( 406 ) 



dried, fir^t at 40'— 50° C. and then at 100° C, until the weight 

 remained constant. So we found that ])cr litre 180 milli^ranis of 

 bacterial matter were produced, and that, after deduction of 'J 4 

 milligrams, used by a litre of our tap-water itself, the corresponding 

 permanganate number \vas 94. We can thus, with an accuracy 

 sufficient for our purpose, accept that tlie relation between the two 

 iigures is as 2:1, that is to say, that the doulding of the permanganate 

 number gives the weight of the dry bacterial substance, and, as 

 this latter number is much more quickly to be found than the 

 weight, we have contented ourselves with it in most of our further 

 determinations. 



We shall now give some more figures. Like the preceding they 

 all relate to bacterial fdms produced in ERLP:NMEYER-flasks on 100 cM'. 

 liquid with a free liquid-surface of about 80 cM*. 



By weighing we found in one case on : 

 Tap-water 100 



after 5 months 220 milligrams per litre. 



Some numbers, found by the permanganate method follow, and 

 in the first place some relating to tap-water. 



The greatest production which we had, was obtained with tap- 

 water 0.02 K^HPO^ and 0.02 KNOg, after a year's culture and 

 amounted to 250 mgrs. of permanganate [)er litre, nearly corresponding 

 with 250 X 2 = 500 milligrams of dry bacterial substance. 



After a shorter time the production is likewise smaller; so we 

 found in a culture on: 



after 5 months' culture (January to May) 202 mgrs. of permajiganate, 

 corresponding with 404 mgrs. of bacterial matter per litre. 



