﻿4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 59 



abraded skin surface may be v the source of a diphtheric or scarlet 

 fever infection. 



The mere presence of highly invasive and infectious bacteria upon 

 a mucous surface is not tantamount to infection. In every epidemic 

 of disease, we either know or have reasons for believing that many 

 more persons carry the germ of the disease than actually come down 

 with it. Thus diphtheria bacilli and meningitis cocci — to mention 

 two examples only — are, during epidemics of their respective affec- 

 tions, found in the throat and nose of many more healthy than dis- 

 eased persons ; and similarly during the prevalence of cholera, dysen- 

 tery, and typhoid fever, the bacilli causing them are present in the 

 intestinal tract of persons in health. And yet, while these healthy 

 carriers of infection may escape illness altogether, they are often the 

 means of transporting disease to other and susceptible persons who 

 succumb to it. 



The reason for this phenomenon is to be sought in an adequate 

 system of external defensive mechanisms in the group resisting in- 

 fection, and an inadequate system in the other acquiring it. That 

 this is the true explanation is indicated by the effects of indiscretion 

 in diet or the ingestion of irritating substances upon such a potential 

 cholera case, for through these a healthy carrier may be transformed, 

 in a few hours, into a severe and often hopeless case of cholera. 



That the broken skin surfaces admit infection is common experi- 

 ence, but luckily the infections thus produced are relatively insignifi- 

 cant. And yet, as the result of injury or a surgical wound, they may 

 be severe. There is, however, no difficulty in following such coarse 

 phenomena as these instances present. It is somewhat more difficult 

 to follow the more remote infections, from this source, that lead 

 finally to tetanus, or lockjaw, or to hydrophobia. In the former, the 

 spores of the tetanus germ, which are enduring and highly resistant 

 bodies, are introduced into the wound with foreign matter — dirt, 

 splinters of wood, wads of paper, etc. — and in the latter, the germ of 

 hydrophobia is injected into the tissues by the bite of a rabid animal. 

 In both instances, the infection develops slowly, often after the orig- 

 inal wound is healed and perhaps forgotten. In neither case has the 

 infecting organism power to penetrate the unbroken skin. In both, 

 again, the infection attacks the central nervous system, to which it 

 gains access by travelling along the peripheral nerves; and the 

 seriousness of the respective diseases produced arises from this direct 

 attack upon the important cells of the brain and spinal cord. 



