THE PROBLEM OF VIRULENCE 13 



the case of a very limited number of diseases infection seems to take 

 place even through the unbroken skin, and the method, often spoken 

 of as the vaccination method of Kolle, employed in many instances 

 when it is desired to produce experimental plague infection in rats 

 or guinea pigs, consists in merely rubbing a small amount of cul- 

 tural material into a shaven area of the skin. However, in this 

 case, as well as in other instances where mere massage of bacteria 

 into unbroken skin has led to successful* inoculation, it is more 

 than likely that success has depended upon either microscopic 

 lesions or possibly the violent introduction of the organisms into the 

 sebaceous glands, the sweat glands, or hair follicles. The defense 

 of intact mucous membranes, however, is by no means impervious. 

 While many organisms can be implanted upon mucous membranes 

 with impunity, there are a number of others that can cause local 

 inflammations upon these and can further pass through them into the 

 deeper tissues and thence into the general system. Thus gonorrhea 

 is ordinarily a disease of implantation upon a mucous membrane, 

 and diphtheria bacilli and streptococci give rise to localized disease 

 on the pharyngeal and nasal mucosse, the latter not infrequently 

 penetrating from the initial point of lodgment upon the mucosa into 

 the deeper tissues and the circulation, causing a condition of "septi- 

 cemia" or "bacteriemia." For the experimental determination of 

 the penetrative power of organisms through mucous membranes the 

 conjunctiva has been a favorite test object, and it has been shown 

 that plague 14 and glanders, 15 as well as hydrophobia, may be trans- 

 mitted by simple instillation of infectious material into the unin- 

 jured conjunctival sac. In the case of hydrophobia 16 it is related 

 that in Paris a young man contracted hydrophobia by rubbing his 

 eyes with a finger contaminated with the saliva of a rabid dog. In 

 the case of syphilis, though often claimed, there is no positive proof 

 to show that infection may take place through the uninjured sur- 

 faces. It has been definitely shown, however, that tubercle bacilli 17 

 may pass into the lymphatics through the intestinal mucosa without 

 there being any traceable injuries on this membrane. 



It may well be, however, that even without the existence of 

 demonstrable morphological lesions penetrability by micro-organisms 

 may presuppose local physiological or functional injury, such as con- 

 gestion or catarrhal inflammation. 



Thus it is seen that the mechanical obstacle to the entrance of 

 micro-organisms offered by skin and mucous membranes, though 

 important and not to be underestimated, is by no means a perfect 

 safeguard. 



14 Germ. Plague Com. Arb. a. d. kais. Gesundheitsamte, Vol. 16, 1899. 



15 Conte. Rev. veterin., Vol. 18, 1893. 



16 Galtier. Compt. rend, de la soc. biol, 1890. 

 17 Bartel. Wien. Klinikhandt, 1906-1907. 



