308 AGRICULTUBAL AND INDUSTRIAL BACTEEIOLOGY 



termed a septicemia. Some authors use the term septicemia 

 and bacteremia as entirely synonymous. A toxemia is a 

 disease such as diphtheria or tetanus in which the causal 

 microorganism remains more or less localized in or on the 

 tissue where it produces a poison or toxin which enters the 

 circulation and causes injury to the various body tissues. In 

 some diseases the microorganisms tend to remain localized 

 and produce marked inflammation without any generalized 

 symptoms. Infections of this type are sometimes referred 

 to as phlogistic. A sapremia is a disease caused by the 

 absorption of poisonous putrefactive products from decay- 

 ing or necrotic tissue. For example, the retention of the 

 placenta or afterbirth in a cow after parturition and its 

 subsequent decay or decomposition in the uterus may lead 

 to the development of a sapremia. 



Diseases are sometimes named after the causal organism. 

 A disease caused by a Bacterium, for example, might be 

 termed a bacteriosis, one caused by a Spirillum- a. spirillosis, 

 and one caused by a Spirochceta a spirocJicetosis. 



Diseases of plants produced by bacteria are sometimes 

 known as galls or tumors, as for example, crown gall of the 

 the apple ; blights, such as pear blight ; leaf spots ; rots, such 

 as the blackrot of cabbage; and wilts, such as the wilt of 

 cucumber or sweet corn. 



The infectious diseases, that is, the diseases caused by 

 microorganisms, may be divided into two general groups; 

 those in which the causal agency is definitely known, and 

 those in which it is not definitely described. Under the 

 first heading we have diseases which may be caused by 

 bacteria, by yeasts, by molds and by protozoa. Under the 

 second heading there are diseases caused by filterable 

 viruses, that is, microorganisms apparently so smaU that, 

 at least in certain phases of their life history, they can pass 

 through the porcelain filters. In still other cases the causal 

 organism has completely eluded the search of the bacteriol- 

 ogist thus far. 



