360 Buu,etin 167 



is customary with the doors of safes or refrigerators. The 

 cover was formed in sections so as to permit opening one end 

 without admitting cold air to the entire contents. 



It was the first intention to maintain the temperature by 

 introducing hot freestones into the incubator when the tempera- 

 ture of the sap began to fall. It soon appeared, however, dur- 

 ing the extremely cold weather encountered shortly after start- 

 ing the first series of the year, that this means of control was 

 inadequate and the more satisfactory method of introducing 

 buckets of boiling water was resorted to. This raised the air 

 temperature in the incubator very promptly and the heat was 

 gradually imparted to the sap. The temperature of the samples 

 was occasionally tested by introducing a sterile thermometer 

 into the buckets, and whenever necessary additional heat was 

 supplied. 



A self recording thermometer was placed in the incubator 

 from the tracing's of which the temperature curves here repro- 

 duced were obtained. It should be borne in mind, however, 

 that these curves by no means represent the temperature of the 

 sap which was far more constant than that of the air. It never 

 fell as low nor did it rise as high. The graphs are of value, how- 

 ever, in that they give some indication of the conditions of in- 

 cubation. 



The material was incubated in new tin buckets which were 

 thoroughly scalded immediately before filling. They had a 

 capacity of 20 quarts and were provided with covers. Inocula- 

 tion was made with a 70 cc. young culture of the specific organ- 

 ism employed. The controls were treated with an equivalent 

 amount of the sterile medium which consisted of 65 cc. of sap 

 and 5 cc. of nutrient bouillon. 



Before being made into sirup each sap was thoroughly mixed 

 and a small sample was withdrawn and sterilized to be preserved 

 for the purposes of another investigation, the results of which it 

 is expected will eventually be published by the station chemist. 

 As a rule the reaction was determined by titrating aefainst 



