v] METHODS OF INOCULATION 85 



or Agar, well shaken, and then plate-cultivations are 

 made. 



In Carnelly's experiments the nutrient gelatine is allowed 

 to set at the bottom of a large sterile flask, the mouth of 

 which is closed by a sterile indiarubber stopper, through 

 which two glass tubes are passed — one long one through 

 which the air passes from the gas meter, the other a short 

 one connected with the aspirator : as the air passes into 

 and out of the flask the microbes are deposited on the 

 surface of the set gelatine. 



Examination of Ice. — A piece of ice is dug out from a 

 block, the surface of this having been previously well washed 

 with sterile water ; the piece is placed into a sterile test- 

 tube and after it has melted is treated like water. 



Milk, for thev detection of the number and general 

 character of bacteria, is treated like water — viz., a small 

 quantity, -^^ to i cc, is used for ordinary plate-culture. If 

 bacillus coli, bacillus of typhoid, sewage bacillus, or cholera 

 vibrio are searched for, the best method is this ; — 



The whole or half of the quantity of milk sent for ex- 

 amination is put into a sterile flask or flasks, then of a 5 per 

 cent, phenol solution is added, so as to make the whole 

 contain 0-05 per cent, phenol ; then it is incubated at 37° C. 

 Next day phenol gelatine plates are made as in the case . of 

 water. For cholera vibrios the same method is used as for 

 water. 



Examination of soil, mud, earth, food-stuffs, or any other 

 solid material. Here, as in the examination of water, the deter- 

 mination is {a) of the number and (1^) of the character of the 

 organisms, and it is followed on exactly the lines described 

 of water examination. 



(a) To determine the number : a definite weighed amount 

 of the solid material is distributed in a definite quantity of 



