Four of Leinster's enjoyable "Med Service" stories make up this collection.
The Medical Service is an organization that sends small medical starships out to the various colonized worlds of the galaxy. Each ship includes one human medical doctor and one tormal, a small cat-like mammal with a remarkable immune system that's both human-compatible and resistant to nearly all infectious diseases. The Med Service stories follow the adventures of the Med Ship, Asclepius Twenty, crewed by the human Calhoun and the tormal Murgatroyd. Each story presents a new challenge for the team, sometimes directly in their line of work, such as a plague, and sometimes indirectly, such as interplanetary political shenanigans that need to be sorted out.
There are many Med Service stories and there are a confusing assortment of incomplete books. I picked this one up at random in a used book store. If you're interested in the series, I suggest looking instead for the Baen Books volume titled "Med Ship", first published in 1983 and reprinted in 2002. As far as I know that's the only single volume containing all the stories. Most other books, like this one, contain only three or four.
The stories are typical to above average 1950/1960 pulp fare. If you're a fan of Leinster or science fiction of that era, these are readable, enjoyable stories.