INTRODUCTION 7 



materials as grape juice, wine, blood, tissues of plants and animals 

 and preserve them free from decomposition and from all microbic 

 life, merely by effectively avoiding contact with germs during 

 collection and storage. 



The agency of microbes in fermentation was ridiculed by 

 Liebig, the most prominent chemist of the time, who steadfastly 

 continued to regard decomposition of organic material as a 

 purely chemical process uninfluenced by biological activity. His 

 ideas prevailed for a time because of his prominent position. 

 The correctness of Pasteur's contention is now universally ac- 

 cepted. Nevertheless it should not be forgotten that many 

 organic substances are in themselves so unstable that even in the 

 absence of microbic life they disintegrate, or become oxidized in 

 the presence of the air. These changes are different from those 

 ordinarily known as fermentation and putrefaction. 



Pathology and Hygiene.- — The history of the development of 

 our ideas concerning the relation between microbes and disease 

 is one of the most interesting and perhaps the most important 

 chapter in the history of bacteriology. The customs and rec- 

 ords of the ancients give evidence that they recognized the pres- 

 ence of an unseen agency in the body of the diseased individual 

 capable of causing sickness in others. This was recognized by 

 the ancient Persians as recorded by Herodotus. The isolation 

 of lepers by the ancient Hebrews shows that the infectious char- 

 acter of this disease has long been known, though other affec- 

 tions than leprosy were probably confused with this disease. "He 

 is unclean; he shall dwell alone; without the camp shall his 

 habitation be." (Lev. XHI, 46.) There is, in fact, much in the 

 laws of Moses that points to some knowledge of the nature of 

 infection. "This is the law, when a man dieth in a tent all that 

 come into the tent and all that is in the tent shall be unclean for 

 seven days. And every open vessel that has no covering on it 

 shall be unclean." (Numb, y IX, 14, i s .) " Everything that may 

 abide the fire, ye shall make it go through the fire, and it shall 



