Insidekick

Excerpt-The Zark, meanwhile, was not idle despite the outside interests. The majority of its structure was busily engaged in checking and cataloguing the body of its host, an automatic process that didn't interfere with the purely intellectual one of enjoying the new sensations. Albert's body wasn't in too bad shape. A certain amount of repair work would have to be done, but despite the heavy padding of fat, the organs were in good working condition.
The Zark ruminated briefly over what actions it should take as it dissolved a milligram of cholesterol out of Albert's aorta and strengthened the weak spot in the blood vessel with a few cells of its own substance until Albert's tissues could fill the gap. Its knowledge of human physiology was incomplete, but it instinctively recognized abnormality. As a result, it could help the host's physical condition, which was a distinct satisfaction, for a Zark must be helpful.