booq wrote in linguaphiles

gas bag, please

Hi everybody,

Would anybody explain what does 'gas bag' mean in the following passage, please?

In the early days of practice in cases of this nature, earache with red congested drums and tenderness over mastoid, I frequently went to a case with fear and trembling on the second visit, gas bag and ear instruments, fine scalpels, etc., all at hand in case of need, but it was never necessary.

Thank you in advance!