176 THE AMERICAN MONTHLY [August, 



of their medical treatment was groping in the dark, and it is only since 

 the genesis of many of the most dangerous diseases has been traced to 

 micro-organisms that the right treatment of them has become proba- 

 ble. The announcement that Dr. Robert Koch, of Berlin, has discov- 

 ered a method of inoculation, by which all except the most advanced 

 stages of tubercular consumption can be cured, has given an immense 

 stimulus to scientific medical experiment, and it is hoped that his dis- 

 coveries may be carried to all stages of this dreaded malady. Con- 

 sumption and malaria are two of the most dreaded microbe diseases 

 with which the human race is afflicted, and the discovery of the means 

 of curing them, and preventing their spread, will undoubtedly be the 

 greatest benefit to humanity that medical science can give us. For it 

 is said that owing to the exposure which soldiers are compelled to un- 

 dergo, one-half of the deaths in the German army are caused by tuber- 

 culosis ; and if medical statistics are true, malaria, in all its direct and 

 indirect results, is held accountable for at least one-half of the mortality 

 of the human race. 



Since these are microbe diseases, it may be well to state briefly a few 

 facts concerning the germs of disease. Many bacteria are not more 

 than one-fifteen-thousandth or one-twenty-thousandth of an inch in 

 length, and it has been estimated that it would require four hundred 

 million of them of average size to cover one square inch of surface. 



Bacteria are present in many kinds of matter. They always inhabit 

 the air we breathe and the food we eat, and even the purest natural 

 water is never free from them. A cubic centimetre of average spring 

 or deep well-water generally contains from several hundred to several 

 thousand of them, while a single wine glass full of polluted water is 

 often found to contain more bacteria than there are people on the face 

 of the earth. Bacteria are indeed so abundant in nature and so diffi- 

 cult to separate from living tissue, that when our fingers, even after a 

 thorough washing, have been brought in contact with the biologists 

 sterilized microscope slide, a dozen or more groups of them can be 

 cultivated from it. And they are the most prolific organisms of which 

 we have any knowledge, for in its multiplication a single bacterium 

 may become the causative parent of sixteen million five hundred thou- 

 sand descendants in a day. 



Bacteria are classified according to their shape and structure. Thus 

 the micrococci are composed of single, spherical, or oblong cells ; the 

 strepticocci are composed of cells arranged in chains ; the bacilli are 

 rod-like forms, while the spirilla are of a corkscrew or spiral shape. 



Although our most dreaded diseases are produced by bacteria, the 

 harmless forms of these micro-organisms have their beneficent uses in 

 the economy of nature. Through their efforts sugar is converted into 

 alcohol, and from the carbonic anhydride evolved, the cork of the 

 champagne bottle is discharged with almost explosive violence. While 

 one class is thus engaged in making alcohol, another class is ferment- 

 ing it into acetic acid ; and still other classes are servants to the baker 

 in raising his bread. 



It is to bacteria that we owe the phenomena of fermentation and de- 

 cay. They are the common scavengers of the earth. It has long been 

 known that plants and animals bear a reciprocal relation, each produc- 

 ing the food that is required by the other. Plants take up simple com- 



