Crude coal tar ointments are among the most valuable and indispensable of topical medicaments, but the almost magical antieczematous effect of these preparations has seemed inseparable from their ability to produce irritation, as well as from the color and the odor. Four years ago a modified crude coal tar ointment was developed at the State University of Iowa. This ointment, although retaining some of the color and odor of coal tar, has proved to be relatively nonirritating to the diseased skin.
No matter how carefully coal tar ointment U. S. P. XIV is made, using all of the modern techniques and equipment, microscopic examination of thin films of the ointment demonstrates that the tar is unevenly dispersed in the vehicle in coarse particles of extremely variable size. Figure 1 shows the coarse tar particles, some as large as 100μ. It seemed quite possible that some of