That depends on which Enterprise one is discussing.I thought the Enterprise had multiple sickbays, or at least a large sickbay complex the parts we saw on the TV shows were only a small fraction of.
Obviously the TNG one was massive compared to TOS, just because of the ship scales and the number of people needed to be treated on a daily basis.
GOOGLE provides this pictorial comparison for those interested.
https://www.google.com/search?q=ent...KHd6zDF4Q9QF6BAgGEAE&biw=1280&bih=617&dpr=1.5
These are mostly Trek Fan depictions, but considering our persnickety attention to minute detail, they are probable accurate down to the square inch.
