192 



PHARMACEUTICAL BACTERIOLOGY 



part at least, to a variety or form of PenicilUum glaucum. The qualities 

 and properties of some Swiss and soft Belgian cheeses are largely due to 

 Oidium lactis. The ripening of hard cheeses (Cheddar, Edam, American, 

 some Swiss varieties, and others) is due exclusively to bacterial action. 

 Cream, butter and cheese are very prone to the attacks of objectionable 

 bacteria and moulds which cause very unpleasant flavors and bitter taste. 

 It must also be borne in mind that cream, cheese and butter may carry 

 disease germs. Tubercle baciUi have been reported in these food arti- 

 cles, but it has not been demonstrated that they are frequently present. 

 Typhoid infections have been traced to the use of cream, but no case of 

 typhoid fever has ever been definitely traced to eating butter or cheese. 

 Of course, these articles may become infected after manufacture and thus 

 become a possible means of spreading disease. 



B. The Bacteriological and Microscopical Examination of Milks 



The examination and rating of milk is largely a municipal affair and 

 every city of any considerable size has a Board of Health or an officer 

 who is empowered to enforce the regulation governing the quality of the 

 milk to be sold. Dealers in milk and dairy men are required to produce 

 evidence that they are complying with the health ordinances pertaining 

 to the sale of milk for human consumption. Score cards are provided 

 which the keepers of dairies must fill out. Evidence as to the conditions 

 under which the cows are kept must be furnished. Samples are taken 

 from time to time and analyzed in the city laboratory, which examination 

 is generally chemical and bacteriological. The legal definitions of the 

 different kinds of milk are given and the analysts are required to show 

 whether or not the quality of the milk under examination conforms to the 

 definition. The 'following statements will make these points clear. 



I. General Statement as to Quality. — The lacteal secretion obtained 

 from the domesticated cow and from other animals, as goat, mare, and 

 ass, is a highly important food article. The chief food ingredients which 

 it contains are casein, fat, and sugar (lactose). The major bulk is water. 

 Milk happens to be an ideal food for many bacteria and raw milk freely 

 exposed to air undergoes complete bacterial decomposition in a compara- 

 tively short time, the rate of decomposition depending on temperature, 

 oxygen supply and degree of contamination. The organisms which 

 may be considered as the normal milk decomposers are the group of lactic 

 acid formers, or the milk sourers. These appear to be omnipresent in 

 the air and upon the earth's surface, entering air exposed milks and by 

 their rapid multiplication soon crowd out other associated air bacteria. 



The production of pure milk is all-important and, pure milk can be 



