42 JOURNAL AND PROCEEDINGS 



acquired au active immunity. But suppose we decide to assist the 

 child in his battle against the infection by injecting into his system 

 an antitoxin which we have obtained from some outside source, 

 and in this way render the toxin harmless, we say the child has an 

 2iC(\}x\XQ.di passive immunity, i.e., an immunity not due to any activ- 

 ity on the part of the tissues. 



Nature has provided the human body with a splendid arma- 

 mentarium wherewith to resist the continuous onslaughts of its 

 microbic enemies. Surrounding the outside of the body is the skin, 

 which, when unbroken, forms an impenetrable barrier to the mil- 

 lions of germs normally residing on its surface ; and as the outer 

 layers of the skin are being constantly thrown off from the body, 

 they carry with them the invading microbes. When the skin is 

 broken there occurs a serous exudate that not only forms a scab, 

 and thus mechanically protects the injured surface, but also con- 

 tains germicidal substances. Should the bacteria alight on any of 

 the mucous surfaces of the body, here again they meet resistance. 

 Not only does a layer of mucus offer mechanical protection to un- 

 derlying parts, but it has also an attenuating effect on the virulence 

 of many organisms, and being constantly excreted, embedded or- 

 ganisms are continuously removed from mucous surfaces. 



The mucous lining of the eye — the conjunction — has an out- 

 side guard of eye brows, eye lashes and eye lids. Should a microbic 

 invader carry these outer defences, it has yet to encounter the 

 tears, which neutralize its poison and wash it away from its danger- 

 ous position. 



Should we breathe contaminated air, the germ elements have 

 many difficulties to overcome before they find a lodging place 

 suited to their purpose. At the opening of the nostril the hair 

 filters out many invaders at the start. Those that successfully 

 pass this barrier travel along a very tortuous highway where they 

 strike against moist mucous surfaces, become embedded in mucus 

 and are thus expelled. Should any pass still further and reach the 

 lung passages they are caught on the ciliated epithelium and grad- 

 ually carried toward the exterior or are expelled by coughing. 



At least thirty varieties of micro organisms flourish in the 



