HOW BACTERIA ENTER THE BODY 495 



the body. For example, diphtheria toxins produce soreness in a 

 throat on which the diphtheria bacilli are multiplying, and the 

 blood carries the exotoxins around the body. The heart, kidney, 

 or some other remote organ may be affected. The tetanus bacilli 

 develop their exotoxin at the place where they enter the body. 

 This toxin then goes to the various tissues, especially the nerves. 



Bacterial poisons or endotoxins result from the breaking down 

 or the disintegrating of certain bacteria. It is thought by some 

 scientists that these endotoxins are never produced, as are the 

 exotoxins, by the bacteria themselves, but are only set free during 

 the breaking down of the bacterial body. The typhoid germs 

 contain a very powerful endotoxin; tuberculosis, too, has a 

 strong endotoxin. These are probably due to the breaking down 

 of the proteins in the bacteria cell and the consequent formation 

 of substances that are poisonous to the tissues. They are more 

 correctly called poisonous split-proteins. There is still a fourth way 

 in which bacteria are related to disease. Protein foods are some- 

 times attacked by bacteria and are only partly digested or broken 

 down to a group of products called ptomaines, some of which are 

 injurious to the body. Ptomaines differ from toxins in that they 

 are products of food decomposition, while the toxins are products 

 of bacterial manufacture. The ptomaines are usually formed in 

 foods under storage conditions in the shop or house, and not in the 

 body. For example, if protein foods are not properly preserved, 

 bacteria may attack them, causing disintegration. Partially dis- 

 integrated fish, crabs, cheese, oysters, or milk often contain 

 injurious ptomaines and, when eaten, will have a poisonous 

 effect on the body. 



How bacteria enter the body. One of the common avenues of 

 invasion for bacteria is the alimentary canal. Bacteria of typhoid 

 fever and tuberculosis are frequently taken in with milk or other 

 food through the mouth. Pencils, finger nails, and drinking cups 

 are often responsible for an attack of diphtheria or scarlet fever. 



