54 BIOLOGY AND TECHNIQUE 



vestigating this function of bacteria, originated by Ejkniami, 10 con- 

 sists in covering the bottom of a Petri dish with tallow and pouring 

 over this a thin layer of agar. Upon this, the bacteria are planted. 

 Any diffusion of lipase from the bacterial colonies becomes evident 

 by a formation of white, opaque spots in the tallow. Carriere 11 was 

 able to demonstrate a fat-splitting ferment for the tubercle bacillus. 

 Apart from the importance of these enzymes in nature for the 

 destruction of fats, they are industrially important because of their 

 action in rendering butter, milk, tallow, and allied products rancid, 

 and are medically of interest for their action upon fats in the intes- 

 tinal canal. 



Enzymes of Fermentation (The Cleavage of Carbohydrates by 

 Bacteria). The power to assimilate carbon dioxide from the 

 atmosphere is possessed only by the green plants and some of the 

 colored alga?, and the sulphur or thiobacteria. All other living 

 beings are thus dependent for their supply of carbon upon the 

 synthetic activities carried on by these plants to the same degree 

 in which they are dependent upon similar processes for their nitrogen 

 supply. The return of this carbon to the atmosphere is, of course, 

 brought about to a large extent by the respiratory processes of the 

 higher animals. The carbon, which, together with nitrogen, forms 

 a part of protein combinations, is freed, as we have seen in a previous 

 section, by the processes of protein cleavage. That, however, which 

 is inclosed in the carbohydrate molecule, is set free by the action 

 of yeasts, molds, or bacteria, by an enzymatic process similar in 

 every respect to that described above for the process of protein 

 cleavage. 



FERMENTATION. The power of carbohydrate cleavage is possessed 

 by a large number of the yeasts and bacteria. The process, as has 

 been indicated, is of great importance in the cycle of carbon com- 

 pounds for the return of carbon to its simplest forms, and is, further- 

 more, as will be seen in a later section, of great utility in the indus- 

 tries. In each case the power to split a particular carbohydrate 

 is a more or less specific characteristic of a given species of micro- 

 organism, and for this reason has been extensively used as a method 

 for the biological differentiation of bacteria. In the course of much 

 careful work upon this question it has been ascertained that the 



Ejkmann, Cent. f. Bakt., I, xxix, 1901. 



11 Carriere, Comptes rend, de la soc. de biol., 53, 1901. 



