138 THE MICROSCOPE. Sept. 



diseases, it was not until the researches of Davaine, Pasteur 

 and R. Koch that positive proof was offered. Since that 

 time the etiology(cause) of many of the contagious dis- 

 eases has been determined and the life history of the 

 organisms so thoroughly studied that the experienced 

 bacteriologists can select them from a numl)er of other 

 kinds with the ease and certainty that a farmer separates 

 the goats from the sheep. And while we do not know 

 what organism causes even some of the most common dis- 

 eases such as small-pox, rabies and scarlet fever, it simply 

 serves to demonstrate the youth of the science and the 

 vast possibilities before it. And when we remember 

 what has been accomplished in the last two decades we 

 can but stand amazed at the possibilities before us. 



There is still much to be desired in our knowledge of 

 infectious diseases and their therapeutics, but there is 

 within ouE grasp sufficient knowledge of their manner of 

 attack, as that with the proper care most of the diseases 

 can be prevented, and the prevention of a disease is much 

 more desirable than its cure. 



The Mode of Infection by Bacteria. — Now that it 

 is definitely settled that the bacteria are the sole cause of 

 infectious diseases, it is interesting to understand their 

 mode of attack. First, they may be inhaled and attack 

 the lungs or respiratory passages, as in the case of 

 pneumonia, tuberculosis and diphtheria. Second, they 

 may enter the stomach with the food or drink and find 

 lodgment in the intestines, e. g., cholera and typhoid 

 fever. The third channel is through wounds, illustrated 

 in the case of rabies and lockjaw. A few organisms like 

 anthrax can enter the system in all of those ways. It 

 finds its way into the body through the lungs in the 

 "woolsorter's disease," through the stomach in cattle, 

 causing splenic fever, by means of cuts in animals and 

 man, the latter causing malignant pustule. 



