8 MICRO-ORGANISMS AND FERMENTATION. 



Another kind of moist chamber, invented by BOETTCHER 

 (Fig. 2), consists of a glass ring cemented to a common object 

 glass, upon which, within the ring, some drops of water are 

 placed. A cover-glass, on the under side of which a small 

 drop of nutritive liquid containing the organisms has been 

 placed, is fastened to the edge of the glass ring by means of 

 vaseline. 



This apparatus is brought under the microscope, and the 

 changes of the organisms are observed from time to time ; or 

 it may be placed in an incubator, maintained at a suitable, 

 constant temperature, and withdrawn at intervals for a thorough 

 microscopical examination. 



These forms of apparatus are adapted to morphological or 

 botanical examinations under the microscope. If, on the other 

 hand, a physiological examination is to be carried out, it is 



FIG. 2. BOETTCHER'S Moist Chamber : a, thin cover-glass ; b, layer of nutritive material ; 

 c, glass ring ; d, water. 



necessary that the pure cultures should be developed on an 

 extensive scale. Among the investigators who have developed 

 this line of work, PASTEUR, LISTER, KOCH, and HANSEN deserve 

 special mention. (See " Preparation of the Pure Culture," 7.) 

 Every fermentation, no matter whether the product be beer, 

 wine, spirit, vinegar, or other liquid, is caused by a growth of 

 living organisms, " organised ferments," and, in practice, our en- 

 deavour is to obtain, as far as actual circumstances will permit, 

 a pure culture of the forms best suited to the manufacture. 

 Although, in our time, with a better understanding of aims and 

 means, great progress has been made in this direction, yet there 

 must always be limits which, from purely practical reasons, 

 cannot be surpassed ; the cultures in the factories will probably 

 never reach such perfection as to keep indefinitely in a state 

 of absolute purity. It is, however, one of the most salient 

 features in the present development of the industry of fer- 



