II. 



THE LOWER MICRO-ORGANISMS AND THEIR RELATION TO 



EVERY-DAY LIFE. 



By D. H.UIVEY Attfield, M.A., M.B., CM., D.P.H. (Cantab.). 



A Lecture delivered at Watford, 2Zrd January, 1894. 



(Abridged. ) 



My subject is so extensive that anything like a comprehensive 

 survey of it woukl require not merely one lecture but a series. 

 Hence the particular micro-organisms I can deal with are only 

 those which one is constantly hearing of, either as our kindly friends 

 or fierce foes. To the naked eye they are in\'isible, yet they are 

 quite capable of working an infinity of good or harm that might 

 well have earned for them in years gone by, before their corporeal 

 existence was demonstrated, the names of good and evil spirits. 

 One at least really was, as we now know, of service to the old 

 miracle-mongers — I allude to the micro-organism which is the cause 

 of what they termed the *' Blood-portent on Bread," and the cause 

 of milk changing into so-called blood. This is the Bacillus pro- 

 digiosus, which, when growing on bread or milk gives to either a 

 reddish appearance. 



To micro-organisms we owe that conversion of sugar into alcohol 

 which is essential to the production of wine, beer, and spirits, and 

 they are essential to that rising of dough which is a part of the 

 e very-day process of bread -making. There is one bacterium which 

 lives, moves, and multiplies in alcohol. So far from being a tee- 

 totaler, it swallows or absorbs nothing but alcohol from birth to 

 death. I allude to the Bacterium aceti, the active principle of the 

 so-called vinegar plant, whose life-work is to convert the alcohol 

 of beer and wine into the acetic acid characteristic of vinegar; 

 indeed, ordinary vinegar cannot be produced without this micro- 

 organism. 



The greater number of these very important yet excessively 

 minute bodies are plants of the simplest structure, with the most 

 elementary modes of propagation, but yet with extraordinary 

 powers of multiplication. With regard to this latter statement I 

 may say that in the course of some experiments made by Professor 

 Watson Cheyne with a microbe known as the Staphylococcus 

 pyrogenes-aureus, 248 individuals became over 20,000,000 in the 

 short space of twenty-four hours. 



These micro-organisms are often, though from an etymological 

 point of view incorrectly, designated under the general title of 

 Bacteria. As far back as 1728, Leuwenhoeck saw something in 

 putrid water, but in those early days microscopes were poor, and 

 though he may have seen bacteria his observations were far from 

 definite. Xot till 100 years later were any authenticated observa- 

 tions made, when Ehrenberg stated that we were surrounded on all 

 sides by micro-organisms. Schwann, a few years after this, stated 



