BACTERIOLOGICAL TECHNIC. 69 



0.5 c.c. normal salt solution and make counts of pus cells and leucocytes 

 per c.c. from the amount (0.5 c.c.). Abundant pus cells and leucocytes indi- 

 cate abscess or other pathological condition of milk ducts or glands. This 

 test is, however, of little significance excepting in the hands of authorities 

 on diseases of cows. It is stated that as many as 100,000 leucocytes per c.c. 

 may occur in apparently healthy animals. 



Gelatin-liquefying organisms may be looked upon with suspicion 

 when found in milk, water and other liquid-food substances intended for 

 human consumption, as has already been explained. 



It should be borne in mind that the colon bacillus is one of a group of 

 some fifteen or more species and varieties of closely related micro-organisms 

 which resemble each other in the following particulars: 



1. Do not form spores. 



2. Do not liquefy gelatin. 



3. Produce acid in milk and cause milk coagulation. 



4. Produce acid and gas in glucose and lactose media. 



5. Produce acid and gas in bile-salt-glucose broth. 



6. Grow well in temperatures ranging from 38 to 42 C. 



In differentiating the colon bacillus, remember that this organism is 

 rod-shaped (2 to 3/1 long by 0.5 to o.6/* wide), is motile, produces indol, 

 gives rise to pink colonies on lactose (or glucose) litmus agar and reduces 

 neutral red glucose (or lactose) agar with a greenish-yellow fluorescence. 



It should also be remembered that sewage is a highly complex substance 

 and contains micro-organisms in great variety and in great abundance. 

 Among the organisms present are species of Spirillum, Vibrio, Proteus and 

 Beggiatoa in addition to the bacilli and streptococci already mentioned. 

 The typhoid bacillus does not thrive well in sewage. The number of bac- 

 teria present in crude or ordinary sewage (domestic, city, hospital, mixed, 

 etc.) ranges from 1,000,000 to 100,000,000 and more per c.c. The work 

 of these organisms is to break down and render soluble and assimilable 

 (for plants) the organic matter composing the sewage, thus assisting the work 

 of rotting bacteria generally. 



The following is a tabulation of the bacteriological testing that should 

 be made of foods (including pastes, catsups, milk, ice creams, water supplies, 

 mineral waters, alcoholic beverages, etc.) that may show an excess of bacterial 

 growth or which may be sewage contaminated: 



BACTERIOLOGICAL EXAMINATION. 



I. Direct Count. 



1. Bacilli per c.c 



2. Cocci, per c.c . 



