524 INFECTION AND IMMUNITY. 



general resistance is lowered, as in typhoid, typhus, 

 variola, measles, etc. Yon Lingelsheim character- 

 izes their relation to diphtheria as follows : they 

 injure the tissues locally, penetrate beneath the 

 membrane into the tissues and take part in the 

 formation of the membrane; they increase the 

 virulence of the diphtheria bacillus; alone, or in 

 conjunction with the diphtheria bacillus, they may 

 invade the lungs, causing bronchopneumonia, or 

 enter the circulation and injure various organs, 

 but particularly the kidneys. Their method of 

 entering the lungs from the upper respiratory pas- 

 sages probably is similar to that involved in pneu- 

 mococcus infection. Furthermore, having obtained 

 a footing in the pharynx, for example, they may 

 reach the bronchi and perhaps the alveoli by exten- 

 sion along the surface. 



Streptococci are usually the essential organisms 

 in follicular tonsillitis, are frequently found in 

 alveolar abscesses, but in both instances may be 

 mixed with other organisms, especially the staphy- 

 lococcus and pneumococcus. Streptococci in the 

 throat may appear in diplococcus form in fresh 

 preparations. Beginning primarily in the nose, 

 tonsils or pharynx, streptococcus infection may 

 extend to the adjacent sinuses, the middle ear, 

 meninges, or through the tonsils may cause sys- 

 temic infection with endocarditis as a frequent 

 complication. 



Endocarditis. The endocarditis caused by streptococci usually 

 is vegetative in character, but may be ulcerative, 

 and may result in metastatic foci of infection 

 (e. g., septic infarcts). Infarcts from strepto- 

 coccus endocarditis are not alwavs infected, how- 



