618 



are of no importance. In ttc ripening of cheese, however, this class of 

 bacteria is of great siguiflca^Mje. 



In addition to these common forms of bacteria other spt'cies are 

 occasionally present which give rise to certain foiins of diseased milk. 

 Three distinct species of organisms are Ivtiown to produce red milk. 

 One much studied bacterium gives rise to blue mi!k. Tliree species are 

 known to curdle the milk and theu rapidly dissolve the curd into a 

 yellow liquid of various degrees of brilliancy. Four different species 

 have been found which produce a slimy milk. These have been 

 described by different observers aud have been found in different places 

 Adametz has himself found one of the slime formiug species iu the 

 waters of brooks. Besides these well-marked troubles a miscellaneous 

 series of "milk diseases" very auuoyiiig to cheese-makers, are men- 

 tioned, and their origin is found in the growth of various bacteria aud 

 yeasts. 



Special attention is given to alcoholic fermentation of milk known as 

 "kefir." This form of fermented milk is a favorite beverage among the 

 people of the Caucasus Mountains, and is produced by putting into the 

 milk small bodies known as " kefir grains." The fermentation has been 

 found to be the result of a complicated growth of bacteria and yeasts. 

 Several species of bacteria and several yeasts have been found iu these 

 kefir grains and iu the fermeutiug milk. Among the bacteria are a 

 number of the peptonizing species, and some which have the power of 

 inverting sugar. The common form of yeast familiar to the beer maker 

 {Saccharonujces cerevisiw) has not been found in this connection. The 

 alcoholic fermentation is the result of the combined action of these 

 organisms, but the share taken by each has not yet been determined. 



In addition to these bacteria, which produce troublesome, though com- 

 paratively harndess effects in milk, certain species which are injurious 

 to the consumer occasionally get into the milk. Some of the common 

 putrefactive bacteria give rise to poisons while growing in milk. These 

 poisons are in general known as ])tomaines, and when taken into the 

 stomach of the person who drinks the milk or eats the cheese, produce 

 various dangerous symptoms and occasionally death. The best known 

 of these poisons connected with milk is tyrotoxicon. Several species 

 of bacteria have been studied which can thus infect the milk with 

 jioisonous material. The poisoning from this source is especially com- 

 mon from cheese. Accounts of over 300 cases of such poisoning were 

 collected by Professor Vaughan in two years. 



Milk is also an excellent nourishing medium for several of the path- 

 ogenic germs. This is especially true of sweet milk, sour milk offering 

 a less fixvorable medium for their growth. Some of them grow readily 

 in milk without producing any visible effect. The germs of typhoid 

 fever, tuberculosis, and diphtheina may thus grow without indicating 

 their presence by any external changes iu the milk. Adametz thinks 

 that typhoid fever is frequently si)read by means of the milk supply 



