No one now doubts that herpes zoster is a specific microbic disease. Although it is not known to be transmitted from person to person, it occurs in communities in groups of cases at a given time. It has also an almost regular sequential course, an invasion, a status of maintenance and a decrease which take place in a limited period, and its onset and sometimes its status of maintenance are often accompanied by fever. Furthermore, one attack appears to grant immunity, as a second attack is rare. Finally, the characteristic neural lesion on which, since Barensprung's day, the eruption has been conceded to depend, is inflammatory. It is an inflammation of the posterior root ganglion, just such as would be produced by a micro-organism.
THE UNILATERALITY OF HERPES ZOSTER AND ITS LIMITATION TO A REGION
Attention may here be drawn to the fact that only one ganglion, or two at