In this paper, three strains of the herpes virus have been dealt with. The H.F. II strain was obtained from the subject H.F. 4 years after the H.F. I strain was secured. H.F. is a victim of recurrent herpes. If the subject is also a chronic carrier of the herpes virus, then it is not one, but two or more strains which are persistently carried. The H.F. II strain is of mitigated pathogenic action for the rabbit, as compared with the H.F. I strain; it is to be classed as dermatotropic rather than neurotropic. And yet, in the subject there was no indication that the attack of herpes provoked was different from the other attacks associated with the H.F. I virus.
The other two herpes strains derive their interest from the fact that they came also from persons who suffer from repeated attacks of labial herpes. One strain proved highly neurotropic, resembling in this respect the H.F. I strain; the other was hardly neurotropic at all, but was none the less definitely dermatotropic. It may be possible at a later date to secure other samples of virus from these individuals for comparison. The dermatotropic F. strain penetrates to the central nervous system far more readily and certainly from the skin than from corneal surfaces.
The recovered inoculated rabbits showed only relative protection to reinoculation of the herpes virus. A notable difference appeared in the degree of protection acquired, on the one hand by the cornea and on the other by the brain. While the one was partial, the other was complete. The complete resistance of the brain was shown (a) by the complete failure of the intracerebral inoculation, and (b) by the absence of circling movements following corneal inoculation.