persons to produce instantaneous unconsciousness and death (Allred and Berntson, 1986; Vanderwolf et al., 1988), just how quickly death by decapitation occurs has been questioned (Mikeska and Klemm, 1975). Recommendations for sedation of all animals before decapitation, unless the head will be immediately frozen in liquid nitrogen (AVMA, 1986), are controversial. Decapitation below the level of the atlanto-occipital joint should be avoided, because it fails to interrupt all afferent fibers. If restraint is a problem or one is not confident that severance will be above this level, prior sedation is recommended.

Distress vocalizations, fearful behavior, and release of odors or pheromones by a frightened animal can cause anxiety and apprehension in other animals (AVMA, 1986). That can affect the well-being of nearby animals and the validity of experimental data on animals to be euthanatized later by compromising their physiologic stability. Therefore, it is recommended that, whenever possible, animals be euthanatized in an area separated from other live animals, especially of their own species.

Relief of pain and distress is of primary concern during the euthanasia procedure, so it might be necessary to administer drugs other than those used expressly for euthanasia, especially to nervous or intractable animals. Thus, tranquilizers, analgesics, or narcotics may be given before euthanasia to minimize apprehension and assist in animal control.

It is imperative that death be verified. Proper techniques of euthanasia should include a followup examination to confirm the absence of a heartbeat, which is a reliable indicator of death. Monitoring respiration is not sufficient. In some animals, particularly under deep CO₂ anesthesia, heartbeat can be maintained after visible respiration has ceased, and the animal might eventually recover.

A means of euthanasia is chosen on the basis of animal species, size, tractability, excitability, presence of painful injury, distress, disease, restraint of the animal, protocol requirements for tissue collection or analysis, and other considerations. Suitable physical control of the animal being killed is critical for satisfactory euthanasia to minimize fear, anxiety, and pain and to ensure the safety of attending