The purpose of making the second paragraph a single sentence is one of timing. It sets a quick pace with no interruptions. This is intended to mirror the actual experience of walking into the warehouse and looking at the slaves being sold. In this way, the author wants you to imagine the situation the way he is describing it.
The author uses the lists "husbands, wives..." and "sold, leased..." for a couple different purposes. One is similar to the previous one: to create a certain pace. The author provides several quick and short options in a row, which mimics the quickness, confusion and overload of sights when walking into the warehouse. Although the behaviour of the seller is calm, the mind of the viewer is going quickly as it considers the implications of the scene. The second one is to highlight the reality of the slaves. By giving you all the options, he shows that no matter what your condition was, you were sold in the same way and with no concern for your individuality. Finally, the author also gives us these lists of characteristics as factual information that describes the condition of the slaves.
