Производные местоимения some, any, no. text. “the founder of virology”

To prove this phenomenon D.I.Ivanovsky had to make many experiments on various plants. He had to pass the juice of the diseased plan through a fine filter which was able to catch the smallest bacteria. At that time a little over 70 years ago everybody considered that bacteria were the smallest living organisms. But when D.I.Ivanovsky had completed to pass the juice through a fine filter, he was able to come to the conclusion that the living organisms smaller that bacteria existed in the environment, because when he introduced the filtrate of the diseased plants to healthy ones they became infected.