NOVY ON BENEFITS OP BACTERIOLOGY. 15 



single-celled organism, the chief representative of which are the bacteria, 

 these complex dead molecules are split up in CO., HN0 2 , HNO s , and other 

 products which are then utilized by new life. The law of conservation 

 of energy and of matter finds its parallel in conservation of life. 

 Decay and putrefaction from this standpoint is not, as Pasteur has 

 pointed out, a phenomenon of death so much as a phenomenon of life. 



The relation of bacteria to fermentation is of the greatest practical 

 importance. Many of the products to which they give rise are directly 

 utilized by man. In this sense bacteria are directty beneficial — a fact 

 which is too often lost sight of and indeed overshadowed by the in- 

 jurious action of some forms of bacteria on man and animals. To illus- 

 trate what great practical and industrial importance is attached to cer- 

 tain microorganisms we may mention the yeast plant. All the alcohol of 

 commerce is derived by fermentation induced by the yeast cell. Practi- 

 cally all the acetic acid, that is vinegar, is obtained through the fermen- 

 tative action of bacteria on alcohol. Other substances such as lactic acid, 

 butyric acid, etc., are obtained from the same source. The vast deposits 

 of soda saltpetre in South America and the saltpetre of India owe their 

 origin unquestionably to the industrious bacterial cell. 



Bacterial decompositions or fermentations occur to a large extent 

 among certain foods. Indeed many articles of food, such as cheese, 

 butter, koumiss, etc., owe their special flavors and characteristics 

 largely to the fermentation changes which have taken place. The study 

 of bacteria has further shown that many foods, as meat, milk, cheese, etc.. 

 may take on poisonous properties, the result of the formation of poisons 

 within the food by the special bacteria which have been introduced and 

 have developed therein. Some of these bacterial poisons, especially those 

 which are basic in character, and thus chemically closely allied to the 

 vegetable alkaloids, are of great practical importance in legal medicine. 

 In their chemical reactions they may easily be mistaken for poisonous 

 alkaloids and thus lead to the conviction of otherwise innocent persons. 

 That such fatal mistakes have been committed is perhaps only too true. 

 The lessons that have been gained by experience and through the labors 

 of Selmi are now so well recognized that it is no longer an easy matter 

 to secure conviction in such well known poisonings as strychine, mor- 

 phine, etc. 



That which has brought bacteria most into • prominence is un- 

 questionably their relation to disease. Ever since the discovery of the 

 microscope there have been bold thinkers who did not hesitate to declare 

 that communicable diseases as syphilis, smallpox, etc.. were due to living 

 forms. The germ theory of disease, which may be said to have been born 

 in the mind of Kireher more than two hundred years ago. has after a ser- 

 ies of remarkable vicissitudes become firmly established. A theory ceases 

 to be a theory when facts have been accumulated and proofs furnished. 

 This has been done with a large number of infectious diseases, so that 

 today, to speak of the germ theory of disease is to confess a lack of famil- 

 iarity and a lack of knowledge of the growth of one of the most important 

 branches of medicine. The germ theory is a thing of the past. Bacteria 

 and other organisms are the causes of infectious disease. This has been 

 proven as clearly as any demonstration ran be made. We do not theorize 

 when we state that arsenic, strychine, morphine and similar chemical 



