Dr. Lucia Z. Lewis, teacher of microbiology at Duquesne University, writes authoritatively and lucidly about microbes in this introductory survey. What they are, how they grow, their discovery and their numbers, are explained in the first sections. Following them are descriptions of various common plant and animal microbes and at the last, the good and harmful ones and what mankind is doing to use their benefits and to prevent their evils. A brisk text maintains the fascination of the subject, and pictures by Marguerite Scott show the minute beings in magnification. Good reference.