Introduction to Animal Physiology and Physiological Genetics, deals with topics on physiological measurement, comparisons, and analysis of the role of genotypes. This book emphasizes two aspects the changes of physiological patterns in the course of development and the wide variation that can be found within a species. The text discusses the response mechanisms of living organisms from nerve impulses, chemical sense, muscle reaction, and includes some studies made on brain function. The effects of nutrition and energy such as the intake of food, water, oxygen, and the calculation of basic metabolic rates are explained. The book then discusses the role of the internal environment and that of the interstitial body fluid in the higher animals. The discussion covers blood circulation, cardiac cycle, and a special section on the function of the heartbeat in the spider Limulus showing that stimulation of the abdominal ganglia increases the heartbeats.