282 HUMAN PHYSIOLOGY CHAP, xix 



tissue of the body, others almost anywhere. Many 

 kinds of bacteria are entirely harmless when taken into 

 the body, because they do not find conditions favorable 

 for rapid multiplication. We think that all bacteria 

 would produce diseases if they grew as fast in the body 

 as they can under favorable conditions. It is well 

 known that bacteria produce poisonous products to 

 which .diseases are due. There are then two important 

 factors to consider : first, the ability to multiply, and 

 second, the capacity to manufacture poisons. The dis- 

 ease germs may become so numerous as to interfere, 

 by their very presence, with the circulation, and cause 

 diseases in any part of the body. The chief danger 

 comes from the poisonous products formed out of the 

 body substances and foods and given to the blood or 

 tissue cells. Just as soon as a sufficient amount of 

 poison has been absorbed fever is produced. 



Consumption, diphtheria, pneumonia, typhoid fever, 

 cholera, lockjaw, malaria, grippe, smallpox, scarlet 

 fever, measles, mumps, whooping cough, meningitis, 

 erysipelas, scarlatina, leprosy, chicken pox, yellow fever, 

 relapsing fever, anthrax, glanders, and dysentery are 

 among the communicable diseases, many of which are 

 known to be due to these little germs. 



193. How Disease Germs get into the Body. If we 

 wish to war against the disease germs, we must know 

 where they come from, how they travel from one place 

 to another, and how they get into the body. Many 

 germs can live in the body of the host, and may be 

 transferred to another person by actual contact as, for 



