1. Kuban fermented milk is characterised by two types of fermentation, i.e. lactic acid fermentation and alcoholic fermentation.

2. The micro-flora of such milk always embrace the following components: (a) a lactic acid producing streptococcus resembling Str. hollandicus; (b) a lactic acid producing rod of the type of L. bulgaricus; and (c) three types of yeast.

3. There is close symbiosis between the component organisms. The two lactic acid producing organisms can function normally in the absence of the yeasts. The latter, however, prolong the vitality of the starter and also impart a specific taste to the fermented milk.

4. Inoculation of the natural starter with Str. lactis results in a rapid multiplication of this organism and an over-production of acid, which imparts to the fermented milk the taste of ordinary sour milk. A similar undesirable taste is produced if the fermented product is prepared from raw, instead of heated, milk.

Iodometric methods have been applied to the determination of lactose in milk by Kolthoff(1), who used freshly precipitated zinc ferrocyanide as protein precipitant, and by Fine(2) who made use of colloidal iron. The reduction of ferricyanide by reducing sugars has been used as a semi-micro method by Issekutz and von Both(3) and has been applied to the estimation of lactose in milk by Gohr(4) who also used ferrocyanide as protein precipitant.