8 ESSAYS ON BACTERIOLOGY. 



the fact that so-called membranous croup is usually 

 laryngeal diplitheria, and is therefore to be looked 

 upon as an infectious disease. A similar thing is true 

 of pneumoma, and notably of tuberculosis, over tbe 

 character and classification of which a controversy 

 was waged. We now know that tuberculosis is an 

 infectious disease; a half -century ago this was only 

 surmise. 



We have learned, too, as a result of bacteriological 

 studies, more of the importance of infection as an in- 

 direct cause of suffering and death. Thus, while we 

 do not consider apoplexy an infectious disease, we 

 have come to see more and more clearly that, in the 

 last analysis, it is frequently a product of infection. 

 The blood vessels of the brain do not break unless 

 they are injured or diseased, and the disease which 

 thus makes a cerebral apoplexy possible is often of in- 

 fectious character or the indirect result of an infec- 

 tion. It matters not that this indirect result is some- 

 times seen only after many years: the fact remains, 

 and must constantly be borne in mind in practical 

 medicine. The man who falls by an apoplectic stroke 

 often falls from an infectious blow struck years be- 

 fore, perhaps when sowing the proverbial wild oats of 

 youth. And thus one may literally reap a harvest of 

 death from seeds sown and long since forgotten. 



Thus we learn, notwithstanding the charge some- 

 times brought that the germ theory of disease is made 

 to account for too much, that its field of action is 



