Investigations have been made into the various cells of the tendon sheath, synovial bursa and articular capsule in man and the goat. We have further injected trypan blue into the tendon sheath and synovial bursa of rabbit and observed the vital staining of their cells.
The cells of synovial membrane lining the tendon sheath, synovial bursa and articular capsule are flat, polygonal or ovoid, the cytoplasm abounding in granules and vacuoles, and there being nuclei which are flat, ovoid or of reniform. In contrast with these cells, there are observed cells with comparatively large vesicular nucleus (nucleolus is clearly seen) with an extended cytoplasm. Intermingled with these cells are seen in considerable numbers cells. resembling fibrocytes, fibrohistiocytes, histiocytes and monocytes. In portions, where the inner stratum of synovial membrane is rugose, or cells are lifted out of the inner surface of synovial membrane, the cytoplasm are small in size and have not spread out extensively, with the nuclei being lightly stained.
Cells constituting villi resemble those of the adjacent synovial membrane, with no presence of special cells.
By injection of trypan blue, synovial cells resembling fibrohistiocytes or histiocytes are capable of receiving and accumulating the dye into their cytoplasm, and as time passes gradually grow in size. The majority cells isolated from the synovial membrane resemble fibriohistiocytes or histio ytes except for leucocytes,
