THE FUNGI 



257 



the blood and causes the symptoms of the disease in man and 

 animals. To counteract the effect of the toxin the body cells 

 of the diseased person secrete antitoxins, which, if secreted in 

 sufficient amount, can neutralize the effects of the diphtheric 

 toxin and thus arrest or stop the progress of the disease. Other 



FIG. 138. Bacterial colonies growing on a gelatin culture 



A sterilized plate of gelatin exposed for five minutes in the hallway of a school- 

 room, and then closed for five days, developed the above colonies. This illustrates 

 the dissemination of bacteria in the air and the danger of increasing the normal 

 number by stirring up the dust on the floor of a room. From Bergen and Caldwell's 

 " Introduction to Botany " 



antitoxins produced in animals may, as in the case of diphtheria, 

 be injected into the blood of the diseased person and thus aid 

 in checking the progress of the disease. Antitoxin treatment is 

 especially helpful in diphtheria and tetanus, or lockjaw. 



The ptomaines are complex chemical bodies which develop in 

 various organic substances, including canned foods, ice cream, 

 etc. They are sometimes poisonous and sometimes harmless, and 

 must not be confused with the toxins, which are definite poisonous 



