to these authors contains no appreciable quantities of the 

 water soluble vitamin furnished the carbohydrate of the 



diet 39 . 



Source of Vitamin B, Treatment and Manner in Which it 

 Was Fed. Dried skimmed milk was used as a convenient source 

 of vitamin B. It permits the study of the effect of heat on the 

 vitamin both in the wet and dry state. By using skimmed 

 milk powder from the same lot throughout one experiment, 

 possible variation in vitamin content is eliminated. 



The dry milk was heated at 100 C. for six, twenty-four 

 and forty-eight hours in a constant temperature oven. It was 

 spread out in thin layers about one-half inch in thickness and 

 the temperature taken by means of a thermometer extending 

 into the dry milk. Two hours were allowed, which was the 

 time found to be necessary for the milk to come to 100 C. 

 The portions heated six, twenty-four and forty-eight hours 

 respectively actually remained in the oven eight, twenty-six 

 and fifty hours. 



The reconstructed milk was prepared by weighing out 

 100 grams of the air-dry powder and making it up to 1,000 cc. 

 with* water. For the heat treatment 250 cc. of this was poured 

 into an Erlenmeyer flask and tightly stoppered with cotton. 

 This was heated in a vigorously boiling water bath for six 

 hours. A thermometer extending into the milk actually re- 

 corded a temperature of 99.5 C. to 99.8 C. At the end of 

 six hours the flask was removed from the bath and rapidly 

 cooled under the tap. Since the volume diminished, due to 

 evaporation through the stopper, the milk was again made up 

 to volume before using. 



The milk was fed in doses of 8 cc. per rat per day for 

 seven days a week, this, as will later, be shown, being the 

 amount which would best reveal any variation in vitamin con- 

 tent. The milk was measured into a small cup by means of a 

 graduated pipette and placed into the cage each day. If the 

 rat did not drink the milk readily, the water cup was removed 

 for the day and replaced in the evening. Usually this treat- 

 ment brought the desired results. After two to three days all 

 the rats took all the- milk that was given them. The milk 



