OTHER GERM DISEASES 337 



branes of the air passages, they may grow and produce 

 colonies of bacteria. These colonies in their grow-th may 

 break up the surrounding tissues or may produce poisons 

 or toxins which are absorbed by the blood and carried to 

 parts where they produce serious harm and may even pro- 

 duce death. 



Tuberculosis or consumption is one of these bacterial 

 diseases. The bacteria which cause it are rod-shaped 

 bodies, known as the bacillus tuberculosis. These bacteria 

 infest the air passages and sacs and gradually destroy the 

 surrounding tissues. Unless removed, they eventually 

 produce death. The sputum which a consumptive coughs 

 up consists of masses of these bacteria and broken down 

 tissue, and soon sets free the bacilli if allowed to dry on the 

 floor or street; these may then be blown about by the 

 air and thus be inhaled. It is on this account that Boards 

 of Health make strenuous rules against spitting in public 

 places, and are also coming to insist more and more upon 

 the isolation of consumptives in special sanatoriums where 

 they will not be able to spread this dangerous disease. 



Diphtheria, membranous croup, and la grippe are all 

 germ diseases produced by special kinds of bacteria which 

 settle in the throat and grow there. These forms produce 

 their effect by poisons called toxins, which they give off, and 

 which enter the blood, sometimes with fatal results. An 

 effective cure for diphtheria has been found in a liquid called 

 diphtheria anti-toxin; when this is introduced into the cir- 

 culation it destroys the toxin produced by the bacteria. 

 All diseases that are produced by bacteria are called 

 communicable diseases, since they may be transmitted 

 from one person to another by the air which carries the 

 dread germs. Some of these bacterial diseases are produced 



EDDY. PHYS. — 22. 



