Final answer:
Restlessness and aggression in dogs can be due to rabies or overzealous restraint, and proper training of service animals is important for public safety.
Step-by-step explanation:
The issue of a dog exhibiting restlessness and aggression can be caused by various factors, including rabies, a neurological disease that affects mammals and can be transmitted to humans, as illustrated in Figure 26.1. The story of the yapping dog in an airport waiting area suggests that the aggression can also stem from improper restraint or inadequate training. Both rabies and overzealous restraint can lead to aggressive behaviors in animals. Proper handling and training of service animals are crucial to prevent such issues and ensure the safety and comfort of the public and other service animals, such as the case with the trained Labrador retriever guide dog. Aggression in dogs can thus be multifactorial, influenced by disease or by the environment and handling of the animal, as the author's tone of disapproval towards the unrestrained, untrained dog implies.