PARASITES AND DISEASE (VEGETABLE PARASITES) 157 



cerations, in phagedenic ulcer, and the local tissue death 

 of dental caries. Degenerative changes also occur 

 secondary to many of the proliferative processes, as in 

 the necrosis of tubercles. 



The effects of the products of bacteria are sometimes 

 local, but they are more often of a general nature. The 

 toxins may cause local suppuration or they may enter 

 the circulation and become localized in some special 

 tissue, as the localization of tetanus toxin in the cells 

 of the central nervous system, to which it is highly 

 destructive, though harmless to other tissues of the 

 body. Other toxins have a selective action also, as 

 the preference of the diphtheria toxin for involuntary 

 muscle cells. 



DISEASES DUE TO BACTERIA 



SUPPURATIVE DISEASES (FURUNCULOSIS, ABSCESS, OSTEO- 

 MYELITIS, OTITIS MEDIA, MASTOIDITIS, ETC.) 



Definition. Diseases characterized by the formation 

 of pus. 



Etiology. The usual cause of these disorders is the 

 introduction into the tissues of the Staphylococcus 

 albus, aureus, and citreus, streptococcus, under certain 

 conditions the pneumococcus, and the gonococcus. The 

 typhoid bacillus and the colon bacillus give rise to sup- 

 purative diseases, and they are sometimes present as 

 mixed infections, with the ordinary pus microbes. 



A lowered resistance, debility, anemia, and lowered 

 opsonic index are contributory causes. That these 



