, pomatum or tinder mixed with water, to find that blinded bats could not navigate without hearing. He was still suspicious that deafness alone was the cause of disoriented flight and that hearing was vital that he conducted some rather painful experiments such as burning and removing the external ear, and piercing through the inner ear. After these operations, he became convinced that hearing was fundamental to normal bat flight, upon which he noted: