Using preserved animals during teacher-led demonstrations and student experimentation may help students appreciate the anatomy of animals but does not allow them to design experiments to develop an understanding of the physiology. The crayfish hindgut allows for easy physiologic recordings through visually monitoring peristaltic activity, which can be used as a bioassay for various peptides, biogenic amines, neurotransmitters and environmental substances. The neurogenic crustacean and the myogenic Drosophila larva hearts clearly show the affect of environmental stimuli (temperature, CO2) and modulators (serotonin, nicotine) that enter the hemolymph. These robust preparations are well suited for training students in physiology and pharmacology.