ORIGIN OF BACTERIA AND THEIR DISTRIBUTION 25 



Proteins. The proteid contents of the bacterial cell may 

 cause inflammation and fever. 



Putrefaction. When fermentation is accompanied by 

 development of offensive gases, a decomposition occurs, which 

 is called putrefaction, and this, in organic substances, is due 

 entirely to bacteria. 



Producers of Disease. Various pathologic processes are 

 caused by bacteria, the name given to such diseases being 

 infectious diseases, and the germs themselves called disease- 

 producing or pathogenic bacteria. Those which do not form 

 any pathologic process are called non-pathogenic bacteria. 



Ferments may be diastatic, changing starch into sugar, or 

 proteolytic, transforming albumins into more soluble substances, 

 of which gelatin liquefaction is an example. Inverting, chang- 

 ing a sugar from one that does not undergo fermentation into 

 one that does. 



Coagulating, fat-splitting, hydrolytic ferments are some of the 

 other varieties. 



Toxins and toxalbumins are various albuminoids produced 

 in the animal organism and in culture-media which are very 

 poisonous, and are considered the prime cause of disease. 



Pigmentation. Some bacteria are endowed with the 

 property of forming pigments either in themselves, or pro- 

 ducing a chfomogenic body which, when set free, gives rise to 

 the pigment. In some cases the pigments have been isolated 

 and many of the properties of the anilin dyes discovered in them. 



Phosphorescence. Many bacteria have the power to form 

 light, giving to various objects which they inhabit a character- 

 istic glow or phosphorescence. 



Fluorescence. An iridescence, or play of colors, develops 

 in some of the bacterial cultures. 



Gas-formation. Many bacteria, anaerobic ones especially, 

 produce gases, noxious and odorless; in the culture-media the 

 bubbles which arise soon displace the media. 



Odors. Some germs form odors characteristic of them : some 

 are pleasant and even fragrant; others, foul and nauseous. 



Effect of Age. With age, bacteria lose their strength and 

 die. 



