"As long as we do not know the cause of a disease, we can do nothing for its prevention."

"The greatest joy of a scientist is to make a new discovery."

"I have devoted my life to the study of bacteria, and I have found it to be a most rewarding pursuit."

"It is a great satisfaction to know that my work has contributed to the well-being of humanity."

"The isolation of disease-causing microorganisms is the first step towards controlling them."