293 



prostokwacha and the veranetz of Russia, which Metchnikoff mentions. 

 In the kephir of the Caucasus, the koumys of Central Asia, ') and the mazun 

 of Armenia 2 ) occurs moreover, lactose yeast, which may, however, under certain 

 circumstances be wanting, without the character of these beverages being lost. 

 All other microbes, which are mentioned in literature as occurring in the said 

 beverages or their ferments, such as Oidium, Mucor, other moulds, torula, red 

 yeast, vinegar bacteria, butyric acid ferment, proteolytic bacteria, are only present 

 by deficient preparation, so that it may be said that in all examined cases a 

 pure lactic acid fermentation proves to be the wanted process, whilst eventually 

 also an alcoholic fermentation is whised for or suffered 3 ). 



Hence, in the commercial preparations which start from yoghurt, only lactic 

 acid ferments are cultivated. I have in particular investigated the products of 

 Le ferments mentioned beneath, as also a substance, sold as maya or Bul- 

 garian ferment, 4 ) to which my attention was drawn by Dr. De Lint at Sche- 

 veningen. Here I will shortly describe the latter preparation. 



It consists in a yellowish strongly acid reacting powder, composed, after 

 chemical, microscopical and bacteriological examination, of caseine lactic acid, 

 lactose, fat and lactic acid bacteria; it is evidently nothing else but yoghurt 

 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 I took 40, as 45 proved too high and 37 too low, and 

 on a quantity of 250 c.c., so much ferment is strewn as can be put in a little 

 spoon distributed with the flacon containing the maya. After 6 hours already 

 the curdling of the milk becomes perceptible, after 24 hours I titraded 12 c.c. 

 and after 3X 2 4 hours 20 to 23 c.c. of normal lactic acid per 100 c.c. of the 

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



As a titer of 10 c.c. corresponds to 0.9% of lactic acid, the titer 20 corre- 

 sponds to somewhat less than 2/o of the vanished milk sugar. Supposing that 

 the evaporated milk contains about 9.6/o of milksugar it follows that 7% of 

 milksugar has remained undecomposed. The caseine is of course curdled and the 

 whole has changed into a solid but soft, sweet tasting mass. 



') For Kephir and Koumys see Weigmann in Lafar Technische Mykologie. Bd. 2. 

 p. 128. 1905. 



-~) Centralblatt fur Bacteriologie, 2te Abt., Bd. 15, p. 577, 1906. 



3 ) The study of literature leads at first view to a quite other result, as many 

 microbiological descriptions are made by beginners, not sufficiently acquainted with 

 the properties of lactic acid ferments, and who have attributed an exaggerated weight 

 to the different kinds of infections named above. 



4 ) On the bottle stands: Maya bulgare, Societe de la maya bulgare, Gamier &Co., 

 Paris, 16 Rue Popincourt. The Societe de Pury, Montreux, brings into commerce a 

 ferment of the same nature under the name of maya bacilline, and theSociete Henne- 

 berg, Geneva, a liquid preparation as lacticose. Besides there are to be had in Paris 

 Lactobacilline de Metchnikoff in Le Ferments Fournisseur de 1'Assistance pu- 

 blique, 77 Rue Denfert-Rochereau, who sells also, the Biolactyle of Fournier and 

 the Baciline paralactique of Tissier (the preparations of this firm make a very 

 good impression). 



