Footnote 23: Teachers may take up parts or all of Chapter XXIV at this point. I have found it advisable to repeat much of the work on bacteria _after_ the students have taken up the study of the human organism. REFERENCE BOOKS ELEMENTARY Hunter, _Laboratory Problems in Civic Biology_. American Book Company. Bigelow, _Introduction to Biology_. The Macmillan Company. Conn, _Bacteria, Yeasts, and Molds in the Home_. Ginn and Company. Conn, _Story of Germ Life_. D. Appleton and Company. Davison, _The Human Body and Health_. American Book Company. Frankland, _Bacteria in Daily Life_. Longmans, Green, and Company. Overton, _General Hygiene_. American Book Company. Prudden, _Dust and its Dangers_. G. P. Putnam's Sons. Prudden, _The Story of the Bacteria_. G. P. Putnam's Sons. Ritchie, _Primer of Sanitation_. World Book Company. Sharpe, _Laboratory Manual in Biology_, pages 123-132. American Book Company. ADVANCED Conn, _Agricultural Bacteriology_. P. Blakiston's Sons and Company. Coulter, Barnes, and Cowles, _A Textbook of Botany_, Vol. I. American Book Company. De Bary, _Comparative Morphology and Biology of the Fungi, Mycetozoa, and Bacteria_. Clarendon Press. Duggar, _Fungous Diseases of Plants_. Ginn and Company. Hough and Sedgwick, _The Human Mechanism_. Ginn and Company. Hutchinson, _Preventable Diseases_. Houghton, Mifflin and Company. Lee, _Scientific Features of Modern Medicine_. Columbia University Press. Muir and Ritchie, _Manual of Bacteriology_. The Macmillan Company. Newman, _The Bacteria_. G. P. Putnam's Sons. Sedgwick, _Principles of Sanitary Science and Public Health_. The Macmillan Company. XII. THE RELATIONS OF PLANTS TO ANIMALS _Problems.--To determine the general biological relations existing between plants and animals._ _(a) As shown in a balanced aquarium._ _(b) As shown in hay infusion._ SUGGESTIONS FOR LABORATORY WORK _Demonstration of life in a "balanced" and "unbalanced" aquarium._--Determination of factors causing balance. _Demonstration of hay infusion._--Examination to show forms of animal and plant life. Tabular comparison between balanced aquarium and hay infusion.