AND COLLEGE, PUSA, FOR 1915-16 95 



substratum (in this case the walls and floor of the vat) upon 

 which they remain from one operation until the next; this 

 supposition is supported by observation of the easily veri- 

 fied fact that fermentation commences in the immediate 

 neighbourhood of the walls of the vat and gradually 

 spreads therefrom toward the centre. Here we have an 

 analogy with such functions as that of the " starter ' in 

 dairy work and the bacterial slime of the sewage filter bed, 

 and very probably under natural conditions with the micro- 

 organisms responsible for the retting of jute and flax. 

 Many industries depend upon the intervention of micro- 

 organisms, but whereas in some of them the presence of 

 desirable species and the absence of deleterious ones is 

 ^ensured by artificial measures as in the case of brewing and 

 distilling, in others it is assumed that the proper organisms 

 will be naturally present in sufficient predominance to 

 ensure satisfactory results. This is the case with such native 

 Indian industries as the fermentation of " Toddy " and 

 " Mahua," the retting of jute and the steeping of indigo, 

 but it is becoming daily more clear that the distribution of 

 the necessary and proper micro-organisms is by no means 

 so universal or so fortunate as to carry these and similar 

 operations outside the range of practical artificial regula- 

 tion. 



The enquiry in connection with indigo is at present m 

 too early a stage to warrant any confident assumption that 

 it will be possible to apply the methods of the distillery or 

 the dairy with economic success to a raw material such as 

 the indigo plant, but should further work confirm the con- 

 clusions set forth above, it would appear that very consider- 

 able improvements in the methods of manufacture may be 

 obtained by artificially ensuring the presence of the neces- 

 sary organisms in the steeping vat. 



It has been ascertained that two distinct types of fer- 

 mentation may be found in the steeping vats, one in which 

 copious evolution of nitrogen takes place, the only other gas 

 £iven off being carbon dioxide, and the other in which 



