342 CARRIERS OF DISEASE 



with the air into the air-passages and the lungs ; and 

 once in these chambers, which have only soft lining- 

 surfaces, they are able to penetrate into the substance of 

 the body. Many of those which enter the digestive canal 

 do not require to penetrate further, but multiply exces- 

 sively in the contents of the bowel, and there produce 

 poisons, which are absorbed and produce deadly results 

 such are the bacteria which produce Indian cholera and 

 ordinary diarrhoea whilst the kind causing typhoid fever 

 not only multiplies in the gut, but penetrates its surface. 



The protective surface of man's body is broken, and 

 the way laid open for the entrance of microbes in various 

 ways. A slight scratch, abrasion, or even " chapping " is 

 enough. Thus, a mere breaking of the skin of the 

 knuckles by a fall on to dirty ground lets in the deadly 

 bacterium of lockjaw (tetanus), which is lurking in the 

 soil. Leprosy is communicated from a leper in the same 

 way. The almost ubiquitous bacteria of blood-poisoning 

 (septicaemia) may enter by the smallest fissure of the 

 skin, still more readily by large cuts or wounds. The 

 bites and stabs of small and large animals wolves, dogs, 

 flies, gnats, fleas and bugs, also open the way, and often 

 the deadly microbe has associated itself with the biting 

 animal and is carried by it, ready to effect an entrance. 

 Thus rabies (hydrophobia) is introduced by the bites of 

 wolves and dogs, and a whole series of diseases such as 

 plague, malaria, sleeping-sickness, gaol-fever (typhus), 

 yellow fever, relapsing fever, and others, are introduced 

 into the human body by blood-sucking insects. Hence 

 the immense importance of treating every slightest wound 

 and scratch with chemicals (called " antiseptics "), which 

 at once destroy the invading microbe and of keeping a 

 wounded surface covered and protected from their ap- 

 proach. In ways at one time unsuspected, such openings 

 may be made by which poisonous microbes enter the body. 



