406 Chapter XIII 



does not prevent him from defending himself against the entry of 

 micro-organisms by the cutaneous path. Sabouraud^, a well-known 

 dermatologist, has given a very concise and at the same time very 

 complete sketch of the part played by the skin in the protection 

 [426] of the body against micro-organisms ; from this author the following 

 data are borrowed. 



The epidermic layer sets up a defenc e by the_ production and 

 expulsion of corneaLnfills. In the normal course of the li^ of The 

 epidermis, the cells of the deeper layers,„co ming to t he s urface, be- 

 come exfoliated and are jt hrown o ff. "There is thus produced, a 

 continual exfoliation of Jihe jdead_laye^ and a continual eviction 

 of such micro-organisms as are living._on theuh The epidermis is 

 dense and its cells have a hard envelope ; the micro-organism is 

 not endowed with motion, or at least not with sufficient to be of 

 service in effecting an entrance. It can only penetrate the epidermis 

 by multiplication in situ, a micro-organism originates alongside 

 another, another in front of it, and in front of this again others. In 

 this way they burrow between the apposed cells just as a root 

 penetrates into the ground ; so great is the resistance of the horny 

 cells that we never find any micro-organisms within them, but 

 between them only " (p. 734). The epidermic cells, containing micro- 

 organisms, exfoliate, and the skin is thus ridded of them. Frequently 

 the process, as it goes on constantly and slowly, is invisible ; but 

 often, on the other hand, it becomes exaggerated and manifests itself 

 in the form of a cuticular desquamation which leads to the elimination 

 of a large number of micro-organisms. The patient may retain " such 

 pellicles for ten years, and even longer, without presenting anything 

 else but these, and there are many other chronic squamous infections 

 in which the course is uncomplicated by even an erosion or the 

 slightest wound.'' 



The connective tissue of the human skin is also fully able to 

 defend itself ; it is extremely vigorous and represents a real obstruct- 

 ing and resisting tissue. The penetration of parasites sets up in it 

 a thickening of ^he^ fibrous tissue ; this effects a localisation of the 

 microbial focus. To appreciate the effectiveness of this dermic de- 

 fence, we have only to compare the slow growiih of lupus, a form of 

 cutaneous tuberculosis, with that of tuberculosis of the lungs and 

 other viscera, or the slow evolution of farcy, or cutaneous glanders, 

 with that of the visceral form of the disease. 



^ Ann, de dermat. et de syph., Paris, 1900, t. x, p. 7*29. 



