Bone marrow contains mostly hematopoeitic stem cells, and they remain round in shape; they may be still viable. If you want to know whether they are dead or alive, you can stain by trypan blue, blue cells are dead, and white shining cells are viable. Mesenchymal stem cells in bone marrow are very few, so they only can be seen here and there. In the beginning they are difficult to find and to be seen. You should wait around 5 to 7 days, you may be can see some cluster of cells. The cells will become more and more and easily to be found. At 19 hours of culture, it will be difficult to find the mscs, as they are very few and scattered as single cell. With time they will form a clone that is easily to be seen.

Be patient.