A gloved hand
Surgical gloves were protective hand coverings used by medical staff to decrease the likelihood of cross-contamination and infection during medical procedures. They were sometimes accompanied by transparent sleeves that extended from the arm to the elbow.
Surgical gloves were still in use as late as 2266, when Doctor Leonard McCoy and Nurse Christine Chapel were operating on Lieutenant junior grade Joe Tormolen. (TOS: "The Naked Time")
Sometime after that, they were all but replaced by more advanced quarantine fields. In 2368, Berlinghoff Rasmussen mentioned that he and a colleague had visited a 22nd century ship. Beverly Crusher replied that he likely saw surgical masks and gloves. (TNG: "A Matter Of Time")
Despite this, surgical gloves were occasionally still in use. In 2365, the medical personnel participating in Jean-Luc Picard's cardiac replacement surgery wore red gloves as part of their scrubs. (TNG: "Samaritan Snare") In 2381, holographic nurses in the Medical Ethics holoprogram also wore the same gloves. (LD: "I, Excretus")