A Guide Dog with Harness (IMAGE) University of Veterinary Medicine -- Vienna Caption Guide dogs walk under constant tension. A well-fitting harness is extremely important for the animals. Credit Photo: Bernkopf / Vetmeduni Vienna Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.