278 CLEAN MILK 



EXAMINATIONS FOR B. COLI IN MILK. 



This examination, like that for pus and for streptococci, has not 

 yet had its true value or significance determined. Its advocate, 

 Stokes, finds a relation between the frequency with which it is 

 found and the number of bacteria present — i. e., high count milk 

 is much more likely to yield colon bacilli than low count milk. It is 

 unlikely that this test as a rule indicates more than the admission 

 of manure to the milk in unusual proportions. Stokes' method is 

 as fallows: 



Ox bile is collected from slaughter houses; i% of lactose 

 added; this medium is placed in fermentation tubes and sterilized. 

 For the test, i/iooo c.c. of the milk in question is added and the 

 tube incubated at 37" C. for 72 hours; if more than 15% of the 

 length of the closed arm of the fermentation tube is occupied by 

 gas at the end of this time, plates are made from the fluid, and 

 colonies isolated and tested as for B. coli. 



LIST OF APPARATUS REQUIRED FOR A SIMPLE LABORATORY FOR BACTERIAL WORK 



RELATED TO MILK. 



Work table, of wood, firm and smooth, not painted or varnished, but oiled or vaselined 

 (hot) or treated with aniline black mixture; well lighted by a north window: 40 

 inches above floor for " stand up " work, 30 inches for " sit down " work. 



Water supply: Preferably hot and cold, emptying into a large sink (about 3' x i'-i' x + ); 

 a much smaller sink, and 1 supply consisting of a barrel with faucet, or even a large 

 chamber pitcher, may be used. 



Waste pipes of ordinary plumbing may be used : or wooden rain-troughs (eave pipes) 

 may be set below the sink outlet and used to conduct the waste to an appropriate 

 outlet. 



Gas supply. Oas-pipes, fitted with simply keyed gas outlets for attachment of rubber 

 hose for Kunsen burners and gas stoves of one and two plates may be used; or 

 alcohol lamps of the Larthel type may replace the Bunsen burners; of the Glogau 

 type, the gas stoves. 

 Sterilizers. A very satisfactory hot-air oven for empty glassware of all descriptions 

 consists of an ordinary gas stove oven, used on a two-plate gas stove or on a Glogau 

 type alcohol stove ; even the oven of an ordinary cook range may be used. 

 Jirnold sterilizers for media, contained in flasks, test tubes, etc., for free steam ; these may- 

 be obtained of tin or of copper ; or a good home-made substitute may be constructed 

 by attaching to the lip of a deep tin or agate four-quart pan (to contain the boiling; 

 water) a tin cylinder with vertical sides, a fairly tight cover and a perforated bottom. 



