Another unclassified group occasionally present in milk is represented by moulds, particularly _Oidium lactis_, the mould which causes a white fur, possessing a sour odour. It is allied to the _Mycoderma albicans_ (_O. albicans_), which also occurs in milk, and causes the whitish-grey patches on the mucous membrane of the mouths of infants (_thrush_). These and many more are occasionally present in milk. 3. _The Disease-Producing Power of Milk_ The general use of milk as an article of diet, especially by the younger and least resistant portion of mankind, very much increases the importance of the question as to how far it acts as a vehicle of disease. Recently considerable attention has been drawn to the matter, though it is now a number of years since milk was proved to be a channel for the conveyance of infectious diseases. During the last twenty years particular and conclusive evidence has been deduced to show that milch cows may themselves afford a large measure of infection. The recent extensive work in tuberculosis by the Royal Commission has done much to obtain new light on the conveyance of that disease by milk and meat. The enormous strides in the knowledge of diphtheria and other germ diseases have also placed us in a better position respecting their conveyance by milk. Generally speaking, for reasons already given, milk affords an ideal medium for bacteria, and its adaptibility therefore for conveying disease is undoubted. We may now suitably turn to speak shortly of the outstanding facts of the chief diseases carried by milk.