122 Transactions of the Canadian Institute. [Vol. V'II. 



Klein and Kirsten rendered heated milk suitable for cheese-making 

 by adding calcium chloride. In their experiments they were able to 

 produce normal cheese of several varieties (Bachstein, Spitz, Remoudou, 

 Kloster, etc.) by heating the milk to temperatures varying from 85" C. 

 to 100° C. for different periods of time, treating it with calcium chloride 

 (twenty-five grams of calcium oxide per litre) and adding either cultures 

 or starters. Cheese made by this method not onl}' ripened normally 

 but also gave a larger )'ield than cheese made from non-heated milks. 



My own studies on the bacterial content of cheese were com- 

 menced in 1896 at the Bacteriological Laborator\' of Dr. Russell, at 

 the University of Wisconsin. During that summer and the following 

 one of 1897, many analyses of Canadian Cheddar cheese were made, the 

 methods of analyses being similar to those already published in the 

 various reports of the Wisconsin Experiment Station. Briefly described, 

 they are as follows : 



A sterilized test-tube was sent to a factory with the request that a 

 plug of cheese be placed therein, and asking that the cheese trier be 

 sterilized with steam before use. A typewritten form accompanied each 

 tube, upon which the cheesemaker filled out particulars as to the age of 

 the cheese, condition of manufacture, amount of rennet used, etc. 

 From one to five days elapsed between the taking of the sample and the 

 making of the analyses ; and, on many occasions, the cheese received 

 was very greasy or had otherwise deteriorated owing to the very hot 

 weather, and the length of time taken in transit. Doubtless these facts 

 have contributed to bring about the diversity of the results shewn in my 

 first table. 



On arrival at the laboratory, one gram of cheese was weighed out 

 and triturated with ten grams of sterilized sugar, sand or powdered 

 glass. Sterilized water was then added and various dilutions made, 

 differing with the age of the cheese. The medium used at Wisconsin 

 was the ordinary beef peptone gelatin, with or without the addition of 

 milk sugar. From two to five plates were made. 



Subsequently this method was improved on, b\' using sterilized 

 warm water (t,j C.) for the dilutions, and yeast water lactose gelatin for 

 medium. To this a small quantity of precipitated chalk was usually 

 added. This medium gave excellent results compared with the ordinary 

 nutrient gelatin or whey peptone gelatin, the colonies of the lactic acid 

 bacteria were larger, and the dissolving action of these germs on the 

 chalk materially aided the labour of counting. 



