(30 ) 



else bul yoghürl evaporated at low temperature, perhaps in the 

 vacuum. As to the preparation of the "yoghurt" itself by means of 

 this ferment, it is done as follows and gives good results. 



Milk is evaporated to half its volume, cooled to a (not nearer 

 indicated) temperature, for which 1 took 40 , as 45 J proved too 

 high and 37° too low, and on a quantity of' 250 e.c, so much 

 ferment is strewn as can he put in a little spoon distributed with the 

 flacon containing the maya. A lier 6 hours already the curdling Of 

 the milk becomes perceptible, after 24 hours I titrated 12 e.c. and 

 after 3X24 hours 20 to 23 e.c. id' normal lactic acid per 100 e.c. 

 of the evaporated milk, which by that time is changed into yoghurt. 



As a titer of 10 e.c. corresponds to 0.9 % of lactic acid, the 

 titer 20 corresponds to somewhat less than 2 " „ of the vanished 

 milk sugar. Supposing that the evaporated milk contains about 9.6 % 

 of milksugar it follows that 7 ° „ of milksugar has remained un- 

 decomposed. The caseine is of course curdled and the whole has 

 changed into a solid hut soft, sweet tasting mass. 



The evaporation of the milk is not necessary, hut when prepared 

 from ordinary milk, the yoghurt remains more liquid, and as the 

 acid formation is equally strong as in evaporated material, there 

 remains about 2.5 "/„ of the original 4.8% milksugar, so that 

 in this case the taste is much less sweet. 



If in the said way yoghurt has been prepared in the presence of 

 air and is re-inoculated into a new quantity id' milk, then the result 

 is yoghurt of the same acidity as the first time. But after 3 or 4 trans- 

 ferrings difficulties arise and only with great quantities of infection 

 material further souring can be obtained. The experiment succeeded 

 much better when the yoghurt was prepared in a quite tilled stop- 

 pered bottle; the transferring can then be longer continued, but 1 

 do not know whether this will do in the long run. Evidently the 

 difficulty here, too, is the right choice of oxygen pressure, whereby 

 the inferred lactic acid bacteria preserve their properties unchanged; 

 and this difficulty is still increased by the presence of two different 

 forms, with unequal optima as to temperature, and probably as to 

 oxygen pressure also. 



One of these forms is again a Lactococcus, the other a Lactobacillus. 



The former deviates somewhat from the common Lactococcus, in 

 as much as it is more extended, reminding of short rods, and further- 

 more by possessing a higher optimum as to the temperature whereby 

 the growth is quickest, which optimum proves nearer to 37° than 

 to 30° C. Hence, this form is as it were a transition to a Lactobacillus. 

 Isolation on milk agarplates was verj easy, even at 30 C. 



