BACTERIUM LACTIS LISTKK 171 



oxygen, and consequently liable to turn sour with unusual rapidity. The 

 opinion of FJIKMY and BOUTRON-CHALARD (I.) (formed in 1841, under the 

 influence of Liebig's theory), that casein was the cause ("ferment") of lactic 

 fermentation, was revived, though with little success, by A. P. FOKKER (I.) 

 in 1889. 



Pasteur (X.) was the first to describe (1857) an organism characteristic of 

 lactic fermentation, and to prove the same capable of producing acidification in 

 a sweet, sterile milk. This organism, which Pasteur named the " ferment, or 

 yeast, of lactic fermentation," was a bacterium. A pure culture of this, in the 

 present meaning of the term, was at that time unattainable, no suitable method 

 having then been devised. Pasteur demonstrated the difference existing between 

 this "ferment" and that of alcoholic fermentation, and proved that in nutrient 

 media containing sugar, the former organism always sets up lactic fermentation, 

 whilst the other invariably gives rise to alcoholic fermentation. 



This discovery formed an important and welcome support to the theory of 

 specific ferments promulgated by Fr. Kiitzing in 1837, and implying that 

 chemically different fermentations are carried out by physiologically different 

 species of organisms. 



135. Bacterium lactis Lister, and Bacillus acidi lactici Hueppe. 



The important work issued in 1873 by the English surgeon and founder of 

 the antiseptic treatment of wounds has already been noticed ( 68). In that 

 paragraph the methods of working employed by him at that time were referred 

 to as defective and misleading. It was also stated that the name, Bacterium 

 lactis, employed by him was erroneous, the bacterial culture to which it was 

 applied not being a uniform species, but an indefinite (and very probably highly 

 diversified) mixture of different species. 



LISTER (II.) himself very soon recognised the weakness of his arguments, and 

 sought for a remedy. This he found in the so-called dilution method, by the aid 

 of which, in 1877, he produced from sour milk a pure culture of a fission fungus 

 to which he applied the name of Bacterium lactis as before this time correctly. 

 The twofold origin of this name should therefore always be remembered. Lister 

 was also the first to make the observation, subsequently confirmed by Cohn, that 

 lactic acid bacteria, though of frequent occurrence in the rooms of dairies, are 

 comparatively seldom found in the open air. 



The introduction of gelatinised nutrient media into bacteriology also furthered 

 the study of lactic fermentation. By means of this new method of pure culti- 

 vation HUEPPE (IV.) in 1884 isolated from sour milk a microbe known as 

 Bacillus acidi lactici, which, in so far as can be gathered from the description 

 given, was identical with Lister's bacterium. Hueppe also made the more important 

 discovery that several different species of bacteria are capable of setting up lactic 

 fermentation. However, before noticing these other organisms, we will examine 

 more closely the Bacillus acidi lactici, which occurs in the form of non-motile 

 rods 1.0-1.7 P l n g an d 0.3-0.4 p. broad, mostly in pairs and but rarely united 

 to form a four-cell chain ; it is aerobic and forms endospores. This ferment 

 acidifies milk between the temperatures of 10 and 40 C., the reaction being 

 accompanied by the precipitation of casein, and an evolution of gas. On gelatin 

 plates the organism forms white colonies which do not liquefy the nutrient 

 medium. 



In addition to the five species of lactic acid bacteria discovered by Hueppe 

 and to which Aficroooxas pro iigiosus belongs many others possessed of the same 

 property have been nude known to us, by Maddox in England (1885), Beyer in 

 North America (1886), and FOKKER (II.) in Holland (1890). 11. KRUEGER (I.) 



