Gulliver's role on his first voyage is that of a surgeon.

Explanation:
Gulliver is the main character in the novel "Gulliver's Travels" written by Jonathan Swift. In the beginning of the story, Gulliver takes on the role of a surgeon in his first voyage.

Surgeon on the ship:
As a surgeon, Gulliver is responsible for the medical care of the crew and passengers on the ship. Surgeons on ships during that time were essential as they provided medical treatment and performed surgeries when necessary. They were responsible for treating injuries, illnesses, and diseases that could occur during long voyages.

Gulliver's job as a surgeon required him to have knowledge of medical procedures, medicines, and basic surgical skills. He would have been responsible for treating wounds, setting broken bones, amputations, and providing general medical care to the crew and passengers.

Importance of a surgeon:
Having a surgeon on board was crucial during long voyages as there were many dangers and risks involved. Sailors and passengers could get injured or fall ill due to various factors such as accidents, poor hygiene, lack of nutrition, and exposure to harsh weather conditions.

The surgeon played a vital role in maintaining the health and well-being of the crew and passengers. Their skills and expertise were essential in preventing and treating illnesses and injuries that could potentially be life-threatening.

Gulliver's experiences as a surgeon:
Throughout his first voyage, Gulliver encounters various medical situations that require his expertise as a surgeon. He describes treating crew members who suffer from diseases, injuries caused by storms, and even performing a surgical procedure on a fellow sailor.

Gulliver's experiences as a surgeon not only showcase his medical knowledge and skills but also provide insights into the medical practices and conditions of the time.

Conclusion:
In conclusion, Gulliver's role on his first voyage is that of a surgeon. As a surgeon, he is responsible for providing medical care and treatment to the crew and passengers on the ship. His experiences as a surgeon during his first voyage play a significant role in shaping the narrative of "Gulliver's Travels."