The aim of this book is to present current information about the fundamentals of microbiology in a simple, straighforward, and concise form and in as interesting and readable manner as possible. The book is intended for the student who wishes to acquire an introdcution to the field of microbiology, whether for future professional specialization or as part of a well-rounded general education. It is thus an appropriate text for liberla arts, premedical, and veterinary stundents as well as for those who plan to specialize in such fields as pharmacy, home economics, agriculture, and industry. The author assumes that the student who will use the text has at last an elementary knowledge of chemistry, physics, and biology.